Biodiversity is the measure of variety of the Earth’s animal, plant and microbial species; of genetic differences within species and of the ecosystems that support those species.
The term first came to public attention in 1992 at the Rio Earth Summit at which a convention for the preservation for the maintenance of biodiversity was signed by over 100 world leaders [excluding the USA as they feared it would undermine the patents and licences of US biotechnology companies]
The maintenance of biodiversity is important for ecological stability and maintaining the gene pool, and as a resource for research into, for example, new drugs and crops
What is causing a reduction in biodiversity in both the developed [EDC] and less developed [ELDC] worlds?
Most of the threats currently faced by species of plants and animals are linked to human action. In some cases this action, for example, hunting, deliberately aims to reduce species numbers[ e.g. White Rhino-sole purpose of which is to cut the horn off for illegal sale to Asian (mainly China) who mistakenly believe it has aphrodisiac powers]. There few Rhinos left and some subspecies have disappeared altogether e.g. Javan and Sumatran. Similar fate is facing the tiger e.g. Bengal down to 1,500 in number, Siberian circa 250 left.
In other situations species are inadvertently affected, for example, where habitats are destroyed or modified by people wishing to use the land for other purposes [For example, Korean Hyundai Company has just been given concession for deforestation and mineral exploration in key Siberian Tiger territory].
In extreme cases, a species may become extinct- this is irreversible- a loss of biodiversity. Extinction in the wild means that some individuals may still exist in captivity or in a seed bank. Extirpation is localized loss.
The reasons for human action are well known- land cleared for farming, herding, settlement and industry. Although much attention has been focused on the biologically rich ecosystems such as rainforests, coral reefs and mangrove swamps, widespread alterations have already occurred in the habitats of temperate latitudes such as in the UK.
In the UK, farmland occupies 72% of the [present land area. 5000 years ago, UK was almost entirely covered in forest. Today, the Uk is 0ne of the least wooded countries in Europe. [8% land cover in England and Wales- most of this is recent conifer planting]; land covered by ancient woodland e.g. oak/beech/ash/elm is 2.5%.
There are many examples of species driven to edge of extinction because of habitat destruction. Possibly the best known is the Giant Panda, once found all over China, now confined to a few sites near the city of Chengtu in the Province of Szechwan in western China. The giant panda relies heavily on a diet of bamboo but China’s bamboo forests have been converted to farmland. Despite conservation attempts by WWWF [World Wide Fund for Nature (panda emblem)] and breeding programmes in zoos [largely unsuccessful], genetic biodiversity so reduced that species will probably die out.
Fragmented destruction of habitats as well as total destruction can also bring about reductions in biodiversity by reducing the chances of normal dispersion and colonization processes of species and reduces areas for foraging
People have been responsible for the extinction of species through hunting for food for a long time. Such affects can be traced back to the Stone Age. The loss of large mammals such as the mammoth and sabre toothed tiger has been linked to over hunting.
Large animals which are easy to see coupled with the use of a firearm enhanced out ability to exterminate species in large numbers. For example in the USA the passenger pigeon declined to the point of extinction by 1900 because of habitat destruction and shooting. In first half of the 19th century it was estimated there were 10,000 million !, 1 billion were shot in Michigan State in 1869. Main reason for shooting them was for their meat- easy to shoot as they lived in huge flocks of *1000 million- they would darken skies for up to three days!
Of course the bison comes to mind as the classic example of over exploitation by a colonizing people who also destroyed its habitat.
The list of species drive to extinction by hunters in the present century is a sad one. it includes Rhinos and elephant in Africa [although the latter is making a comeback in some areas and needs culling (interference with farming activity)] and most species of Whale. As with the tiger, killing is driven by the high market price for products derived from the dead carcass.
The market for floral species is also a factor behind reductions in biodiversity. Many species of cacti and orchids are at risk form collectors, and numerous tree species in the tropics have been dramatically reduced by logging.
Another reason for loss of diversity is through the knock on effect of the loss of a species. For example, the death of the last Dodo on the island of Mauritius in 1681 mean’t that the tambalocque tree has been unable to reproduce for 300 years. its seeds cannot germinate because the fruit eating bird prepared the fruit for germination in its gizzard[stomach].
Introduction of species
In most cases this is the result of human actions. Especially vulnerable are islands where species are endemic [found only on that island] and having evolved in isolation they are susceptible to competitors, predators and diseases.
For example, goats were introduced on the South Atlantic island of St Helena in the 15,00’s and within 75 years vast herds were grazing the island. There were once estimated to be 100 plant species, today 40 are known, 7 are now extinct and the rest are under threat.
The brown tree snake was introduced on the Pacific island of Guam in the 1940’s [accidently] and played havoc with birds and their nests. Before the arrival of this snake there were 18 species of birds, by the mid 1980’s 7 species were extinct and another 4 critically endangered.
Clearly the rate of reduction of species is a cause for concern, especially in the tropics where there is massive habitat destruction. Because only a small proportion of the species on the planet have been documented,calculating the rate of loss is very difficult. However, the Rio Summit, Darwin Initiative and so on has focussed people’s attention on this critical global issue. What remains to be seen is the political will to carry legislation through at a global scale to manage environments much better so that biodiversity can be maintained.