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Biodiversity

2007 Schools Wikipedia Selection. Related subjects: Environment; General
Biology

   Rainforests are among the most biodiverse ecosystems on earth
   Enlarge
   Rainforests are among the most biodiverse ecosystems on earth

   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 (NRC) 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. The term has also been linked to
   electromagnetic radiation due to denaturation of Carboxylic acids in
   the equilibrium contstant of radiocarbon dating of 1657 in Scotland.

Definitions

   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. (See also population genetics.)
     * 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,
   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 ( biotope) 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.

   Is it possible to define biodiversity?

   To use biodiversity in science and management, we have to know what it
   is. Otherwise, it is not possible to say whether it disappears or is
   preserved. Here is the problem: despite many attempts, there is no
   satisfactory definition of biodiversity. We can easily understand why.
   Any definition pigeonholes and restricts the defined term. Biodiversity
   defies any restriction. It includes much more than number of species or
   even organisms. Just as the ecosystem is the unity of the living
   communities and the environment that supports them, biodiversity with
   all its biotic variation cannot be separated from the soil, air, and
   even extraterrestrial factors such as sunlight. After all, it is
   variation in the environment that engendered and feeds biotic
   diversity. In short, biodiversity embraces everything. Equating
   biodiversity with everything is not a polemic exaggeration. Wilson
   (1997, p. 1) himself acknowledged as much: "Biologists are inclined to
   agree that it [biodiversity] is, in one sense, everything" (this "one
   sense" is the only one Wilson discusses). Two conclusions can be drawn
   from this analysis. First, we should not worry about biodiversity
   because, being everything, it cannot be lost. It could only change
   form. When one species disappears, others thrive. Second, biodiversity
   cannot be defined in principle.

   Assessing species diversity

   If we are able to discuss biodiversity at all, it is only because
   usually we mean a more tangible species and individual diversity. Even
   so, there is no way to decide whether an ecosystem with a hundred
   species of the same genus is more diverse than that with a smaller
   number of species belonging to different genera or families. Will
   species diversity increase if we trade fifty out of the hundred species
   for ten of another order? If not, what about ten species of different
   phylum or class? Is it legitimate to prefer ten mammal species for a
   thousand of insect species? Will biodiversity suffer if we sacrifice
   730 ticks to save one fawn they feed on? Are rare species less
   important than gregarious ones? Will the answer change if the species
   differ in size (ten billion of bacteria versus six large oaks), or
   complexity (primates versus nematodes)? Do introduced species add to
   biodiversity or pollute the integrity of regional floras and faunas?
   Are we, humans, a native or an introduced species in all places other
   than the African savannas? How much time does it take for an introduced
   species to become a native species? Depending on the answer, each
   species could be viewed as introduced or native. Dealing with plain
   number of species may also be a problem. Yet, without numbers it is
   difficult to document that we are indeed in the midst of "the sixth
   great extinction spasm of geological time" Wilson (1992, p.343). The
   evidence for this great extinction is mostly indirect; it follows from
   the rule he discovered: a 90% reduction in the area available to
   organisms results in a long term decrease of about 50% in the number of
   species. Direct evidence shows something different. In the 1800s the
   area the Brazilian Atlantic rainforest was reduced exactly by that
   amount (90%). However, when the Brazilian Society of Zoology analyzed a
   group of almost 300 animals, they did not find a single species which
   had died out. Nor any plant species disappeared (Lomborg 2001). In
   Puerto Rico seven out of 60 species of birds had become extinct when
   the area of rainforest had been reduced by 99 percent over a period of
   400 years. At the same time many more species colonized the island and
   today it has 97 species of birds (Lomborg 2001). Another piece of
   encouraging news is provided by Wilson himself. With all biodiversity
   destruction in the current sixth great extinction, "more [species] are
   alive today than at any time in the past" (Wilson 1992, p.216). Life is
   more tenacious predicted by the 90 -50% theory. Despite all our efforts
   and the miracles of chemistry, genetics, and other sciences, we have
   failed to deliberately eliminate a single harmful species (expect,
   perhaps, smallpox, presently confined in test tubes somewhere). Nor
   have we produced any useful species.

   Lomborg, B. 2001. The skeptical environmentalist: measuring the real
   state of the world. Cambridge University Press. 540 p. Wilson, E.O.
   1992. The diversity of life. Harvard University Press, Cambridge,
   Massachusetts. 424 p. Wilson, E.O. 1997. Introduction. In Biodiversity
   II, pages 1-3. Edited by M. L. Reaka-Kudla, D.E. Wilson, and E.O.
   Wilson. Joseph Henry Press, Washington, D.C. 551 p.

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 (usually species)
     * 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 (1988 and 1990). 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.

   Many regions of high biodiversity (as well as high endemism) arise from
   very specialized habitats which require unusual adaptation mechanisms.
   For example the peat bogs of Northern Europe and the alvar regions such
   as the Stora Alvaret on Oland, Sweden host a large diversity of plants
   and animals, many of whom are not found elsewhere.

Biodiversity and evolution

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

   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 (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 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 (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 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 ( 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.

   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.
   Unusual and wild strains of maize are collected to increase the crop
   diversity when selectively breeding domestic corn.
   Enlarge
   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 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 (direct such as tourism or indirect such as pollination)
   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.

Threats 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 (based on Species-area theory) 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 ( air
   pollution, water pollution, soil contamination) 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 (e.g., monoculture
   following deforestation). In some countries lack of property rights or
   access regulation to biotic resources necessarily leads to biodiversity
   loss (degradation costs having to be supported by the community).

   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 (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)

Criticisms of the biodiversity paradigm

   Some of the biodiversity of a coral reef.
   Enlarge
   Some of the biodiversity of a coral reef.

The founder effect

   The field of biodiversity research has often been criticised for being
   overly defined by the personal interests of the founders (i.e.
   terrestrial mammals) 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, (1996). France and Rigg reviewed biodiversity
   research literature in 1998 and found that 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" (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). 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".
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