Ecology for a small planet

Prof Bob Scholes Inaugural lecture

21 June 2016

• Picture of an elephant eating a tree, with other herbivore present

What does that ecologist see in

me?

A Systems Ecologist’s view of the world

Very Large Plant-Eater

Plants that VLPE eats +

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+

Plants VLPE doesn’t eat

Other plant-eaters

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+

-

- -

What happens if I give the system a shove here?

Solving an old puzzle Why is some veld ‘sweet’ and some ‘sour?’

‘Sweetveld’ and ‘sourveld’ are not properties of the species,

but a property of the system!

Cold, wet, infertile places

Hot, dry, fertile places

%N too low to digest in winter

%N above threshold all

year

Generate and keep more N

Time of year spring winter summer

0.5

% N

in g

rass

digestion threshold in ruminants

Retain relatively more carbon than

nitrogen N leak from fire & denitritfication

Biological Nitrogen Fixation

Blackmore A.C., M.T. Mentis & R.J. Scholes. 1990. The origin and extent of nutrient rich patches in a nutrient poor savanna. Journal of Biogeography 17, 463-470.

Ellery, W., M.C. Scholes & R.J. Scholes. 1995. The distribution of sweetveld and sourveld in South Africa’s grassland biome in relation to environmental factors. African Journal of Range and Forage Science 12, 38-45

Three things that interest me

• Biogeochemistry, especially of carbon

• Earth Observation, especially putting it together

• Ecosystem dynamics, especially at the edge

The common thread is taking ecology to big scales

Is that 2 ½ things to many?

A salutary experience

… but the flow in the river is only 20 x 106m3/y !

NA

SA

Botany Hons Field Trip, July 1978

Calculation of transpiration by trees in the Kuiseb river, by scaling up from leaf measurements

Picture of Jane and porometer

Gobabeb

Rossing

Multiplied by Explanation Yields

0.3 g/m2Leaf/s Acacia transpiration rate

22.9 m2/m2 Leaf area per stem XS area 6.87 g/m2stem/s

0.001 m2/m2 Rooted fraction in riparian belt 0.01 g/s/m2ground

100 m Mean width of riparian 0.69 g/s/river

440000 m Length of riparian 3.02E+05 g/s/river

3.15E-05 s/y seconds per year; g per 106m3 9.54 x 106m3/y

Where did we go wrong? …we neglected the interactions!

Leaflet

Branch

Canopy

Landscape

advection, partioning

root and canopy

resistance

humidity

Jarvis PG, McNaughton KG. 1986. Stomatal control of transpiration: scaling up from leaf to region. Advances in Ecological Research, 15(1): 49.

Incr

eas

ing

scal

e

xylem resistance

Is big ecology just little ecology

with lots of zeros?

Scholes, R.J. & B.H. Walker.1993. An African savanna: synthesis of the Nyslvley study. Cambridge University Press, Cambridge

Prentice, I.C…, R.J. Scholes et al. 2001. The carbon cycle and atmospheric carbon dioxide. Third Assessment Report of the Intergovernmental Panel on Climate Change, WG1. Cambridge University Press, Cambridge. 1(3):183-237. Falkowski, P., R.J. Scholes,..et al. 2000. The global carbon cycle: a test of our knowledge of earth as a system. Science 290, 291-296.

1015 g/0.51x 1015m2 100 g/m2

Scaling up through ‘paint-by-numbers’ Map ecosystems, assign a mean value to each, multiply by area and add up

my bit!

But ecosystems are not internally homogeneous! You can do better by replacing the classes with a continuous function

Scholes, R.J., J. Kendall & C.O. Justice. 1996. The quantity of biomass burned in southern Africa. Journal of Geophysical Research 101: 23667-76. Scholes, R.J., C.O. Justice & D. Ward. 1996. Emissions of trace gases and aerosol particles due to vegetation burning in southern-hemisphere Africa. Journal of Geophysical Research 101: 23677-23682.

Scholes et al 1996 500 Gg CH4/y

Hao et al (1990) 4163 Gg CH4/y

Fire-related greenhouse gas emissions from Africa south of the equator

Pyrogenic emission = area burned* fuel load * combustion fraction * emission factor

The carbon stock of South Africa A recent example of continuous field modelling

https://www.environment.gov.za/sacarbonsinkatlas Based on Scholes et al 2014 National Terrestrial Sink Assessment. CSIR for DEA.

A better way: measure the phenomenon at its actual scale

Stömmel diagram

Vance, T and R Doel 2010 Graphical Methods and Cold War Scientific Practice: The Stommel Diagram’s Intriguing Journey from the Physical to the Biological Environmental Sciences . In: Historical Studies in the Natural Sciences (DOI: 10.1525/hsns.2010.40.1.1.) Scholes et al 2013 Multiscale and cross-scale assessments of social ecological systems and the their services COSUST 5:1-10

Measuring carbon exchange at the leaf scale

Infrared gas analyser and leaf chamber

Scholes, R.J., P. R. Dowty, K. Caylor , D.A.B. Parsons, P.G.H. Frost and H.H. Shugart 2002 Trends in savanna structure and composition on an aridity gradient in the Kalahari. Journal of Vegetation Science 13, 419-428.

Measuring carbon exchange at the landscape scale

Stömmel diagram

Scholes, R.J., et al. 2001. The environment and vegetation of the flux measurement site near Skukuza, Kruger National Park. Koedoe 44(1), 73-83. Archibald, S. and R.J. Scholes.2007. Leaf green-up in a semi-arid African savanna – separating tree and grass responses to environmental cues. Journal of Vegetation Science 18, 583-594. Kutsch, W.L., N. Hanan, R.J. Scholes, I. McHugh, W. Kubheka, H. Eckhardt, C. Williams. 2008. Response of carbon fluxes to water relations in a savanna ecosystem in South Africa. Biogeosciences 5, 1797-1808.

Measuring carbon exchange at the Africa scale

Valentini, R., Arneth, A., Bombelli, A., Castaldi, S., Cazzolla Gatti, R., Chevallier, F., ... & Scholes, R. J. (2014). A full greenhouse gases budget of Africa: synthesis, uncertainties, and vulnerabilities. Biogeosciences, 11, 381-407. Nickless, A., Ziehn, T., Rayner, P. J., Scholes, R. J., & Engelbrecht, F. (2014). Greenhouse gas network design using backward Lagrangian particle dispersion modelling–Part 2: Sensitivity analyses and South African test case. Atmospheric Chemistry and Physics Discussions, 14(8), 11301-11342.

Southern Africa in a test-tube: the SAFARI 2000 campaign

Annegarn, H.J., L. Otter, R.J. Swap and R.J. Scholes. 2002. Southern Africa’s ecosystem in a test-tube; a perspective on the Southern African Regional Science Initiative (SAFARI 2000). South African Journal of Science 98, 111-113.

Scholes, R.J., G. M. Mace, W. Turner, G. N. Geller, N. Jürgens, A. Larigauderie, D. Muchoney, B. A. Walther and H. A. Mooney. 2008. Toward a Global Biodiversity Observing System. Science 321, 1044-1045. Fritz, S., R.J. Scholes, M.Obersteiner , J. Bouma and B. Reyers. 2008. A conceptual framework for assessment of the benefits of a Global Earth Observation System of Systems. IEEE Systems Journal, 2(3), 338-348. Scholes, R.J., P.M.S. Monteiro, C.L. Sabine and J.G. Canadel. 2009. Systematic long-term observations of the global carbon cycle. Trends in Ecology and Evolution. 24, 427-430. Verstraete, M.M., … R.J. Scholes, et al. 2010. Towards a Global Drylands Observing System: Observational Requirements and Institutional Solutions. Land Degradation & Development DOI: 10.1002/ldr.1046 (15 pp) Scholes, R.J., et al 2012. Building a global observing system for biodiversity. Current Opinion in Environmental Sustainability 2012, 4:1–8.

Taking the pulse of the planet

GEOBON

Can we usefully measure biodiversity loss? How many variables do you need?

Scholes, R.J. and R. Biggs.2005. A biodiversity intactness index. Nature 434, 45-49. Biggs, R., B. Reyers and RJ Scholes. 2006 . A biodiversity score for South Africa. South African Journal of Science, 102, 277-283. Pereira, H.M., …Scholes et al 2013. Essential Biodiversity Variables for Global Earth Observation. Science 339,277 – 278.

The Biodiversity Intactness Index and Essential Biodiversity Variables

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i j k

i j kBII

An evolving science-policy interface observing, evaluating, acting

2000

2010

1990

Ozone Assessment

IPCC 3AR Lead Author

Synthesis Author

IPCC 4AR Lead Author

IPCC 5AR Convening Lead

Synthesis author

IPCC

Millenium Assessment WG Co-chair

Land Degradation

Co chair

IPBES formed

2020

1980

GCOS

GTOS chair

IGBP -DIS

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Observation systems Assessment systems

Elephant Leader

Shale Gas Co-leader

…and in South Africa

Stability in savannas

Scholes, RJ & S. Archer. 1997. Tree-grass interactions in savannas. Annual Review of Ecology and Systematics 28, 517-44. Scholes RJ 2003 Convex relationships in ecosystems containing trees and grass. Environment and Resource Economics 26, 559-574

…more on savanna dynamics

The Walter Hypothesis is inadequate to explain savannas

Multiple stable states are ubiquitous

There are lots of ways to get a stable outcome: picking one is hard!

Equilibrium and disequilibrium models are not mutually exclusive

Sankaran, M…, R.J. Scholes, et al 2005. Determinants of woody cover in African savannas. Nature 438, 846-849. Vezzoli, R., C. De Michele, H. Pavlopoulos and R.J. Scholes. 2008. Dryland ecosystems: the coupled stochastic dynamics of soil water and vegetation and the role of rainfall seasonality. Physical Review E, 77 (5) DOI: 10.1103/PhysRevE.77.051908 De Michele., R. Vezzoli, H. Pavlopoulos, and R.J. Scholes . 2008. A minimal model of soil water –vegetation interactions forced by stochastic rainfall in water-limited ecosystems. Ecological Modelling, 212 (3-4), 397-407. Accatino, F, C. DeMichele, R.Vezzoli, D. Donzelli, R.J. Scholes. 2010. Tree–grass co-existence in savanna: Interactions of rain and fire. Journal of Theoretical Biology, 267, 235–242. DeMichele, C., F.Accatino, R.Vezzoli, and R.J.Scholes. 2011. Savanna domain in the herbivores-fire parameter space exploiting a tree–grass–soil water dynamic model. Journal of Theoretical Biology 289 74–82. Donzelli, D., C. De Michele, R.J. Scholes. 2013. Competition between trees and grasses for both soil water and mineral nitrogen in dry savannas. Journal of Theoretical Biology 332 181–190.

Stability and resilience at the global scale

Neufeldt, H.; …Scholes, R….; 2013. Beyond climate-smart agriculture: toward safe operating spaces for global food systems. Agriculture & Food Security, 2:12. Mace, G M.,…, Robert J. Scholes, et al. 2014. Approaches to defining a planetary boundary for biodiversity. Global Environmental Change 28 : 289-297.

An accidental scientist Complex nonlinear systems as a metaphor for Life

Lucky birth

Game Ranger

Biologist

Local scale

Clipboard & binoculars

Pure scientist

Researcher Worked for a scientist

Systems ecology

Inspiring lecturer

Earth System Science

IGBP GCTE

Earth Observation

Adopted by NASA

Science-policy

IPCC & MEA

Two paths diverged in a wood, and I – I took the one less travelled by

And that has made all the difference. Robert Frost

Bob.Scholes@wits.ac.za