Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions. Species richness is sometimes considered synonymous with species diversity, but the formal metric species diversity takes into account both species richness and species evenness.
Sampling considerations
Depending on the purposes of quantifying species richness, the individuals can be selected in different ways. They can be, for example, trees found in an inventory plot, birds observed from a monitoring point, or beetles collected in a pitfall trap. Once the set of individuals has been defined, its species richness can be exactly quantified, provided the species-level taxonomy of the organisms of interest is well enough known. Applying different species delimitations will lead to different species richness values for the same set of individuals.
In practice, people are usually interested in the species
richness of areas so large that not all individuals in them can be
observed and identified to species. Then applying different sampling methods
will lead to different sets of individuals being observed for the same
area of interest, and the species richness of each set may be different.
When a new individual is added to a set, it may introduce a species
that was not yet represented in the set, and thereby increase the
species richness of the set. For this reason, sets with many individuals
can be expected to contain more species than sets with fewer
individuals.
If species richness of the obtained sample is taken to represent species richness of the underlying habitat or other larger unit, values are only comparable if sampling efforts are standardised in an appropriate way. Resampling methods can be used to bring samples of different sizes to a common footing.
Properties of the sample, especially the number of species only
represented by one or a few individuals, can be used to help estimating
the species richness in the population from which the sample was drawn.
Trends in species richness
The
observed species richness is affected not only by the number of
individuals but also by the heterogeneity of the sample. If individuals
are drawn from different environmental conditions (or different habitats),
the species richness of the resulting set can be expected to be higher
than if all individuals are drawn from similar environments. The
accumulation of new species with increasing sampling effort can be
visualised with a species accumulation curve. Such curves can be constructed in different ways.
Increasing the area sampled increases observed species richness both
because more individuals get included in the sample and because large
areas are environmentally more heterogeneous than small areas.
Many organism groups have most species in the tropics, which leads to latitudinal gradients in species richness.
There has been much discussion about the relationship between
productivity and species richness. Results have varied among studies,
such that no global consensus on either the pattern or its possible
causes has emerged.
Applications
Species richness is often used as a criterion when assessing the relative conservation values of habitats or landscapes. However, species richness is blind to the identity of the species. An area with many endemic
or rare species is generally considered to have higher conservation
value than another area where species richness is similar, but all the
species are common and widespread.
Prescribed burning is a technique used in ecosystem management. This indirectly benefits society via the maintenance of ecosystem services and the reduction of severe wildfires.
Ecosystem management is an approach to natural resource management that aims to ensure the long-term sustainability and persistence of an ecosystems function and services while meeting socioeconomic, political, and cultural needs. Although indigenous communities
have employed sustainable ecosystem management approaches for
millennia, ecosystem management emerged formally as a concept in the
1990s from a growing appreciation of the complexity of ecosystems, as
well as humans' reliance and influence on natural systems (e.g., disturbance, ecological resilience).
Building upon traditional natural resource management,
ecosystem management integrates ecological, socioeconomic, and
institutional knowledge and priorities through diverse stakeholder
participation. In contrast to command and control approaches to natural resource management, which often lead to declines in ecological resilience,
ecosystem management is a holistic, adaptive method for evaluating and
achieving resilience and sustainability. As such, implementation is
context-dependent and may take a number of forms, including adaptive management, strategic management, and landscape-scale conservation.
The term “ecosystem management” was formalized in 1992 by F. Dale Robertson, the then Chief of the U.S. Forest Service.
Robertson stated, “By ecosystem management, we mean an ecological
approach… [that] must blend the needs of people and environmental values
in such a way that the National Forests and Grasslands represent
diverse, healthy, productive and sustainable ecosystems.” A variety of additional definitions of ecosystem management exist, although definitions of this concept are typically vague. For example, Robert T. Lackey
emphasizes that ecosystem management is informed by ecological and
social factors, motivated by societal benefits, and implemented over a
specific timeframe and area. F. Stuart Chapin and co-authors highlight that ecosystem management is guided by ecological science to ensure the long-term sustainability of ecosystem services,
while Norman Christensen and coauthors underscore that it is motivated
by defined goals, employs adaptive practices, and accounts for the
complexities of ecological systems. Peter Brussard and colleagues suggest ecosystem management balances preserving ecosystem health while sustaining human needs.
As a concept of natural resource management,
ecosystem management remains both ambiguous and controversial, in part
because some of its formulations rest on contested policy and scientific
assertions.
These assertions are important to understanding much of the conflict
surrounding ecosystem management. Professional natural resource
managers, typically operating from within government
bureaucracies and professional organizations, often mask debate over
controversial assertions by depicting ecosystem management as an
evolution of past management approaches.
Principles of ecosystem management
A fundamental principle of ecosystem management is the long-term sustainability of the production of goods and services by ecosystems, as "intergenerational sustainability [is] a precondition for management, not an afterthought".
Ideally, there should be clear, publicly-stated goals with respect to
future trajectories and behaviors of the system being managed. Other
important requirements include a sound ecological understanding of the
system, including connectedness, ecological dynamics, and the context in
which the system is embedded. An understanding of the role of humans as
components of the ecosystems and the use of adaptive management is also important. While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems (e.g., agroecosystem and close to nature forestry).
Core principles and common themes of ecosystem management:
Systems thinking: Management has a holistic perspective, instead of focusing on a particular level of biological hierarchy in an ecosystem (e.g., only conserving a specific species; only preserving ecosystem functioning).
Ecological boundaries: Ecological boundaries are clearly and
formally defined, and management is place-based and may require working
across political or administrative boundaries.
Ecological integrity: Management is focused on maintaining or reintroducing native biological diversity, and on preserving natural disturbance regimes and other key processes that sustain resilience.
Data collection: Broad ecological research and data
collection is needed to inform effective management (e.g., species
diversity, habitat types, disturbance regimes, etc.).
Monitoring: The impacts of management methods are tracked, allowing for their outcomes to be evaluated and modified, if needed.
Adaptive management: Management is an iterative process in which methods are continuously reevaluated as new scientific knowledge is gained.
Interagency cooperation: As ecological boundaries often cross
administrative boundaries, management requires cooperation among a
range of agencies and private stakeholders.
Organizational change: Successful implementation of management requires shifts in the structure and operation of land management agencies.
Humans and nature: Nature and people are intrinsically linked, and humans shape, and are shaped by, ecological processes.
Values: Humans play a key role in guiding management goals,
which reflect a stage in the continuing evolution of social values and
priorities.
History
Sustainable harvest of glaucous-winged gull eggs maintains the species' population size, while preserving traditional Huna Tlingit customs.
Pre-industrialization
Sustainable ecosystem management approaches have been used by societies throughout human history. Prior to colonization, Indigenous cultures often sustainably managed their natural resources through intergenerational traditional ecological knowledge (TEK).
In TEK, cultures acquire knowledge of their environment over time and
this information is passed on to future generations through cultural
customs, including folklore, religion, and taboos. Traditional management strategies vary by region, and examples include the burning of the longleaf pine ecosystem by Native Americans in what is today the southeastern United States; the ban of seabird guano harvest during the breeding season by the Inca; the sustainable harvest practices of glaucous-winged gull eggs by the Huna Tlingit; and the Maya milpa intercropping approach, which is still used today.
Post-industrialization
In industrialized Western society, ecosystems have been managed primarily to maximize yields of a particular natural resource. This method to managing ecosystems can be seen by the U.S. Forest Service's
shift away from sustaining ecosystem health and toward maximizing
timber production to support residential development following World War
II. Further, underlying traditional natural resource management
is the view that each ecosystem has a single equilibrium and minimizing
variation around this equilibrium results in more dependable, greater
yields of natural resources. For example, this perspective informed the long-held belief in forest fire suppression in the United States, which has driven a decline in populations of fire-tolerant species as well as fuel buildup, leading to higher intensity fires.
Additionally, traditional approaches to managing natural systems tended
to be site- and species-specific, rather than considering all
components of an ecosystem collectively; employ a “command and control”
approach; and exclude stakeholders from management decisions.
The latter half of the 20th century saw a paradigm shift in how
ecosystems were viewed, with a growing appreciation for the importance
of disturbance and for the intrinsic link between natural resources and overall ecosystem health. Simultaneously, there was acknowledgement of society's resilience on ecosystem services, beyond provisioning goods, and of the inextricable role human-environment interactions play in ecosystems.
In sum, ecosystems were increasingly seen as complex systems, shaped by
non-linear processes, and thus, they could not be managed to achieve a
single, predictable outcome.
As a result of these complexities and often unforeseeable feedbacks
from management strategies, DeFries and Nagendra deem ecosystem
management to be a “wicked problem”.
Thus, the outcome of traditional natural resource management's
"evolution" over the course of the 20th century is ecosystem management,
which explicitly recognizes that technical and scientific knowledge,
though necessary in all approaches to natural resource management, are
insufficient alone.
Stakeholders
Stakeholders are individuals or groups who are affected by or have an interest in ecosystem management decisions and actions. Stakeholders may also have power to influence the goals, policies, and outcomes of management. Ecosystem management stakeholders fall into the following groups based on their diverse concerns:
Stakeholders whose lives are directly tied to the ecosystem (e.g., members of local community)
Stakeholders who are not directly not impacted, but have an interest
in the ecosystem or its ecosystem services (e.g., NGOs, recreational
groups)
Stakeholders concerned with the decision-making processes (e.g., environmental advocacy groups)
Stakeholders representing public interest (e.g., public officials)
Strategies to stakeholder participation
The
complexity of ecosystem management decisions, ranging from local to
international scales, requires the participation of stakeholders with
diverse understandings, perceptions, and values of ecosystems and ecosystem services.
Due to these complexities, effective ecosystem management is flexible
and develops reciprocal trust around issues of common interest, with the
objective of creating mutually beneficial partnerships. Key attributes of successful participatory ecosystem management efforts have been identified:
Stakeholder involvement is inclusive, equitable, and focused on trust-building and empowerment.
Stakeholders are engaged early on, and their involvement continues beyond decision and into management.
Stakeholder analysis
is performed to ensure parties are appropriately represented. This
involves determining the stakeholders involved in the management issue;
categorizing stakeholders based on their interest in and influence on
the issue; and evaluating relationships between stakeholders.
Stakeholders agree upon the aims of the participatory process from
its beginning, and the means and extent of stakeholder participation are
case-specific.
Stakeholder participation is conducted through skilled facilitation.
Social, economic, and ecological goals are equally weighed, and
stakeholders are actively involved in decision making, which is arrived
at by collective consensus.
Multidisciplinary data are collected, reflecting multidisciplinary
priorities, and decisions are informed by both local and scientific
knowledge.
Economic incentives are provided to parties responsible for implementing management plans.
To ensure long-term stakeholder involvement, participation is institutionalized.
Ecosystem management decisions for the Malpai Borderlands were determined through active participation of diverse stakeholder groups.
Examples of stakeholder participation
Malpai Borderland management:
In the early 1990s, there was ongoing conflict between the ranching and environmentalist communities in the Malpai Borderlands.
The former group was concerned about sustaining their livelihoods,
while the latter was concerned about the environmental impacts of
livestock grazing.
The groups found common ground around conserving and restoring
rangeland, and diverse stakeholders, including ranchers, environmental
groups, scientists, and government agencies, were engaged in management
discussions. In 1994, the rancher-led Malpai Borderlands Group was
created to collaboratively pursue the goals of ecosystem protection,
management, and restoration.
Helge å River & Kristianstads Vattenrike Biosphere Reserve:
In the 1980s, local government agencies and environmental groups noted declines in the health of the Helge å River ecosystem, including eutrophication, bird population declines, and deterioration of flooded meadows areas. There was concern that the Helge å, a Ramsar Wetland of International Importance,
faced an imminent tipping point. In 1989, led by a municipal
organization, a collaborative management strategy was adopted, involving
diverse stakeholders concerned with the ecological, social, and
economic facets of the ecosystem. The Kristianstads Vattenrike Biosphere Reserve was established in 2005 to promote the preservation of the ecosystem's socio-ecological services.
Strategies to ecosystem management
Several
strategies to implementing the maintenance and restoration of natural
and human-modified ecosystem exist. Command and control management and
traditional natural resource management are the precursors to ecosystem management. Adaptive management,
strategic management, and landscape-level conservation are different
methodologies and processes involved in implementing ecosystem
management:
Command and control management
utilizes a linear problem solving approach, in which a perceived
problem is resolved through controlling devices such as laws, threats,
contracts, and/or agreements.
This top-down approach is used across many disciplines, and it is best
suited for addressing relatively simple, well-defined problems, which
have a clear cause and effect, and for which there is broad societal
agreement as to policy and management goals. In the context of natural systems, command and control management attempts to control nature in order to improve natural resource extractions, establish predictability, and reduce threats. Command and control strategies include the use of herbicides and pesticides to improve crop yields; the culling of predators to protect game bird species; and the safeguarding of timber supply, by suppressing forest fires.
However, due to the complexities of ecological systems, command and control management may result in unintended consequences. For example, wolves were extirpated from Yellowstone National Park
in the mid-1920s to reduce elk predation. Long-term studies of wolf,
elk, and tree populations since wolf reintroduction in 1995 demonstrate
that reintroduction has decreased elk populations, improving tree
species recruitment.
Thus, by controlling ecosystems to limit natural variation and increase
predictability, command and control management often leads to a decline
the resilience of ecological, social, and economic systems, termed the
“pathology of natural resource management”. In this “pathology”, an initially successful command and control practice drives relevant institutions to shift their focus toward control, over time obscuring the ecosystem’s natural behavior, while the economy becomes reliant on the system in its controlled state.
Consequently, there has been a transition away from command and control
management, and increased focus on more holistic adaptive management
approaches and on arriving at management solutions through partnerships
between stakeholders.
Natural resource management
Shelterwood cutting allows for timber extraction, while maintaining ecosystem structure and allowing forest regeneration.
The term natural resource management is frequently used in relation to a particular resource for human use, rather than the management of a whole ecosystem.
Natural resource management aims to fulfill the societal demand for a
given resource without causing harm to the ecosystem, or jeopardizing
the future of the resource. Due to its focus on natural resources, socioeconomic factors significantly affect this management approach.
Natural resource managers initially measure the overall condition of an
ecosystem, and if the ecosystem's resources are healthy, the ideal
degree of resource extraction is determined, which leaves enough to
allow the resource to replenish itself for subsequent harvests.
The condition of each resource in an ecosystem is subject to change at
different spatial and time scales, and ecosystem attributes, such as watershed and soil health, and species diversity and abundance, need to be considered individually and collectively.
Informed by natural resource management, the ecosystem management
concept is based on the relationship between sustainable ecosystem
maintenance and human demand for natural resources and other ecosystem services.
To achieve these goals, ecosystem managers can be appointed to balance
natural resource extraction and conservation over a long-term timeframe.
Partnerships between ecosystem managers, natural resource managers, and
stakeholders should be encouraged in order to promote the sustainable
use of limited natural resources.
Historically, some ecosystems have experienced limited resource
extraction and have been able to subsist naturally. Other ecosystems,
such as forests, which in many regions provide considerable timber resources, have undergone successful reforestation
and consequently, have accommodated the needs of future generations. As
human populations grow, introducing new stressors to ecosystems, such
as climate change, invasive species, land-use change, and habitat fragmentation, future demand for natural resources is unpredictable.
Although ecosystem changes may occur gradually, their cumulative
impacts can have negative effects for both humans and wildlife. Geographic information system (GIS) applications and remote sensing can be used to monitor and evaluate natural resources and ecosystem health.
Adaptive management
Adaptive management is based on the concept that predicting future influences and disturbances to an ecosystem is limited and unclear. Therefore, an ecosystem should be managed to it maintain the greatest degree of ecological integrity and management practices should have the ability to change based on new experience and insights.
In an adaptive management strategy, a hypotheses about an ecosystem and
its functioning is formed, and then management techniques to test these
hypotheses are implemented. The implemented methods are then analyzed to evaluate if ecosystem health improved or declined, and further analysis allows for the modification of methods until they successfully meet the needs of the ecosystem. Thus, adaptive management is an iterative approach, encouraging “informed trial-and-error”.
This management approach has had mixed success in the field of ecosystem management, fisheries management, wildlife management, and forest management,
possibly because ecosystem managers may not be equipped with the
decision-making skills needed to undertake an adaptive management
methodology. Additionally, economic, social, and political priorities can interfere with adaptive management decisions.
For this reason, for adaptive management to be successful it must be a
social and scientific process, focusing on institutional strategies
while implementing experimental management techniques.
Strategic management
As it relates to ecosystem management, strategic management
encourages the establishment of goals that will sustain an ecosystem
while keeping socioeconomic and politically relevant policy drivers in
mind.
This approach differs from other types of ecosystem management because
it emphasizes stakeholders involvement, relying on their input to
develop the best management strategy for an ecosystem. Similar to other
methods of ecosystem management, strategic management prioritizes
evaluating and reviewing any impacts of management intervention on an
ecosystem, and flexibility in adapting management protocols as a result
of new information.
Landscape-level (or landscape-scale) conservation is a method that considers wildlife needs at a broader landscape scale when implementing conservation initiatives.
By considering broad-scale, interconnected ecological systems,
landscape-level conservation acknowledges the full scope of an
environmental problem. Implementation of landscape-scale conservation is carried out in a number of ways. A wildlife corridor, for example, provides a connection between otherwise isolated habitat patches, presenting a solution to habitat fragmentation. In other instances, the habitat requirements of a keystone or vulnerable species is assessed to identify the best strategies for protecting the ecosystem and the species.
However, simultaneously addressing the habitat requirements of multiple
species in an ecosystem can be difficult, and as a result, more
comprehensive approaches have been considered in landscape-level
conservation.
In human-dominated landscapes, weighing the habitat requirements
of wild flora and fauna versus the needs of humans presents challenges. Globally, human-induced environmental degradation is an increasing problem, which is why landscape-level approaches play an important role in ecosystem management. Traditional conservation
methods targeted at individual species may need to be modified to
include the maintenance of habitats through the consideration of both
human and ecological factors.
In ecology, overexploitation describes one of the five main activities threatening global biodiversity.
Ecologists use the term to describe populations that are harvested at
an unsustainable rate, given their natural rates of mortality and
capacities for reproduction. This can result in extinction at the
population level and even extinction of whole species. In conservation biology,
the term is usually used in the context of human economic activity that
involves the taking of biological resources, or organisms, in larger
numbers than their populations can withstand. The term is also used and defined somewhat differently in fisheries, hydrology and natural resource management.
Overexploitation can lead to resource destruction, including extinctions. However, it is also possible for overexploitation to be sustainable, as discussed below in the section on fisheries. In the context of fishing, the term overfishing can be used instead of overexploitation, as can overgrazing in stock management, overlogging in forest management, overdrafting in aquifer management, and endangered species
in species monitoring. Overexploitation is not an activity limited to
humans. Introduced predators and herbivores, for example, can
overexploit native flora and fauna.
History
When the giant flightless birds called moa were overexploited to the point of extinction, the giant Haast's eagle that preyed on them also became extinct.
Concern about overexploitation is relatively recent, though
overexploitation itself is not a new phenomenon. It has been observed
for millennia. For example, ceremonial cloaks worn by the Hawaiian kings
were made from the mamo bird; a single cloak used the feathers of 70,000 birds of this now-extinct species. The dodo, a flightless bird from Mauritius,
is another well-known example of overexploitation. As with many island
species, it was naive about certain predators, allowing humans to
approach and kill it with ease.
From the earliest of times, hunting
has been an important human activity as a means of survival. There is a
whole history of overexploitation in the form of overhunting. The overkill hypothesis (Quaternary extinction events) explains why the megafaunal extinctions occurred within a relatively short period. This can be traced to human migration.
The most convincing evidence of this theory is that 80% of the North
American large mammal species disappeared within 1000 years of the
arrival of humans on the western hemisphere continents. The fastest ever recorded extinction of megafauna occurred in New Zealand, where by 1500 AD, just 200 years after settling the islands, ten species of the giant moa birds were hunted to extinction by the Māori. A second wave of extinctions occurred later with European settlement.
Overexploitation does not necessarily lead to the destruction of the resource, nor is it necessarily unsustainable. However, depleting the numbers or amount of the resource can change its quality. For example, footstool palm
is a wild palm tree found in Southeast Asia. Its leaves are used for
thatching and food wrapping, and overharvesting has resulted in its leaf
size becoming smaller.
In 1968, the journal Science published an article by Garrett Hardin entitled "The Tragedy of the Commons". It was based on a parable that William Forster Lloyd
published in 1833 to explain how individuals innocently acting in their
own self interest can overexploit, and destroy, a resource that they
all share. Lloyd described a simplified hypothetical situation based on medieval land tenure in Europe. Herders share common land on which they are each entitled to graze
their cows. In Hardin's article, it is in each herder's individual
interest to graze each new cow that the herder acquires on the common
land, even if the carrying capacity
of the common is exceeded, which damages the common for all the
herders. The self-interested herder receives all of the benefits of
having the additional cow, while all the herders share the damage to the
common. However, all herders reach the same rational decision to buy
additional cows and graze them on the common, which eventually destroys
the common. Hardin concludes:
Therein is the tragedy. Each man is locked into a system that compels
him to increase his herd without limit—in a world that is limited. Ruin
is the destination toward which all men rush, each pursuing his own
interest in a society that believes in the freedom of the commons.
Freedom in a commons brings ruin to all.
In the course of his essay, Hardin develops the theme, drawing in many examples of latter day commons, such as national parks, the atmosphere, oceans, rivers and fish stocks. The example of fish stocks had led some to call this the "tragedy of the fishers". A major theme running through the essay is the growth of human populations, with the Earth's finite resources being the general common.
The tragedy of the commons has intellectual roots tracing back to Aristotle, who noted that "what is common to the greatest number has the least care bestowed upon it", as well as to Hobbes and his Leviathan. The opposite situation to a tragedy of the commons is sometimes referred to as a tragedy of the anticommons: a situation in which rational individuals, acting separately, collectively waste a given resource by underutilizing it.
The tragedy of the commons can be avoided if it is appropriately
regulated. Hardin's use of "commons" has frequently been misunderstood,
leading Hardin to later remark that he should have titled his work "The
tragedy of the unregulated commons".
Fisheries
The Atlantic bluefin tuna
is currently overexploited. Scientists say 7,500 tons annually is the
sustainable limit, yet the fishing industry continue to harvest 60,000
tons.
In wild fisheries, overexploitation or overfishing occurs when a fish stock has been fished down "below the size that, on average, would support the long-term maximum sustainable yield of the fishery". However, overexploitation can be sustainable.
When a fishery starts harvesting fish from a previously unexploited stock, the biomass
of the fish stock will decrease, since harvesting means fish are being
removed. For sustainability, the rate at which the fish replenish
biomass through reproduction must balance the rate at which the fish are
being harvested. If the harvest rate is increased, then the stock
biomass will further decrease. At a certain point, the maximum harvest
yield that can be sustained will be reached, and further attempts to
increase the harvest rate will result in the collapse of the fishery.
This point is called the maximum sustainable yield,
and in practice, usually occurs when the fishery has been fished down
to about 30% of the biomass it had before harvesting started.
It is possible to fish the stock down further to, say, 15% of the
pre-harvest biomass, and then adjust the harvest rate so the biomass
remains at that level. In this case, the fishery is sustainable, but is
now overexploited, because the stock has been run down to the point
where the sustainable yield is less than it could be.
Fish stocks are said to "collapse" if their biomass declines by more than 95 percent of their maximum historical biomass. Atlantic cod stocks were severely overexploited in the 1970s and 1980s, leading to their abrupt collapse in 1992. Even though fishing has ceased, the cod stocks have failed to recover. The absence of cod as the apex predator in many areas has led to trophic cascades.
About 25% of world fisheries are now overexploited to the point
where their current biomass is less than the level that maximizes their
sustainable yield.
These depleted fisheries can often recover if fishing pressure is
reduced until the stock biomass returns to the optimal biomass. At this
point, harvesting can be resumed near the maximum sustainable yield.
The tragedy of the commons can be avoided within the context of fisheries if fishing effort and practices are regulated appropriately by fisheries management. One effective approach may be assigning some measure of ownership in the form of individual transferable quotas
(ITQs) to fishermen. In 2008, a large scale study of fisheries that
used ITQs, and ones that did not, provided strong evidence that ITQs
help prevent collapses and restore fisheries that appear to be in
decline.
Water resources, such as lakes and aquifers, are usually renewable resources which naturally recharge (the term fossil water is sometimes used to describe aquifers which do not recharge). Overexploitation occurs if a water resource, such as the Ogallala Aquifer,
is mined or extracted at a rate that exceeds the recharge rate, that
is, at a rate that exceeds the practical sustained yield. Recharge
usually comes from area streams, rivers and lakes. An aquifer which has
been overexploited is said to be overdrafted or depleted. Forests enhance the recharge of aquifers in some locales, although generally forests are a major source of aquifer depletion. Depleted aquifers can become polluted with contaminants such as nitrates, or permanently damaged through subsidence or through saline intrusion from the ocean.
This turns much of the world's underground water and lakes into finite resources with peak usage debates similar to oil.
These debates usually centre around agriculture and suburban water
usage but generation of electricity from nuclear energy or coal and tar
sands mining is also water resource intensive. A modified Hubbert curve applies to any resource that can be harvested faster than it can be replaced. Though Hubbert's original analysis did not apply to renewable resources, their overexploitation can result in a Hubbert-like peak. This has led to the concept of peak water.
Forest resources
Clear cutting of old growth forests in Canada.
Forests are overexploited when they are logged at a rate faster than reforestation
takes place. Reforestation competes with other land uses such as food
production, livestock grazing, and living space for further economic
growth. Historically utilization of forest products, including timber
and fuel wood, have played a key role in human societies, comparable to
the roles of water and cultivable land. Today, developed countries
continue to utilize timber for building houses, and wood pulp for paper. In developing countries almost three billion people rely on wood for heating and cooking. Short-term economic gains made by conversion of forest
to agriculture, or overexploitation of wood products, typically leads
to loss of long-term income and long term biological productivity. West Africa, Madagascar, Southeast Asia and many other regions have experienced lower revenue because of overexploitation and the consequent declining timber harvests.
One of the key health issues associated with biodiversity is drug discovery and the availability of medicinal resources. A significant proportion of drugs are natural products derived, directly or indirectly, from biological sources. Marine ecosystems are of particular interest in this regard. However, unregulated and inappropriate bioprospecting could potentially lead to overexploitation, ecosystem degradation and loss of biodiversity.
Endangered species
It is not just humans that overexploit resources. Overgrazing
can be caused by native fauna, as shown in the upper right. However,
past human overexploitation (leading to elimination of some predators)
may be behind the situation.
Overexploitation threatens one-third of endangered vertebrates, as well as other groups. Excluding edible fish, the illegal trade in wildlife is valued at $10 billion per year. Industries responsible for this include the trade in bushmeat, the trade in Chinese medicine, and the fur trade. The Convention for International Trade in Endangered Species of Wild Fauna and Flora, or CITES
was set up in order to control and regulate the trade in endangered
animals. It currently protects, to a varying degree, some 33,000 species
of animals and plants. It is estimated that a quarter of the endangered
vertebrates in the United States of America and half of the endangered
mammals is attributed to overexploitation.
All living organisms require resources to survive.
Overexploitation of these resources for protracted periods can deplete
natural stocks to the point where they are unable to recover within a
short time frame. Humans have always harvested food and other resources
they have needed to survive. Human populations, historically, were
small, and methods of collection limited to small quantities. With an
exponential increase in human population, expanding markets and
increasing demand, combined with improved access and techniques for
capture, are causing the exploitation of many species beyond sustainable levels.
In practical terms, if continued, it reduces valuable resources to
such low levels that their exploitation is no longer sustainable and can
lead to the extinction of a species, in addition to having dramatic, unforeseen effects, on the ecosystem. Overexploitation often occurs rapidly as markets open, utilising previously untapped resources, or locally used species.
Today, overexploitation and misuse of natural resources is an ever-present threat for species richness. This is more prevalent when looking at island ecology and the species that inhabit them, as islands can be viewed as the world in miniature. Island endemic populations are more prone to extinction from overexploitation, as they often exist at low densities with reduced reproductive rates. A good example of this are island snails, such as the Hawaiian Achatinella and the French Polynesian Partula. Achatinelline snails have 15 species listed as extinct and 24 critically endangered while 60 species of partulidae are considered extinct with 14 listed as critically endangered. The WCMC have attributed over-collecting and very low lifetime fecundity for the extreme vulnerability exhibited among these species.
As another example, when the humble hedgehog was introduced to the Scottish island of Uist,
the population greatly expanded and took to consuming and
overexploiting shorebird eggs, with drastic consequences for their
breeding success. Twelve species of avifauna are affected, with some species numbers being reduced by 39%.
Where there is substantial human migration, civil unrest, or war,
controls may no longer exist. With civil unrest, for example in the Congo and Rwanda,
firearms have become common and the breakdown of food distribution
networks in such countries leaves the resources of the natural
environment vulnerable. Animals are even killed as target practice, or simply to spite the government. Populations of large primates, such as gorillas and chimpanzees, ungulates and other mammals, may be reduced by 80% or more by hunting, and certain species may be eliminated altogether. This decline has been called the bushmeat crisis.
Overall, 50 bird species that have become extinct since 1500
(approximately 40% of the total) have been subject to overexploitation, including:
Great Auk – the penguin-like bird of the north, was hunted for its feathers, meat, fat and oil.
Carolina parakeet – The only parrot species native to the eastern United States, was hunted for crop protection and its feathers.
Other species affected by overexploitation include:
Overexploitation of species can result in knock-on or cascade effects. This can particularly apply if, through overexploitation, a habitat loses its apex predator. Because of the loss of the top predator, a dramatic increase in their prey
species can occur. In turn, the unchecked prey can then overexploit
their own food resources until population numbers dwindle, possibly to
the point of extinction.
A classic example of cascade effects occurred with sea otters.
Starting before the 17th century and not phased out until 1911, sea
otters were hunted aggressively for their exceptionally warm and
valuable pelts, which could fetch up to $2500 US. This caused cascade
effects through the kelp forest ecosystems along the Pacific Coast of North America.
One of the sea otters’ primary food sources is the sea urchin. When hunters caused sea otter populations to decline, an ecological release of sea urchin populations occurred. The sea urchins then overexploited their main food source, kelp,
creating urchin barrens, areas of seabed denuded of kelp, but carpeted
with urchins. No longer having food to eat, the sea urchin became locally extinct
as well. Also, since kelp forest ecosystems are homes to many other
species, the loss of the kelp caused other cascade effects of secondary
extinctions.
In 1911, when only one small group of 32 sea otters survived in a
remote cove, an international treaty was signed to prevent further
exploitation of the sea otters. Under heavy protection, the otters
multiplied and repopulated the depleted areas, which slowly recovered.
More recently, with declining numbers of fish stocks, again due to
overexploitation, killer whales have experienced a food shortage and have been observed feeding on sea otters, again reducing their numbers.
The myth of superabundance is the belief that earth has more than sufficient natural resources
to satisfy humanity's needs, and that no matter how much of these
resources humanity uses, the planet will continuously replenish the
supply. Although the idea had existed previously among conservationists in the 19th century, it was not given a name until Stewart Udall's 1964 book The Quiet Crisis.
Udall describes the myth as the belief that there was "so much land, so much water, so much timber, so many birds and beasts"
that man did not envision a time where the planet would not replenish
what had been sowed. The myth of superabundance began to circulate
during Thomas Jefferson's
presidency at the beginning of the nineteenth century and persuaded
many Americans to exploit natural resources as they pleased with no
thought of long-term consequences. According to historian of the North American west George Colpitts, "No theme became as integral to western promotion as natural abundance." Especially with respect to the west after 1890, promotional literature
encouraged migration by invoking the idea that God had provided an
abundant environment there such that no man or family would fail if they
sought to farm or otherwise live off the land out west. Since at that time environmental science and the study of ecology barely allowed for the possibility of animal extinction
and did not provide tools for measuring biomass or the limits of
natural resources, many speculators, settlers, and other parties
participated in unsustainable practices that led to various extinctions,
the Dust Bowl phenomenon, and other environmental catastrophes.
Early manifestations
In 1784, John Filson wrote The Discovery, Settlement And present State of Kentucke, which included the chapter "The Adventures of Colonel Daniel Boon".
This work represents one of the earliest instance of the myth of
superabundance, acting as something of a promotional ad enticing
settlers to Kentucky based on the abundance of resources to be found
there.
Warning signs
Udall describes many large-scale impacts on natural resources, terming them "The Big Raid on resources". The first was the need for lumber in a growing nation for fuel, housing and paper.
Udall states that it was with this first big raid on the earth's
natural resources that the myth of superabundance began to show its
fallacy. It was only towards the end of the nineteenth century that
people were awakened to the empty hillsides and the vastness of
blackened woods from the lumber industry. Petroleum
followed, as it was widely believed that oil was constantly made inside
the earth, and so, like everything else, was inexhaustible. Then came seal hunting, and by 1866 the seal population that originally numbered approximately five million was drastically cut in half. Many of the seals were shot in the water and never recovered, allowing for enormous waste. The Fur Seal Treaty
which came about in 1911 saved the seals from becoming the first major
marine species to become extinct thanks to the myth of superabundance.
The passenger pigeon
was the largest wildlife species known to humanity in the early
nineteenth century, when the bird's population was estimated at about
five billion. By the early 20th century, due to overhunting
and habitat destruction brought about by the timber industry, the
species had become extinct, the last passenger pigeon having died in the
Cincinnati Zoo. The passenger pigeon became extinct in under a century and was just one of the many victims of the myth of superabundance.
Likewise, the American buffalo
was threatened by the myth of superabundance. They were considered to
be the largest and most valuable resource because just about every piece
of them was usable. The big kill of the buffalo began at the end of the
Civil War when armies wanted the animals killed in order to starve out the Plains Indians.
Railroad men wanted them killed in order to supply heavier and
profitable loads of hides. Buffalo were killed for their tongues and
hides, and some hunters simply wanted them as trophies. Pleas of
protection for the buffalo were ignored, nearly wiping out the species.
The Great Leap Forward in China in 1958 corresponded closely with the myth of superabundance;
economic planners reduced the acreage space for planting wheat and
grains, trying to force farmers and agricultural labourers into
accepting new forms of industry. As a result, production of wheat and grain was slowed dangerously, and floods in the South and droughts in the North struck in 1959, leading China into the record-breaking Great Chinese Famine.
The myth exposed
George Perkins Marsh, who wrote Man and Nature
in 1864, rejected the idea that any resource could be exploited without
any concerns for the future. Perkins was a witness to natural
destruction; he saw that mistakes of the past were destroying the
present prosperity. He believed that nature should be second nature to
all and should not be used as an exploitation for economics and
politics. He was, after all, "forest born".
Man's role as a catalyst of change in the natural world intrigued him.
He believed that progress was entirely possible and necessary, if only
men used wisdom in the management of resources. He deflated, but did not
destroy the myth of superabundance. He began the spin into doubt, which made way for John Muir
in 1874. Muir, who had grown up surrounded by wilderness, believed that
wildlife and nature could provide people with heightened sense
abilities and experiences of awe that could be found nowhere else.
Entering into civilization with a desire to see preservation of some of
what he believed to be America's most beautiful nature, he built upon
steps that had been taken by Frederick Law Olmsted, a young landscape architect who designed Central Park in New York City. Olmsted had persuaded Congress to pass a bill preserving much of Yosemite Valley, which President Lincoln had then approved in 1864. In 1872 President Grant signed the Yellowstone Park bill, saving over two million acres of wildlife.
Early successes
Muir saw overgrazing destruction in Yosemite, in parts of it that were not under protection. It was a result of nearby sheepmen and their herds.
In 1876, Muir wrote an article "God’s First Temples – How Shall We
Preserve Our Forests", which he published in the newspaper, pleading for
help with protection of the forests. At first he failed against the
overriding ideal of the myth of superabundance, but he did inspire bills
in the 1880s that sought to enlarge Yosemite's reservation. Muir formed
the Sierra Club,
a group of mountaineers and conservationists like him who had responded
to his many articles. The Sierra Club's first big fight came as a
counter-attack on lumbermen and stockmen
who wanted to monopolize some of Yosemite County. Yosemite Valley,
which was still owned by the state, was mismanaged and natural reserves
like the meadows and Mirror Lake, which was dammed for irrigation, were
still being destroyed even under supposed protection. In 1895, Muir and
the Sierra Club began a battle that would span over ten years, fighting
for natural management of Yosemite Valley. Theodore Roosevelt
met with Muir in 1903 and was instantly fascinated with Muir's passion
for the wilderness. Roosevelt approved Muir's argument for Yosemite
Valley, and so the Sierra Club took their decade long campaign to
Sacramento, where they finally won against California legislature in
1905. With Roosevelt on Muir's side, Yosemite Valley finally became part
of the Yosemite National Park and was allowed natural management.
Moving backwards
Udall asserts that the myth of superabundance, once exposed, was replaced in the 20th century by the myth of scientific supremacy: the belief that science can eventually find a solution to any problem. This leads to behaviors which, while recognizing that resources are
not infinite, still fail to properly preserve those resources, putting
the problem off to future generations to solve through science. "Present the repair bill to the next generation" is their silent motto. George Perkins Marsh had said that conservation's greatest enemies were "greed and shortsightedness". Men reach a power trip thinking they can manipulate nature the way that they want.
Next steps
In
order for man to live harmoniously with nature, as Muir and Perkins and
many others have fought for, Patsy Hallen in the article, "The Art of
Impurity" says that an ethics development must occur in which respect
for nature and our radical dependency on it can take place. Humans see
themselves as superior to nature, and yet we are in a constant state of
continuity with it. Hallen argues that humanity cannot afford such an
irrational state of mind and ecological denial if it expects to prosper
in the future.
.jpg)
.jpg)
_01.jpg)
.jpg)
