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Biodiversity 生物多样性  

2009-03-06 07:00:11|  分类: 生物遗传天地 |  标签: |举报 |字号 订阅

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 Biodiversity  the existence of a wide variety of plant and animal species in their natural environments, which is the aim of conservationists concerned about the indiscriminate destruction of rainforests and other habitats

Biodiversity is the variation of  life forms within a given ecosystem, biome(生物群落), or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems. The biodiversity found on Earth today consists of many millions of distinct biological species, which is the product of nearly 3.5 billion years of evolution.

Evolution and meaning

Biodiversity is a portmanteau word, from biology and diversity. The Science Division of The Nature Conservancy used the term "natural diversity" in a 1975 study, "The Preservation of Natural Diversity." The term biological diversity was used even before that by conservation scientists like Robert E. Jenkins and Thomas Lovejoy. The word biological diversity was first used by wildlife scientist and conservationist Raymond F. Dasmann in a lay book advocating nature conservation, Another Kind of Country, published by The Conservation Foundation in 1968. Its contracted form biodiversity may have been 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[1] of that forum.[2] 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 "natural heritage" pre-dates "biodiversity", though it is a less scientific term and more easily comprehended in some ways by the wider audience interested in conservation. "Natural Heritage" was used when Jimmy Carter set up the Georgia Heritage Trust while he was governor of Georgia; Carter's trust dealt with both natural and cultural heritage. It would appear that Carter picked the term up from Lyndon Johnson, who used it in a 1966 Message to Congress. "Natural Heritage" was picked up by the Science Division of The Nature Conservancy when, under Jenkins, it launched in 1974 the network of State Natural Heritage Programs. When this network was extended outside the USA, the term "Conservation Data Center" was suggested by Guillermo Mann and came to be preferred.

[3] 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

Genetic diversity is a level of biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary.

The academic field of population genetics includes several hypotheses regarding genetic diversity. The neutral theory of evolution proposes that diversity is the result of the accumulation of neutral substitutions. Diversifying selection is the hypothesis that two subpopulations of a species live in different environments that select for different alleles at a particular locus. This may occur, for instance, if a species has a large range relative to the mobility of individuals within it. Frequency-dependent selection is the hypothesis that as alleles become more common, they become less fit. This is often invoked in host-pathogen interactions, where a high frequency of a defensive allele among the host means that it is more likely that a pathogen will spread if it is able to overcome that allele.

Importance of genetic diversity

There are many different ways to measure genetic diversity. The modern causes for the loss of animal genetic diversity have also been studied and identified.[1][2] A 2007 study conducted by the National Science Foundation found that genetic diversity and biodiversity are dependent upon each other -- that diversity within a species is necessary to maintain diversity among species, and vice versa. According to the lead researcher in the study, Dr. Richard Lankau, "If any one type is removed from the system, the cycle can break down, and the community becomes dominated by a single species."[3]

inbreeding.[4]

When humans initially started farming, they used selective breeding to pass on desirable traits of the crops while omitting the undesirable ones. Selective breeding leads to monocultures: entire farms of nearly genetically identical plants. Little to no genetic diversity makes crops extremely susceptible to widespread disease. Bacteria morph and change constantly. When a disease causing bacteria changes to attack a specific genetic variation, it can easily wipe out vast quantities of the species. If the genetic variation that the bacterium is best at attacking happens to be that which humans have selectively bred to use for harvest, the entire crop will be wiped out.[5]

A very similar occurrence is the cause of the infamous Potato Famine in Ireland. Since new potato plants do not come as a result of reproduction but rather from pieces of the parent plant, no genetic diversity is developed, and the entire crop is essentially a clone of one potato, it is especially susceptible to an epidemic. In the 1840s, much of Ireland’s population depended on potatoes for food. They planted namely the “lumper” variety of potato, which was susceptible to a rot-causing mold called Phytophthora infestans.[6] This mold destroyed the vast majority of the potato crop, and left tens of thousands of people to starve to death.

 

The natural world has several ways of preserving or increasing genetic diversity. Among oceanic plankton, viruses aid in the genetic shifting process. Ocean viruses, which infect the plankton, carry genes of other organisms in addition their own. When a virus containing the genes of one cell infects another, the genetic makeup of the latter changes. This constant shift of genetic make-up helps to maintain a healthy population of plankton despite complex and unpredictable environmental changes. [7]

Cheetahs are a threatened species. Extremely low genetic diversity and resulting poor sperm quality has made breeding and survivorship difficult for cheetahs –- only about 5% of cheetahs make survive to adulthood.[8] About 10,000 years ago, all but the jubatus species of cheetahs died out. The species encountered a population bottleneck and close family relatives were forced to mate with each other, or inbreed.[9] However, it has been recently discovered that female cheetahs can mate with more than one male per litter of cubs. They undergo induced ovulation, which means that a new egg is produced every time a female mates. By mating with multiple males, the mother increases the genetic diversity within a single litter of cubs. [10]

polymorphic loci across the genome.

  • Heterozygosity is the mean number of individuals with polymorphic loci.
  • Alleles per locus is also used to demonstrate variability.

    Genetic variability

    Genetic variability is a measure of the tendency of individual genotypes in a population to vary from one another. Variability is different from genetic diversity, which is the amount of variation seen in a particular population.[1] The variability of a trait describes how much that trait tends to vary in response to environmental and genetic influences.[1] Genetic variability in a population is important for biodiversity, because without variability, it becomes difficult for a population to adapt to environmental changes and therefore makes it more prone to extinction. Variability is an important factor in evolution as it affects an individual's response to environmental stress and thus can lead to differential survival of organisms within a population due to natural selection of the most fit variants. Genetic variability also underlies the differential susceptibility of organisms to diseases and sensitivity to toxins or drugs — a fact that has driven increased interest in personalized medicine given the rise of the human genome project and efforts to map the extent of human genetic variation such as the HapMap project.

    recombination is one source of variability; during meiosis in sexual creatures two homologous chromosomes from the male and the female cross over one another and exchange gene sequences. The chromosomes then split apart and are ready to form an offspring. The cross-over is random and is governed by its own set of genes that code for where crossovers can occur (in cis) and for the mechanism behind the exchange of DNA chunks (in trans). Being controlled by genes means that recombination is also variable in frequency, location, thus it can be selected to increase fitness by nature, because the more recombination the more variability and the more variability the easier it is for the population to handle changes.[2]

    Immigration, emigration, and translocation – each of these is the movement of an individual into or out of a population. When an individual comes from a previously genetically isolated population into a new one it will increase the genetic variability of the next generation if it reproduces.[3]

    Polyploidy – having more than two homologous chromosomes allows for even more recombination during meiosis allowing for even more genetic variability in one's offspring.

    Diffuse centromeres – in asexual organisms where the offspring is an exact genetic copy of the parent, there are limited sources of genetic variability. One thing that increased variability, however, is having diffused instead of localized centromeres. Being diffused allows the chromatids to split apart in many different ways allowing for chromosome fragmentation and polyploidy creating more variability.[4]

    Genetic mutations – contribute to the genetic variability within a population and can have positive, negative, or neutral effects on an fitness.[5] This variability can be easily propagated throughout a population by natural selection if the mutation increases the affected individual's fitness and its effects will be minimized/hidden if the mutation is deleterious. However, the smaller a population and its genetic variability are, the more likely the recessive/hidden deleterious mutations will show up causing genetic drift.[5]

    Human Variome Project

    The Human Variome Project (HVP) is an international initiative to collect and curate in a global repository, data on all human genetic variation.

    Professor Richard Cotton, a leader in the field of human genetic variation. His group, the Genomic Disorders Research Centre, based at the University of Melbourne and St. Vincent's Hospital, has established a consortium that covers genomic variation and its health implications in a comprehensive form. This consortium has encouraged the creation and supported many of the 571 gene specific variation databases currently available on the internet. However, these databases are of varying completeness and individualistic, so the Human Variome Project was born to establish a central project to encourage the collection and sourcing of this data, verifying it and ultimately using it for improved health outcomes.

    Geneticists, Diagnosticians, Researchers and Bio-informatics scientists came together in June 2006 at the Human Variome Project Meeting, organized by Professor Cotton’s team, and agreed take on the task of organising data collection and unifying the systems of data access and storage. This initiative builds on substantial pilot work and achievements of the Human Genome Variation Society. The authority of those initiating this project is evidenced by the fact that major international bodies were present. These included WHO, OECD, European Commission, UNESCO, March of Dimes (US), Centers for Disease Control and Prevention (US), Google, representatives of two dozen international genetics bodies, numerous genetics journals, 20 countries and Australian State and Federal Governments.

    This major international project, a natural partner to the Human Genome Project, will require substantial funding to get it to a sustainable position. A five year secure budget period of approximately US$12m per year has been proposed to initiate the project. This will enable the project to be organized and find operational funds for the tasks of system development, informatics, database curation and clinical access as well as collection systems that are open and accessible to all.

    The Human Variome Project seeks to provide open access to the full realm of genetic variation for the benefit of everyone.

    The Centre for Arab Genomic Studies (CAGS) has initiated efforts to proceed with the Arab Human Variome Project under the Human Variome Project. CAGS was one of the participants of the HVP meeting in Melbourne. Since then, several meetings have been held between officials of HVP and CAGS members to discuss the nature of work involved.

    The International Union for the Conservation of Nature and Natural Resources (IUCN) commissioned B. A. Wilcox to author a paper for the 1982 Bali World National Parks Conference describing ideas applicable to protected area design from the then new field of conservation biology, which included what may be the first explicit definition of biological diversity to be published. [4] The definition given in this paper was "Biological diversity is the variety of life forms...at all levels of biological systems (i.e., molecular, organismal, population, species and ecosystem." Subsequently, 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.

    If the gene is the fundamental unit of natural selection, according to E. O. Wilson, the real biodiversity is 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.

    Polar bears on the sea ice of the Arctic Ocean, near the north pole.

    It has been suggested that some content from this article be split into a separate article entitled Measurement of biodiversity. (Discuss)

    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[5] described three common metrics used to measure species-level biodiversity, encompassing attention to species richness or species evenness:

    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.

    A conifer forest in the Swiss Alps (National Park).

    Selection bias continues to bedevil modern estimates of biodiversity. In 1768 Rev. Gilbert White succinctly observed of his Selborne, Hampshire "all nature is so full, that that district produces the most variety which is the most examined."[6]

    Nevertheless, biodiversity is not distributed evenly on Earth. It is consistently richer in the tropics and in other localized regions such as the California Floristic Province. As one approaches polar regions one generally finds fewer species. Flora and fauna diversity depends on climate, altitude, soils and the presence of other species. In the year 2006 large numbers of the Earth's species were formally classified as rare or endangered or threatened species; moreover, many scientists have estimated that there are millions more species actually endangered which have not yet been formally recognized. About 40 percent of the 40,177 species assessed using the IUCN Red List criteria, are now listed as threatened species with extinction - a total of 16,119 species.[7]

    Even though biodiversity declines from the equator to the poles in terrestrial ecoregions, this is still a hypothesis to be tested in aquatic ecosystems and especially marine ecosystems where causes of this phenomenon are unclear [8]. In addition, particularly in marine ecosystems, there are several well stated cases where diversity in higher latitudes actually increases. Therefore, the lack of information on biodiversity of Tropics and Polar Regions prevents scientific conclusions on the distribution of the world’s aquatic biodiversity.

    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.[9][10] Dense human habitation tends to occur near hotspots. Most hotspots are located in the tropics and most of them are forests.

    Brazil's Atlantic Forest is considered a hotspot of biodiversity and contains roughly 20,000 plant species, 1350 vertebrates, and millions of insects, about half of which occur nowhere else in the world. The island of Madagascar including the unique Madagascar dry deciduous forests and lowland rainforests possess a very high ratio of species endemism and biodiversity, since the island separated from mainland Africa 65 million years ago, most of the species and ecosystems have evolved independently producing unique species different from those in other parts of Africa.

    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.

    Apparent marine fossil diversity during the Phanerozoic Eon.

    Biodiversity found on Earth today is the result of 4 billion years of evolution. The origin of life has not been definitely established by science, however some evidence suggests that life may already have been well-established a few hundred million years after the formation of the Earth. Until approximately 600 million years ago, all life consisted of archaea, bacteria, protozoans 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.[11] Estimates of the present global macroscopic species diversity vary from 2 million to 100 million species, with a best estimate of somewhere near 13–14 million, the vast majority of them arthropods.[12]

    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. It has been argued that the present rate of extinction is sufficient to eliminate most species on the planet Earth within 100 years.[13]

    New species are regularly discovered (on average between 5–10,000 new species each year, most of them insects) and many, though discovered, are not yet classified (estimates are that nearly 90% of all arthropods are not yet classified).[12] Most of the terrestrial diversity is found in tropical forests.

    Summer field in Belgium (Hamois).

    There are a multitude of anthropocentric benefits of biodiversity in the areas of agriculture, science and medicine, industrial materials, ecological services, in leisure, and in cultural, aesthetic and intellectual value. Biodiversity is also central to an ecocentric philosophy. It is important for contemporary audiences to understand the reasons for believing in conservation of biodiversity. Support for conservation includes our benefit from biological diversity and the things that we lose as a result of species extinction, which has taken place over the last 600 years. There are many benefits that are obtained from natural ecosystem processes. Some ecosystem services that benefit society are air quality, climate (both global CO2 sequestration and local), water purification, disease control, biological pest control, pollination and prevention of erosion. Non-material benefits that are obtained from ecosystems include spiritual and aesthetic values, knowledge systems and the value of education. Biodiversity addresses the importance of life and provides modern audiences with a more clear understanding of the current threat to life on Earth.

    Irish potato blight of 1846, which was a major factor in the deaths of a million people and migration of another million, was the result of planting only two potato varieties, both of which were vulnerable.

  • When rice grassy stunt virus struck rice fields from Indonesia to India in the 1970s. 6273 varieties were tested for resistance.[14] One was found to be resistant, an Indian variety, known to science only since 1966.[14] This veriety formed a hybrid with other varieties and is now widely grown.[14]
  • Coffee rust attacked coffee plantations in Sri Lanka, Brazil, and Central America in 1970. A resistant variety was found in Ethiopia.[15]

    Monoculture, the lack of biodiversity, was a contributing factor to several agricultural disasters in history, including the Irish Potato Famine, the European wine industry collapse in the late 1800s, and the US Southern Corn Leaf Blight epidemic of 1970.[16] See also: Agricultural biodiversity

    Higher biodiversity also controls the spread of certain diseases as pathogens will need to adapt to infect different species.

    Amazon Rainforest in Brazil.

    Biodiversity provides food for humans. Although about 80 percent of our food supply comes from just 20 kinds of plants, humans use at least 40,000 species of plants and animals a day. Many people around the world depend on these species for their food, shelter, and clothing. There is untapped potential for increasing the range of food products suitable for human consumption, provided that the high present extinction rate can be stopped.[13]

    microorganisms.

    Through the field of bionics, considerable technological advancement has occurred which would not have without a rich biodiversity.

    Eagle Creek, Oregon hiking

    ecosystem services that are often not readily visible. It plays a part in regulating the chemistry of our atmosphere and water supply. Biodiversity is directly involved in water purification, recycling nutrients and providing fertile soils. Experiments with controlled environments have shown that humans cannot easily build ecosystems to support human needs; for example insect pollination cannot be mimicked by human-made construction, and that activity alone represents tens of billions of dollars in ecosystem services per annum to humankind.

    hiking, birdwatching or natural history study. Biodiversity has inspired musicians, painters, sculptors, writers and other artists. Many cultural groups view themselves as an integral part of the natural world and show respect for other living organisms.

    Popular activities such as gardening, caring for aquariums and collecting butterflies are all strongly dependent on biodiversity. The number of species involved in such pursuits is in the tens of thousands, though the great majority do not enter mainstream commercialism.

    The relationships between the original natural areas of these often 'exotic' animals and plants and commercial collectors, suppliers, breeders, propagators and those who promote their understanding and enjoyment are complex and poorly understood. It seems clear, however, that the general public responds well to exposure to rare and unusual organisms—they recognize their inherent value at some level. A family outing to the botanical garden or zoo is as much an aesthetic or cultural experience as it is an educational one.

    Philosophically it could be argued that biodiversity has intrinsic aesthetic and spiritual value to mankind in and of itself. This idea can be used as a counterweight to the notion that tropical forests and other ecological realms are only worthy of conservation because they may contain medicines or useful products.

    [17]

    However the total number of species for some phyla may be much higher:

    Loss of old growth forest in the United States; 1620, 1850, and 1920 maps:

    From William B. Greeley's, The Relation of Geography to Timber Supply, Economic Geography, 1925, vol. 1, p. 1–11. Source of "Today" map: compiled by George Draffan from roadless area map in The Big Outside: A Descriptive Inventory of the Big Wilderness Areas of the United States, by Dave Foreman and Howie Wolke (Harmony Books, 1992). These maps represent only virgin forest lost. Some regrowth has occurred but not to the age, size or extent of 1620 due to population increases and food cultivation.

    During the last century, erosion of biodiversity has been increasingly observed. Some studies show that about one eighth known plant species is threatened with extinction[22]. Some estimates put the loss at up to 140,000 species per year (based on Species-area theory) and subject to discussion.[23] This figure indicates unsustainable ecological practices, because only a small number of species come into being each year. Almost all scientists acknowledge [22] 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.

    The factors that threaten biodiversity have been variously categorized. Jared Diamond describes an "Evil Quartet" of habitat destruction, overkill, introduced species, and secondary extensions. Edward O. Wilson prefers the acronym HIPPO, standing for Habitat destruction, Invasive species, Pollution, Human OverPopulation, and Overharvesting.[24][25]. The most authoritative classification in use today is that of IUCN’s Classification of Direct Threats[26] adopted by most major international conservation organizations such as The Nature Conservancy, The World Wildlife Fund, Conservation International, and Birdlife International.

    habitats. Raised rates of extinction are being driven by human consumption of organic resources, especially related to tropical forest destruction.[27] 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 a third of the Earth's biomass[28] is tied up in only the few species that represent humans, 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.

    There are systematic relationships between the area of a habitat and the number of species it can support, with greater sensitivity to reduction in habitat area for species of larger body size and for those living at lower latitudes or in forests or oceans.[29] 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).

    A September 14, 2007 study conducted by the National Science Foundation found that biodiversity and genetic diversity are dependent upon each other—that diversity within a species is necessary to maintain diversity among species, and vice versa. According to the lead researcher in the study, Dr. Richard Lankau, "If any one type is removed from the system, the cycle can break down, and the community becomes dominated by a single species."[30]

    At present, the most threathened ecosystems are those found in fresh water. The marking of fresh water ecosystems as the ecosystems most under threat was done by the Millennium Ecosystem Assessment 2005, and was confirmed again by the project "Freshwater Animal Diversity Assessment", organised by the biodiversity platform, and the French Institut de recherche pour le développement (MNHNP).[31]

    Introduced species

    The rich diversity of unique species across many parts of the world exist only because they are separated by barriers, particularly large rivers, seas, oceans, mountains and deserts from other species of other land masses, particularly the highly fecund, ultra-competitive, generalist "super-species". These are barriers that couldn't have be easily crossed by natural processes, except through continental drift. However humans have invented transportation with the ability 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.

    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 invasive species often have features, due to their evolutionary background and new environment, that make them highly competitive; able to become well-established and spread quickly, reducing the effective habitat of endemic species.

    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 relatively a few, aggressive, cosmopolitan "super-species". In 2004, an international team of scientists estimated that 10 percent of species would become extinct by 2050 because of global warming[32]. “We need to limit climate change or we wind up with a lot of species in trouble, possibly extinct,” said Dr. Lee Hannah, a co-author of the paper and chief climate change biologist at the Center for Applied Biodiversity Science at Conservation International.

    species can be threatened with extinction[33] through the process of genetic pollution i.e. uncontrolled hybridization, introgression and genetic swamping which leads to homogenization or replacement of local genotypes as a result of either a numerical and/or fitness advantage of introduced plant or animal.[34] Nonnative species can bring about a form of extinction of native plants and animals by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact. These phenomena can be especially detrimental for rare species coming into contact with more abundant ones. The abundant species can interbreed with the rarer, swamping the entire gene pool and creating hybrids, thus driving the entire native stock to complete extinction. Attention has to be focused on the extent of this under appreciated problem that is not always apparent from morphological (outward appearance) observations alone. Some degree of gene flow may be a normal, evolutionarily constructive, process, and all constellations of genes and genotypes cannot be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence.[35][36]

    agriculture and animal husbandry, the green revolution popularized the use of conventional hybridization to increase yield by creating "high-yielding varieties". Often the handful of hybridized breeds originated in developed countries and were further hybridized with local varieties in the rest of the developing world to create high yield strains resistant to local climate and diseases. Local governments and industry have been pushing hybridization which has resulted in several of the indigenous breeds becoming extinct or threatened. Disuse because of unprofitability and uncontrolled intentional and unintentional cross-pollination and crossbreeding (genetic pollution), formerly huge gene pools of various wild and indigenous breeds have collapsed causing widespread genetic erosion and genetic pollution. This has resulted in loss of genetic diversity and biodiversity as a whole.[37]

    A genetically modified organism (GMO) is an organism whose genetic material has been altered using the genetic engineering techniques generally known as recombinant DNA technology. Genetically Modified (GM) crops today have become a common source for genetic pollution, not only of wild varieties but also of other domesticated varieties derived from relatively natural hybridization.[38][39][40][41][42]

    Genetic erosion coupled with genetic pollution may be destroying unique genotypes, thereby creating a hidden crisis which could result in a severe threat to our food security. Diverse genetic material could cease to exist which would impact our ability to further hybridize food crops and livestock against more resistant diseases and climatic changes.[37]

    Effect of Climate Change on Plant Biodiversity

    The recent phenomenon of global warming is also considered to be a major threat to global biodiversity.[citation needed]

    Conservation biology

    A schematic image illustrating the relationship between biodiversity, ecosystem services, human well-being, and poverty.[43] The illustration shows where conservation action, strategies and plans can influence the drivers of the current biodiversity crisis at local, regional, to global scales.

    Conservation biology matured in the mid- 20th century as ecologists, naturalists, and other scientists began to collectively research and address issues pertaining to global declines in biodiversity.[44][45][46] The conservation ethic differs from the preservationist ethic, historically lead by John Muir, who advocate for protected areas devoid of human exploitation or interference for profit.[45] The conservation ethic advocates for wise stewardship and management of natural resource production for the purpose of protecting and sustaining biodiversity in species, ecosystems, the evolutionary process, and human culture and society.[44][47][48][46] Conservation biologists are concerned with the trends in biodiversity being reported in this era, which has been labeled by science as the Holocene extinction period, also known as the sixth mass extinction.[49] Rates of decline in biodiversity in this sixth mass extinction exceeds the five previous extinction spasms recorded in the fossil record.[50][51][52][53][54] In response to the extinction crisis, the research of conservation biologists is being organized into strategic plans that include principles, guidelines, and tools for the purpose of protecting biodiversity.[55][56][57] Conservation biology is a crisis orientated discipline and it is multi-disciplinary, including ecological, social, education, and other scientific disciplines outside of biology. Conservation biologists work in both the field and office, in government, universities, non-profit organizations and in industry.[44][46] The conservation of biological diversity is a global priority in strategic conservation plans that are designed to engage public policy and concerns affecting local, regional and global scales of communities, ecosystems, and cultures.[58] Conserving biodiversity and action plans identify ways of sustaining human well-being and global economics, including natural capital,market capital, and ecosystem services.[59][60]

    fishing rights, hunting rights).

  • Law regarding species is a more recent issue. It defines species that must be protected because they may be threatened by extinction. The U.S. Endangered Species Act is an example of an attempt to address the "law and species" issue.
  • Laws regarding gene pools are only about a century old[citation needed]. While the genetic approach is not new (domestication, plant traditional selection methods), progress made in the genetic field in the past 20 years have led to a tightening of laws in this field. With the new technologies of genetic analysis and genetic engineering, people are going through gene patenting, processes patenting, and a totally new concept of genetic resources[61]. A very hot debate today seeks to define whether the resource is the gene, the organism itself, or its DNA.

    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 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)

    [62] Biodiversity researcher Sean Nee 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).[63] 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.

    The size bias is not restricted to consideration of microbes. Entomologist Nigel Stork states that "to a first approximation, all multicellular species on Earth are insects".[64] Even in insects, however, the extinction rate is high and indicative of the general trend of the sixth greatest extinction period that human society is faced with.[65][66] Moreover, there are species co-extinctions, such as plants and beetles, where the extinction or decline in one is reciprocated in the other.[67]

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