ecological and evolutionary processes
TRANSCRIPT
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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