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Biodiversity or biological diversity is a neologism and a portmanteau word, from bio and diversity. It is the diversity of and in living nature. Diversity, at its heart, implies the number of different kinds of objects, such as species. However, defining biodiversity or measures of biodiversity, is not so simple.

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 world-wide. This use has coincided with the expansion of concern over extinction observed in the last decades of the 20th century.


Biodiversity definitions

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, 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:

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 we come 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

See also biodiversity and evolution

Biodiversity found on Earth today is the result of 3.5 billion years of evolution. Until the emergence of humans, the Earth supported more biodiversity than in any other period in geological history. Since the advent of humans, however, biodiversity has begun a rapid decline, with one species after another suffering extinction.

Estimates of global species diversity vary from 2 million to 100 million species, with a best estimate of somewhere near 10 million.

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 gives that about 40% of freshwater fishes from South America are not classified yet). Most of the 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 an ecosystem is better able withstand environmental stress and consequently is more productive. The loss of a species is thus likely to decreases 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 likley 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 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. Such 'crop diversity' 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 is 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, Edward 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) or 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 thanks to 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, the role of biodiversity is to be a mirror of our relationships with the other living species, an ethical view with rights, duties, and education. If humans consider species have a right to exist, they cannot voluntarily cause their extinction. Besides, biodiversity is also part of many cultures spiritual heritage (see indigenous people and cultural diversity).

Scientific role of biodiversity

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 more economically defensible definition is that measures should allow to ensure continued possibilities both for 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 around one 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:

  • 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.

Is biodiversity threatened?

During the last decades, erosion of biodiversity has been increasingly observed. The majority of biologists believe that a mass extinction is under way. While estimates over extinction rates range from a handful to upwards of 200 species a day, most scientists believe that the rate of species loss is greater now than at any time in human history- with extinctions occuring 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. Every year, between 17,000 and 100,000 species vanish from our planet . This figure indicates unsustainable ecological practices, because only a small number of species come into being each year. Some people say that up to 1/5 of all living species could disappear within 30 years. Nearly all say 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 further reduced in complexity.

Some justify this situation not so much by a species overuse or ecosystem degradation than 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).

Among the dissenters, some argue that there are 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.

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 and ex-situ conservation. In-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, seedbank, IUCN, Global 200.

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 on biodiversity. It is related to properties 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.
  • "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 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 (Convention on Biological Diversity), now gives sovereign national rights over biological resources (not property). The idea of static conservation of biodiversity is disappearing and being replaced by the idea of a dynamic conservation, through the notion of resource and innovation.

The new agreements commit countries to conserve the 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.

Sovereignety 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.

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

External links


Last updated: 10-19-2005 04:30:09
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