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Ecological and Evolutionary Processes

By Roland C. de Gouvenain1 and Gopalasamy Reuben Clements

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1Department of Biology, Rhode Island College, Providence, Rhode Island, USA

2School of Marine and Tropical Biology, James Cook University, Cairns, Australia

Abstract

Because many of the natural resources we harvest are the products of ecosystems, overexploitation of

these resources can degrade the ecological and evolutionary processes that sustain these ecosystems. Loss

of species and genetic diversity from unsustainable resource extraction removes the natural variation upon

which natural selection operates to allow evolutionary change, and without which the Earth’s biota may

no longer be able to adapt to human-induced or natural environmental changes. Sustainable resource

extraction ensures not only that future human generations will enjoy these resources, but also that the

ecosystems that generate these resources will maintain the capacity to do so as Earth’s environments

change.

Keywords

Biodiversity, ecosystem, extraction, harvesting, natural selection, sustainability

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Introduction

Natural resources, whether renewable like forests or fisheries, or non-renewable like crude oil or

minerals, have provided generations of human beings with food, shelter, and spiritual or aesthetical

enjoyment. Unfortunately, these resources are being destroyed or extracted at unsustainable rates. Only

when we begin responsibly managing our resources within an ecosystem framework that considers long-

term social good will we achieve some equilibrium between extraction and conservation.

Natural resources are components of ecosystems

Biotic (living) natural resources such as forests, wildlife, fisheries, and microbes are vital components of

the different ecosystems on our planet; for instance, sphagnum moss is a component of arctic tundra

ecosystems, and grey reef sharks are components of tropical coral reef ecosystems. Abiotic (non-living)

natural resources (for instance, the atmosphere, water, and soils) influence the health of those ecosystems.

Thus ecosystems are the source of many of our natural resources (1, 2). Soils, which took thousands of

years to develop under the activity of microbes, fungi, and invertebrates, are also products and

components of ecosystems; they sustained the advent of agriculture 10,000 years ago and support today’s

agricultural productivity (1, 3). Located deep underground where no life is found today, abiotic natural

resources such as fossil fuels are nonetheless products of ancient forest or marine ecosystems now

fossilized (3).

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Ecosystems and their resources are shaped by evolutionary changes

All living natural resources such as forests, fisheries, and wildlife are not only shaped by ecosystems; they

also influence how these ecosystems function and evolve. From the beginning of life on Earth 3.5 million

years ago, ecosystems and their biotic and abiotic natural resources have been shaped by evolutionary

changes in the world’s biota (all the living organisms that inhabit the Earth). In fact, evolutionary forces

were already in motion between three and two billion years ago, when immense colonies of single-celled

cyanobacteria were slowly transforming the early atmosphere of the Earth from a reducing one (low in

oxygen gas) to an oxidizing one (high in oxygen gas) as a result of their photosynthetic activity (4). This

atmospheric transformation itself would, about two-and-a-half billion years ago, foster the evolution of

more complex organisms that relied on aerobic respiration to harvest the energy contained in their food.

These primitive eukaryotes would eventually (around 550 million years ago) evolve into animals, plants,

and fungi (4, 5). Approximately 350 million years ago, during the tropical climate of the Carboniferous

period, the Earth’s biota would similarly shape its ecosystems when newly-evolved tree-size vascular

terrestrial plants produced vast Carboniferous forests. These ancient forests were then fossilized over

millions of years into thick coal deposits that fueled the industrial revolution and still powers today’s

electricity production (3, 5). Just as an oxygen-rich atmosphere was the product of photosynthesis by

cyanobacteria colonies, and just as today’s coal deposits are the product of the Carboniferous forests,

today’s ecosystems are the product of their component organisms that have themselves evolved over

millions of years in response to abiotic and biotic sets of natural selection factors relevant to each

ecosystem.

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Natural resource overexploitation jeopardizes ecosystem health

Current natural resource management is driven by the exponential growth of the human population

(around seven billion people as of 2011) and socio-economic goals that seek to maximize resource

extraction with little attention to the perils of overexploitation (1, 6). Technological evolution has

accelerated the rate at which resources are being harvested, and this has resulted in irreversible alterations

to ecosystems, especially those that are not managed according to sustainability guidelines, such as forest

concessions that do not carry out reduced-impact logging. By increasing the amount and rate of extraction

of biotic and abiotic natural resources, human populations change (often irreversibly) the species

composition and the ecology of natural ecosystems. This in turn influences the natural selection processes

that shape these ecosystems, in addition to impacting the amount and location of natural resources

available for future generations.

From the cold-adapted microorganisms in the permafrost soils of Siberia to the salt-adapted trees

of tropical mangroves, many plant, animal, and fungi species are pushed to the limit of their ecological

tolerance as a result of the loss or transformation of their natural environment by humans. Perhaps the

most well-known example is that of polar bears faced with an ever-shrinking polar ice cap under the

influence of global climate change, but many more examples abound, including the disappearance of

migratory bird species due to loss of stop-over wetlands, the collapse of oceanic fisheries due to

overfishing, the poaching of charismatic large mammals in increasingly logged rainforests, and the

replacement of endemic dipterocarp forests with oil palm or rubber plantations in Southeast Asia (7-13).

Although some documented cases of rapid evolutionary adaptive response of plants and insects to

environmental degradation or to climate change have been documented (14, 15), most studies report

negative impacts (including species extinction) from the overharvesting of biotic resources or from the

impacts of abiotic resource extraction (11, 13, 15).

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By reducing the biodiversity (the diversity of species) of the Earth, we are not only losing plant,

animal, and fungi species that could potentially provide future generations with critical resources,

including yet undiscovered medicinal compounds; we are also losing the ecological services these

ecosystems provide us with (such as the storage of clean water in forest watersheds). Furthermore, we are

destroying the very species and ecological processes that have made these ecosystems productive and

resilient to natural or human-induced environmental changes (15, 16). Losing walleye pollock (a prey

species for predatory marine fish, birds, and mammals) because of climate change affects the other

marine species in the Bering Sea food web, and degrades the health and productivity of the oceanic

ecosystems that supports economically valuable fisheries (17).

Loss of intertidal species (for instance mangrove trees and seagrass beds) to development reduces

the ability of coastal ecosystems to filter polluted effluents or to protect shorelines from storm flooding

(13), which can hinder future evolutionary adaptation of these coastal ecosystems to climate and sea level

changes. As species diversity is lost, the raw material upon which natural selection operates is lost as

well. Worldwide, nearly 30% of currently fished species are considered collapsed (>90% decline), and

this decline occurred faster in species-poor ecosystems than in species-rich ones, suggesting that

maintaining ecosystem biodiversity is the key to future ecosystem resilience in the face of human impact

(13, 16). Monoculture plantations of cash crops, such as oil palm and rubber, are rapidly transforming

tropical forests into biological deserts (7, 18). Southeast Asia has the highest rate of tropical deforestation

losing around 1.0% of its forests per year (19), and some countries like the Philippines and Singapore

have nearly no forest cover left. Indonesia’s forest ecosystems are impacted by even higher rates of

deforestation (2.6% per year), and 2/3 of its original forests are now replaced with oil palm plantations. In

large part as a result of this rapid deforestation, more than 25% of the mammals, more than 20% of the

birds, and more than 15% of the native plants species of Southeast Asia are now extinct (11).

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Ecologically sustainable natural resource management can protect

evolutionary processes

To be ecologically sustainable, management of natural resources must protect the ecological integrity of

ecosystems, including their biodiversity, so that the evolutionary processes that generated these

ecosystems can be maintained in the future. This will increase the likelihood that these ecosystems will be

able to evolve in response to changing global conditions (16, 20), especially since it is difficult to predict

with certainty the characteristics of future terrestrial and aquatic environments (21). For example,

ensuring that habitat connectivity is maintained (through wildlife corridors for instance) can help ensure a

beneficial exchange of genetic material among populations isolated by habitat conversion (9, 22, 23).

Maintaining the health of soil ecosystems by protecting them from erosion and maintaining a diversity of

nutrient-cycling microbes can ensure that future generations will enjoy sustained agricultural productivity

(24).

Perhaps the single-most important indicator of ecosystem health is biodiversity, and the genetic

diversity it manifests is what natural selection can operate on to allow the natural processes of evolution

to keep these ecosystems healthy, resilient, and productive (16, 20). Not only can productive fisheries not

exist in species-poor oceans, or economically viable wood supplies not be maintained in unsustainably

logged landscapes, but species-poor ecosystems are also much more likely to collapse in the face of

natural or human-induced environmental change that species-rich ones (16). Terrestrial and marine

species diversity enhances ecosystem processes such as nutrient cycling and primary production, and

increases the resilience of ecosystems to disturbance, and therefore the capacity of these ecosystems to

provide services to future human generations (13). Sustainable resource extraction is not only common

sense for long-term economic benefits to humans; it is also a management practice that can give the

ecosystems of the world a chance to adapt to and persist (20). For instance, sustainably logged Malaysian

tropical forests can still support reasonable densities of tiger populations (25), and as long as forest

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structure and biodiversity are maintained, even old logging roads are travelled regularly by the big cats

(Fig. 1).

To be sustainable, natural resource management should be both ecologically responsible, that is,

it should respect the “economy of nature” as defined by the German biologist Ernst Haeckel, and socially

ethical, as suggested by the American ecologist Aldo Leopold (26). Societal decisions regarding both the

exploitation and the conservation of natural resources should be based on ecological knowledge and

research, since ecological sustainability is the key to long-term success (23, 27), and on social justice,

since extracting and conserving resources involve tradeoffs that have ecological and social costs (28-30).

This is especially urgent given the fact that most of the world’s biodiversity “hotspots” (areas with both

high biodiversity and high rates of natural habitat loss) (10) are also areas of relatively high human

population density and growth (31).

To assess these tradeoffs and make socially fair decisions regarding the extraction and

conservation of natural resources, other points of view besides the dominant market-oriented western

perspective should be solicited and appraised, including the traditional ecological knowledge of the

world’s rural cultures (32). By giving resource management more legitimacy, involving local human

communities in the decision process concerning the extraction and conservation of natural resources is

likely to yield management actions that are not only ecologically but socially sustainable as well (28). For

instance, conservation of the Tampolo coastal rainforest in Madagascar has enjoyed support from local

communities by mixing traditional covenant ceremonials, agricultural development, ecotourism, native

tree species planting, and environmental education (Fig. 2). The Tampolo Forest, although only 800 ha in

size, is home to 90 species of ants, 56 bird species, 16 species of amphibians, 31 reptiles species, and six

species of lemur (33, 34). Elsewhere in Thailand, a successful community-based conservation approach

has even resulted in the recovery of ungulate populations that were previously subjected to poaching

pressure (35). Community-based conservation approaches may involve negotiating tradeoffs and

compromises that are complex and thus require more time to achieve than the traditional “top down”

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conservation approach. However, the process itself may not only empower local communities to own and

manage their resources as caretakers; it may also enhance the educational benefit for all parties involved,

and allow stakeholders to understand the necessary commitment to long-term resource conservation for

the sake of future human generations.

Conclusion

Although unsustainable extraction of natural resources and pollution from the use of these resources has

modified nearly the entire set of ecosystems found on Earth, as long as ecological processes are not

irremediably impacted and species diversity is maintained, intrinsic properties of these ecosystems can

allow natural processes to restore the health and productivity of these impacted ecosystems (9). It

behooves us, as de-facto caretaker of the Earth’s environment, to keep its biota diverse and healthy so that

natural evolutionary processes can help us provide future generations with an ecologically and socially

livable future.

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Figure 1. Tiger on abandoned logging road, Tembat Forest Reserve, Terengganu, Peninsular Malaysia.

Photo: Rimba/Reuben Clements.

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Figure 2. Forest Reserve and local inhabitants at a native tree and vegetable nursery, Tampolo

Madagascar. Photos: Roland de Gouvenain