Encyclopedia
Biodiversity or
biological diversity is the diversity of life. There are a number of definitions and measures of biodiversity.
Etymology
Biodiversity is a neologism and a portmanteau word, from
bio and diversity.
The term
biological diversity was coined by Thomas Lovejoy in 1980, while the word
biodiversity itself was coined by W.G. Rosen in 1985 while planning the
National Forum on Biological Diversity organized by the National Research Council which was to be held in 1986, and first appeared in a publication in 1988 when entomologist
E. O. Wilson used it as the title of the proceedings of that forum. The word
biodiversity was deemed more effective in terms of communication than
biological diversity.
Since 1986 the terms and the concept have achieved widespread use among biologists, environmentalists, political leaders, and concerned citizens worldwide. It is generally used to equate to a concern for the natural environment and nature conservation. This use has coincided with the expansion of concern over
extinction observed in the last decades of the
20th century.
Definitions
Biodiversity has no single standard definition. The most straightforward definition is "variation of life at all levels of biological organization".
A second definition holds that biodiversity is a measure of the relative diversity among organisms present in different ecosystems. "Diversity" in this definition includes diversity within a species and among species, and comparative diversity among ecosystems.
A third definition that is often used by ecologists is the "totality of genes, species, and ecosystems of a region". An advantage of this definition is that it seems to describe most circumstances and present a unified view of the traditional three levels at which biodiversity has been identified:
- genetic diversity - diversity of genes within a species. There is a genetic variability among the populations and the individuals of the same species.
- species diversity - diversity among species in an ecosystem. "Biodiversity hotspots" are excellent examples of species diversity.
- ecosystem diversity - diversity at a higher level of organization, the ecosystem. To do with the variety of ecosystems on Earth.
This third definition, which conforms to the traditional five organization layers in biology, provides additional justification for multilevel approaches.
The 1992
United Nations Earth Summit in
Rio de Janeiro defined "biodiversity" as "the variability among living organisms from all sources, including, 'inter alia', terrestrial, marine, and other aquatic ecosystems, and the ecological complexes of which they are part: this includes diversity within species, between species and of ecosystems".
This is, in fact, the closest thing to a single legally accepted definition of biodiversity, since it is the definition adopted by the United Nations Convention on Biological Diversity. The parties to this convention include all the countries on
Earth, with the exception of
Andorra,
Brunei Darussalam, the
Holy See,
Iraq,
Somalia,
Timor-Leste, and the
United States of America.
If the gene is the fundamental unit of
natural selection, according to E. O. Wilson, the real biodiversity is the genetic diversity. For geneticists,
biodiversity is the diversity of genes and
organisms. They study processes such as mutations, gene exchanges, and genome dynamics that occur at the DNA level and generate evolution.
For biologists, biodiversity is the gamut of organisms and species and their interactions. Organisms appear and become extinct; sites are colonized and some species develop social organizations to improve their varied strategies of
reproduction.
For
ecologists, biodiversity is also the diversity of durable interactions among species. It not only applies to species, but also to their immediate environment and their larger ecoregion. In each ecosystem, living organisms are part of a whole, interacting with not only other organisms, but also with the air, water, and soil that surround them.
Measurement of biodiversity
Biodiversity is a broad concept, so a variety of objective measures have been created in order to empirically measure biodiversity. Each measure of biodiversity relates to a particular use of the data.
For practical conservationists, this measure should quantify a value that is broadly shared among locally affected people.
For others, a more economically defensible definition should allow the ensuring of continued possibilities for both adaptation and future use by people, assuring environmental sustainability.
As a consequence, biologists argue that this measure is likely to be associated with the variety of genes. Since it cannot always be said which genes are more likely to prove beneficial, the best choice for
conservation is to assure the persistence of as many genes as possible. For ecologists, this latter approach is sometimes considered too restrictive, as it prohibits
ecological succession.
Biodiversity is usually plotted as taxonomic richness of a geographic area, with some reference to a temporal scale. Whittaker described three common metrics used to measure species-level biodiversity, encompassing attention to species richness or species evenness:
- Species richness - the most primitive of the indices available.
- Simpson index
- Shannon index
There are three other indices which are used by ecologists:
- Alpha diversity refers to diversity within a particular area, community or ecosystem, and is measured by counting the number of taxa within the ecosystem
- Beta diversity is species diversity between ecosystems; this involves comparing the number of taxa that are unique to each of the ecosystems.
- Gamma diversity is a measure of the overall diversity for different ecosystems within a region.
Distribution of biodiversity
Biodiversity is not distributed evenly on Earth. It is consistently richer in the
tropics. As one approaches polar regions one finds fewer species. Flora and fauna vary depending on
climate, altitude,
soils and the presence of other species. For a listing of distinct ecoregions. In the year 2006 large numbers of the Earth's species are formally classified as rare or
endangered or threatened species; moreover, most scientists estimate that there are millions more species actually endangered which simply have not been formally recognized.
A biodiversity hotspot is a region with a high level of endemic species. These biodiversity hotspots were first identified by Dr. Norman Myers in two articles in the scientific journal
The Environmentalist . Hotspots unfortunately tend to occur near areas of
dense human habitation, leading to threats to their many endemic species. As a result of the pressures of the rapidly growing human population, human activity in many of these areas is increasing dramatically. Most of these hotspots are located in the
tropics and most of them are forests.
For example,
Brazil's Atlantic Forest contains roughly 20,000 plant species, 1350 vertebrates, and millions of insects, about half of which occur nowhere else in the world. The
Madagascar dry deciduous forests and lowland rainforests possess a very high ratio of species endemism and biodiversity, arising from the fact that this island separated from mainland
Africa 65 million years ago.
Biodiversity and evolution
Biodiversity found on
Earth today is the result of 4 billion years of
evolution. The
origin of life is not well known to science, though limited evidence suggests that life may already have been well-established only a few 100 million years after the formation of the Earth. Until approximately 600 million years ago, all life consisted of
bacteria and similar single-celled organisms.
The history of biodiversity during the
Phanerozoic , starts with rapid growth during the
Cambrian explosion—a period during which nearly every phylum of multicellular organisms first appeared. Over the next 400 million years or so, global diversity showed little overall trend, but was marked by periodic, massive losses of diversity classified as
mass extinction events.
The apparent biodiversity shown in the
fossil record suggests that the last few million years include the period of greatest biodiversity in the
Earth's history. However, not all scientists support this view, since there is considerable uncertainty as to how strongly the fossil record is biased by the greater availability and preservation of recent
geologic sections. Some argue that corrected for sampling artifacts, modern biodiversity is not much different from biodiversity 300 million years ago. Estimates of the present global macroscopic species diversity vary from 2 million to 100 million species, with a best estimate of somewhere near 10 million.
Most biologists agree however that the period since the emergence of humans is part of a new mass extinction, the Holocene extinction event, caused primarily by the impact humans are having on the environment. At present, the number of species estimated to have gone extinct as a result of human action is still far smaller than are observed during the major mass extinctions of the
geological past. However, it has been argued that the present rate of extinction is sufficient to create a major mass extinction in less than 100 years. Others dispute this and suggest that the present rate of extinctions could be sustained for many thousands of years before the loss of biodiversity matches the more than 20% losses seen in past global extinction events.
New species are regularly discovered and many, though discovered, are not yet classified . Most of the terrestrial diversity is found in
tropical forests.
Benefits of biodiversity
Biodiversity has contributed in many ways to the development of human culture, and, in turn, human communities have played a major role in shaping the diversity of nature at the genetic, species, and ecological levels.
Biodiversity is what underlies many important ecological goods and services that provide benefits to humans.
There are three main reasons commonly cited in the literature for the benefits of biodiversity.
Ecological role of biodiversity
All species provide at least one function in an ecosystem. Each function is an integral part of regulating the species balance, species diversity and species health: all aspects which are intrinsic for the ecosystem as a whole to survive and prosper.
Ecosystems also provide various
infrastructure of production and services such as purification of the air and water, stabilisation and moderation of the
climate, decrease of flooding, drought, and other environmental disasters.
Research suggests that a more diverse ecosystem is better able to withstand environmental stress and consequently is more productive. The loss of a species is thus likely to decrease the ability of the system to maintain itself or to recover from damage or disturbance. Just like a species with high genetic diversity, an ecosystem with high biodiversity may have a greater chance of adapting to
environmental change. In other words, the more species comprising an ecosystem, the more resilient and stable the ecosystem is likely to be. The mechanisms underlying these effects are complex and hotly contested. In recent years, however, it has become clear that there are real ecological effects of biodiversity.
Economic role of biodiversity
For all humans, biodiversity is a
resource for daily life. One element of biodiversity is
crop diversity. Many see biodiversity as a
reservoir of resources to be drawn upon for the manufacture of food,
pharmaceutical, and cosmetic products. This concept of biological resources management probably explains most fears of resource disappearance related to erosion of biodiversity.
However, it is also the origin of new conflicts dealing with rules of division and appropriation of natural resources.
Ecologists and environmentalists were the first to insist on the economic aspect of biological diversity protection. Thus, E. O. Wilson wrote in 1992 that:
biodiversity is the one of the greater wealths of the planet, and nevertheless less recognized as such. Estimation of the value of biodiversity is a necessary precondition to any discussion on the distribution of biodiversity richness. This value can be divided into use value and non-use or intrinsic value. The concept of ecosystem services attempts to quantify the economic value to mankind of all the functions the natural environment performs.
Since biological resources represent an ecological interest for the community, their economic value is also increasing. New products are developed because of biotechnologies, and new markets created. For society, biodiversity also is a field of activity and profit. It requires a proper management setup to determine how these resources are to be used. Some of the important economic commodities that biodiversity supplies to humankind are: unique
scientific research tools,
food,
medicine,
industry,
recreation and Ecotourism.
Scientific role of biodiversity
Finally, biodiversity is important because each species can give scientists some clue as to how life evolved and will continue to evolve on Earth. In addition, biodiversity helps scientists understand how life functions and the role of each species in sustaining ecosystems. The availability of unique genetic material for each living species may have incalculable value as evidenced by medical and genetic research that can lead to discoveries that may reduce mortality.
As of 2005 there have been numerous cases where genetic material unique to a given species has been utilized in developing a disease cure or producing a biochemical that is instrumental in medical research beneficial to humans. If genetic materials are lost through the present Holocene extinction event numerous medical cures will be foreclosed and lost forever.
See also Environmental economicsThreats to biodiversity
During the last century, erosion of biodiversity has been increasingly observed. Some studies show that about one of eight known plant species is threatened with
extinction. Some estimates put the loss at up to 140,000 species per year and subject to discussion. This figure indicates unsustainable ecological practices, because only a small number of species come into being each year. Most of the species extinctions from 1000 AD to 2000 AD are due to human activities, in particular destruction of plant and animal habitats. Almost all scientists acknowledge that the rate of species loss is greater now than at any time in human history, with extinctions occurring at rates hundreds of times higher than background extinction rates.
Elevated rates of extinction are being driven by human
consumption of organic resources, especially related to
tropical forest destruction. While most of the species that are becoming extinct are not food species, their
biomass is converted into human food when their habitat is transformed into
pasture,
cropland, and
orchards. It is estimated that more than 40% of the Earth's biomass is tied up in only the few species that represent
humans, our
livestock and
crops. Because an ecosystem decreases in stability as its species are made extinct, these studies warn that the global ecosystem is destined for collapse if it is further reduced in complexity. Factors contributing to loss of biodiversity are:
overpopulation,
deforestation,
pollution and
global warming or climate change, driven by human activity. These factors, while all stemming from overpopulation, produce a cumulative impact upon biodiversity.
Some characterize loss of biodiversity not as ecosystem degradation but by conversion to trivial standardized ecosystems . In some countries lack of property rights or access regulation to biotic resources necessarily leads to biodiversity loss .
The widespread introduction of
exotic species by humans is a potent threat to biodiversity. When exotic species are introduced to ecosystems and establish self-sustaining populations, the endemic species in that ecosystem, that have not evolved to cope with the exotic species, may not survive. The exotic organisms may be either
predators, parasites, or simply aggressive species that deprive indigenous species of nutrients, water and light. These exotic or
invasive species often have features due to their evolutionary background and environment that makes them very competitive, and similarly makes endemic species very defenceless and/or uncompetitive against these exotic species.
The rich diversity of unique species across many parts of the world exist only because they are separated by barriers, particularly seas and oceans, from other species of other land masses, particularly the highly fecund, ultra-competitive, generalist "super-species". These are barriers that could never be crossed by natural processes, except for many millions of years in the future through continental drift. However humans have invented ships and aeroplanes, and now have the power to bring into contact species that never have met in their evolutionary history, and on a time scale of days, unlike the centuries that historically have accompanied major animal
migrations.
As a consequence of the above, if humans continue to combine species from different ecoregions, there is the potential that the world's ecosystems will end up dominated by a very few, aggressive, cosmopolitan "super-species".
Biodiversity management: conservation, preservation and protection
The
conservation of biological diversity has become a global concern. Although not everybody agrees on extent and significance of current extinction, most consider biodiversity essential.
There are basically two main types of conservation options, in-situ conservation and ex-situ conservation. In-situ is usually seen as the ideal conservation strategy. However, its implementation is sometimes unfeasible. For example, destruction of rare or endangered species' habitats sometimes requires ex-situ conservation efforts. Furthermore, ex-situ conservation can provide a backup solution to in-situ conservation projects. Some believe both types of conservation are required to ensure proper preservation.
An example of an in-situ conservation effort is the setting-up of protection areas. Examples of ex-situ conservation efforts, by contrast, would be planting germplasts in seedbanks, or growing the
Wollemi Pine in nurseries. Such efforts allow the preservation of large populations of plants with minimal genetic erosion.
At national levels a
Biodiversity Action Plan is sometimes prepared to state the protocols necessary to protect an individual species. Usually this plan also details extant data on the species and its habitat. In the
USA such a plan is called a Recovery Plan.
The threat to biological diversity was among the hot topics discussed at the UN World Summit for Sustainable Development, in hope of seeing the foundation of a Global Conservation Trust to help maintain plant collections.
Juridical status of biological diversity
Biodiversity must be evaluated and its evolution analysed then it must be taken into account in political decisions. It is beginning to receive a juridical setting.
- "Law and ecosystems" relationship is very ancient and has consequences for biodiversity. It is related to property rights, private and public. It can define protection for threatened ecosystems, but also some rights and duties .
- "Laws and species" is a more recent issue. It defines species that must be protected because threatened by extinction. Some people question application of these laws. The U.S. Endangered Species Act is an example of an attempt to address the "law and species" issue.
- "Laws and genes" is only about a century old. While the genetic approach is not new , progress made in the genetic field in the past 20 years lead to the obligation to tighten laws. With the new technologies of genetic and genetic engineering, people are going through gene patenting, processes patenting, and a totally new concept of genetic resource. A very hot debate today seeks to define whether the resource is the gene, the organism, the DNA or the processes.
The 1972
UNESCO convention established that biological resources, such as plants, were the
common heritage of mankind. These rules probably inspired the creation of great public banks of genetic resources, located outside the source-countries.
New global agreements , now give
sovereign national rights over biological resources . The idea of static conservation of biodiversity is disappearing and being replaced by the idea of dynamic conservation, through the notion of resource and innovation.
The new agreements commit countries to
conserve biodiversity,
develop resources for sustainability and
share the benefits resulting from their use. Under these new rules, it is expected that bioprospecting or collection of natural products has to be allowed by the biodiversity-rich country, in exchange for a share of the benefits.
Sovereignty principles can rely upon what is better known as Access and Benefit Sharing Agreements . The Convention on Biodiversity spirit implies a prior informed consent between the source country and the collector, to establish which resource will be used and for what, and to settle on a fair agreement on benefit sharing. Bioprospecting can become a type of
biopiracy when those principles are not respected.
Uniform approval for use of biodiversity as a legal standard has not been achieved, however. At least one legal commentator has argued that biodiversity should not be used as a legal standard, arguing that the multiple layers of scientific uncertainty inherent in the concept of biodiversity will cause administrative waste and increase litigation without promoting preservation goals. See
Criticisms of the biodiversity paradigm
The founder effect
The field of biodiversity research has often been criticised for being overly defined by the personal interests of the founders giving a narrow focus, rather than extending to other areas where it could be useful. This is termed the
founder effect by Norse and Irish, . France and Rigg reviewed biodiversity research literature in 1998 and found that a there was a significant lack of papers studying marine ecosystems, leading them to dub marine biodiversity research the
sleeping hydra.
Size bias
Biodiversity researcher Sean Nee, writing in the 24 June 2004 edition of
Nature, points out that the vast majority of Earth's biodiversity is microbial, and that contemporary biodiversity physics is "firmly fixated on the visible world" . For example, microbial life is very much more metabolically and environmentally diverse than multicellular life . Nee has stated: "On the tree of life, based on analyses of small-subunit ribosomal RNA, visible life consists of barely noticeable twigs. This should not be surprising — invisible life had at least three billion years to diversify and explore evolutionary space before the 'visibles' arrived".
Notes
See also
...
- World Conservation Monitoring Centre
External links
- Science for Ecological Health and Livelihoods Network, SHALIN Suomi ry, Finland
- at Indian Institute of Science, India
- at Indian Institute of Science, India
- by the Millennium Ecosystem Assessment
- by GreenFacts.
- , a project of the American Institute of Biological Sciences that examines biodiversity, environment, genomics and other issues in bioscience.
- - fully indexed and crosslinked with other documents
- , an ongoing programme to map the past, current and future impacts of human activities on biodiversity
- an interactive map from the United Nations Environment Programme World Conservation Monitoring Centre
- - SciDev.Net
- - A not-for-profit organization dedicated to preserving biodiversity
- - cooperative effort of organizations to connect people with the information they need
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