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(section incorporates material from http://www.jri.org.uk/brief/biodiversity.htm)
Biodiversity is shorthand for biological diversity or the variability of living organisms and the ecological complexes of which they are part. It is the total variety of genetic strains, species and ecosystems.
Worldwide there are an estimated 5 to 30 million species of animals and plants, each genetically unique. Most remain unidentified. Some 1.4 million animal species alive today have been named and described. Named plant species are far fewer, numbering around 400,000. Biodiversity is not uniformly distributed over the earth’s surface. The tropics cover 42% of all land but contain two-thirds of all animal species. Rain-forests cover 6 % of all land but contain two-fifths of all plant and animal species. Comprehensive measurement of biodiversity is difficult. However, we can compare numbers of species between sites as a simple index of relative biodiversity.
We all depend on the natural world to sustain us with food, clothing and other necessities, establishing a set of use values. But there are many less obvious values of biodiversity, of equal importance, to be considered (see Box 4.6).
Box 4.6: Value of biodiversity
Values from human use
- Direct uses of biodiversity: consumptive - food, medicines, non-consumptive - eco-tourism
- Subject to trade & commerce, monetary value readily assigned, varies with demand
A total of about 3,000 plant species, 200 of which have been domesticated, are used worldwide as a food source. However, just 20 of these plants provide more than 80% of our food at the present time. In order to maintain the high level of production such consumption demands, plant breeders frequently turn to the wild relatives of domestic crops in search of desirable genetic traits such as resistance to disease or drought: wild plants are a valuable reservoir of genetic diversity. A smaller number of animal species provide human food but the scale is often enormous. For example, in 1989 world landings of fish and other aquatic life forms totalled 99.5 mega-tonnes, 70 % of which was for human consumption.
In addition to food, many of our drugs and raw materials for manufacturing also originate from either plants or animals. Globally 3.5 billion people rely on plant-based medicine for primary health care, and in the USA a quarter of medicines prescribed are based on compounds originally found in plants. Many industrial materials, such as fibres, resins, dyes, waxes, pesticides, lubricants and perfumes derive from plant or animal sources. Trees provide more than 3.8 million cubic metres of wood annually for use as fuel, timber or pulp.
In addition to these long established patterns of consumptive utilisation, there is now a rapidly growing leisure industry, which involves the non-consumptive "use" of the living world. For example, eco-tourism, based on the observation of wild animals and wilderness habitats, generates between 100 and 200 billion US dollars annually, much of it in needy developing economies.
Non-use values
- Indirectly related to humans, ecosystem services, future options, aesthetics
- Monetary valuation difficult
While we can readily identify uses of biodiversity which directly support human life and are commercially valued, we often overlook a host of ‘hidden’ functions of living organisms which are equally vital to human well-being. Foremost among these are ‘free’ environmental services, such as nutrient cycling, soil formation, watershed protection, waste disposal, pollination, oxygen production, carbon sequestration and climate regulation. Placing a cash value on these services is not easy, but one estimate of their global value is US$ 33 trillion per annum, compared to a world GNP of US$ 18 trillion.
There are also many species which are not exploited themselves but have indirect value because they are food for economically valuable species. For example, molluscs and crustaceans are eaten by edible fishes. Other non-use values derive from the as yet undiscovered possibilities for future uses of wild flora and fauna, such as new drugs from plants and genes usable in breeding new characteristics into crops and domestic animals.
A totally different set of non-use values attaches to the significant contribution of wild organisms to human art, literature and religion. Christianity values biodiversity as a potent reminder to humans of God’s personality, power and creative genius (Rom.1:20) and Psalm 104 exclaims: "O Lord, what a variety you have made! And in wisdom you made them all! The earth is full of your riches."
Source: Article by John Sale available at http://www.jri.org.uk/brief/biodiversity.htm |
In our eagerness to improve living conditions for the six billion people on the planet , we are imposing serious threats to the survival of much biodiversity, including many species whose direct value is clearly established. Almost all ecosystems are greatly modified by humans, who transform habitats and exterminate rivals and competitors.
The greatest threat is the loss and fragmentation of natural habitats (Table 4.1) . This includes clearing forests for timber or plantations, overgrazing, draining wetlands and the destruction of heathlands and coral reefs.
Table 4.1: Conversion of natural habitat to agriculture
Source: Pearce and Moran, 1994 [link to references]. Figures given are in million hectares p.a. cropland
| Region |
1900 |
1980 |
% change |
| Sub-Saharan Africa |
73 |
222 |
+ 204 |
| Latin America |
33 |
142 |
+ 330 |
| South Asia |
89 |
134 |
+ 51 |
| China |
89 |
134 |
+ 267 |
| South East Asia |
15 |
55 |
+ 53 |
| North America |
133 |
203 |
- 5 |
| Europe |
145 |
137 |
+ 58 |
| Former USSR |
147 |
233 |
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Pollution also degrades habitats. Pesticides, sewage, oil, combustion emissions and acid rain contaminate soils, freshwater, oceans and air.
One alarming effect of atmospheric pollution is accelerating changes in climatic patterns to which ecosystems are adapted by long-term evolutionary processes. Anticipated results include dramatic changes in the geographical distribution of some species leading to ecosystem imbalance, and the extermination of others due to flooding and other climate-related phenomena.
Excessive exploitation has pushed some species to the verge of extinction. Included are the tiger, Giant Panda, Black Rhinoceros, cod and several whale species. Between 1979 and 1989 the African elephant population was halved by ivory poaching. Other species have been relentlessly persecuted as vermin, often based on wrong assumptions about the supposed harm they caused. For centuries in Britain, Red Kites had a price on their head as ‘lamb-killers’, in spite of their lack of strength for such a task.
Resulting from this array of human threats, rates of extinction are now estimated to be between 1,000 and 10,000 times greater than in the recent past. Tropical forests are being destroyed at the rate of 0.8 to 2.0% per annum, sending some of their estimated 5 million species into extinction. 484 species of animal and 654 plants have become extinct since 1600 AD. IUCN considers that one in eight plant species is at risk of extinction.
In the animal world too, many species face imminent extinction. For example, 116 species of European farmland birds are now of conservation concern. It is estimated that over the last 20 years in Britain alone ten species of farmland birds have between them ten million fewer breeding individuals. This is just one of the devastating effects of the intensification of agriculture on biodiversity.
Responses
The international Convention on Biological Diversity, agreed at Rio in 1992, focused attention on the need for sustainable use (rather than non-use) of the components of biodiversity, and the fair and equitable sharing of benefits - such as profits from new drugs based on tropical plants. Nations are required to develop their own strategies that integrate biodiversity conservation and sustainable use into the entire range of national decision-making.
Conservation legislation is costly to enforce and only works well if it reflects widely accepted values in the community. Attempts to tackle biodiversity loss politically are unlikely to succeed unless they fully take into account the underlying causes of the crisis, viz. the social organization and growth of the human population; patterns of natural resource consumption; global trade; economic systems and policies that fail to value the environment; and inequity in ownership, management and the flow of benefits from the use and conservation of biological resources.
Many governments rely on technical fixes to combat the problem. Conservation-conscious nations set up parks and reserves to protect and rehabilitate wildlife and examples of natural vegetation. However, it is calculated that a 90 % habitat loss can result in a 50 % loss of species (Michael Soulé, cited by Sale in http://www.jri.org.uk/brief/biodiversity.htm). This means that a country protecting 10% of its area (an ambitious target; many aim at only 5 %) may lose 50 percent of its species.
In Britain, schemes offering incentives to farmers to preserve traditional landscape features between them encompass only about 12.5% of agricultural land. A preferred approach would be to temper all of agricultural production with conservation measures, as well as encouraging organic farming, which promotes habitat diversity of benefit to many forms of wildlife.
Reduction of industrial and domestic pollution is a worldwide priority, particularly in the rich nations. In many cases the technology for pollution reduction is available if industry is willing to pay for it.
Over-exploitation has been restrained by bodies such as the International Whaling Commission [link to http://iwcoffice.org/] and the Convention on International Trade in Endangered Species (CITES). Both organizations aim to ensure that use of wild species is sustainable, rather than to attempt absolute bans. However, continual vigilance is required and trade in thousands of less conspicuous species such as orchids or tropical butterflies is often difficult to assess and regulate.
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