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Biodiversity or biological diversity is the diversity of and in living nature. There are a number of definitions and measures of biodiversity.



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 the entomologist E. O. Wilson in 1986, in a report for the first American Forum on biological diversity organized by the National Research Council (NRC). The word biodiversity was suggested to him by the staff of NRC, to replace biological diversity, considered to be less effective in terms of communication.

Since 1986 the terms and the concept have achieved widespread use among biologists, environmentalists, political leaders, and concerned citizens worldwide. This use has coincided with the expansion of concern over extinction observed in the last decades of the 20th century.

Biodiversity definitions

Biodiversity is the variety of life: the different plants, animals and micro-organisms, their genes and the ecosystems of which they are a part.

Biological diversity has no single standard definition. One definition holds that biological diversity is a measure of the relative diversity among organisms present in different ecosystems. Diversity in this definition includes diversity within species and among species, and comparative diversity among ecosystems.

Another definition, simpler and clearer, but more challenging, is the totality of genes, species, and ecosystems of a region. An advantage of this definition is that it seems to describe most instances of its use, and one possibly unified view of the traditional three levels at which biodiversity has been identified:

Intraspecific diversity within Dog
Intraspecific diversity within Dog

The lattermost definition, which conforms to the traditional five organisation 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, thus of evolution, some, like E. O. Wilson, say that the real biodiversity is the genetic diversity. However, the species diversity is the easiest one to study.

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 diversity of populations of organisms and species, but also the way these organisms function. Organisms appear and disappear; sites are colonized by organisms of the same species or by another. Some species develop social organisations to improve their reproduction goals or use neighbor species that live in communities. Depending on their environment, organisms do not invariably use the same 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 (biotope) and the ecoregions the organisms live in. In each ecosystem, living organisms are part of a whole; they interact with one another, but also with the air, water, and soil that surround them.

Origin of life and biodiversity evolution

Apparent marine fossil diversity during the Phanerozoic
Apparent marine fossil diversity during the Phanerozoic

See also biodiversity and evolution

Biodiversity found on Earth today is the result of 4 billion years of evolution.

The original 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 (the last 540 million years), 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 (e.g. Alroy et al. 2001) argue that corrected for sampling artifacts, modern biodiversity is not much different than 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 (on average about three new species of birds each year) and many, though discovered, are not yet classified (an estimate states that about 40% of freshwater fish from South America are not yet classified). Most of the terrestial 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.

There are three main reasons commonly cited in the literature for the benefits of biodiversity.

Ecological role of biodiversity

All species provide some kind of function to an ecosystem. They can capture and store energy, produce organic material, decompose organic material, help to cycle water and nutrients throughout the ecosystem, control erosion or pests, fix atmospheric gases, or help regulate climate.

Ecosystems also provide various supports of production (soil fertility, pollinators of plants, predators, decomposition of wastes...) and services such as purification of the air and water, stabilisation and moderation of the climate, decrease of flooding, drought, and other environmental disasters.

These functions are important for ecosystem function and human survival.

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 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.

Unusual and wild strains of maize are collected to increase the crop diversity when selectively breeding domestic corn.
Unusual and wild strains of maize are collected to increase the crop diversity when selectively breeding domestic corn.

Economic role of biodiversity

For all humans, biodiversity is first a resource for daily life. One important part of biodiversity is 'crop diversity', which is also called agrobiodiversity.

Most people 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 resources disappearance related to the erosion of the biodiversity. However, it is also the origin of new conflicts dealing with rules of division and appropriation of natural resources.

Some of the important economic commodities that biodiversity supplies to humankind are:

Ecologists and environmentalists were the first to insist on the economic aspect of biological diversity protection. Thus, E. O. Wilson wrote in 1992 that : The biodiversity is the one of the bigger wealths of the planet, and nevertheless the less recognized as such.

Estimation of the value of biodiversity is a necessary precondition to any discussion on the distribution of biodiversity richnesses. This value can be divided into use value (direct such as tourism or indirect such as pollination) and non-use or intrinsic value.

If 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.

The majority of species have yet to be evaluated for their current or future economic importance.

Ethical role of biodiversity

Finally, biodiversity has an ethical role if humans consider that other species have an intrinsic right to exist. Ecophilosophies such as deep ecology assert that a recognition of this intrinsic right makes it morally wrong to voluntarily cause extinction. The level of biodiversity is a good indicator of the state of our relationships with other living species. Biodiversity is also part of many cultures' spiritual heritage (see indigenous people and cultural diversity).

Scientific role of biodiversity

This is a fourth benefit separate from the three main ones. 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.

See also Environmental economics

Evaluation of biodiversity

Measurement of biodiversity

From the viewpoint previously defined, no single objective measure of biodiversity is possible, only measures relating to particular purposes or applications.

For practical conservationists, this measure should quantify a value that is at the same time broadly shared among locally affected people.

For others, a broader and economically more defensible definition is that measures should allow the ensuring of continued possibilities for both adaptation and future use by people, assuring environmental sustainability. As a consequence, biologists argued 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 approach is sometimes considered inadequate and too restricted.

Biodiversity: time and space

Biodiversity is not static: it is a system in constant evolution, from a species, as well as from an individual organism point of view. The average half-life of a species is estimated at between one and four million years, and 99% of the species that have ever lived on earth are today extinct.

Biodiversity is not distributed evenly on earth. It is consistently richer in the tropics. As one approaches polar regions one finds larger and larger populations of fewer and fewer species. Flora and fauna vary depending on climate, altitude, soils and the presence of other species. For a listing of distinct ecoregions based on these distributions, see the WikiProject Ecoregions.

Species inventory

Systematics assesses biodiversity simply by distinguishing among species. At least 1.75 million species have been described; however, the estimates of the true number of current species range from 3.6 to more than 100 million. Some also say that the knowledge of the species and the families became insufficient and must be supplemented by a greater comprehension of the functions, interactions and communities. Moreover, exchanges of genes occurring between the species tend to add complexity to the inventory.

Hotspots of biodiversity

One definition of a biodiversity hotspot is a region with many endemic species. Hotspots tend to occur in areas of historically limited human impact and are generally very productive. As a result of the pressures of the growing human population, human activity in many of these areas is increasing dramatically. Most of these hotspots are located in the tropics.

Some examples are the following:

  • Brazil is said to represent 1/5 of the world biodiversity, with 50,000 plant species, 5,000 vertebrates, 10-15 million insects, millions of microorganisms, etc.
  • India is said to represent 8% of the recorded species, with 47,000 plants species and 81,000 animals.

See also: biogeography, Amazonian forest, extinction, unified neutral theory of biodiversity.

Threats to biodiversity

During the last century, erosion of biodiversity has been increasingly observed. Estimates of extinction rates are controversial, ranging from very low to upwards of 200 species a day, but 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.

Some studies show that about one of eight known plant species is threatened with extinction. Some estimates put the loss at thousands of species per year, though these are based on Species-area theory and are controversial. This figure indicates unsustainable ecological practices, because only a small number of species come into being each year. All agree that the losses are due to human activities, in particular destruction of plant and animal habitats.

An increasing number of studies indicate that elevated rates of extinction are being driven by human consumption of organic resources. 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.

Some justify this situation not so much by a species overuse or ecosystem degradation as by their conversion in very standardized ecosystems (e.g., monoculture following deforestation). Before 1992, others pointed out that no property rights or no access regulation of resources necessarily lead to their decrease (degrading costs having to be supported by the community).

Dissenters (notably economist Bjørn Lomborg) argue that there is not enough data to support the view of mass extinction, and say abusive extrapolations are being made on the global destruction of rainforests, coral reefs, mangrove swamps, and other rich habitats.

There is also a growing awareness that the movement and the introduction of exotic species around the world by humans is a potent threat to biodiversity.

When exotic species are introduced to ecosystems by humans and establish self-sustaining populations, the endemic species in that ecosystem, that have not evolved to cope with the exotic species in question, cannot automatically be expected to survive. Indeed, in many situations some will not. The exotic organisms in questions may be predators and/or 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 that humans treasure exist only because they a 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 human beings have invented ships and aeroplanes. Now human beings have the power to bring into contact species that would never have encountered each other in their evolutionary history, and to do it with ease in weeks, days or even just hours.

As a consequence of the above, it is likely that if human beings continue to unleash species of the world against each other by introductions - species that otherwise would never have encountered each other in their evolutionary history - many of the worlds ecosystems will end up dominated by a very few, 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 ultimate 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. An example of an ex-situ conservation effort, by contrast, would be planting germplasts in seedbanks. Such efforts allow the preservation of large populations of plants with minimal genetic erosion.

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.

See also: Conservation, Earth Day, Global 200, IUCN, Seedbank, World Ocean Day.

Juridical status of biological diversity

Biodiversity must be evaluated and its evolution analysed (through observations, inventories, conservation...) 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 (for example, fishing rights, hunting rights).
  • "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 (domestication, plant traditional selection methods), 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 (e.g.Convention on Biological Diversity), now give sovereign national rights over biological resources (not property). 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 (ABAs). 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 Fred Bosselman, A Dozen Biodiversity Puzzles, 12 N.Y.U. Environmental Law Journal 364 (2004)

Biodiversity and 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 science is "firmly fixated on the visible world" (Nee uses "visible" as a synonym for macroscopic). For example, microbial life is very much more metabolically and environmentally diverse than multicellular life (see extremophile).

Quotes from Sean Nee

  • "the contribution of visible life to biodiversity is very small indeed".
  • "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".

Measures of biodiversity

There are three common metrics used to measure biodiversity.

See also

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