H u m a n B e h a v i o u r i n S o c i a l - E c o l o g i c a l S y s t e m s : I n s i g h t s f r o m e c o n o m i c e x p e r i m e n t s a n d a g e n t - b a s e d m o d e l l i n g

Caroline Schill

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Human Behaviour in Social-Ecological Systems Insights from economic experiments and agent-based modelling

Caroline Schill

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Abstract

Progress towards sustainability requires changes in our individual and collective behaviour. Yet, our fundamental understanding of behaviour in relation to environmental change remains severely limited. In particular, little attention has been given to how individual and collective behaviours respond to, and are shaped by, non-linear environmental change (such as ‘regime shifts’) and its inherent uncertainties. The thesis makes two main contributions to the litera-ture: 1) it provides one of the first accounts of human behaviour and collective action in relation to ecological regime shifts and associated uncertainties; and 2) extends the incipient behavioural common-pool resource literature that acknowledges social-ecological dynamics and ecological complexity. The over-arching aim of this thesis is to further advance an empirically grounded under-standing of human behaviour in social-ecological systems. In particular, the thesis attempts to unravel critical social-ecological factors and mechanisms for the sustainability of common-pool resources. This is especially relevant for contexts in which livelihoods can be more directly threatened by regime shifts. The following methods are applied: behavioural economic experiments in the lab (with students; Papers I and II) and in the field (with small-scale fishers from four different communities in the Colombian Caribbean; Paper III), and agent-based modelling empirically informed by a subset of the lab experiments (Paper IV). Paper I tests the effect of an endogenously driven regime shift on the emergence of cooperation and sustainable resource use. Paper II tests the effect of different risk levels of such a regime shift. The regime shift in both papers has negative consequences for the productivity of the shared resource. Paper III assesses the effect of different degrees of uncertainty about a cli-mate-induced threshold in stock dynamics on the exploitation patterns; as well as the role of social and ecological local context. Paper IV explores critical individual-level factors and processes affecting the simultaneous emergence of collective action and sustainable resource use. Results cumulatively suggest that existing scientific knowledge indicating the potential for ecological regime shifts should be communicated to affected local communities, including the remain-ing uncertainties, as this information can encourage collective action for sus-tainable resource use. Results also highlight the critical role of ecological knowledge, knowledge-sharing, perceived ecological uncertainties, and the role local contexts play for sustainable outcomes. This thesis enriches the literature on social-ecological systems by demonstrating how a behavioural experimental

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approach can contribute new insights relevant for sustainability. Overall, these insights indicate that, given the opportunity and the willingness of people to come together, share knowledge, exchange ideas, and build trust, potential eco-logical crises can encourage collective action, and uncertainties can be turned into opportunities for dealing with change in constructive ways. This provides a hopeful outlook in the face of escalating environmental change and inherent uncertainties.

Keywords Human behaviour; Common-pool resources; Ecological complexity; Collective action; Sustainable resource use; Regime shifts; Thresholds; Uncertainty; Com-munication; Knowledge-sharing; Economic experiments; Laboratory and field experiments; Agent-based modelling; Complex adaptive systems; Social-ecological systems

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Sammanfattning

För att kunna uppnå och sedan upprätthålla ett bärkraftigt samhälle krävs stora förändringar, inte minst vad gäller våra individuella och kollektiva beteenden. Detta i sin tur kräver en ökad förståelse av mänskligt beteende i förhållande till de hållbarhetsutmaningar vi står inför idag. Mer specifikt har frågan om mänsk-ligt beteende i relation till biosfären, inklusive dess inneboende komplexitet, fått relativt lite uppmärksamhet, vilket är anmärkningsvärt med tanke på att denna biosfär upprätthåller människans existens. Det övergripande syftet med denna avhandling är att genom empirisk forskning bidra till en ökad förståelse av mänskligt beteende i så kallade social-ekologiska system (SES). Målet med detta är att identifiera kritiska social-ekologiska faktorer och mekanismer som kan främja en hållbar resurshantering av så kallade gemensamma naturresurser (CPR). Detta görs genom att koppla individuella och kollektiva beteenden till två nyckelfunktioner i biosfärens ekologiska komplexitet: icke-linjära miljöför-ändringar (regimskiften) och osäkerhet. Således bidrar denna avhandling till två viktiga forskningsluckor genom att den 1) undersöker mänskligt beteende (indi-viduellt och kollektivt) i relation till ekologiska regimskiften och deras innebo-ende osäkerheter; samt 2) inför och undersöker konsekvenserna av social-ekologisk dynamik och ekologisk komplexitet i analyser kring gemensamma resurser. Metodiskt bidrar avhandlingen till dessa två forskningsfronter genom ekonomiska beteende-experiment i såväl laboratoriemiljö som i fältmiljö, samt genom en agentbaserad modell. Lab-experimenten genomfördes med studenter som deltagare (Uppsats I och II). Fältexperimenten genomfördes med småska-liga fiskare från fyra olika samhällen vid den Colombianska Karibiska kusten (Uppsats III). Den agentbaserade modellen bygger på de experimentella studi-erna (Uppsats IV). I uppsats I och II studeras hur olika grader av risk för endo-gent drivna regimskiften påverkar förekomsten av samarbete och exploatering-en av en gemensam naturresurs. Resultaten visar att en hög risk för ett regim-skifte med negativa konsekvenser (för återväxten av naturresursen), kan fungera som en koordineringspunkt där användarna kan samordna åtgärder för ett mer hållbart nyttjande. Uppsats III söker blottlägga hur exploateringsmönster på-verkas av grader av vetenskaplig osäkerhet kring klimatdrivna regimskiften i olika social-ekologiska sammanhang. Resultaten visar tydligt att användare ex-ploaterar naturresursen mer hållbart då osäkerheten om, och i så fall när, ett regimskifte kan inträffa, är hög. I uppsats IV undersöks hur samarbete kan uppstå och när detta samarbete är mer troligt att leda till en hållbar resursan-vändning, och hur denna utveckling i sin tur påverkas av faktorer och processer

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på individnivå. Resultaten visar att samspelet mellan fördelningen av enskilda individers ekologiska kunskap, osäkerheten som individer upplever i denna kunskap, och huruvida kunskapen delas, påverkar hur hållbart resursen utnytt-jas. Denna avhandling berikar litteraturen kring SES genom att belysa hur stu-dier och metoder med avsikt att studera och förstå mänskligt beteende kan bidra med nya insikter. Samtidigt berikar den litteraturen kring gemensamma resurser genom att introducera en dynamisk social-ekologisk kontext. Insikterna från denna avhandling bidrar också till den pågående omvärderingen av anta-ganden om mänskligt beteende som implementeras i modeller, som i sin tur har inflytande i miljöpolitiken. Den bidrar också till den pågående efterfrågan av institutionella arrangemang som främjar kollektivt beslutsfattande samt arenor för lärande och kunskapsutbyte, vilka kan göra det möjligt för utsatta samhällen att upprätthålla de ekologiska funktioner som de är beroende av. Trots de eska-lerande miljöförändringarna (och deras inneboende osäkerheter) vi står inför, ger denna avhandling en relativt positiv syn. Som denna avhandling visar, kan potentiella ekologiska kriser mobilisera samarbeten, ge möjlighet för människor att utbyta idéer, dela kunskap och bygga upp ett gemensamt förtroendekapital. Kriser och osäkerheter kan vändas till möjligheter för att hantera dessa utma-ningar på ett konstruktivt sätt.

Nykelord Mänskligt beteende; Gemensamma naturresurser; Ekologisk komplexitet; Sam-arbete; Hållbar resursanvändning; Regimskiften; Tröskelvärden; Osäkerhet; Kommunikation; Kunskapsdelning; Laboratorie- och fältexperiment; Agentba-serade modeller; Komplexa adaptiva system; Social-ekologiska system

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Zusammenfassung

Nachhaltige Entwicklung erfordert Veränderungen in unserem individuellen und kollektiven Verhalten. Allerdings ist unser grundlegendes Wissen über menschliches Verhalten in Bezug auf ökologische Umweltveränderungen und den Herausforderungen, die eine nachhaltige Entwicklung stellt, äußerst be-grenzt. So ist speziell der Zusammenhang zwischen individuellem und kollekti-vem Verhalten und der Komplexität von Ökosystemen und deren Veränderun-gen weiterhin nicht ausreichend geklärt. Es ist das übergreifende Ziel dieser Doktorarbeit, ein empirisch-fundiertes Verständnis menschlichen Verhaltens in sozial-ökologischen Systemen herzustellen und bisheriges Wissen weiter zu entwickeln. Der dazu gewählte Ansatz verknüpft individuelles und kollektives Verhalten mit zwei Aspekten ökologischer Komplexität: drastische Verände-rungen ökologischer Umweltbedingungen (wie z.B. sogenannte „regime shifts“) und Unsicherheit. Dadurch sollen wichtige sozial-ökologische Faktoren und Mechanismen identifiziert werden, die gemeinschaftlich genutzte Ressourcen (Allmendegüter) erhalten können. Diese interdisziplinäre Arbeit liefert 1. eine erste Analyse menschlichen Verhaltens und kollektiver Handlungen im Zu-sammenhang mit drastischen ökologischen Umweltveränderungen und damit verbundenen Unsicherheiten; und erweitert 2. die verhaltensorientierte For-schungsliteratur zu Allmendegütern durch die innovative Weise, auf die sozial-ökologische Dynamik und ökologische Komplexität einbezogen werden. Me-thodisch nutzt die Arbeit verhaltensökonomische Experimente, sowohl im Labor (mit Studenten; Papier I-II), als auch im Feld (mit Fischern aus vier Dorfgemeinschaften entlang der kolumbianischen Karibikküste; Papier III), und eine agentenbasierte Modellierung (Papier IV), deren Konzept auf Teilen der Erkenntnisse aus den Laborexperimenten beruht. Papier I analysiert den Effekt negativer endogener und drastischer Umweltveränderungen auf koope-ratives Verhalten und nachhaltige Ressourcennutzung. Papier II analysiert den Effekt unterschiedlicher Risikoniveaus solcher Umweltveränderungen. Papier III untersucht den Effekt unterschiedlicher Unsicherheitsniveaus bezüglich klimabedingter, negativer Umweltveränderungen auf das Ressourcennutzungs-verhalten sowie die Rolle, die dabei der lokalen, sozialen und ökologischen Kontextbedingungen zukommt. Papier IV untersucht die relevanten Individual-faktoren und -prozesse, die nicht nur zu kollektivem Verhalten sondern auch der nachhaltigen Nutzung der gemeinschaftlichen Ressourcen führen. Als übergreifendes Ergebnis lässt sich feststellen, dass, sofern wissenschaftliche Erkenntnisse über mögliche drastische Umweltveränderungen sowie damit

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verbundene Unsicherheiten zur Verfügung stehen, diese auch kommuniziert werden sollten, da diese Information kollektives Verhalten und nachhaltige Ressourcennutzung begünstigen kann. Die Ergebnisse dieser Arbeit unterstrei-chen auch die kritische Rolle von ökologischem Wissen, individuell wahrge-nommenen Umweltunsicherheiten, der sozialen Fähigkeit, Wissen zu teilen, und lokalen Kontextbedingungen für die nachhaltige Nutzung gemeinschaftli-cher Ressourcen. Die vorliegende Arbeit zeigt, dass und wie verhaltensexperi-mentelle Forschung wichtige Erkenntnisse für die Nachhaltigkeit sozial-ökologischer Systeme liefern kann und bereichert dadurch die Literatur bezüg-lich sozial-ökologischer Systeme. Die Ergebnisse tragen auch zu der zuneh-mend relevanten Neubewertung der Verhaltensannahmen in wissenschaftlichen Modellen, auf welchen Umweltregulierungen basieren, bei und bietet Argumen-te für institutionelle Arrangements, die kollektive Handlungen, Wissenstransfer und Lernumgebungen begünstigen. Insgesamt nimmt diese Arbeit trotz der schnell fortschreitenden Umweltveränderungen und den damit verbundenen Unsicherheiten eine grundsätzlich positive Perspektive ein. Solange wir die Möglichkeit und Bereitschaft haben, zusammen zu kommen, Wissen auszutau-schen und Vertrauen aufzubauen, kann eine mögliche ökologische Krise sogar kollektive Handlungen fördern und Unsicherheiten können uns dabei helfen, mit solchen Veränderungen konstruktiv umzugehen. Schlüsselwörter Menschliches Verhalten; Allmendegüter (gemeinschaftlich genutzte Ressour-cen); Ökologische Komplexität; Kollektive Handlungen; Nachhaltige Ressour-cennutzung; Zusammenarbeit; Regime shifts (drastische Umweltveränderun-gen); Schwellenwerte; Unsicherheit; Kommunikation; Wissenstransfer; Verhal-tensökonomische Experimente; Labor- und Feld-Experimente; Agentenbasierte Modellierung; komplexe, Adaptive Systeme; Sozial-ökologische Systeme

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Resumen

El progreso hacia la sostenibilidad requiere de cambios en nuestro comporta-miento individual y colectivo. Sin embargo, nuestro conocimiento básico sobre el comportamiento humano en relación al cambio ambiental es aún bastante limitado. En particular, poca atención se le ha dado a la forma en la que el comportamiento individual y colectivo es influenciado por el cambio ambiental no-linear (como las ‘transiciones críticas’) y sus incertidumbres inherentes. Esto es lo que esta tesis examina, a través de la aplicación de los siguientes métodos: experimentos económicos-comportamentales en el laboratorio (con estudiantes; Artículos I y II) y en campo (con pescadores artesanales de cuatro comunidades del Caribe Colombiano; Artículo III), y modelamiento basado en agentes (Ar-tículo IV) informado empíricamente por un subconjunto de los experimentos de laboratorio. El objetivo general de esta tesis es continuar avanzando el cono-cimiento sobre el comportamiento humano en sistemas socio-ecológicos (SSE), con una base empírica. En particular, esta tesis busca esclarecer factores y me-canismos socio-ecológicos clave para la sostenibilidad de recursos de uso co-mún (RUC). Esto es de especial importancia en contextos en los que las transi-ciones críticas pueden afectar más directamente los medios de vida. Esta tesis hace dos contribuciones principales a la literatura: 1) provee una de las primeras aproximaciones al estudio del comportamiento humano y la acción colectiva en relación con transiciones críticas ecológicas y las incertidumbres asociadas; y 2) extiende la incipiente literatura comportamental sobre RUC que reconoce di-námicas de SSE y complejidad ecológica. El Artículo I evalúa el efecto de una transición crítica endógena sobre la emergencia de la cooperación y el uso sos-tenible de recursos. El Artículo II evalúa el efecto de diferentes niveles de ries-go con respecto a esta transición crítica. En los dos artículos, la transición críti-ca tiene consecuencias negativas en la productividad del recurso común. El Artículo III evalúa el efecto de diferentes grados de incertidumbre con respecto a un umbral inducido climáticamente, y que afecta la dinámica del recurso, so-bre los patrones de uso; así como el rol del contexto social y ecológico local. El Artículo IV explora factores y procesos clave a nivel individual que afectan la emergencia de acción colectiva y el uso sostenible del recurso. Los resultados muestran que el conocimiento científico existente con respecto a potenciales transiciones ecológicas críticas, incluyendo las incertidumbres remanentes, debe ser comunicado a las comunidades afectadas, ya que esta información puede promover la acción colectiva para el uso sostenible de recursos. Los resultados también resaltan la importancia del conocimiento ecológico, la incertidumbre

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ecológica percibida, la habilidad social para compartir conocimiento, así como el contexto local, para la sostenibilidad del recurso. Esta tesis enriquece la litera-tura de SSE al demostrar cómo una aproximación comportamental-experimental puede develar nuevos aspectos relevantes para la sostenibilidad. En general, estos resultados indican que, cuando la gente tiene la oportunidad y le deseo de interactuar, compartir su conocimiento, intercambiar ideas, y cons-truir confianza, las crisis ecológicas pueden promover acción colectiva, y las incertidumbres pueden ser convertidas en oportunidades para lidiar con el cambio en formas constructivas. Esto ofrece una perspectiva esperanzadora de cara a la actual intensificación del cambio ambiental y las incertidumbres inhe-rentes.

Palabras clave Comportamiento humano; Recursos de uso común; Complejidad ecológica; Acción colectiva; Uso sostenible de recursos; Transiciones críticas; Umbrales; Incertidumbre; Comunicación; Conocimiento compartido; Experimentos eco-nómicos; Experimentos de laboratorio y en campo; Modelamiento basado en agentes; Sistemas complejos adaptativos; Sistemas socio-ecológicos

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Table of Contents

List of Papers .............................................................................................................................. 18

Introduction ................................................................................................................................ 21

Theoretical and Conceptual Background ............................................................................... 25 Situating this Thesis ....................................................................................................................................... 25 Ecological Regime Shifts and Associated Uncertainties .......................................................................... 26 Common-Pool Resources ............................................................................................................................. 29 Human Behaviour in Complex and Uncertain Environments ............................................................... 34 Research Gaps and Questions ..................................................................................................................... 38

Methods ....................................................................................................................................... 41 Behavioural Economic Lab and Field Experiments ................................................................................. 42 Agent-Based Modelling ................................................................................................................................. 45

Core Findings - Individual Papers ........................................................................................... 48

Discussion ................................................................................................................................... 52 Key Insights .................................................................................................................................................... 52 Methodological Contributions ..................................................................................................................... 55 Limitations and Additional Considerations ............................................................................................... 57

Conclusions and Looking Ahead ............................................................................................ 61

Acknowledgements .................................................................................................................... 64

References ................................................................................................................................... 65

Thank you ................................................................................................................................... 78

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List of Papers

Paper I Lindahl, T., A.-S. Crépin, and C. Schill. 2016. Potential disasters can turn the tragedy into success. Environmental and Resource Economics 65(3):657–676.

Paper II Schill, C., T. Lindahl, and A.-S. Crépin. 2015. Collective action and the risk of ecosystem regime shifts: insights from a laboratory experiment. Ecology and Socie-ty 20(1):48.

Paper III Schill, C., and J. Rocha. Uncertainty can help protect the commons in the face of climate change. Manuscript.

Paper IV Schill, C., N. Wijermans, M. Schlüter, and T. Lindahl. 2016. Cooperation is not enough - Exploring social-ecological micro-foundations for sustainable com-mon-pool resource use. PLoS ONE 11(8):e0157796.

Contributions to included papers In Paper I, I contributed to the design of the research, did most of the data collection, contributed to the data analysis and the writing of the paper. I con-ceived and designed the research in Papers II-III with inputs from my co-authors. I collected all the data for Paper II. In Paper III I did that jointly with my co-author. I led the data analysis and the writing process of both pa-pers and wrote the majority of the text. Paper IV was jointly conceived and designed with my co-authors. I contributed to the model implementation and testing. I performed the simulation experiments, led the paper writing process and wrote the majority of the text.

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Publications outside the thesis Haider, J., J. Hentati-Sundberg, M. Giusti, J. Goodness, M. Hamann, V. Mas-terson, M. Meacham, A. Merrie, D. Ospina, C. Schill, and H. Sinare. The undis-ciplinary journey: Early-career perspectives in sustainability science. In review in Sustainability Science. Nyborg, B. K., J. M. Anderies, A. Dannenberg, T. Lindahl, C. Schill, M. Schlüt-er, W. N. Adger, K. J. Arrow, S. Barrett, S. Carpenter, F. Stuart, C. Iii, A. Crépin, G. Daily, P. Ehrlich, C. Folke, W. Jager, N. Kautsky, S. A. Levin, O. J. Madsen, S. Polasky, M. Scheffer, E. U. Weber, J. Wilen, A. Xepapadeas, and A. De Zeeuw. 2016. Social norms as solutions. Science 354(6308):42–43.

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Introduction

There is growing evidence that human actions are now the main driving force of global environmental change, with implications from local to global scales (Steffen et al. 2011, 2015, Ellis 2015). The impact of humans on the earth sys-tem and ecosystems can be seen with respect to major sustainability challenges including climate change, biodiversity loss, and fisheries collapse. Over the past decades, global change research has substantially advanced our scientific under-standing of how natural and human drivers have changed, and are likely to continue to change our biosphere and, hence, our societies and our lives (e.g. Steffen et al. 2002). But how do we (humans) respond to these changes, and, in turn, what are the results of our responses? We need to urgently address these questions in order to guide development along more sustainable pathways, to meet the needs of society while sustaining our life support systems.

Researchers and policy makers across the board agree (Reid et al. 2010, Fischer et al. 2012, ISSC and UNESCO 2013, O’Brien and Sygna 2013, World Bank 2015) – Progress towards sustainability requires changes in human behaviour. However, in order to guide behaviour along more sustainable pathways, we need to first improve our fundamental understanding of human behaviour in relation to environmental change and the sustainability challenges of our time. The first editorial of the brand-new journal Nature Human Behaviour, which launched in January 2017, stated that: “Progress in achieving any of the 17 Sus-tainable Development Goals of the 2030 Agenda for Sustainable Development partly hinges on making progress in understanding, predicting, and changing human behaviour.” It is for this same reason that the World Development Report of the year 2015, entitled Mind, Society, and Behavior (World Bank 2015) was devoted entirely to the topic of human behaviour. The social sciences have generated a large body of knowledge relevant for the interface of human behav-iour and environmental change, most prominently perhaps, subfields of psy-chology, economics, and sociology. However, in studying this relationship, the inherent complexities and the uncertainties of ecosystems and the biosphere have not been given sufficient attention. In particular, the possibility of abrupt, drastic and potentially irreversible environmental change as a direct conse-quence of our actions. This thesis addresses the gap between human behaviour and the dynamics of environmental change.

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At the heart of these questions lies not only the behaviour of individuals, but also that of human collectives and groups of different sorts. Many, if not most, of the sustainability challenges we face today are associated with collective ac-tion problems in which a group of people benefit from a certain action, but no individual has the incentive to take that action on her own. This can explain why, for example, despite overwhelming evidence of the global threat of cli-mate change, actions are only picking up slowly and discussions about costs and responsibilities further delay urgent actions (e.g. Battersby 2017). Solving collec-tive action problems, with their inherent complex social dynamics and uncer-tainties, is far from trivial, and indeed, this quandary has puzzled and fascinated scholars from various backgrounds for decades (e.g. Ostrom 1990, Bromley et al. 1992, Barrett 2007). There is vast evidence from case studies at the local level, as well as evidence from behavioural experiments, that people can solve collective action problems and sustainably manage scarce resources (e.g. Ostrom 1990, Ostrom et al. 1994). Communication, endogenous rule for-mation, and social norms have all been identified as critical for facilitating co-operation (Ostrom 2000, 2006, Fehr et al. 2002). At the global level, solutions are less straight forward, but potential ways have been identified (e.g. Barrett 2016, Nyborg et al. 2016). However, with anthropogenic pressures at the global scale deepening sustainability challenges (Rockström et al. 2009, Steffen et al. 2015), eroding the resilience of ecosystems, and thus making them more vul-nerable to drastic changes (i.e. regime shifts; Biggs et al. 2012) (Folke et al. 2004, Rocha et al. 2015a), the emergence of collective action will be potentially more difficult, yet even more critical to achieve.

In this thesis, I interpret human-environment interactions as an intertwined social-ecological system (Berkes and Folke 1998), in which understanding of the interplay between individuals and their social and ecological environment cannot be gained by studying either in isolation. The overarching aim of this thesis is to build and advance an empirically grounded understanding about human behaviour, both individual and collective, in social-ecological systems. This is done through linking individual and collective behaviour to two features of ecological complexity: regime shifts and uncertainty. This thesis provides one of the first accounts of human behaviour and collective action in relation to these features of ecological complexity. It is well documented that different ecosystems, at local and regional scales, have already undergone large, abrupt and potentially persistent changes with dramatic consequences, for example on the productivity of fisheries (e.g. Österblom et al. 2007, Lade et al. 2015) or agricultural landscapes (e.g. Gordon et al. 2008). It has even been proposed that regime shifts are possible at the global scale, with potential consequences for and impact on global climate regulation (Lenton et al. 2008, Brook et al. 2013, Hughes et al. 2013). While scientific understanding about the drivers and im-pacts (Rocha et al. 2015a, 2015b), and early warning signals (e.g. Dakos et al. 2015) of ecosystem regime shifts is growing, understanding how people behave

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in the face of regime shifts that can be triggered by their own actions, and how behaviour is shaped by the inherent uncertainties of such shifts, is a significant research gap this thesis aims to address.

I focus on contexts in which people are dependent on local ecosystems, be-cause it is in these contexts that people’s livelihoods are more directly threat-ened by ecosystem regime shifts. Since such communities often rely upon shared natural resources that are either difficult to fence off and, that can be depleted through exploitation (i.e. common-pool resources; Ostrom and Ostrom 1977), I adopt a common-pool resource framework. The experimental work on human behaviour in the common-pool resource literature has so far focused mostly on interactions within the resource user group and the influence of social and institutional factors, without allowing for dynamic interactions between the resource users and their shared resource (e.g. Anderies et al. 2011, Cardenas et al. 2013). This thesis extends the behavioural literature focusing on common-pool resources by linking human behaviour with two features of eco-logical complexity, with the objective of unravelling critical social-ecological factors and mechanisms for the sustainability of common-pool resources.

Building and advancing an empirically grounded understanding of human be-haviour within social-ecological systems is also urgent for the revaluation of standard theoretical models of human behaviour and their specific behavioural assumptions. There is a growing body of work that suggests that, in complex and uncertain contexts and collective action situations, the standard assump-tions of human behaviour - such as self-interest, or motivation by material in-centives only - might not be appropriate or particularly useful (e.g. Tversky and Kahneman 1974, Ostrom 1998, Gintis et al. 2005). Yet, natural resource man-agement models, which often inform policy, commonly fall back on these standard assumptions (Van den Bergh et al. 2000, Shogren and Taylor 2008, Schlüter et al. 2017), potentially leading to costly or even counterproductive policy recommendations. The literature on common-pool resources in fact provides a striking example for why the assumption of individuals as being purely self-regarding can be costly or even detrimental. As a response to the bleak prediction of ‘the Tragedy of the Commons’ (Hardin 1968), national bu-reaucracies were replacing locally crafted institutions for governing small-scale CPR. This led not only to disempowerment of individuals and communities, but in some cases also to worse environmental conditions rather than to im-provements (Ostrom 2005). At the heart of the behavioural approach that I take in this thesis is the recognition that human behaviour is complex, and that a myriad of factors can influence our behaviour, from biological and genetic factors, to cognitive processes and individual motivations and perceptions, to social and environmental influences. This is in line with the calls of common-pool resource scholars, most prominently Elinor Ostrom, to go beyond ideo-logically inflected policy panaceas and design better policies and institutional

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arrangements to address sustainability challenges (Ostrom 2007). In this thesis, I focus on the interplay of cognitive (intra-individual), social (inter-individual) and ecological (social-ecological) factors influencing individual and collective behaviour. The starting point are individuals within a group and within a specif-ic ecological context (i.e. a common-pool resource context).

Evidence suggests that a behavioural approach can point to policy changes which, although seemingly minor (so-called ‘nudges’; Thaler and Sunstein 2008) and readily enacted within existing institutions, can have unexpectedly large impacts on behaviour (World Bank 2015). A behavioural approach can also provide solutions that have previously been overlooked, such as the potential for social norms to solve major collective action problems (Nyborg et al. 2016). Under certain conditions, policy could help in turning vicious cycles of socially damaging behaviour into virtuous cycles that could help in addressing large-scale environmental problems. By studying human behaviour in relation to ecological regime shifts and their inherent uncertainties in common-pool re-source contexts, this thesis can contribute insights to better discern what is and what is not reasonable to assume about human behaviour in these contexts.

This thesis consists of four papers in total, which are methodologically based on behavioural economic experiments and agent-based modelling. Behavioural experiments allow us to directly observe human behaviour in a specific situa-tion, as opposed to inferring behaviour from system-level observations. Addi-tionally, this method allows us to observe actual behaviour rather than eliciting hypothetical behaviour or individuals’ attitudes.1 Both methods allow us to study individuals within group settings and in interaction with a given ecological context (i.e. a context characterised by regime shifts and inherent uncertainties). Agent-based modelling allows for studying how individual behaviour translates to that of groups, and vice versa. It also allows us to explicitly incorporate rele-vant cognitive processes into the models.2

1 Eliciting hypothetical behaviour, which is done by asking individuals how they would behave given a certain situation is prone to the problem of so-called ‘hypothetical bias’ (Schulze et al. 1981), and elicited individuals’ attitudes have been shown to deviate from actual behaviour (the so-called ‘attitude-behaviour gap’, Kollmuss and Agyeman 2002). 2 Parts of this Kappa is based on the Kappa of my Licentiate thesis Making complex commons work: identifying critical social-ecological factors and mechanisms for sustainable ecosystem management (2015).

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Theoretical and Conceptual Background

Situating this Thesis

This thesis is situated within the field of sustainability science (e.g. Kates et al. 2001, Clark and Dickson 2003, Clark 2007), and consequently aims to gain and advance both fundamental and applied understanding understanding of human-environment interactions, in order to guide long-term societal development along more sustainable trajectories. Sustainability science is an interdisciplinary problem-driven research field. Along these lines, this thesis is informed by, builds upon, and connects different research fields, disciplines, and theoretical and analytical frameworks from both the natural and social sciences, namely resilience thinking, common-pool resources, complex adaptive systems, as well as subfields within behavioural economics and social and cognitive psychology focusing on the commons and behaviour in complex and highly uncertain envi-ronments. Below, and in the subsequent sub-sections, I will outline these fields and frameworks, explain how this thesis relates to them, and identify existing research gaps. By way of summary, I will formulate the four research questions that guide my work, each addressed in one of four papers, and present an inte-grative figure.

This thesis is inspired by resilience thinking (Walker and Salt 2006, Folke et al. 2010, Biggs et al. 2015), which can be regarded as an approach, perspective or sub-field of sustainability science (Folke 2006, 2016, Biggs et al. 2015). Resili-ence thinking is a lens “to ask questions, learn, and improve understanding of social-ecological systems” (Folke 2016). The social-ecological systems perspec-tive (SES; Berkes and Folke 1998), which I take in this thesis, not only empha-sises the dynamic two-way interactions between humans and the biosphere, but also argues for humanity’s dependence on the biosphere (Fischer et al. 2015, Folke et al. 2016).

Resilience thinking builds on the theoretical framework of complex adaptive systems (CAS; Levin 1998, 1999). In such systems, macro-level patterns emerge from micro-level interactions, which in turn feedback across macro, meso and micro levels. Other characteristic properties of CAS relevant for this thesis are the potential for non-linear change and, that uncertainties are inherent to CAS. Resilience thinking emphasizes cross-scale dynamics and the complexity of

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ecological, social and, social-ecological dynamics. These dynamics include; un-certainty and surprise, emergence, non-linearity and self-organization (Folke 2016).

Ecological Regime Shifts and Associated Uncertainties Resilience thinking (Folke 2016) emerged from the scientific finding that eco-systems can have multiple basins of attraction (Holling 1973, May 1977). The notion of a regime shift refers to the crossing between these alternate basins of attraction, whether as a result of changes of the external conditions that reshape the basins of attraction, a perturbation or shock that pushes the system state across the basins’ boundary, or a combination of both (see Figure 1; Scheffer et al. 2001, Scheffer 2009). As a consequence, rather than responding smoothly to gradual change in external conditions, ecosystems can exhibit non-linear change in their structure and internal dynamics (Scheffer et al. 2001). Moreover, when the regime shift is the result of crossing a threshold in the external conditions, the critical threshold value leading back to the original ecosystem regime often differs from the one where the initial shift happened (Figure 1). This feature is called hysteresis, and results from the presence of internal feedbacks that main-tain the new regime, making it difficult to reverse (Biggs et al. 2012). Given this hysteretic behaviour, preventing regime shifts is usually the desired manage-ment strategy (e.g. Mäler 2000), as it can be difficult, costly and sometimes even impossible to restore ecosystems that have shifted, as embodied in the folk saying ‘A stitch in time saves nine’. Similarly, the proponents of the planetary boundaries framework propose a safe operating space and advise the adoption of the precautionary principle to maintain the Earth in a Holocene-like state (Rockström et al. 2009, Steffen et al. 2015).

Alternate ecosystem regimes are often characterised by contrasting differences in the flows and bundles of ecosystem services they generate. Hence, regime shifts can imply an abrupt and potentially persistent disruption in the flow of ecosystem services that generate human well-being, such as the provision of food, clean water, or climate regulation (Millenium Ecosystem Assessment 2005). It has been well documented at the local and regional level that such changes have occurred in different ecosystems, with negative effects on, for example, the abundance of fish stocks (Österblom et al. 2007, Nyström et al. 2012, Lade et al. 2015), coral reefs (e.g. Hughes 1994), or the productivity of agricultural landscapes (e.g. Gordon et al. 2008). It has even been proposed that such non-linear changes are possible at the global scale with potential impacts on the climate system (Lenton et al. 2008, Brook et al. 2013, Hughes et al. 2013).

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potential for any specific ecosystem to exhibit threshold dynamics is uncertain. We therefore focus in Paper II and III on uncertainty about the existence of a threshold. To our knowledge, this is a first for behavioural economic experi-ments. Recently, progress has been made in developing techniques to detect regime shifts (e.g. Biggs et al. 2009, Lade and Gross 2012, Scheffer et al. 2012, Dakos et al. 2015). However, it remains unclear whether such ‘early warnings’ are detectable early enough to implement necessary actions to reduce the risk of a regime shift occurring (Biggs et al. 2009).

Environmental and resource economists have recently taken these insights from ecology and studied the implications of potential regime shifts for optimal management. Results point to considerable management challenges (see Crépin et al. 2012 for a review on regime shifts and management). For example, in the face of potential regime shifts, it can be difficult to correct for management errors (Levin et al. 2013). Considering contexts under uncertainty, a study by Polasky et al. (2011), shows that management consequences depend, inter alia, on whether it is in the power of the resource users to trigger or avoid an unde-sirable regime shift (i.e. endogenous) or whether it is caused by external events (i.e. exogenous). If the latter is the case, theoretical studies show that the possi-bility of stock collapse may lead to increased exploitation to secure resources and avoid losing them in the future (Polasky et al. 2011 and references therein). If the former is the case, it may be optimal to be precautionary and reduce the rate of exploitation to sustain higher stocks (Polasky et al. 2011). Considering common-pool resource settings, as in this thesis, it has been found that endog-enously driven regime shifts can complicate the management of shared re-sources, for example, by causing over- or under-exploitation of common re-sources (Crépin and Lindahl 2009), and that non-cooperation can trigger re-gime shifts (Mäler et al. 2003).3

In summary, scientific understanding is growing regarding the drivers of regime shifts and their impacts on ecosystem services. Progress has also been made in developing ‘early warning signals’ of impending regime shifts in ecosystems, and resulting management challenges. However, empirical research on how human behaviour relates to regime shifts and their uncertainties, and in particu-lar, how resource users deal with the possibility that their actions might induce such shifts, has received hardly any attention. Papers I-III in this thesis aim to fill this research gap by providing crucial components for an empirically grounded understanding of human behaviour and collective action in relation to potential endogenously driven ecological regime shifts and uncertainty.

3 See also special issue of JEBO on “Thresholds, tipping points, and random events in dynamic economic systems” (Sims et al. 2016).

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Common-Pool Resources Common-pool resources (CPR) are natural or human-made resources charac-terised by subtractability (also called rivalry in consumption) and costly exclud-ability (Ostrom and Ostrom 1977). The first characteristic means that extrac-tion or use of resource units diminishes the availability of the resource for all users. The excludability characteristic means that it is difficult, very costly, or socially or ecologically infeasible or undesirable to exclude others from using the resource. Prominent examples of CPR include grazing grounds, irrigation systems or fisheries (Ostrom 1990). These two characteristics make CPR vul-nerable to overexploitation and depletion, especially if there are no institutions in place that can facilitate collective action, and may lead to what is commonly referred to as ‘the Tragedy of the Commons’ (Hardin 1968). The Tragedy is one classic example of a collective action (or social) dilemma, a situation in which there is a tension between individual and social interests (Kollock 1998): “[…] each fisher benefits from catching as many fish as possible, but the aggre-gate outcome of these individually reasonable decisions can be disaster—[…] fish species depleted to the point of extinction” (Kollock 1998, p184). CPR can be governed through different kinds of property rights systems, which deter-mine authority and allocation mechanisms regarding how and by whom a spe-cific resource is used and/or owned: private, public, common-property, or open access (McGinnis 2011). The insights of this thesis are mostly relevant for renewable, natural, and local CPR in which there is the potential for self-governance but a relatively low level of top-down regulation, such as small-scale fisheries.4

Common-Pool Resources as Social-Ecological Systems I regard CPR as complex SES, which are in turn CAS (Levin et al. 2013). In such systems resource users interact with and affect not only each other (social-social) but also the local ecosystem (social-ecological) they depend on. Interac-tions at lower levels, e.g. among the group of resource users or between the user group and the ecosystem, lead to emergent patterns at a higher level, for example, a specific institutional arrangement (e.g. rules and norms, but also specific organizational structures, such as cooperatives), whether or not re-source users cooperate, and specific resource use patterns (e.g. sustainable or not). These higher-level patterns in turn create feedbacks which influence both resource users and ecosystem components, and these feedbacks also influence whole systems at higher scales (Ostrom 2007, 2009). Articulating CPR as SES requires taking both social and ecological complexities into account. Whereas social dynamics and complexities have been mostly in focus in CPR research, 4 I understand self-governance according to the language of the ‘Ostrom Workshop’: “The capac-ity of communities to organize themselves so they can actively participate in all (or at least the most important) decision processes relating to their own governance” (McGinnis 2011 p. 171).

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social-ecological dynamics as well as ecological complexities and uncertainties have been given significantly less attention. Questions of emergence, a key fea-ture of CAS, have featured prominently in the CPR literature. Much attention has been paid to the question of what makes collective action emerge and per-sist (or not), for which the theoretical framework of CAS is particularly well suited. Such questions have been evaluated since the 1980s (Axelrod 1984), often through the application of agent-based modelling (cf. Poteete et al. 2010). In this thesis, I focus on the emergence of communication, collective action and sustainable resource use by explicitly taking into account social-ecological dynamics (all Papers) and features of ecological complexity, namely the afore-mentioned regime shifts and their associated uncertainties (Paper I-III).

A Brief Historical Account of the Study of Common-Pool Resources With the seminal work of the economist Scott Gordon (1954) on common-property resources, the ‘theory of collective inaction’ by economist Mancur Olson (1965), the ecologist Garrett Hardin’s powerful metaphor of the ‘Trage-dy of the Commons (1968), and substantial work in non-cooperative game theory about public goods and CPR, CPR became the subject of an on-going debate about the capability of resource users and communities to sustain them. Early work in the social sciences failed to distinguish clearly between open-access and community-property CPR (including Gordon and Hardin), and, hence, the role of institutions in facilitating cooperation (Ciriacy-Wantrup and Bishop 1975, Walker 2014). This led to the rather pessimistic assertion that the Tragedy can only be prevented by privatisation or government intervention (Ciriacy-Wantrup and Bishop 1975). These two policy prescriptions have been (mis) used by policy-makers, but also by various scholars, to argue for central-ized government control of CPR (Ciriacy-Wantrup and Bishop 1975, Ostrom et al. 1999).

Elinor Ostrom, a political scientist and economist, and undoubtedly the most prominent CPR scholar, described the 1960s and 70s as an era “in which con-siderable faith existed in the capacity of strong national governments to solve both social and environmental problems through the application of rational planning and the design of incentives to induce positive and deter negative behaviour” (Ostrom 2005 p. 266). Especially in developing countries, national bureaucracies were replacing locally crafted institutions for governing local CPR. This led in some cases not only to the disempowerment of individuals and communities but also to worse environmental conditions rather than to improvements (Bromley et al. 1992, Ostrom 2005 and references therein).

This led to a strong response from many place-based researchers to gather empirical evidence about successful community-governed CPR, with Ostrom’s work (1990) probably the most prominent (but also see Wade 1988, Berkes

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1989, McCay and Acheson 1990). In her influential book ‘Governing the Commons’, Ostrom proposed – based on an extensive set of case studies of different long-enduring and self-governed CPR in different countries – seven ‘Design Principles’5 which could account for the sustainability of CPR. Field evidence also suggested that in many cases, the two proposed solutions of state control and privatisation would not be necessary or feasible, and might even be counterproductive (e.g. McCay and Jentoft 1998) for the governance of CPR. Additionally, a growing body of behavioural economic lab experiments showed that when participants can communicate to discuss exploitation strategies and rules, or can make use of internal punishment mechanisms, the Tragedy can be avoided (Ostrom et al. 1994, Ostrom 2009).

Since then, the CPR literature has been growing enormously. The question of what makes local collective action emerge, become self-sustaining, and be suc-cessful has puzzled and fascinated scholars for decades (Dawes 1980, Poteete et al. 2010). Scholars have attempted to solve this puzzle using an array of meth-ods, including case studies (Ostrom 1990), game theory, behavioural lab and field experiments (Ostrom et al. 1994), and agent-based simulations (Axelrod 1984). As a result of this interest, substantial progress has been made in this interdisciplinary research field (cf. Berkes 1989, McCay and Acheson 1990, Ostrom 1990, Bromley et al. 1992, Ostrom et al. 2002, Bardhan and Ray 2008). Today there is a broader acceptance that the conventional theory of collective action should not be universally applied (Basurto and Ostrom 2009).

Behavioural Experimental Work on Common-Pool Resources The behavioural experimental work in the CPR literature has primarily focused on individual and collective behaviour in relation to social interactions and institutional factors studied in static social dilemmas (i.e. repeated single-trial games in which past decisions do not influence current and future conditions of the shared resource) (Sturm and Weimann 2006, Cardenas et al. 2013), thereby ignoring key linkages of SES (Ostrom 2009, Anderies et al. 2011).

The bulk of experimental work in the CPR literature originates from the work of Ostrom (1990) on the governance of CPR.6 These experiments showed that successful self-organisation is more likely than predicted by conventional eco-nomic theory and demonstrated the importance of trust and communication and the role costly punishment can play in initiating and sustaining collective action (Ostrom et al. 1994, Ostrom 1998, 2006). Experimental approaches have only begun to take social-ecological dynamics and ecological complexities into

5 Eight for CPR that are part of large systems. 6 See Ostrom et al. (1994) on the so-called CPR baseline game.

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account in the past decade (Poteete et al. 2010, Cardenas et al. 2013).7 For ex-ample, Janssen et al. (2010) and Janssen (2010) introduced spatial and temporal resource dynamics and found that they increase the importance of communica-tion for sustainable resource use and that different institutional rules emerge depending on ecological context. Other notable studies are Osés-Eraso et al. (2008), who compared the effects of exogenous vs. endogenous resource scar-city, and Kimbrough and Vostroknutov (2015) who determined the effects of differing resource replenishment rates. All these experimemtal designs are dy-namic in the sense that past decisions influence resource stock levels in current and future rounds, and were conducted with students (i.e. lab experiments).8

Another relevant strand of experimental CPR work comes from social psy-chologists working on environmental uncertainty (Messick et al. 1988). In vari-ous experiments, social psychologists have investigated how resource users react to uncertainty in the availability of a shared resource or its regeneration rate. Studies of the former, employing repeated single-trial games, show that experiment participants request significantly more from a shared resource as the uncertainty about its size increases (Rapoport et al. 1992, Budescu et al. 1992, Gustafsson et al. 1999). This result also extends to framed and dynamic games on regeneration rate uncertainty (Hine and Gifford 1996). Explanations for these results may be found in what Gustafsson et al. (1999) call ‘optimism bias’, according to which experiment participants are likely to overestimate the size of the shared resource. Other studies suggest that in the face of stock size uncertainty, and in the absence of communication, commonly applied equal sharing norms lose their potential for coordination, leading to the breakdown of collective action (De Kwaadsteniet et al. 2006).

In none of these social psychology experiments, and in only a few of the above-mentioned experiments that originated from the work of Ostrom, was commu-nication allowed, namely only in the studies of Janssen (2010), and Janssen et al. (2010). However, in these two experimental studies, communication was either introduced after one round of non-communication (Janssen 2010) or as a treatment after all groups played a baseline stage (Janssen et al. 2010). In all other experiments, groups needed to rely on tacit coordination and could not make cooperative agreements, set up rules, or share knowledge or opinions about how to collectively manage the shared resource in the game.

7 A notable exception is the work by Walker and Gardner (1992), who, quite early on, went be-yond a static ecological environment. They extended the CPR baseline game by including path dependence, so that past choices influenced the probability of CPR destruction in the following round, to investigate how this affects resource management efficiency. They found that resource destruction prevailed, in most cases quite rapidly. 8 See also Janssen (2015) for a recent overview of experimental studies including more ecological complexity, also in other contexts than CPR.

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One key finding in the behavioural CPR literature, as well as from case studies, is that communication is a crucial cooperation facilitator and, hence, can be instrumental for sustainable resource use and governance of CPR (Pretty 2003, Ostrom 2006, Balliet 2009). Communication can foster a sense of group identi-ty and increase trust (Shankar and Pavitt 2002), which also reduces social uncer-tainty, i.e. whether others will act in the interest of the group. In all experiments employed in this thesis, we allow for face-to-face communication from the start, rather than introducing it as a treatment. We have chosen to do so not only due to the vast evidence on the positive effects of communication but also simply because, in reality, resource users are not banned from communicating. They might, however, choose to communicate or not depending on the specific situation or context. At this juncture it is worth mentioning (even though they are not CPR games) the experiments on threshold location uncertainty (Barrett and Dannenberg 2012, 2014) and threshold impact uncertainty (Milinski et al. 2008, Barrett and Dannenberg 2012) in the public goods game literature. Communication also plays a critical role in these experiments. In the absence of large threshold location uncertainties, communication can drastically increase the chances of preventing the breakdown of collective aciton, as it allows par-ticipants to coordinate their actions around the (relatively well known) thresh-old (Tavoni et al. 2011, Barrett and Dannenberg 2012).

Another fairly recent development in the experimental CPR literature is to con-duct experiments with actual CPR users (such as farmers or fishers), rather than ‘WEIRD’ students from Western, Educated, Industrial, Rich, and Democratic countries (Henrich et al. 2010), see ‘Methods’ section. Whereas previous results from the lab, such as the criticality of communication could be confirmed (Cardenas 2000), it has also been found that depending on the social, cultural and ecological context, experimental outcomes can differ significantly (Henrich et al. 2005, Castillo et al. 2011, Prediger et al. 2011, Gneezy et al. 2016, Cárdenas et al. 2017). It is also from field experiments that we have some in-sight on collective action in the context of regime shift like situations (Castillo et al. 2011, Prediger et al. 2011, Cardenas et al. 2013). In these experiments, which have been used in different field contexts, participants make two decisions in each round of the game – where (choosing from two locations) and how much of the resource to harvest. Locations experiencing too high exploitation pres-sure become temporarily degraded, which is costly to reverse. Although not explicitly stated by the authors, this could be interpreted as an ecological regime shift. Overall, these studies demonstrate unsustainable resource use - degrada-tion with no recovery was the most common outcome. In some cases, howev-er, groups managed the resource more carefully to avoid degradation, an out-come that the authors attribute to the cultural and ecological context partici-pants face in reality (Prediger et al. 2011). More specifically, they found that groups with longer experience in community-governed CPR and where intact social norms exist, as well as higher pay-offs for cooperation due to specific

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ecological conditions in reality, did better in the game (Prediger et al. 2011). However, communication was not allowed in all of these field experiments, and therefore these studies did not address the relevant factors and mechanisms to explore the emergence of cooperative agreements. Whereas Paper I and II of this thesis are concerned with lab experiments, Paper III is a field experiment with Colombian small-scale fishers as participants in a CPR game.

Human Behaviour in Complex and Uncertain Environments The importance of building an empirically grounded understanding about hu-man behaviour and collective action in SES emerges from growing evidence from psychology, in particular cognitive psychology, that, in complex and un-certain environments, human behaviour is not adequately described by the ‘rational actor model’ (or Homo economicus). This model is not only the standard model in economics, including in environmental and resource economics (Van den Bergh et al. 2000, Shogren and Taylor 2008) but also often used in political science (Monroe 2001), philosophy, several cognitive sciences, as well as in biology (Gigerenzer 2008). It is also the rational actor model that underlies the Tragedy of the Commons of Hardin (1968). Moreover, formal models in natu-ral resource management used to study human-environment interactions and to inform policy also commonly fall back on this model (Schlüter et al. 2017). The rational actor model assumes agents to be rational (or ‘unboundedly rational’), purely self-regarding and equipped with perfect will-power.9 They are further-more motivated by material incentives only, and maximize their expected utility based on stable and consistent preferences (Rabin 1998). This has been a useful model for making analytical derivations and predictions possible (for example in the optimal management models mentioned above) and, depending on context, it might be a ‘good enough’ prediction of human behaviour and decision-making, e.g. of consumers in a market setting. However, like any other model, it is a simplification of reality, which in some cases is not good enough nor adequate. This might be especially true for environmental problems, as the settings in which such problems arise are often characterised by a lack of functioning markets (Shogren and Taylor 2008) and frequently involve the commons (CPR or public good settings) in which social dynamics are a characteristic feature. This is preciely why we need to search for better models and more appropriate behavioural assumptions. A first step along this path is to gain insights into behavioural patterns from which behavioural assumptions can be determined and on which new models can be built.

9 It is important to note that economists do not assume that people are, e.g. ‘unboundedly ration-al’; they assume that they behave as if they would be (Conlisk 1996).

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The aforementioned optimal management models (see section ‘Ecological Re-gime Shifts and Associated Uncertainties’) are all theoretical mathematical models that also rest on specific behavioural assumptions. For example, the agents are rational in the sense that they make use of all available information, including probabilities of future events (in case uncertainties are involved), to maximize their expected utility. Furthermore, for the CPR models described above, it is further assumed that resource users either cooperate or not, and if cooperation does occur, that the groups cooperating are rational (i.e. are able to manage the resource optimally). These assumptions allow for predicting the optimal management strategy. However, these models do not tell us anything about how we can expect people to behave and make decisions in situations pervaded by ecological uncertainties, including in situations where there is the potential for ecological regime shifts.

Building on the growing body of evidence that the rational actor model often fails to describe human behaviour adequately, the field of Behavioural Eco-nomics has emerged, relying heavily on the experimental method. Behavioural economics is concerned with the exploration of how human behaviour deviates from the standard economic model (Homo economicus) and when these deviations matter for economic contexts by including insights from social and cognitive psychology (e.g. Rabin 1998, Kahneman 2003, Sent 2004).10 Behavioural eco-nomics commonly refers to the following three categories of deviations from Homo economicus: bounded will-power, bounded self-interest, and bounded ra-tionality (Mullainathan and Thaler 2000). Bounded willpower implies our (occa-sional) lack of self-control, e.g. we eat too much, or save too little (e.g. Kahneman 2011). Bounded self-interest reflects the idea that individuals care about other’s well-being too, and that individuals have social preferences, such as fairness or reciprocity (e.g. Gintis et al. 2005). Bounded rationality refers to the observation that individuals’ capacity to take into account all available in-formation to make decisions is limited (Simon 1955). Instead, decisions are said to be commonly biased (e.g. Kahneman et al. 1982) or that people make use of heuristics (e.g. Gigerenzer and Gaissmaier 2011). For this thesis, the latter two serve as starting point and motivation to gather empirical data about human behaviour in CPR due to the social interactions at their core and the complexi-ties and uncertainties present in SES.

10 This body of work has also led to the development of the field of behavioural game theory (Camerer 2003), which is concerned with the mathematical deviations of what “normal” players with cognitive limits, emotions, doubts, preferences for fairness, etc., are likely to do in strategic interactions (games). A more recent field is neuroeconomics, which combines research methods and insights from neuroscience, experimental and behavioural economics, and cognitive and social psychology to study human decision-making (e.g. Glimcher et al. 2009).

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Bounded Rationality Herbert A. Simon (1955, 1979), a social scientist, was the first scholar to pro-pose that decision-makers might be better described as ‘bounded rational’ due to the physiological limitations of human cognition11, which often makes utility maximisation or optimisation unavailable (Simon 1990). In the 1970s, the cog-nitive psychologists Daniel Kahneman and Amos Tversky (1973, 1974, 1979), probably the most prominent scholars studying bounded rationality, started their research program, encompassing three research streams: heuristics and biases in decision-making under uncertainty; prospect theory; and framing ef-fects (Kahneman 2003). The first stream is especially relevant for this thesis. They found that people typically violate the principles of expected utility theo-ry, the predominant economic theory for decisions under uncertainty (Machina 1987), and rely instead on shortcuts of reasoning or heuristics (Tversky and Kahneman 1974). For example, they found that in situations in which we need to make judgments about uncertain future events, we tend to assess the likeli-hood of an event by the ease with which occurrences or associations of relevant examples come to mind, the so-called ‘availability heuristic’ (Tversky and Kahneman 1974). In general, they found that people can have problems with interpreting probabilities (Kahneman and Tversky 1979, Tversky and Kahneman 1992).12

Building on the earlier work of Simon, the psychologist Gerd Gigerenzer sug-gested re-defining rationality rather than calling it ‘bounded rationality’ which inherently implies that ‘unbounded rationality’ is an appropriate yardstick (Gigerenzer 2008). With the normative concept of ‘ecological rationality’, which considers the relationship between cognition and the physical and social envi-ronment, rather than the relationship between cognition and logic and statistical thinking, he emphasises the importance of the decision-making environment in which the thinking and reasoning happens. Gigerenzer and colleagues contrib-uted a considerable amount of evidence on the power of fast and frugal heuris-tics to cope with uncertainty in decision-making (Gigerenzer and Gaissmaier 2011).

In the 1960s, Daniel Ellsberg (1961) challenged predicitons of expected utility theory: he found that most people choose risk (i.e. ‘measurable uncertainty’, 11 These physiological bounds refer to, e.g. the limits of our short-term memory regarding how much information it can store and that even very simple human reactions can take hundreds of milliseconds rather than microseconds, imposing time constraints (Simon 1990). Simon in fact describes cognitive psychology as “the study of computational capabilities in the face of diverse tasks” (Simon 1990 p. 7). Based on this reasoning, he put forward a decision-making model based on ‘satisficing’ (instead of utility maximisation), in which agents limit their searches until they reach a decision they regard as satisfactory enough (Simon 1956). 12 See also Conlisk (1996) for an overview of wide-ranging evidence on bounded rationality including rationality tests on individuals, evidence from games, and confounded evidence from work that tested rationality together with other hypotheses.

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where probabilities and outcomes are known) over ambiguity, a scenario in which the probabilities of the potential outcomes are not known (i.e. ‘un-measurable uncertainty’). This even holds if the probability of winning a lottery is low in the risk scenario and the ambiguity scenario could be a safe bet, fol-lowing the saying ‘better the devil you know…’. The Ellsberg paradox inspired much empirical research, which Camerer and Weber (1992) review. They find that people are commonly averse to ambiguity. All the papers that make up this thesis refer to complex and uncertain decision-making environments, in which the outlined evidence suggests that people might not make use of all available information, or people might, and often do, over- or under-estimate risks. Pa-per II and III will allow us to say something about the effects of various de-grees of risk of an endogenously driven ecological regime shift on individual and collective behaviour (Paper II). And in Paper III, we test regime shifts which are characterised by both risk and ambiguity.

Bounded Self-Interest Evidence from everyday life (e.g. voluntary blood donations, or giving money to charity), lab and field experiments across different cultures (e.g. Camerer and Thaler 1995, Fehr and Gächter 2000, 2002, Henrich et al. 2005), and fMRI studies, in which brain regions are linked to particular behaviours (e.g. Rilling et al. 2002, Fehr et al. 2005, Fehr and Camerer 2007), show that we are other-regarding13 too and that we care about what others gain or lose. Some neurosci-entists even argue that “our brains are wired to connect” (Lieberman 2013). Moreover, we are often highly influenced by our social context (e.g. Ross and Nisbett 1991), we adhere to social norms (e.g. Ostrom 2000, Young 2015), respond to peer pressure (e.g. Schultz et al. 2007) and shaming (e.g. Alpízar and Gsottbauer 2015). In fact, the economist and philosopher Adam Smith could be described as a behavioural economist, as in 1776, he not only famously wrote that: “It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their self-interest” in The Wealth of Nations. Rather less well-known, he also wrote in 1759: “How selfish soever man may be supposed, there are evidently some principles in his nature, which interest him on the fortune to others, and render their happiness necessary to him, though he derives nothing from it, expect the pleasure of seeing it” in The Theory of Moral Sentiments.

The assumption of individuals as being purely self-regarding also implies that we would only care about the outcome of an interaction, rather than how the outcome is achieved, whether through chance, coercion, or voluntary transfer (Gintis et al. 2005). However, there is also growing evidence from experi-

13 Self-regarding is different from self-interested. As described by Ginitis et al. (2005), it could be in our self-interest to help others but that very action could be non-self-regarding as it could cost us something.

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ments14 that we; value fairness (e.g. Kahneman et al. 1986, Haidt 2007, Tricomi et al. 2010), are inequity averse (Fehr and Schmidt 1999), and punish norm violators (e.g. Fehr and Gächter 2002). In other words, it is not material self-interest alone on which people base their decisions (e.g. Fehr and Falk 2002). It has in fact been shown that policies built on the assumption of human behav-iour as being motivated by material interest alone can lead to a ‘crowding out’ of intrinsic motivations. For example, Titmuss showed already in 1970 that the motivation to donate blood can be crowded out if donors are offered monetary compensation. Evidence from CPR field experiments also shows that external regulations can crowed-out other-regarding behaviour (Cardenas et al. 2000).

Bounded self-interest can also explain why people cooperate in CPR settings and why non-binding communication (‘cheap talk’) can facilitate cooperation by building a sense of group identity and trust (Ostrom 2000). Based on these insights, Elinor Ostrom also proposed a ‘behavioural approach to the rational choice theory of collective action’, in which she puts reciprocity, reputation, and trust at the centre of an empirically grounded theory of collective action (Ostrom 1998). Gintis and others (2005) also proposed an alternative theory of collective action: ‘strong reciprocity’. It builds on the finding that most of us are conditional co-operators (Kocher et al. 2008) and altruistic punishers; we coop-erate as long as others do so, and we punish norm violators, even if that is cost-ly for us and even when it is not plausible to assume the costs will be recovered at a later stage (Gintis et al. 2005). All papers of this thesis consider a CPR set-ting; hence, aspects of other-regarding preferences come into play. In Paper I-III, behaviour is observed in behavioural economic experiments. In Paper IV, for which we rely on agent-based modelling, some of these findings and insights outlined above complement and motivate our decisions on modelling human behaviour and collective action in a SES.

Research Gaps and Questions

Research Gap 1: Behavioural dimension of ecological regime shifts and associated uncertainties As outlined above, scientific understanding is growing regarding the drivers of regime shifts and their impacts on ecosystems. Progress has also been made in relation to detecting ‘early warning signals’ of regime shifts and the resulting management challenges. However, empirical research on how groups of people 14 The results of Prisoner’s dilemma games serve as a good illustration of bounded self-interest. Cooperation in this game implies less material benefits for both parties involved. However, multiple studies have shown that about a third of the participants choose to cooperate. However, as Lieberman (2013) argues in this book, we might cooperate as we are also getting rewards from being pro-social.

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studied before in a CPR context. In line with the distinct characteristic of emer-gence within CAS, we treat communication in all papers as something that might emerge, rather than treating it as a fixed condition. This too, as far as we are aware, has not been done before. In Paper IV, in which we focus on social-ecological dynamics only, we zoom in on individual-level factors and mecha-nisms and the emergent patterns they create at both the group and the system level. Moreover, there are only a few studies that account for the influence of the social-ecological context in experimental studies, i.e. bringing behavioural experiments to the field to conduct them with actual resource users, as we do in Paper III, see Figure 2.

Research questions Building on these two research gaps, and the objective set out for this thesis, I have formulated the following four research questions, each of which is ad-dressed by one of the four papers in this thesis. All questions consider a self-governed CPR setting and each question assumes that the ecological regime shift, if it were to occur, would have negative and long-lasting consequences for the shared resource.

I.� What is the effect of an endogenously-driven ecological regime shift

on human behaviour, particularly in relation to the emergence of collective action and sustainable resource use? (Paper I)

II.� What is the effect of various degrees of risk associated with such a regime shift on human behaviour, particularly in relation to the emergence of collective action and sustainable resource use? (Paper II)

III.� Can we expect small-scale fishers to adapt to climate-induced thresholds in the dynamics of a shared resource, and what role does the actual social-ecological context and different degrees of uncer-tainty play? (Paper III)

IV.� What are critical individual-level factors and processes, affecting in-dividual behaviour and the simultaneous emergence of collective action and sustainable resource use? (Paper IV)

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Methods

This thesis not only draws on various research fields and disciplines, as outlined above, but it also makes use of multiple methods. The main methods are be-havioural economic lab (Paper I-II) and field experiments (Paper III), and agent-based modelling (Paper IV). Due to the empirical and quantitative nature of this thesis, I make use of descriptive and inferential statistics to analyse the experimental data. The data is gathered on the individual level but analysed (mostly) at the group or system level. In Paper I and II, we relied on behaviour-al economic lab experiments (with students from Stockholm University as par-ticipants), complemented by post-experimental questionnaires and participant observational notes and we also made use of game theory to formulate hypoth-eses to guide the data analysis. In Paper III, we made use of field experiments (with Colombian small-scale fishers as participants), complemented by post-experimental structured interviews and participant observational notes. In Pa-per IV, we employed an agent-based model informed by observations of a sub-set of the lab experiments from Paper I and II, see Figure 3.

Figure 3. Main methods employed in this thesis. Context/control decreases/increases going from left to right. ABM is short for agent-based modelling; lab/field is short for behavioural economic lab/field experiments. Illustrations by E. Wikander/Azote.

Experimental patterns inform ABM

Field Lab ABM

Paper III Paper IV Paper I-II

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In the following subsections, I will briefly outline the motivation for the main methods applied in this thesis, namely; behavioural economic experiments and agent-based modelling, their main characteristics, and an explanation of their concrete implementation.

Behavioural Economic Lab and Field Experiments Behavioural economic experiments are randomized experiments (or ‘controlled experiments’). The experimenter randomly assigns people (or groups of people) to control and treatment groups to test the causal effect of a variable of interest on individual (or group) behaviour. If the randomization works, the iteration of the experiment ensures that the groups are identical apart from the manipulated variable of interest (treatment); hence, observed differences in behaviour can be assigned to the treatment. In other words, randomized experiments allow the construction of a proper counterfactual (Harrison and List 2004), which is probably why this method enjoys growing popularity across different disciplines in the social sciences, including behavioural economics, and scholars within the field of CPR and SES (Harrison and List 2004, Falk and Heckman 2009, Poteete et al. 2010, Janssen et al. 2015). Behavioural economic experiments are typically differentiated between lab and field experiments. In the lab, partici-pants are students and the instructions are commonly described in abstract terminology. By contrast, in the field, participants are non-students and instruc-tions often provide details of the specific field context, i.e. the instructions are framed.15

Apart from the ability to establish causal relationships, we chose behavioural economic experiments for Paper I-III for the following reasons: Firstly, they allow us to collect empirical data on behaviour by directly observing behaviour in a real decision-making situation, i.e. one can avoid the so-called hypothetical bias prevalent when simply asking people how they would behave given a cer-tain hypothetical situation (Schulze et al. 1981). Moreover, they allow us to explicitly take social-ecological dynamics and ecological complexities into ac-count. Secondly, and equally important, due to the limited predictability of re-gime shifts, pre- and post-shift social-ecological data is seldom available. This hinders the possibility of using observational data to elicit individual and collec-tive behavioural responses to such shifts. Moreover, it is equally difficult (if even possible) to identify places in which the likelihood of ecological regime shifts differs. Lab and field experiments, however, allow us to manipulate the experimental design to study behaviour in the face of different degrees of un-certainty (risk and ambiguity, Paper II-III).

15 See Harrison and List 2004 for a taxonomy of experiments.

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The experiments we employed followed the tradition of experimental econom-ics in the following way: First, the decisions taken by the participants had mon-etary consequences (i.e. an individual’s payoff depends directly on her deci-sions, as opposed to e.g. surveys in which participants receive either no reward at all, or simply a flat fee). This was also known to the participants. In this way, we could ensure that participants had ‘skin in the game’, and hence their deci-sions better resemble those of their real life. Second, we refrained from decep-tion16, so participants would understand that the experimenters did not use any tricks, and hence their behaviour would not be affected for that reason (Friedman and Sunder 1994).

The application of behavioural economic experiments has contributed consid-erably to the development of a more refined understanding of various envi-ronmental problems (Sturm and Weimann 2006).17 There is an increasing num-ber of studies showing how human behaviour and collective action can be stud-ied in SES using lab and field experiments, see for example, the special issue in Ecology and Society on “Advancing the Understanding of Behavior in Social-Ecological Systems: Results from Lab and Field Experiments” of which Paper II of this thesis is part. As described above, behavioural economic lab and field experiments have also played a crucial role in theory development in the CPR literature (Poteete et al. 2010).

As mentioned above, originally most experiments (across the social sciences), have been conducted in labs with ‘WEIRD’ students as participants (Henrich et al. 2010). Nowadays however, more and more experimentalists go to the field and run behavioural experiments with participants that are familiar with the decision-making environment of interest. Some argue that this implies losing the “control” the lab provides as a “clean test tube”. However, if one is inter-ested in the behaviour of a specific group and/or a specific field context, the control granted in a lab setting might be of less value. The task and context provided to students might be too artificial, they might lack relevant knowledge and experience and other contextual variables that may influence behaviour are also not present. Hence, conducting different kinds of experiments seems to be a reasonable middle ground (Harrison and List 2004). This, as well as our inter-est in the influence of different social-ecological contexts (Research Question III), is why we employed a field experiment in Paper III. By moving from the lab to the field, we were able to slowly progress towards the ‘real’ situation, and we could learn which factors were of ultimate relevance. Moreover, comparing outcomes from both settings helps us to assess the explanatory power of the

16 In contrast, for example, to experimental studies in social psychology (the most prominent example being the Milgram experiments 1974). 17 For example, experiments have been used to study environmental markets (e.g. markets for tradable emission permits) or the evaluation of environmental goods.

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lab (Levitt and List 2009). Whether considering lab or field experiments, it is important to bear in mind that the experimental design is not intended to mim-ic reality, but to capture the most relevant factors and mechanisms of the phe-nomenon under study, as Friedman and Sunder (1994 p. 12) put it: an “experi-ment should be judged by its impact on our understanding, not by its fidelity either to reality or to a formal model.” Below, I will explain the experiments that we conducted in more detail.

The CPR Experiments Employed in this Thesis The employed experiments, both in the lab (Paper I-II) and in the field (Paper III), are dynamic CPR request games18 (see Budescu et al. 1992). In a request game, in each round, players request (or harvest) units of a shared resource. It is a dynamic game in the sense that the size of the shared resource x in round t depends on the decisions of the players in t-1 (endogenous dynamics). This way we took social-ecological dynamics into account. We allowed for face-to-face communication from the start, and at any time, rather than being restricted to a specific communication phase.19 Decisions though were private and kept confi-dential. To approximate an infinite time horizon, our participants did not know the exact number of rounds to be played, only that the experiment session last-ed at maximum a certain amount of time. We chose pencil and paper instead of computer-based experiments (Janssen et al. 2014), as we intended from the beginning to eventually bring the experiments to the field. The field experiment (Paper III) was a simplified and modified version of the lab to account for low-er levels of education and illiteracy.

Both in the lab and field, groups consisted of four20 participants and the initial and maximum stock size was 50 units/fish. At the beginning of each round, the new stock level was announced. Depending on the stock’s size, the resource regenerated at different rates (see Figure 4). We introduced the regime shift into the experimental design by letting the regeneration rate drop drastically below a certain resource stock size (representing a threshold). Hence, regime shifts could be triggered and avoided by the players (i.e. endogenously driven regime shifts). In Paper II and III we introduced uncertainty about whether or not there is a threshold in the stock dynamics by letting people know that they ei-ther play, by a certain known or unknown probability, the scenario with or without a threshold.

18 They are games in the sense that people interact with each other and the outcomes of the decisions depend on their own, as well as thier group members’ decisions. 19 For practical reasons, in the field, we restricted communication before decision-making to a max. of two minutes to meet time constraints. But participants could still communicate at any other stage of the game too. 20 In the lab, we also had some groups with only three participants. We aimed for four partici-pants, but ran the game also when one participant did not show up.

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Figure 4. Representation of resource dynamics underlying the lab (left) and field (right) experiments. (a) shows the dynamics without a threshold and (b) with a threshold.

In the field, we framed the (potential) threshold as a result of a potential climate event with severe and long-lasting consequences for the shared fishing ground. Units/fish that were left at the end of the game did not have any monetary value for the players. After the game, each player filled out a questionnaire (lab) or was interviewed (field). See the individual papers and appendices for details. In the meantime, the number of units extracted/fish caught by each player was calculated, and the respective amount in cash was paid out privately. Players in Paper II and III also took part in a risk/ambiguity preference elicitation task as those preferences can influence decisions in uncertain situations (see the papers for details).

Agent-Based Modelling Agent-based models (ABM) are one class of computational models that aim to illustrate, understand and sometimes even predict phenomena that are complex and dynamic (Gilbert and Troitzsch 2005). ABM typically consist of heteroge-neous agents interacting with each other and their environment across time and space (Gilbert 2008). Hence, ABM enable us to simulate dynamic processes with a particular focus on how interactions at lower levels translate to emergent patterns at higher levels and how, in turn, these higher-level outcomes affect interactions (Sawyer 2003). In the CPR literature, ABM have been mostly used to study the emergence of collective action and sustainable resource use (see Poteete et al. 2010 for an overview of ABM developed to model collective ac-

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tion). Rather than focusing on social-ecological interactions, most of these CPR ABM studies focus on the evolution of norms and rules, and the effects of different models of human behaviour on cooperative outcomes. Notable ex-ceptions are Bodin and Norberg 2005, Schlüter and Pahl-Wostl 2007, and Pérez and Janssen 2015.

ABM follow an agent-interaction-environment structure (Gilbert 2008, Edmonds and Meyer 2013). The researcher specifies individual agents, their social and biophysical environment as well as their interactions with each other and their environment. Each agent can have unique characteristics (variables or relations) and settings (variable values). Agent heterogeneity is in fact one of the most prominent features of an ABM and the typical reason for researchers choosing this method. Moreover, the internal representation of agents, such as having knowledge, being able to learn, or simply specifying decision-making rules, allows for the representation of a variety of possible mechanism-based explanations of human behaviour (Hedström and Ylikoski 2010, Conte and Paolucci 2014).21 These features make ABM particularly well suited to study individual and collective decision-making in SES/CAS. ABM allow us to em-bed decision-making in dynamic social-ecological contexts, with cross-scale interactions, varying degrees of complexity, and diversity in the social and eco-logical system domains (Rounsevell et al. 2012).

We made use of this particular type of modelling in Paper IV because it allowed us to zoom in on individual-level factors, processes and patterns, and, explore critical social-ecological micro-foundations for sustainable resource use. In an ABM, we can control, measure, and/or manipulate processes and perceptions internal to an individual, and relate these to group level patterns of interest (and vice versa). Moreover, in contrast to behavioural experiments, instead of testing the influence of one variable at a time, an ABM allows us to study interaction effects, including those of social-ecological interactions prevalent in the type of SES considered in this thesis. In this way, we can increase our understanding about specific mechanisms leading to the phenomena of interest, and develop social-ecological, mechanism-based explanations (Rounsevell et al. 2012).

The Agent-based Model Employed in this Thesis The purpose of the ABM we developed for Paper IV (called ‘AgentEx’) is to qualitatively reproduce and provide an explanation for the patterns observed in the behavioural economic experiments of Paper I and Paper II in order to ex-plore the conditions under which cooperation goes hand-in-hand with sustain-able resource use. The model follows the setup of the behavioural experiments closely. The agents in the model represent the experimental participants; the 21 See e.g. Hare and Deadman (2004), and Heckbert et al. (2010) for overviews on applications of ABM for different environmental issues.

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model’s environment is represented by the same (abstract) renewable resource (see Figure 4a; left); and the interactions between the agents and the resource are: communication/knowledge sharing, the development of a group agreement (social-social interactions), and resource extraction (social-ecological interac-tion). We focused on the experiment outcomes of groups that were not faced with (potential) regime shifts for reasons of necessary simplification in aid of analytical clarity.

Our choices on the representation of the agents, their environment and interac-tions were based on the data of the behavioural experiments, as well as on the post-experimental questionnaire and observational data and in some cases they were also informed by literature (e.g. empirical, experimental and theoretical CPR studies, social psychology and communications research). A detailed de-scription of the model is provided in the Appendix S1 of Paper IV, following the standard ODD+D (Overview, Design Concepts and Details + Decision-making) protocol for describing ABM to provide clarity and transparency (Grimm et al. 2006, 2010, Müller et al. 2013). The model was implemented in NetLogo 5.3.1 (Wilensky 1999) and is publicly available on openABM (Wijermans et al. 2016).

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Core Findings - Individual Papers

Paper I In Paper I, we introduced and tested a novel experimental design for the lab that allows us to empirically test how CPR user groups respond to an ecological regime shift that is driven (or avoided) by group actions only (i.e. endogenously driven). The shift leads to a drastic and largely irreversible drop in the regenera-tion rate of the shared resource. We compared two experimental groups: one involving a smooth resource dynamiccs following a growth function of logistic type (control), and the other one involving a resource dynamics with a drastic and largely irreversible drop in the resource renewal rate beyond a critical threshold in the resource stock (treatment; see Figure 4). We conducted the game with 150 students from Stockholm University Campus in 21 control groups and 20 treatment groups (Lindahl et al. 2016). We complemented the experimental data with data from questionnaires and participant observational notes taken by the experimenters. 22

Research Question: What is the effect of an endogenously-driven ecolog-ical regime shift on human behaviour, particularly in relation to the emergence of collective action and sustainable resource use?

•� The results of the behavioural lab experiments in Paper I show that this

kind of regime shift triggers more cooperation and better resource man-agement (higher efficiency), in comparison to groups whose actions could not trigger such a shift.

•� However, we also observed in Paper I that cooperation does not necessari-ly imply sustainable resource use. In fact, some cooperative groups over- or under-exploited, or even depleted, the shared resource; which provides ex-perimental evidence that cooperation can be seen as a necessary – but not a sufficient – condition for the sustainable use of a shared resource.

Paper II In Paper II, we explored with a behavioural economic lab experiment, how the risk of an endogenously driven regime shift described in Paper I affects collec-tive action and resource use. We introduced risk by showing our participants

22 Previous versions of Paper I are two discussion papers: Lindahl et al. (2012, 2014).

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both of the above described scenarios (see Figure 4) and informed them that by a certain likelihood (i.e. 0.1, 0.5, 0.9, 1.0) they will be playing the threshold sce-nario. We then compared these four experimental groups. We conducted the game with 307 students from Stockholm University Campus in 20 ‘threshold’ (probability of 1.0) treatment groups, 21 ‘high risk’ (probability of 0.9) groups 23 ‘medium risk’ (probability of 0.5) groups, and 20 ‘low risk’ (probability of 0.1) groups. Research Question: What is the effect of various degrees of risk associat-ed with such a regime shift on human behaviour, particularly in relation to the emergence of collective action and sustainable resource use?

•� In Paper II, we experimentally explored risk (as one aspect of uncertain-

ty). Risk appears to have a positive effect on collective action, but the magnitude of this effect is influenced by how risk (and probabilities) are communicated and perceived.

•� We did not find a relationship between risk levels and specific resource use strategies, for example, whether or not groups would exploit the re-source beyond its potential critical threshold.

•� However, our results show that when the likelihood of the potential shift is certain or high, groups appear more prone to agree on a common exploita-tion strategy initially, which in turn is a predictor for averting the potential shift.

•� As in Paper I, we also observed that cooperation alone does not necessarily imply sustainable resource use.

Paper III In Paper III, we brought a simplified and modified version of the experimental design from Paper I and II to the field (see Figure 4). Our participants were small-scale fishers from four different communities along the Caribbean coast of Colombia. In the field, all groups first played the game with simplified smooth resource dynamics following a growth function of a logistic type (con-trol) and in a second stage, we introduced different treatments: a threshold treatment (a simplified version from Paper I and Paper II), a treatment in which there is a probabilistic threshold (‘risk treatment’; probability of 0.5), and a treatment in which there is an ambiguous threshold (‘ambiguity treatment’; a probability range of between 0.1 and 0.9). In contrast to the lab, we framed the (potential) threshold, which we introduced after a baseline stage without thresholds, as a result of a (potential) climate event with severe and long-lasting consequences for the shared fishing ground. In the risk and ambiguity treat-ment, we sampled the probability in each round. We then compared these four experimental groups. In each community, 64 fishers, 16 in each treatment, par-ticipated. A total of 256 fishers.

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Research Question: Can we expect small-scale fishers to adapt to cli-mate-induced thresholds in the dynamics of a shared resource, and what role does the actual social-ecological context and different degrees of uncertainty play?

•� The results of the behavioural economic field experiments in Paper III

indicate that groups confronted with uncertain thresholds are likely to adapt in the sense that they sustain higher stock levels compared to groups that are not confronted with any thresholds in the resource dynamics.

•� We also found that exploitation inequalities in the game (which could be regarded as a proxy for cooperation) as well as social and ecological com-munity-level attributes seem to mitigate this effect and potentially even eliminate the effect, demonstrating pronounced community effects in game outcomes.

Paper IV In Paper IV, we started off with the observation in Paper I and II that coopera-tion may be a necessary, but not a sufficient condition for sustainable resource use. We believed that this observation deserved further attention, not least be-cause the focus in the CPR literature has until tnow emphasised what makes people cooperate, rather than how people develop group agreements or how knowledge is shared and acted upon (at least in the experimental, theoretical and modelling work on CPR). This piece of the puzzle is also crucial to explore and study, as it takes not only cooperation for sustainable CPR management but also collective action in accordance with the ecological conditions in place. To explore individual-level factors and mechanisms relevant for cooperation that are aligned with sustainable resource use, we developed an agent-based model, informed by experiments conducted in Paper I and II. After having made sure that the model qualitatively reproduced the observed experimental patterns (i.e. cooperation, non-cooperation, cases of optimal management, over-/ and under-exploitation), we performed simulation experiments to study combinations of individual-level factors that translate to the group behaviour patterns we observed in the experiments. This way, we could explore and ad-vance our understanding in relation to individual-level factors and mechanisms relevant for cooperation to go hand-in-hand with sustainable resource use. Research Question: What are critical individual-level factors and pro-cesses, affecting individual behaviour and the simultaneous emergence of collective action and sustainable resource use?

•� We find that the individual-level factors; ecological knowledge, perceived

environmental uncertainty and social skills, along with trust and social pref-

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erences/preference for equal sharing, are crucial for sustainable resource use and cooperation.

•� Results from the simulation experiments suggest that the overall level of individual understanding of the ecological dynamics within the group does not sufficiently explain the relationship between cooperation and sustaina-ble resource use. Rather, it is the distribution of ecological knowledge among the group members, and how this distribution plays out in combi-nation with the environmental uncertainty the individuals perceive. Wheth-er or not individuals feel comfortable sharing their knowledge with the other group members is also important.

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Discussion

Key Insights Relating back to the objective of this thesis to “unravel critical social-ecological factors and mechanisms for the sustainability of CPR”- three overarching in-sights emerged from the four individual papers. Due to the specific experi-mental design that underlies all four papers of this thesis and in which commu-nication was allowed, these insights emerged in contexts where people can come together, communicate and share knowledge and which explicitly take into account social-ecological dynamics. All three speak to both research gaps. The latter two, which are mechanisms, can be regarded as hypotheses to be tested in future work.

Insight 1 (social-ecological factors): “Confidence is king, knowledge is queen” Ecological knowledge, and perceived ecological uncertainty (confidence in knowledge) are critical for collaborating for sustainable resource use. Social and ecological feedbacks influence both factors (social-ecological).

In all our experimental designs (Paper I-III), players had full information about the ecological system (i.e. the dynamics of the shared resource), including exact (or ranges of) probabilities of a threshold occuring in the resource dynamics. We made sure that all individuals understood the dynamic feature of the shared resource: depending on the stock size, the resource regenerates more or less. However, not everyone was able to figure out what the optimal or sustainable harvest rate was. This heterogeneity in the capacity to determine the best ac-tions highlights the important role of communication not only for reaching collective decisions, but also for sharing knowledge. Additionally, we observed in our games that individuals held different degrees of confidence in their knowledge about the resource dynamics (i.e. ecological knowledge). We inter-preted this confidence as the inverse of perceived environmental uncertainty. This highlights the role individuals’ perceptions play. Rather than uncertainty per se, what influences behviour is how how it is subjectively perceived. Building an ABM using insights from the lab (Paper IV), we show how that the interaction of three key factors was critical in explaining when cooperation led to sustaina-ble resource use: individual ecological knowledge, confidence in that knowledge (or perceived ecological uncertainty), and the social skills to communicate that

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knowledge to the group. Furthermore, the ABM in Paper IV also highlights that it is relevant to consider not only the heterogeneity of individual-level at-tributes between people (inter-personal), such as knowledge or perceived uncer-tainty, but also within a person (intra-personal), which goes a level deeper.

Place-based work in the CPR and SES literature highlights the critical role of local ecological knowledge for dealing with ecological complexity (Ostrom 1990, Berkes and Folke 1998, Berkes et al. 2003). However, the majority of behavioural experimental studies in the CPR literature and beyond overlook the role of ecological knowledge and confidence in this knowledge (or perceived eco-logical uncertainty). However, understanding individual and collective behav-iour of resource users requires an improved awareness of how knowledge and perceived ecological uncertainty, as well as their distribution within the user group, play out in relation to factors that have been stressed before to matter for cooperation, such as communication or trust (e.g. Ostrom 1998, 2006, Balliet 2009).

Insight 2 (social-ecological mechanism): “Threat hypothesis”: Looming regime shifts can mobilize collective action and sustainable resource use A certain or probable endogenously driven ecological regime shift, could be interpreted as a threat that is able to mobilise collective action and serve as a focal point around which people can coordinate their actions and thereby protect the ecosystems and ecological functions on which their wellbeing depends.

We found that under certain conditions, the threat of drastic ecological change, such as ecological regime shifts, can make collective action and sustainable resource use more likely to emerge. These conditions include that the regime shift is in the power of the user group to avoid (endogenously driven), and that it has negative consequences for the availability of the shared resource. Com-munication is key to this proposed mechanism or ‘threat hypothesis’, as it al-lows for the coordination of actions. In the lab (Paper I-II), all groups, no mat-ter the treatment, were provided with the opportunity to communicate without restrictions in respect to time or content. We found that people did not neces-sarily choose to communicate even though they had the opportunity to do so. For our definition of cooperation, a necessary condition was that groups made use of the opportunity to communicate to formulate agreements regarding exploitation levels. We called this effectiveness of communication (Paper I). We found in Paper I that the effectiveness of communication can depend on the degree of ecological complexity, measured as whether there was a threshold in resource dynamics or not. In Paper II, we found that groups that were con-fronted with certain or highly probable thresholds were more likely to make exploitation agreements in the first round compared to groups for which the

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risk of the threshold was lower. We found in Paper I that groups with effective communication were more committed to knowledge sharing. Finally, we found in both papers that a likely regime shift led to more cooperation and, in combi-nation with knowledge sharing, also to sustainable resource use.

This is a hopeful insight and connects to the commonly used metaphor in resil-ience thinking of ‘crisis as window of opportunity’ (Olsson et al. 2004). This however is often stated in rather an obvious way, that in a ‘crisis,’ people will come together to try and avert it. But what happens in this moment of crisis? As such, this insight provides a concrete and empirically-based hypothesis about the mechanisms that mobilise collective action in this moment of crisis. Crisis, in our case the impending threat of an ecological regime shift, seems to improve incentives for stewardship as players engage more in developing coop-erative agreements that enables not only knowledge sharing but also stronger commitment for collective action which can build a sense of group identity and trust. While our methodological approach can only capture ‘adaptive change’ in the face of a potential crisis, our results could inspire new hypotheses regarding the potential of similar threats for ‘transformative change’. Hence, this work also contributes to the field of transformations within resilience thinking and SES research.

Insight 3 (social-ecological mechanism): “Uncertainty – Both a curse and a blessing?” Ecological uncertainty can have a positive influence on collective action and sustainable resource use. Perceived ecological uncertainty can make people sensitive to change and scientific ecological uncertainty can make people cautious, buffer mistakes and anti-social actions.

Uncertainty, i.e. the lack of complete knowledge, is a prominent feature of complex systems such as SES or CPRs. Studies of human behaviour and collec-tive action in relation to uncertainty are thus highly relevant for questions about sustainability. This thesis suggests that uncertainty is not necessarily bad news – in contrast to many other behavioural experimental studies. This thesis contrib-utes a positive outlook and, hence, complementary view on behaviour and col-lective action in relation to uncertainty given that i) people can communicate, share knowledge and opinions, and ii) information feedbacks between the avail-ability of the shared resource and the actions of others are less strong.

The results of Paper II and III stand in contrast to previous CPR games on the effects of uncertainty with respect to the size of the shared resource or its re-generation rate (e.g. Hine and Gifford 1996, Gustafsson et al. 1999). These differences likely stem from the ability of participants to communicate. In our games, groups were allowed to communicate and, hence, could make coopera-tive agreements. Given the possibility to communicate and share knowledge,

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results of Paper IV also show that perceived ecological uncertainty is not neces-sarily bad, as it can make people sensitive to change and facilitate learning, and hence, it has an important role to play for sustainable resource use in CPR set-tings. Also, perceived ecological uncertainty could buffer against the trust eroding actions of other group members, for example in situations where the resource was lower than expected, participants could attribute this deviation to a lack of own knowledge.

In our game, players did not receive direct feedback about other players’ actions in the previous round. They only got to know the new stock size from which they could not precisely deduce if others acted in the interest of the group or as agreed, if there was an agreement in place. This feedback was even more masked in treatments with uncertainty. In a context without scientific uncer-tainty, players could attribute sudden and unexpectedly low stock levels (e.g. below the threshold) to others’ exploitation levels. This could erode trust, no matter whether harvest levels were high intentionally or by mistake. In the face of uncertainty, on the contrary, players could instead attribute low stock levels to a change in the resource dynamics. This then might not as easily erode trust in group members, or at least potentially delay the erosion of trust. As argued in Paper III, this mechanism could explain why we did not find a negative rela-tionship between uncertainty and sustainable resource use, in contrast to previ-ous public good experiments on threshold uncertainty (e.g. Barrett and Dannenberg 2012, Dannenberg et al. 2015). This same mechanism could also explain why we did not find a significant relationship between risk levels of an endogenously driven regime shift and whether or not groups would exploit the resource beyond its potential critical threshold in Paper II. Experimental work suggests that the majority of people are often well described as conditional co-operators (Gintis et al. 2005, Kocher et al. 2008). Norms of reciprocity often guide individual behaviour in CPR settings (Ostrom 1998). This implies that people condition their behaviour to the past actions of their group members. In a repeated public good setting, uncertainty does not mask such feedback, in contrast to our games, as players typically get informed about the contributions of their group members in previous rounds (e.g. Barrett and Dannenberg 2012, Dannenberg et al. 2015).

Methodological Contributions To study human behaviour in SES requires novel methods, and new ways to combine existing methods. These methods must be able to capture intra- and inter-individual (individual- and group-level) factors and processes, as well as the emergent patterns of cooperation and sustainable resource use, in addition to other complex social-ecological dynamics of relevance. In this thesis I fo-cused on two features of ecological complexity in SES/CPR settings, namely

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regime shifts and uncertainties. To address them, this thesis relies on a multi-method approach employing behavioural economic lab and field experiments in combination with agent-based modelling. The novelty lies both in the specific experimental design as well as in combining the methods.

A set of distinct features distinguish our experiments from previous CPR games: a) they are dynamic (explicilty capture social-ecological dynamics) ; b) the resource regenerates according to a specific growth function (see Figure 4) and various features of ecological complexity (regime shifts, thresholds, hyste-resis, and uncertainty) are included; c) the lab experiments were framed, i.e. participants in the lab were asked to extract units of a renewable resource; d) face-to-face communication was allowed from the start. Whereas a) and c) are rare characteristics of CPR games, b) and d) truly distinguish our design. Re-garding b), apart from a very recent framed field experiment with recreational fishers (Noussair et al. 2015), we are not aware of any experimental study that has used the logistic growth function to represent the dynamics of the shared resource. The logistic growth function is the canonical model in the resource economics literature to model renewable resources (see e.g. Clark 1990). As we explain in Paper I, we made use of it, as it can capture thresholds in resource dynamics by adding a so-called sigmoid term, such as a “Holling-type” III pre-dation term (Ludwig et al. 1978) and previous work showed that such a model can simulate the dynamics of relatively complex ecosystems, like forests or grasslands (Scheffer and Carpenter 2003, Crépin 2007). Moreover, most of the few CPR games that account for social-ecological dynamics and ecological complexity test the effect of institutional arrangements, such as communication or punishment, in contexts of increased ecological ‘reality’ in order to evaluate whether previous results hold, such as the positive effects of communication or punishment (cf. Janssen et al. 2010), rather than the effect of features of ecolog-ical complexity itself on behaviour, such as Janssen (2010), Osés-Eraso et al. (2008), Kimbrough and Vostroknutov (2015) and Anderies et al. (2013). Re-garding d), in the vast majority of previous CPR games, with the exception of Janssen (2010)23 and Anderies et al. (2013), communication was either not al-lowed, or was a treatment24. However, we were also interested in what triggers communication in the first place. Hence, this design aspect is itself a contribu-tion to experimental designs for behavioural studies in the CPR literature. Moreover, we complemented both types of experiments (lab and field) with a more extensive survey and observational notes. The use of observational notes

23 However, even though communication in Janssen (2010) is not a treatment, it is only intro-duced after one round of no communication. 24 In the first stage, groups play the game without communication, and then, in a second stage, groups have the opportunity to communicate (see e.g. Ostrom et al. 1994, Cardenas 2000). Due to the resulting stark difference between the two stages, players become very aware of the ad-vantages of communication and, hence, take the opportunity almost always. This typically leads to a significant increase in management performance.

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is particularly novel, as we are not aware of those being used in pen and paper games.

Lastly, the development of the ABM (Paper IV) specifically reflects a novel methodological approach: the ABM was informed by observations from the lab experiments. There are only a few ABMs that are empirically informed by be-havioural economic experiments (Deadman et al. 2000, Janssen and Rollins 2012, Janssen 2014), but none, to our knowledge, are based on experiments that incorporated both communication and learning.

Limitations and Additional Considerations

Methodological Limitations and Considerations With an experiment, it is only possible to test the effect of one variable at a time, which limits the analysis, especially if we want to add layers of complexity. It is, in principle, not a problem to have large experimental programs to test a number of variables and their interactions, but this endeavour would be highly resource intensive. Moreover, behavioural economic experiments allow the researcher to observe behaviour, and also to establish causality. However, the development and testing of potential explanations and underlying motivations or reasons for the participants’ behaviour is severely challenging by means of experiments only. We made use of an ABM in Paper IV, as this method al-lowed us to test hypothesized explanations for what we had observed in the games. This approach allowed us to manipulate and control factors and mecha-nisms, internal to individuals and between them, such as ecological knowledge and perceptions about ecological uncertainty. Other potential options are to conduct in depth interviews or focus groups.

In our experiments and in the ABM, participants (agents) had full information not only about the exact size of the stock, but also about its regeneration rate and carrying capacity, the location of the threshold and the exact (or range of) probabilities of the threshold occuring. This was – of course – a simplification for purposes of method application and analytical clarity. In reality, there is considerable and irreducible uncertainty, e.g. about the actual size of fish stocks as well as their population dynamics, making the identification of an optimal catch level difficult. Therefore, in the real-world, a precautionary approach to ecosystem management might be necessary (Ludwig et al. 1993). Regarding the thresholds, as we explain in Paper III, whereas we might be able to assess for some well-studied ecosystems that thresholds exist, the complexity of ecosys-tems usually only allows for the prediction of a range in which the threshold is located (Biggs et al. 2012). Hence, a natural next step for this research would be to test behaviour as it relates to uncertainty about the threshold location. An-

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other avenue for future work could be to study human behaviour in relation to surprise, such as an unexpected change in the resource dynamics, or uncertainty about hysteresis.

Group size is another limitation. Groups of resource users in our games only consisted of four people. In reality, there are usually more people involved in the governance of CPR. A potential extension therefore would be to play the game with bigger groups or even with several groups at the same time (intra-group interaction), in which a group would replace one individual (intra-individual interaction). This way we could observe cooperation among groups, which might better represent some CPR contexts. A review by Kugler et al. (2012) on games with intra-group interaction suggests that groups tend to be more ‘rational’ and selfish, as they are more competitive and profit-maximization oriented. It would be interesting to see whether we would ob-serve the same trend, with an improvement in efficiency, as individuals within the group are probably more likely to share knowledge from the beginning.

However, models and experiments are meant to strip away all ‘the noise’ of reality. I like to regard them as ‘fables’, an expression which Rodrik (2015) sug-gests as useful when thinking about economic models. This metaphor empha-sises the value of exploring general patterns of behaviour given a specific set-up that is considered relevant to study. In our case, this set-up is a simple represen-tation of a CPR setting in which individuals interact with their group members as well as a dynamic resource with potential threhsolds. In reality, regime shifts and their consequences are likely to be experienced and perceived very differ-ently by individuals, e.g. depending on the resource users’ dependence on the affected local ecosystem. Moreover, while for some community members the regime shift might bring about hardship, for others it might create opportuni-ties as other sources of livelihood might become more lucrative. Hence, it can be problematic to generally describe one alternate stable state producing a spe-cific bundle of ecosystem services as “desirable”, as it might not be desirable for everyone. In reality there may be unequal interests and incentives for avoid-ing a looming regime shift. A fruitful future research avenue for exploring hu-man behaviour in relation to regime shifts could be to complement the ap-proach taken herein with an interpretive approach (e.g. West 2016) which can elicit relevant subjective experiences and un-pack perceptions and other drivers of behaviour inside and outside of the game. This may also help address the question of external validity of game outcomes (see below), as in depth inter-views can elicit whether observed behaviour in the game is likely to translate beyond it.

The external validity of behavioural experiments, i.e. to what extent outcomes can be generalized beyond the experimental setting, is a question frequently raised by social scientists (Levitt and List 2007, Falk and Heckman 2009, List

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2011). Unless we establish a correspondence between the behaviour of experi-ment participants in the game and their everyday behaviour25, we cannot base policy recommendations directly on the outcomes of a particular experiment. A natural first step to address the question of external validity is to bring the de-sign, originally designed for the lab (Paper I-II), to the field (Paper III) and to run the experiments with actual CPR users, who do not only depend on local ecosystems but are also accustomed to the use of shared resources and have potentially experienced drastic ecosystem changes in the past. This allows us to say something about the generalizability of the overall findings from the lab (as, for example, suggested by Harrison and List 2004, Levitt and List 2009). We found in the lab and the field similar behavioural patterns: individuals respond to regime shifts and their associated uncertaintites. However, the biggest differ-ence between the outcomes of the lab experiments and the field is that it is not the potential of a regime shift itself that matters but the uncertainty around it. However, it is important to note, that the framing and design between the lab and the field differed, which make direct comparisons problematic. Moreover, we found pronounced differences in game outcomes between the four com-munities in which we ran the games in the field. Our results indicate that whether or not there is a treatment effect, and the strength of that effect, seems to depend on the community. However, due to sample size limitations, we cannot be certain. These results emphasise that in order to gain confidence inobserved behavioural patterns, we need to test them in different contexts.

Policy Relevance of Insights The behavioural economic experiments (both lab and field) and the ABM in this thesis are both necessary simplifications of real-world decision-making processes and contexts in service of analytical clarity. As such, the games and models themselves should not be directly used to develop real-world policies or management recommendations. However, the understanding gained from all papers offers insights useful for small-scale CPR. Policy relevant insights from the lab and field experiments (Paper I-III) point clearly to communicating in-formation on potential ecological regime shifts and their consequences to those communities that could be potentially affected. Results from the lab and the field (Paper II-III) further suggest that accurate risk levels might not be as deci-sive for behaviour. Rather, it might be critical to think carefully about how to communicate risk and uncertainties, and to invest in governance arrangements that can build social capacities and provide arenas to develop collective agree-ments and rules, but also to share knowledge and learn collectively (Ostrom et al. 1994, Ostrom 2009). This is particularly so given that our results suggest that

25 There is only a limited number of studies about the external validity of CPR experiments (e.g. Gurven and Winking 2008, Fehr and Leibbrandt 2011, Gelcich et al. 2013, Torres-Guevara and Schlüter 2016). The first and the last did not find evidence for external validity, the others did. All but the study by Gurven and Winking did field experiments with fishers.

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collective decision-making fora can be critical to deal with thresholds and their associated uncertainties. Such governance arrangements could include co-management, that combines self-governance with state regulation, and which is often put forward as a strategy for better fisheries governance (Jentoft 1989, Feeny et al. 1990). Recent small-scale fisheries research in Colombia, for exam-ple, also recommends the implementation of co-management at the communi-ty-level, in order to help reduce problems such as over-exploitation or future policy changes (Saavedra-Díaz et al. 2015). The mechanism-based understand-ing from Paper IV (ABM), also highlights the importance of fora for knowledge sharing and learning. As we noted in Paper IV, provided the exist-ence of such fora, “not every member of a resource user community needs to have perfect ecological knowledge in order for the community to secure the long-term provision of the CPR”, and ecological uncertainty is not necessarily something that needs to be eradicated as it can facilitate learning.

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Conclusions and Looking Ahead

This thesis set out to build and advance an empirically grounded understanding of human behaviour in SES. It did so by linking individual and collective be-haviour to two features of ecological complexity: regime shifts (Paper I-III) and uncertainty (Paper I-IV). To this end, it employed behavioural economic lab and field experiments (Paper I-III), and ABM (Paper IV), and connected to, drew on, and built upon different bodies of literature. With the objective of unravelling critical social-ecological factors and mechanisms for the sustainabil-ity of SES and CPR in particular, this thesis addressed two research gaps by 1) providing one of the first accounts of human behaviour and collective action in relation to ecological regime shifts and their associated uncertainties, and 2) extending the incipient behavioural CPR literature that acknowledges SES dy-namics and ecological complexity.

The significance of individual-level factors and processes, how they play out in interaction within a group (or social contexts), and the implications of this for the sustainability of SES represents both the broader theoretical and methodo-logical, significance of this thesis. Rather than inferring behaviour from system-level observations, asking individuals how they would behave given a certain situation, or eliciting individuals’ attitudes, the behavioural approach taken here-in searches for general patterns through directly observing individual and col-lective behaviour given specific contexts. This approach is well suited to SES research and can further strengthen it, as it allows us to not only account explic-itly for complex social-ecological dynamics, but also to put forward empirically-grounded causal relationships (through experimental methods) and gain mech-anism-based understanding (through ABM), providing robust building blocks for theory development. As illustrated, the experimental method can comple-ment modelling approaches, but it can also be useful for place-based research, helping to disentangle the effects of specific factors by rigorously testing alter-native hypotheses originating from the field work (Ostrom 2006).

The thesis focuses on small-scale CPR contexts in which people are dependent on local ecosystems because it is in these contexts that people’s livelihoods can be more directly threatened by ecosystem regime shifts. Overall, we found that existing scientific knowledge indicating the potential for regime shifts should be communicated to affected communities, as well as the remaining uncertainties, as this information can mobilize collective action for sustainable resource use.

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Rather than providing accurate risk levels, it might be critical to think carefully about how to communicate risks and uncertainties, and to invest in governance arrangements that can build social capacities and trust, and provide arenas to develop collective agreements and rules, but also to share knowledge and learn collectively. This can in turn enable vulnerable communities to sustain the eco-logical functions they depend upon. Moreover, ecological complexity, as well as social and ecological uncertainties, are inherent to human-environment interac-tions, and hence, the insights generated here can contribute to the study of SES and their behavioural dimension in more general terms. The insights of this thesis indicate that, given opportunities and the willingness of people to come together, and the social skills to share knowledge, exchange ideas, and build trust, potential ecological crises can mobilize collective action, turning uncer-tainties into opportunities for dealing with change in constructive ways. This provides a hopeful outlook in the face of escalating environmental change and its inherent uncertainties.

To conclude, I would like to look ahead and highlight three potential future research directions emerging from this thesis. The first two build directly on work that was initiated in the papers comprising this thesis, and the third stems from a reflection on the potential complementarity of conceptual, theoretical, and methodological approaches for the study of SES.

The first idea is already work-in-progress, and it connects to Paper III, based on our field experiments in Colombia, in which we studied the effect of differ-ing degrees of scientific uncertainty regarding a climate-induced threshold on behaviour. So far, we have focused only on group-level outcomes (aggregated decisions reflected on stock size), but in a next step, we would like to make use of the disaggregated data, zooming in on the individuals’ decisions to investi-gate critical factors (both at the individual- or community-level), which facilitate cooperative behaviour and sustainable resource use. This would also allow us to test some of the hypotheses we have put forward in Paper III to explain the pronounced differences in game outcomes between the communities.

The second future direction emerges from Paper IV and connects to Insight 1 and 3 of this thesis. As mentioned above, the majority of behavioural experi-mental work in the CPR literature has focused on cooperation facilitators, but has overlooked the role that ecological knowledge and perceived ecological uncertainty can play for sustainable resource use. There is a need, therefore, to further investigate how both factors play out in relation to factors that have pre-viously been stressed as key for collective action to emerge. In a series of lab experiments, informed by the results of Paper IV, we could disentangle the effect of ecological knowledge and perceived ecological uncertainty on behav-iour. Thereafter, we could return to the ABM to further develop and validate the model, as well as to again test mechanisms explaining observed behaviour

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in the lab, but also explore how perceived and scientific ecological uncertainty interact. Based on the results of Paper II and III, one could hypothesise that perceived ecological uncertainty might increase in the face of scientific uncer-tainty or more complex decision-making contexts, potentially reinforcing the learning mechanism that we proposed in relation to perceived ecological uncer-tainty. This bi-directional application of behavioural experiments and ABM, testing ideas empirically and theoretically, can enhance our understanding of how actions and interactions of heterogeneous individuals and collectives lead to (un)sustainable resource use under increasing ecological uncertainty.

The third and final future direction I want to highlight here connects to the many previous calls for multi-method approaches (Ostrom 2006) or a ‘portfolio approach’ (Young et al. 2006) for studying complex human-environment inter-actions. However, what seems to be lacking most within the sustainability sci-ence literature is work that identifies what combinations of approaches are particularly productive (or not) for particular purposes. Sustainability science provides an arena for trying out new ways of combining approaches, negotiat-ing epistemological tensions and building on different methodological skills (Haider et al. in review). We, as a new generation of sustainability scientists, have to be ‘epistemologically agile’ to be able to attempt bolder and potentially fruitful combinations of approaches that can uncover new insights about com-plex phenomena. Specifically for behavioural experimental approaches, this thesis has demonstrated concrete areas for cross-fertilization of methods, but also opens up space for new ways of doing interdisciplinary science.

These future directions have the potential to further advance an empirically-grounded understanding about human behaviour – both individual and collec-tive – in SES. This is necessary to inform efforts that will guide development along more sustainable pathways. Our behaviour is at the same time the great-est challenge to, and opportunity for sustainability. In order to take advantage of these opportunities, we need to apply interdisciplinary approaches to the study of human-environment interactions. While an ever-growing body of re-search shows that a multitude of factors can influence our behaviour and deci-sion-making and, hence, development and sustainability outcomes (World Bank 2015), we need to better understand behaviour in relation to escalating envi-ronmental change and its inherent uncertainties. It seems only reasonable to assume that we cannot address complex social-ecological problems with simple solutions and policy panaceas based on overly simplistic and generic models of human behaviour that disregard the complex social-ecological context in which our lives play out. This thesis is a step in that direction.

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Acknowledgements

The main funder of this work was the Swedish Research Council Formas through the SUPER-project (#250-2010-145) and BEST-project (#211-2013-1120). Additionally, funding was received from the EU FP7 Artic Tipping Point (ATP) project (#226248), the EU FP7 ACCESS project (#265863) under the call Ocean of Tomorrow, Riksbankens Jubileumsfond (#P12-0894:1), the Ebba and Sven Schwartz Foundation, MISTRA through a core grant to Stock-holm Resilience Centre, and the Kjell and Märta Beijer Foundation.

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Thank you

As a PhD student you often hear, or you are telling yourself: “you are more than your thesis”. Now, I want to add “and this thesis is so much more than what you hold in your hands right now.”

To my supervisors. My first and biggest thank you goes without a doubt to my main supervisor: Therese Lindahl. It might sound like a cliché, but it is simply true: I could not have wished for a better one. Your incredibly sharp mind, brilliant research ideas, dedication, sense of humour, positive energy, and warm heart guided me throughout this big, exciting, and at times scary, adventure and contributed immensely to the wholehearted researcher I am today. I have learned so much from you – about research and beyond (though, perhaps not about how to make best use of ‘new’ technologies such as reference manag-ers…). And I cannot wait for all that is yet to come. But first, Therese, it’s time – for real – for a high-five-selfie (you know what I’m talking about). You hold right now the thesis of your first PhD student in your hands! And then there are my three co-supervisors: Anne-Sophie Crépin, Johan Colding and Carl Fol-ke – constant sources of sound advice, comfort, relaxing laughter, and endless inspiration. Your support and trust made my PhD studies possible in the first place – thank you so much for taking me on board, or I guess I should say “thank you for letting me enter Hotel California”. Therese, Anne-Sophie, Johan and Calle – your infectious joy for research and beautiful curiosity paired with your complementarities provided me with all those smaller and bigger stepping stones needed to write this thesis. Thank you for everything.

To my co-authors and collaborators. Therese and Anne-Sophie, you taught me the art of being a good co-author – by example. And it is with you that rejections turn into an ‘epic fail award’. Nanda Wijermans, Maja Schlüter, and Therese – it was with you and through you that I have learned what it can truly mean to do in-terdisciplinary and collaborative research. I am still amazed by the power and excitement that jointly developed ideas can carry. Thank you so much for eve-rything and how glad I am that this was just the beginning of AgentEx. And then there is the BEST Colombia field work team – it was an enormous privi-lege to be with you in the field. Juan Carlos Rocha, Lina Maria Saavedra-Díaz, Alisson Soche Forero and Nidia Vanegas – I have learnt so much from you. ¡Muchas gracias! Juan, thank you for thought-provoking discussions and shared semla love. Lina Maria, I hope the bridges we built will last long. Your passion

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for your work and life is truly inspirational. Juan, Alisson and Nidia, what can I say other than Lulo. Wait. Ceviche perhaps. And thank you to all our experi-ment participants in Stockholm and Colombia. You thaught me more about our complex behaviours than any text book could. This leads me to Nikolina Oreskovic, who deserves a special mention here. You were simply the best partner in crime for running all those experiments in Stockholm. You kept me sane with all the organisational stuff and made me laugh out loud so many times.

To Beijer. I cannot and I would not like to single anyone of you out. To me, Beijer is one of these beautiful examples of “the whole is more than the sum of its parts”, including BENN, the Mäler scholars, the Beijer Young Scholars, and the Askö meeting on social norms I had the privilege to be part of. Thanks to all of you for providing me with such a vibrant and inspiring academic home and work place made for humans. But also for such revitalizing conversations around the Beijer kitchen table, at lunch or during fredags fika, joyful laughter in the hallway, warm smiles, and such generous and smooth administrational support. Thank you all so very much.

To the PhD group. Thank you for making me stop so many times – and think – and (!) dance. You are an outstanding, smart and compassionate bunch of peo-ple I feel honoured to be part of. Special thanks I want to extend to: Jamila, Johan, Simon, Diego, Johanna, Pat and Linus – I feel so lucky and privileged to have started and “done this” together with you, you make everything seem possible, including China course 2.0, and a hip hop career. And a second special thanks goes to the ‘undisciplinarity team’. Our explorations and discussions sparked reflections that did not only make me a much better ‘interdisciplinari-an’, but also enabled me to leave this ‘uncomfortable space’ behind (at least for now). “Say always no to la-la-land!” (but watch the movie – it’s really good). A third one goes to the Kalk Bay gang – so much fun!! Anytime again. And last but not least a special thanks to all of you that helped me out in various ways on the last mile with your superpowers – Andrew, Jamila, Diego, WEST, Emi-lie, JB and Daniel. You did not only provide me with invaluable input for my Kappa and last manuscript but also with not-from-this-world motivation and inspiration boosts. To SRC colleagues. Thank you to my internal reviewers Thomas Hahn and Be-atrice Crona for valuable feedback and discussion, as well as María Mancilla García for taking the time to engage with my Kappa and its philosophical di-mension. And thank you also to Cecilia Lindner, Hanna Ellström and Thérése La Monde for taking such good care of all organizational and admin matters, as well as the SRC education team consisting of Lisa Deutsch, Garry Peterson, Magnus Nyström, and Miriam Huitric. Your efforts should be praised much more often! And Miriam, I hope you know how crucial you were in getting me

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on board the SRC… back in September 2010. And that brings me also to the one and only ERG class (including Miriam). It was the RAT (?) (ART!) class and the Bali case study (the nerd in me must admit) that got me hocked. And then I also want to extend a big thank you to Joanna Sanecka, our BEST intern, for her beautiful and thoughtful work on our fiel work calendar – hopefully soon in the hands of our experiment participants. As well as a big thank you to Elsa Wikander from Azote for the beautiful illustrations for this thesis. An attentive reader might have picked up by now how many female characters I mentioned so far and also that among my supervisors, co-authors and collab-orators women are over-represented, in comparison to the academic world “out there”. I would like to extend a special thank you to all of you for being such inspiring role models. Science needs women like you. And that brings me to three special women all both colleagues and dear friends, that deserve some extra mentioning. To friends and family. Emilie, you are simply a superwoman – at programming, learning-by-modelling, in life and on the dance floor. You are one of these true role models when it comes to how to balance it all, and your friendship, care and the fun we had, made everything just so much better. (Don’t miss her 1-year PhD defence anniversary party on May 19!). Nanda, I feel so privileged to have you as both my colleague and friend in my life. Your spot-on questions, professionalism, dedication (model calendar!), and capacity for reflection taught me a lot about how to be a good researcher. And what a wonderful partner you are in studying human behaviour. And then there is your exceptional emotional intelligence, powerful motivation boosts, encouragements to follow my in-stincts, and joyful laughter – such important ingredients for making this journey to what it is. You keep amazing me. Jamila, what an incredible luck and honour to have started my PhD adventure together with you. You are a wonderful source of creativity and support, and your dedication is truly inspiring. We shared all these ups and downs a PhD (and life) comes with and it is remarkable how you deal with it all – no matter what live throws at you. You helped me enormously in creating space for getting my thoughts out there and on paper, with our Askö hide away in the end as the most beautiful example. All my good energy to you now for your final stretch! A heartfelt thank you also to the whole ‘Lidingö family’ Nanda, Frithjof, Leo (!), Jamila and Toby for your friendship, little hiking/kayaking/skiing adven-tures, and outstanding generosity and support over the past years – but espe-cially in the last months. I could always count on you. And then a special thanks to ‘little Beijer’ (you know who you are). Without your wholehearted support and genuine friendship, this girl from Schwarzwald might have not had the courage to start this adventure in the first place. The Uruguayan poncho was with me all the time. And also to my favourite glaciologist who so often came

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to visit us. Good luck on your final stretch!! Even though there were times in which we hardly saw each other, our good talks, climbing (attempts) and good laughs always provided me with loads of positive energy. Vive le Mont Blanc! Which brings me inevitably to: “Aux Champs Elysées…” and Niko (again). (I really cannot believe that you reside this spring of all places on the other side of the Atlantic). I miss you. Och tack så mycket Sverige för semlorna! (I could not have timed my final stretch better: semla season until one day before hand-in.)

Mama, Papa, Ralf. Ohne euch, eure Unterstützung und euren unerschütterli-chen Glauben an mich und meine Fähigkeiten würde ich nicht hier stehen mit einer Doktorarbeit in der Hand. Danke für Alles. Ohne euch würde es diese Doktorarbeit schlichtweg nicht geben und deshalb widme ich meine Arbeit in erster Linie euch Dreien, aber auch allen anderen Dälern, Wäldern und Offen-burgern in unserer Familie. Ihr alle habt mir die notwendigen Wurzeln, Flügel und Wunderfitz („Warum’e denn?“) mit auf den Weg gegeben. Durchhaltever-mögen und Diskussionsfreude ganz bestimmt auch. Mama und Papa, raus ist es jetzt auch: es scheint eurer Tochter nicht geschadet zu haben, dass ihr sie als Dreijährige auf den Gemmi habt laufen lassen.

Und dann sind da noch Andi, Kris, Floh und Judith. Ich möchte einfach nur Danke sagen – für eure Freundschaft, für Ablenkungen jeglicher (!) Art und für euer Talent, mich in den richtigen Momenten an meine Stärken zu erinnern. Ihr seid die Besten! Kris, an dich auch ein extra Dank für deine last-minute Unter-stützung, tat so gut dich da zu wissen. Und Kris und Andi, ein besonderer Dank auch an euch fürs nie aus der Welt sein, egal wo auf der Welt ihr seid.

And lastly, Daniel. There is no word profound enough to describe the gratitude and happiness I feel deep inside me. This thesis and all the thoughts that went into it would simply not be the same and as meaningful without you. Let me just say: And it does grow exponentially!