SciDev.Net

Mike Shanahan and Eshan Masood summarise 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 is based mostly on the best available sources including Conservation International, the Food and Agriculture Organization of the UN, the World Conservation Union's 2004 Red List of Threatened Species, the World Wildlife Fund Living Planet Report, and the Earth Trends database of the World Resources Institute.

Readers will not have failed to notice that while the majority of the world's biodiversity is found in the developing world, most of the data has been collected and analysed in institutions that are based in richer countries.

Thankfully, policymakers are now turning their attention to this and 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 UK.

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 3-100 million. The UN Convention on Biological Diversity says there are some 13 million species, of which 1.75 million have been described ([1] and see below).  A more updated figure comes from the World Conservation Union's 2004 Red List of Threatened Species that says 1.9 million have been described out of an estimated 5-30 million in existence. [35]

Number of described species on Earth
Species	Number
Bacteria	4,000
Protoctists (algae, protozoa)	80,000
Animals – vertebrates	52,000
Animals – invertebrates	1,272,000
Fungi	72,000
Plants	270,000
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, Ecuador, India, Indonesia, Madagascar, Mexico, Peru and Democratic Republic of Congo. The entire Hindu Kush-Himalayan belt has as many as 25,000 plant species, comprising 10 per cent of the world's flora. [3]

Tropical regions support two-thirds of these estimated 250,000 plant species. The highest tree diversity recorded to date is 1,175 species in a 52-hectare plot in Lambir Hills National Park, Sarawak (Malaysian Borneo). [4] Overall, tropical rainforests are thought to contain 50 to 90 per cent of all species. [5]  Some 2,600 bird species (~30 per cent of the total) depend on tropical forests.

Vascular plant species in the tropics
Region	Number
Mexico and the Caribbean	86,000
Tropical and semi-arid Africa	30,000
Madagascar	8,200
Tropical Asia, including New Guinea and tropical Australia	45,000
Source: World Resources Institute (Ref 5) * A vascular plant is one whose tissues conduct fluids

Bird species dependent on tropical forests
Region	Number
Latin America	1,300
Africa	400
Asia	900
Total	2,600
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. [6]  The best-known proponent of the hotspots thesis is the US group Conservation International (CI). CI 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, they must also have lost more than 70 per cent of original natural vegetation to qualify as a hotspot.

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. [7] Sixty per cent of the plant species endemic to Ecuador'sGalapagos Islands are threatened with extinction, as are 75 per cent of the endemic plant species of the Canary Islands. [8] Twenty-five biodiversity hotspots contain 44 per cent of all plant species and 35 per cent of all terrestrial vertebrate species 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	Terrestrial vertebrates under threat*	Extinct species since 1500*
Atlantic Forest	1,477,500	121,600	33,000	20,000	1,668	116	1
Brazilian Cerrado	1,783,200	356,630	92,729	10,000	1,268	22	0
California Floristic Province	324,000	80,000	31,443	4,426	584	12	0
Cape Floristic Region	74,000	18,000	14,060	8,200	562	15	2
Caribbean	263,500	29,840	41,000	12,000	1,518	99	51
Caucasus	500,000	50,000	14,050	6300	632	10	0
Central Chile	300,000	90,000	9,167	3,429	335	8	0
Chocó-Darién-Western Ecuador	260,600	63,000	16,471	9,000	1,625	32	0
Eastern Arc Mountains and Coastal Forests	30,000	2,000	5,800	4,000	1,109	43	1
Guinean forests of West Africa	1,265,000	126,500	20,324	9,000	1,320	70	0
Indo-Burma	2,060,000	100,000	100,000	13,500	2,185	106	1
Madagascar and Indian Ocean Islands	594,150	59,038	11,548	12,000	987	123	46
Mediterranean Basin	2,362,000	110,000	42,123	25,000	770	42	4
Mesoamerica	1,155,000	231,000	138,437	24,000	2,859	62	4
Mountains of Southwest China	800,000	64,000	16,562	12,000	1,141	34	0
New Caledonia	18,600	5,200	526.7	3,332	190	9	1
New Zealand	270,500	59,400	52,068	2,300	217	61	25
Philippines	300,800	21,000	25,995	7,620	1,114	103	0
Polynesia and Micronesia	46,000	10,024	4,913	6,557	342	88	38
Southwest Australia	309,850	33,336	33,336	5,469	456	25	5
Succulent Karoo	116,000	30,000	2,352	4,849	472	12	0
Sundaland	1,600,000	125,000	90,000	25,000	1,800	82	0
Tropical Andes	1,258,000	314,500	79,687	45,000	3,389	130	2
Wallacea	347,000	52,020	20,415	10,000	1,142	82	0
Western Ghats and Sri Lanka	182,500	12,450	12,450	4,780	1,073	31	0
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 World Conservation Union, which compiles the periodic Red List of Threatened Species. A species being pronounced as extinct is not always the last word, however. The Vietnamese Warty Pig, 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, was rediscovered on the Germany-Austria border in 2000. It had previously not been seen since 1962. [35]

What are 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. [9]

According to the United Nations Environment Programme's 1995 Global Biodiversity Assessment (GBA), species extinction since the year 1600 has occurred at 50 to 100 times the natural rate, and is expected to accelerate to between 1,000 and 10,000 times the natural rate by 2020. [10]   The GBA states that 38 bird and mammal species became extinct between 1600 and 1810, compared to 112 species between 1810 and 1995. Of the 129 recorded bird extinctions, 103 have become extinct since 1800. This indicates an extinction rate that is 50-times that of the background rate. [35]

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.

Mass extinctions
Extinction period	Cause and effects
Late Cambrian (~500 million years ago)	Changing sea levels
Late Ordovician (440 million years ago)	Glaciation (ice age)
Late Devonian (~365 million years ago)	Global cooling
End Permian (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 – caused by fluctuations in sea level and ocean salinity resulting from climate change
Cretaceous-Tertiary (K-T) (65 million years ago)	Famed for extinction of dinosaurs and widely thought to have been caused by meteor impact
Source: BBC Education (Ref 34)

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. [11] The importance of each factor varies geographically. But one study of animal extinctions since 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. [12] Secondary causes of biodiversity loss include human population growth, unsustainable patterns of consumption, increasing production of waste, urban development and international conflict. [13]

How many species have become extinct recently?

At least 784 species have become extinct since the year 1500, according to the 2004  Red List of Threatened Species published by the World Conservation Union. The majority of documented extinctions have been to terrestrial species (582), followed by freshwater species (226) and marine species (15).

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 identified 766 species that have become extinct; and the 1997 Red List identified 380 species.

The numbers of mammals and insects show a decline in extinctions in the 2004 Red List. This is because of changes to the way extinctions are classified, or because they are now known to have become extinct before 1500, rather than their rediscovery. 

Species extinct (or extinct in the wild)
	Extinct	Extinct in wild	Total
Vertebrates
Mammals	73	4	77
Birds	129	4	133
Reptiles	21	1	22
Amphibians	34	1	35
Fishes	81	12	93
Subtotal	338	22	360
	Extinct	Extinct in wild	Total
Invertebrates
Insects	59	1	60
Crustaceans	7	1	8
Molluscs	291	12	303
Others	2	0	2
Subtotal	359	14	373
	Extinct	Extinct in wild	Total
Plants
Mosses	3	0	3
Ferns	3	0	3
Gymnosperms	0	2	2
Dicots	78	20	98
Monocots	2	2	4
Subtotal	86	24	110
Grand total	Extinct	Extinct in wild	Total
	784	60	844
Source: Red List of Threatened Species 2004 (Ref 35)

How many species are threatened with extinction?

The 2004 Red List of Threatened Species published by the World Conservation Union (IUCN) states the number of species threatened with extinction is15,589. This includes one in four mammals and one in eight birds. The total number of threatened animal species increased from 5,205 in 1996 to 7,266 in 2004.

The numbers of threatened species are 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. [9]

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 which its population has been fragmented.

Which species are threatened?

According to the World Conservation Union (IUCN), for most taxonomic groups, only a small or extremely small proportion of described species have been evaluated for threatened status (e.g. less than 0.1 per cent of insects). At present, birds and amphibians are the organisms that have been completely evaluated. Mammals are almost all evaluated (99 per cent), but this figure is decreasing due to a large number of changes in mammalian taxonomy resulting 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 in 2004	Number of threatened species in 1996	Number of threatened species in 2000	Number of threatened species in 2002	Number of threatened species in 2003	Number of threatened species in 2004	Number threatened in 2004, as % of species described
Vertebrates
Mammals	5,416	4,853	1,096	1,130	1,137	1,130	1,101	20%
Birds	9,917	9,917	1,107	1,183	1,192	1,194	1,213	12%
Reptiles	8,163	499	253	296	293	293	304	4%
Amphibians	5,743	5,743	124	146	157	157	1,770	31%
Fishes	28,500	1,721	734	752	742	750	800	3%
Subtotal	57,739	22,733	3,314	3,507	3,521	3,524	5,188	9%
Invertebrates
Insects	950,000	771	537	555	557	553	559	0.06%
Molluscs	70,000	2,163	920	938	939	967	974	1%
Crustaceans	40,000	498	407	408	409	409	429	1%
Others	130,200	55	27	27	27	30	30	0.02%
Subtotal	1,190,200	3,487	1,891	1,928	1,932	1,959	1,992	0.17%
Source: 2004 Red List of Threatened Species (Ref 35)

Which ecosystems are under threat?

The Living Planet Report 2004, published by the World Wildlife Fund (WWF) is an indicator of the state of the world's ecosystems. The report tracks population trends for more than 1,100 freshwater, marine and terrestrial species. Between 1970 and 2000, populations of terrestrial and marine species dropped by 30 per cent; and of freshwater species by 50 per cent. [17]

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'. [18]
  
• 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. [18]
  

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
	1900	1980	% change
North America	1,330,000	2,030,000	+53
Latin America	330,000	1,420,000	+330
Europe	1,450,000	1,370,000	-5
Former USSR	1,470,000	2,330,000	+58
Sub-Saharan Africa	730,000	2,220,000	+204
South Asia	890,000	2,100,000	+136
South-East Asia	150,000	550,000	+267
China	890,000	1,340,000	+51
Source: International Institute for Environment and Development/World Resources Institute (Ref 20

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 [23] 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 (e.g. timber) and, recently, recreation. Southern Africa's wildlife, for instance, attracted more than nine million visitors in 1997, bringing in 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
Edible	30,000
Cultivated	7,000
Important on national scale	120
Making up 90% of world's calories	30
Source: UN Food and Agriculture Organization (Ref 26)

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 150 billion annually. Some 75 per cent of the world’s population rely for health care on traditional medicines, which are derived directly from natural sources. [3]

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. [26]

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 of the United States of America, for example, showed that conserving tropical forests could increase profits for coffee farmers in Costa Rica. [24] The study showed that the closer coffee bushes are planted to patches of forest, the more and better quality beans they produce because of greater pollination by wild bees. Extra pollination provided by bees in those forest patches, increased a Costa Rican coffee farm's income by seven per cent.

Another study reveals direct and indirect financial benefits to humans from urban wetlands in Laos's That Luang Marsh. At 20 sq km, this is the largest wetland in 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 the residents of city as a whole. [27]

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 US, they calculated that the Earth provides a minimum of $16-54 trillion dollars worth of 'services' to humans per year (compared to the global total Gross National Product (GNP) of US$18 trillion). [27] The study generated considerable controversy, not least from traditional economists who remain cautious about attempts to put monetary values on ecological services.

How much of the planet is protected?

The 2003 United Nations List of Protected Areas [28] lists 102,102 sites covering 18.8 million sq km. Of the total area protected, it is estimated that 17.1 million sq km are 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 sq km comprise 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. [29]

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 US$5 to 19 billion annually to run, according to research published in Bioscience in 2004. [30]

Scientists estimate that between US$20-25 billion needs to be spent annually to achieve effective global conservation. [31]

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 World Conservation Union (IUCN) and The Nature Conservancy.  Half of this amount was spent in the United States, according to new research from a team of US university researchers and global conservation organisations. [31]

Biodiversity-related aid has been falling, according to an analysis from the Development Assistance Committee (DAC) of the Organization of Economic Cooperation and Development (OECD). In 1998, the DAC’s 19 members spent close to 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. [31]

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. [32]

The 2010 target

At the 2002 World Summit on Sustainable Development, the international community pledged to slow down the rate of global biodiversity loss by 2010. Member states of the UN Convention on Biological Diversity are in the process of agreeing a series of targets and indicators to help measure progress towards this target. They include: effectively conserving at least ten per cent of the world's ecological regions; improving the status of threatened species; ensuring no species of wild flora or fauna is endangered by international trade; providing new and additional financial resources and technology to developing countries to help them meet their conservation commitments.