Biodiversity

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It has been suggested that Biodiversity information be merged into this article or section. (Discuss)

Biodiversity is the variation of life forms within a given ecosystem, biome 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.

Some of the biodiversity of a coral reef.

[edit] 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 biodiversity itself 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.

[edit] Definitions

The most straightforward definition is "variation of life at all levels of biological organization".^[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
• species diversity
• ecosystem diversity

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.

[edit] Measurement

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

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

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^[4] described three common metrics used to measure species-level biodiversity, encompassing attention to species richness or species evenness:

• Species richness - the least sophisticated of the indices available.
• Simpson index
• Shannon-Weaver 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.

[edit] Distribution

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

Selection bias continues to dedevil 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."^[5]

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.^[6]

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.^[7][8] 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.

[edit] Evolution

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.^[9] 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.^[10]

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.^[11]

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).^[10] Most of the terrestrial diversity is found in tropical forests.

[edit] Human Benefits

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. One way to identify the reasons why we believe in it is to look at what we get from biological diversity and the things that we lose as a result of species extinction, which has taken place over the last 600 years. Mass extinction is the direct result of human activity and not of natural phenomena which is the perception of many modern day thinkers. 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 regional and local), water purification, disease control, biological pest control, pollination and prevention of erosion. Along with those come non- material benefits that are obtained from ecosystems which are spiritual and aesthetic values, knowledge systems and the value of education that we obtain today. However, the public remains unaware of the crisis in sustaining biodiversity. Biodiversity takes a look into the importance to life and provides modern audiences with a clear understanding of the current threat to life on Earth.

[edit] Agriculture

The economic value of the reservoir of genetic traits present in wild varieties and traditionally grown landraces is extremely important in improving crop performance. Important crops, such as the potato and coffee, are often derived from only a few genetic strains. Improvements in crop plants over the last 250 years have been largely due to harnessing the genetic diversity present in wild and domestic crop plants. Interbreeding crops strains with different beneficial traits has resulted in more than doubling crop production in the last 50 years as a result of the Green Revolution.

Crop diversity is also necessary to help the system recover when the dominant crop type is attacked by a disease:

• The 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.^{[citation needed]} One was found to be resistant, an Indian variety, known to science only since 1966.^{[citation needed]} It was hybridised with other varieties and now widely grown.^{[citation needed]}
• Coffee rust attacked coffee plantations in Sri Lanka, Brazil, and Central America in 1970. A resistant variety was found in Ethiopia.^[12]

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.^[13] 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.^[11]

[edit] Science and medicine

A significant proportion of drugs are derived, directly or indirectly, from biological sources; in most cases these medicines can not presently be synthesized in a laboratory setting. About 40% of the pharmaceuticals used in the US are manufactured using natural compounds found in plants, animals, and microorganisms. Moreover, only a small proportion of the total diversity of plants has been thoroughly investigated for potential sources of new drugs. Many drugs are also derived from microorganisms.

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

[edit] Industrial materials

A wide range of industrial materials are derived directly from biological resources. These include building materials, fibers, dyes, resirubber and oil. There is enormous potential for further research into sustainably utilizing materials from a wider diversity of organisms.

Eagle Creek, Oregon hiking

[edit] Other ecological services

Biodiversity provides many 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 (eg sewage), 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.

[edit] Leisure, cultural and aesthetic value

Many people derive value from biodiversity through leisure activities such as hiking in the countryside, 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, even if they would not want the responsibility of caring for them. 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/or spiritual value to mankind in and of itself. This idea can be used as a counterweight to the rather notion that tropical forests and other ecological realms are only worthy of conservation because they may contain medicines or useful products.

[edit] Number of species

As a soft guide, however, the numbers of identified modern species as of 2004 can be broken down as follows:^[14]

287,655 plants, including: 15,000 mosses, 13,025 ferns, 980 gymnosperms, 199,350 dicotyledons, 59,300 monocotyledons; 74,000–120,000 fungi;[15] 10,000 lichens;

1,250,000 animals, including: 1,190,200 invertebrates: 950,000 insects, 70,000 mollusks, 40,000 crustaceans, 130,200 others; 58,808 vertebrates: 29,300 fish, 5,743 amphibians, 8,240 reptiles, 10,234 birds, (9799 extant as of 2006) 5,416 mammals.

Insects make up the vast majority of animal species. The image above are hoverflies mating in midair.

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

• 10–30 million insects;^[16]
• 5–10 million bacteria;^[17]
• 1.5 million fungi;^[15]
• ~1 million mites^[18]

[edit] Threats to Biodiversity

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^[specify]. Some estimates put the loss at up to 140,000 species per year (based on Species-area theory) and subject to discussion.^[19] This figure indicates unsustainable ecological practices, because only a small number of species come into being each year. Almost all scientists acknowledge^{[citation needed]} 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.^[20][21]

[edit] Destruction of habitat

Most of the species extinctions from 1000 AD to 2000 AD are due to human activities, in particular destruction of plant and animal habitats. Raised rates of extinction are being driven by human consumption of organic resources, especially related to tropical forest destruction.^[22] 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^{[citation needed]} 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.^[23] 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."^[24]

At present, the most threathened ecosystems are those found in sweet water. The marking of sweet 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).^[25]

[edit] Exotic species

Main article: 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 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 airplanes, 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.

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 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".

[edit] Further reading

• Leveque, C. & J. Mounolou (2003) Biodiversity. New York: John Wiley. ISBN 0470849576
• Margulis, L., Dolan, Delisle, K., Lyons, C. Diversity of Life: The Illustrated Guide to the Five Kingdoms. Sudbury: Jones & Bartlett Publishers. ISBN 0763708623
• Alexander V. Markov, and Andrey V. Korotayev (2007) "Phanerozoic marine biodiversity follows a hyperbolic trend" Palaeoworld 16(4): pp. 311–318.
• Novacek, M. J. (ed.) (2001) The Biodiversity Crisis: Losing What Counts. New York: American Museum of Natural History Books. ISBN 1565845706

[edit] External links

[edit] Documents

• Convention on Biological Diversity Text of the Convention
• Biodiversity Synthesis Report (PDF) by the Millennium Ecosystem Assessment (MA, 2005)

[edit] Tools

• World Map of Biodiversity an interactive map from the United Nations Environment Programme World Conservation Monitoring Centre
• GLOBIO, an ongoing programme to map the past, current and future impacts of human activities on biodiversity

[edit] Resources

• Biodiversity Heritage Library www.biodiversitylibrary.org - Open access digital library of taxonomic literature
• DMOZ www.dmoz.org - Open Directory Project
• National Biodiversity Network www.searchnbn.net - NBN Gateway
• Encyclopedia of Life www.eol.org - Documenting all species of life on earth
• Biodiversity of Altai-Sayan Ecoregion [3]