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Laura Hood summarises the latest data on the world's biodiversity, with facts and figures on its value and efforts to conserve it.
This feature contains the latest data on the extent and the distribution of the world's biodiversity. It also includes the most recent estimates of extinction threats for different groups of species, as well as facts and figures on the value of biodiversity and efforts to conserve it.
The data are based mostly on the best available sources, including Conservation International, the UN Food and Agriculture Organization, the 2009 Red List of Threatened Species published by the International Union for Conservation of Nature (IUCN), the WWF's Living Planet Report, and the Earth Trends database of the World Resources Institute.
Readers will notice that although the majority of the world's biodiversity is found in the developing world, most data have been collected and analysed in institutions based in richer countries.
Thankfully, several international initiatives are underway to build the biodiversity data-gathering capacity of research institutions in developing countries and to connect them to efforts in the developed world. These include the Global Biodiversity Information Facility and the Proteus project of the UNEP World Conservation Monitoring Centre in the United Kingdom.
What is biodiversity?
Biodiversity (or biological diversity) is a collective term meaning the totality and variety of life on Earth. Biodiversity includes genetic diversity within species, the variety among species, and the range of ecosystems within which life exists and interacts.
How many species?
Estimates of the number of species on Earth vary from 3 million to 100 million. The UN Convention on Biological Diversity says there are some 13 million species, of which 1.75 million have been described ( and see below). A more updated figure comes from an analysis of the IUCN's 2008 Red List of Threatened Species (the issue is not addressed in the 2009 Red List) which states that 1.8 million species have been described out of an estimated 5 million to 30 million in existence. 
|Number of described species on Earth|
|Protoctists (algae, protozoa)||80,000|
|Animals – vertebrates||52,000|
|Animals – invertebrates||1,272,000|
|Total described species||1,750,000|
|Possible total of all species (including unknown species)||14,000,000|
|Source: UNEP/Global Environment Outlook (Ref 3)|
Where is biodiversity greatest?
Generally, species density is greatest in the Southern Hemisphere.
Seventy per cent of the world's species is found in just 12 countries: Australia, Brazil, China, Colombia, Costa Rica, the Democratic Republic of Congo, Ecuador, India, Indonesia, Madagascar, Mexico and Peru. The entire Hindu Kush–Himalayan belt has an estimated 25,000 plant species, comprising 10 per cent of the world's flora. 
Tropical regions support two-thirds of the estimated 250,000 plant species. The highest tree diversity recorded to date is 1,200 species in a 52-hectare plot in Lambir Hills National Park, Sarawak (Malaysian Borneo).  Overall, tropical rainforests are thought to contain 50–90 per cent of all species.  Some 2,600 bird species (about 30 per cent of the total) depend on tropical forests.
|Vascular plant species*|
|Congo, Democratic Republic||11,007|
Source: World Resources Institute, Earth Trends (Ref 5)
* A vascular plant is one whose tissues conduct fluids
|Bird species dependent on tropical forests|
|Source: World Resources Institute (Ref 5)|
What is a 'biodiversity hotspot'?
A biodiversity hotspot is an area of rich biodiversity that faces serious threats to its existence. The concept was developed by environmental scientist Norman Myers of Oxford University in the United Kingdom in an attempt to identify priority areas for biodiversity conservation.  The best-known proponent of the hotspots thesis is the US group Conservation International, which has produced a map of hotspots on the basis of their plant diversity and the impacts upon them. In addition to harbouring at least 1,500 endemic plant species, hotspots must also have lost more than 70 per cent of their original natural vegetation.
Ninety-eight per cent of Madagascar's land mammals, 92 per cent of its reptiles, 68 per cent of its plants and 41 per cent of its breeding bird species exist nowhere else on Earth.  Sixty per cent of the plant species endemic to Ecuador's Galapagos Islands are threatened with extinction, as are 75 per cent of the endemic plant species of the Canary Islands.  Twenty-five biodiversity hotspots contain 44 per cent of all plant species, and 35 per cent of all terrestrial vertebrate species exist in only 1.4 per cent of the planet's land area.
|Hotspots at a glance|
|Area||Original hotspot area (sq km)||Hotspot area today (sq km)||Protected area (sq km)||Total plant species||Total terrestrial vertebrate species||Endemic bird species under threat||Endemic mammal species under threat||
|Extinct species since 1500*|
|California Floristic Province||293,804||73,451||108,715||3,488||566||4||21||8||2|
|Cape Floristic Region||78,555||15,711||10,859||9,000||514||0||1||7||1|
|Chilean Winter Rainfall Valdivian Forests||397,142||119,143||50,745||3,892||335||6||5||15||0|
|Coastal Forests of Eastern Africa||291,250||29,125||50,889||4,000||1,085||2||6||4||0|
|Guinean forests of West Africa||620,314||93,047||108,104||9,000||1,315||31||35||49||0|
|Madagascar and Indian Ocean Islands||600,461||60,046||18,482||13,000||849||57||51||61||45|
|Mountains of Southwest China||262,446||20,996||14,034||12,000||940||2||3||3||0|
|Polynesia and Micronesia||47,239||10,015||2,436||5,330||372||90||8||1||43|
|Western Ghats and Sri Lanka||189,611||43,611||26,130||5,916||865||10||14||87||20|
Source: Conservation International (Ref 6)
* Endemic species of terrestrial vertebrate
What is extinction?
A species is classified as extinct if a single individual member cannot be found despite exhaustive surveys over a long period of time. This summarises the definition used by the IUCN, which compiles the periodic Red List of Threatened Species. A species being pronounced as extinct is not always the last word, however. The Vietnam warty pig (Sus bucculentus), for example, was listed as extinct in 1996. However, it was reclassified following the discovery of a fresh skull the following year. One mammal, the Bavarian pine vole (Microtus bavaricus), was rediscovered on the Germany–Austria border in 2000. It had previously not been seen since 1962. 
What are the current rates of extinction?
The current rate of species extinction is many times higher than the 'background' rate, which has prevailed over long periods of geological time. The background extinction rate varies, but estimates based on the fossil record suggest that in mammals and birds, one species has been lost every 500 to 1,000 years. 
According to Global Environment Outlook 4, species extinction is occurring at 100 times the natural rate, and is expected to accelerate to between 1,000 and 10,000 times the natural rate in the coming decades.  The IUCN says that the current rate of extinction may already be as high as 10,000 times the natural rate (http://www.iucn.org/about/work/programmes/species/red_list/about_the_red_list/).
What is 'mass extinction'?
The permanent loss of large numbers of species over a relatively short period of geological time is known as a mass extinction. According to the fossil record, there have been five historical mass extinctions (see table below). The reasons for these are often related to changes in the Earth's environment and atmosphere. Many scientists now believe that the Earth is facing a sixth mass extinction, in part because of human activities.
|Extinction period||Cause and effects|
(~500 million years ago)
|Changing sea levels|
(440 million years ago)
|Glaciation (ice age)|
(~365 million years ago)
(245 million years ago)
|96 per cent of marine species and 75 per cent of terrestrial vertebrate families became extinct during this, the largest, mass extinction, which was caused by fluctuations in sea level and ocean salinity resulting from climate change|
(65 million years ago)
|Famed for the extinction of the dinosaurs and widely thought to have been caused by a meteor impact|
|Source: BBC Education (Ref 12)|
Why is biodiversity threatened?
The leading threats to biodiversity are: converting land to agriculture, clearing forests, climate change, pollution, unsustainable harvesting of natural resources, and the introduction of so-called alien species to areas where they are not native.  The importance of each factor varies geographically. But one study of animal extinctions since the year 1600 found that 39 per cent arose mainly from the introduction of alien species, 36 per cent from habitat destruction, and 23 per cent from hunting or deliberate extermination.  Secondary causes of biodiversity loss include human population growth, unsustainable patterns of consumption, increasing production of waste, urban development and international conflict. 
How many species have become extinct recently?
At least 803 species have become extinct since the year 1500, according to the IUCN's 2009 Red List of Threatened Species.  The 2004 version put this figure at 784.
The actual number of extinctions may be higher still as many extinctions have either not been detected or belong to a taxonomic group that has not been evaluated by the Red List. For example, the Global Amphibian Assessment recently added 29 extinct species to the list. By comparison, the 2000 edition of the Red List of Threatened Species identified 766 species that have become extinct, and the 1997 edition identified 380 species.
The numbers of mammals and insects can show a decline in extinctions in the Red List of Threatened Species between years. This is because of changes to the way extinctions are classified, or because species are now known to have become extinct before 1500, rather than through their rediscovery.
|Species extinct (or extinct in the wild)|
|Extinct||Extinct in wild||Total|
|Extinct||Extinct in wild||Total|
|Extinct||Extinct in wild||Total|
|Grand total||Extinct||Extinct in wild||Total|
|Source: Red List of Threatened Species 2009 (Ref 9)|
How many species are threatened with extinction?
The 2008 Red List of Threatened Species states that the number of species threatened with extinction is 16,928. This includes one in four mammals, one in three amphibians, and one in eight birds.
The number of threatened species is increasing. In 2000, the Global Biodiversity Outlook, published by the UN Convention on Biological Diversity, reported that 11,046 species are threatened with extinction. These included vertebrates (such as mammals, birds and fishes), invertebrates (such as insects) and plants.
One of the reasons for the increase, however, is that the criteria for listing have changed over time, and some of the changes in status reflect changes to the classification of species. 
To be classified as threatened with extinction, a species is assessed against a set of five quantitative criteria. These criteria are based on biological factors related to extinction risk and include its rate of decline, population size, area of geographic distribution, and the degree to which its population has been fragmented.
Which species are threatened?
According to the IUCN, for most taxonomic groups only a small or extremely small proportion of described species has been evaluated for threatened status (for example, less than 0.1 per cent of insects). At present, birds and amphibians are the only organisms that have been completely evaluated. Mammals are almost all evaluated (99 per cent), but this figure is decreasing because a large number of changes in mammalian taxonomy have resulted in an increasing number of recognised species. Among plants,gymnosperms (mainly conifers and cycads) are the only major plant group to be almost completely evaluated (93 per cent).
|Rate of extinctions in recent years|
|Number of described species||Number of species evaluated by 2010||Number of threatened species in 1996–98||Number of threatened species in 2007||Number of threatened species in 2008||Number of threatened species in 2009||Number of threatened species in 2010||Number threatened in 2010, as percentage of species described|
|Source: 2009 Red List of Threatened Species (Ref 9)|
Which ecosystems are under threat?
The Living Planet Report 2008, published by the WWF, is an indicator of the state of the world's ecosystems. The report tracks population trends for more than 1,600 freshwater, marine and terrestrial species. Between 1970 and 2005, populations of terrestrial species dropped by 33 per cent. Populations of marine species dropped by 14 per cent, and freshwater species by 35 per cent. 
Within each of these categories, some ecosystems are more threatened than others.
Today, just one-fifth of the world's original forest cover remains in large tracts of relatively undisturbed forest — what the World Resources Institute calls 'frontier forest'. 
An estimated 58 per cent of the world's coral reefs, some of which rival tropical rainforests for biodiversity, are at risk from human activities. In South-East Asia, more than 80 per cent of reefs are at risk. 
How is agriculture affecting biodiversity?
Agriculture is a major contributor to loss of biodiversity. The rate at which agricultural land is expanding varies from region to region. However, much of the biodiversity loss due to agriculture is occurring in Latin America, Sub-Saharan Africa, and South and South-East Asia.
|Area of agricultural land by region (1900–1980) in sq km|
|Source: International Institute for Environment and Development/World Resources Institute (Ref 15)|
What is the value of biodiversity?
The importance of biodiversity to the functioning of ecosystems is well established. There is also, however, a considerable body of research on the economic value of biodiversity.
If one species becomes extinct, this can have a knock-on effect on others it interacts with. Indeed, an analysis published in September 2004 in the journal Science  suggested that the number of species globally threatened with extinction is nearly 50 per cent higher than the number currently listed as endangered. This is because the survival of 6,300 non-threatened species depends on the existence of threatened species.
Some species are — by virtue of their interactions with others — important to the continued existence of their ecosystems. These are known as 'keystone' species. The extinction of a keystone species is predicted to cause a cascade of further extinctions.
What is the economic value of biodiversity?
Individual species play a critical role in human food, medicine, biological pest control, materials (such as timber) and, recently, recreation. Southern Africa's wildlife, for instance, attracted more than 9 million visitors in 1997, bringing a total of US$4.1 billion to the region.
|Plant species used as food by humans|
|Human use/classification||Plant species|
|Total described species||250,000|
|Important on national scale||120|
|Making up 90% of world's calories||30|
|Source: UN Food and Agriculture Organization (Ref 18)|
Ten of the world's 25 top-selling drugs in 1997 were derived from natural sources. The global market value of pharmaceuticals derived from genetic resources is estimated at US$75 billion to US$150 billion annually. Some 80 per cent of the world's population relies for healthcare on traditional medicines, which are derived directly from natural sources. 
In China, for example, more than 5,000 of the estimated 30,000 identified domestic species of plants are used for medicinal purposes. More than 40 per cent of all prescriptions written in the United States contain one or more drugs that originated from wild species of fungi, bacteria, plants and animals. 
In addition to the importance of individual species, researchers are discovering that ecosystems, too, play an important role in providing 'services' to humans, and that these services can be given a monetary value.
In 2004, research published in the Proceedings of the National Academy of Sciences, for example, showed that conserving tropical forests could increase profits for coffee farmers in Costa Rica.  The study showed that the closer coffee bushes are planted to patches of forest, the more and better quality beans they produce, thanks to greater pollination by wild bees. Extra pollination provided by bees in these forest patches increased a Costa Rican coffee farm's income by 7 per cent.
Another study reveals direct and indirect financial benefits to humans from urban wetlands in Laos's That Luang Marsh.  At 20 km2, this is the largest wetland in the city of Vientiane, and generates goods and services with an economic value in excess of US$4.8 million per year. These benefits include water purification for people who live around the marsh, as well as for the residents of the city as a whole. 
Ecological economists study the relationship between economics and ecology. In 1997, a group of ecological economists tried to estimate a value for all of the world's 'ecosystem services'. Led by Robert Costanza of the University of Maryland in the United States, they calculated that the Earth provides 'services' worth a minimum of US$16 trillion to US$54 trillion to humans per year (compared to the global total gross national product (GNP) of US$18 trillion).  The study generated considerable controversy, not least from traditional economists who remain cautious about attempts to put monetary values on ecological services.
The 2006 Stern Review on the Economics of Climate Change warned that failing to act on climate change would cost the equivalent of between 5 and 20 per cent of GDP every year, with around 15 to 40 per cent of species potentially facing extinction after only 2 °C of warming.  A similar project is now underway to quantify the economics of biodiversity. It is called The Economics of Ecosystems and Biodiversity (TEEB) and is being coordinated by the UN Environment Programme.
How much of the planet is protected?
The 2003 United Nations List of Protected Areas  lists 102,102 sites covering 18.8 million km2. Of the total area protected, it is estimated that 17.1 million km2 is in terrestrial protected areas, or 11.5 per cent of the global land surface. Marine areas are significantly under-represented in this global system of protected areas. Approximately 1.64 million km2 is in marine protected areas — an estimated 0.5 per cent of the world's oceans, and less than one-tenth of the overall extent of protected areas worldwide.
At least 300 critically endangered, 237 endangered and 267 vulnerable bird, mammal, turtle and amphibian species have no protection in any part of their ranges, according to the most comprehensive analysis of its kind, published in Nature in 2004. 
What is the cost of conserving biodiversity?
A network of marine protected areas covering 20 to 30 per cent of the world's oceans would cost between US$5 billion and US$19 billion annually to run, according to research published in Bioscience in 2004. 
Scientists estimate that between US$20 billion and US$25 billion must be spent annually to achieve effective global conservation. 
In 2002, five international organisations between them spent US$1.5 billion on conserving biodiversity. They are: the World Bank, the Global Environment Facility, the IUCN, The Nature Conservancy and the Wildlife Conservation Society. Half this amount was spent in the United States, according to new research from a team of US university researchers and global conservation organisations. 
Biodiversity-related aid has been falling, according to an analysis from the Development Assistance Committee (DAC) of the Organization for Economic Co-operation and Development (OECD). In 1998, DAC's 19 members spent almost US$1.1 billion on biodiversity-related projects. This fell to a little over US$1 billion the following year, and dropped again to US$865 million in 2000. 
The Global Environment Facility is the main funding mechanism for the UN Convention on Biological Diversity. Donors pledged US$1.8 billion to the fund in 2002. Nearly 17 per cent of this assistance is to be spent on biodiversity-related projects. 
The 2010 target and beyond
At the 2002 World Summit on Sustainable Development, the international community pledged to slow down the rate of global biodiversity loss by 2010. Indicators towards this target included effectively conserving at least 10 per cent of the world's ecological regions; improving the status of threatened species; ensuring that no species of wild flora or fauna is endangered by international trade; and providing new and additional financial resources and technology to developing countries to help them meet their conservation commitments.
However, the target has not been met. The UN has declared 2010 the International Year of Biodiversity and member states of the UN Convention on Biological Diversity plan to meet to discuss future targets. The year will culminate in the Nagoya biodiversity summit in October, where they will set out a vision for 2050 and identify new targets and produce a new strategy to prevent biodiversity loss.
Laura Hood writes on global biodiversity policy for Research Europe (www.researchresearch.com/europe).
This document updates an earlier version produced by Mike Shanahan and Ehsan Masood in October 2004.
 Secretariat of the Convention for Biological Diversity. Sustaining Life on Earth: How the Convention on Biological Diversity promotes nature and human well-being (2002)
 Red List of Threatened Species, IUCN
 World Conservation Monitoring Centre, Global Biodiversity: Status of the Earth's Living Resources (Chapman and Hall, 1992)
 FAO, State of the World's Plant Genetic Resources for Food and Agriculture (1997)
 Ricketts, T. H., Daily, G. C., Ehrlich, P. R. & Michener, C. D. Economic value of tropical forest to coffee production. Proc. Natl Acad. Sci. USA 101, 12579–12582 (2004)
 IUCN That Luang Marsh, Lao PDR: the importance of wetlands for urban populations (2004)
 Costanza, R. et al. The values of the world's ecosystem services and natural capital. Nature 387, 253–260 (1997)
 Rodrigues, A. et al. Global gap analysis: priority regions for expanding the global protected-area network in BioScience54, 1092–1100 (2004)
 Balmford, A. et al. Can we afford to conserve biodiversity? Bioscience 51, 43–52 (2001)
 Halpern, B. S. et al. Gaps and mismatches between global conservation priorities and spending. Conservation Biology20, 50-64 (2006)
 Zedan, H. Indicators for assessing progress towards the 2010 target. Secretariat of UN convention on Biological Diversity 15–16 (2004)