Biodiversity in focus at Earth Summit

Many leading scientists and the United Nations itself have painted a gloomy picture of the planet\'s future. Some experts say we are on the verge of the greatest mass extinction since the dinosaurs died out 65 million years ago. The World Summit on Sustainable Development, which will run from August 26-September 4, will seek to map out concrete strategies to tackle poverty, disease and hunger while providing clean drinking water, sanitation and energy to billions of poor people in developing countries. Here are a few details about the Earth\'s ecosystems and biological wealth and the threats they face: FORESTS: According to the United Nations, an estimated 90 million hectares (222 million acres), or 2.4 percent of the world\'s forests - an area larger than Venezuela - was destroyed in the 1990s. Many of the trees felled were in tropical rain forests in South America, Africa and southeast Asia, renowned for the huge variety and diversity of species that they support. Although tropical forest ecosystems cover less than 10 percent of the earth\'s surface, they are believed to contain as much as 90 percent of the world\'s species, according to the U.N.\'s most recent Global Environment Outlook. The U.N. also says that nine percent of the world\'s tree species are endangered. This is not only a threat to the birds and animals that depend on them for survival, but means a huge loss of potential medicinal benefits from botanical sources. The news on this front is not all bad. Some experts say that global forest cover has actually been relatively stable, increasing to 30.89 percent of the planet\'s land area in 1994 from 30.04 percent in 1950. But much of the growth has been in the temperate forests of North America and Europe, not in the biologically richer rain forests of the tropics. It has also often been the inadvertent result of changing farming and settlement patterns and not the fruit of official policy. A European Union study this month indicated that tropical forests were disappearing more slowly than previously thought. It reckoned the average loss of rainforest was 0.43 percent a year against 0.5 percent estimated previously. SPECIES LOST/ENDANGERED Taxonomists have named around 1.75 million different species, according to the United Nations. It is believed that most have not been identified - including insects, plants and fungi - and that there could be as many as 14 million. About 52,000 vertebrates -- mammals, birds, reptiles, amphibians and some fishes -- have been identified. According to a recent U.N. report, 12 percent of bird species, or 1,183 types, and 1,130 mammal species, or nearly a quarter of the total, are regarded as globally threatened. A main threat to mammals and birds -- not to mention reptiles, fish, insects and plants - is habitat destruction caused chiefly by logging and the clearing of wildlands for farming, industry or human settlement. Climate change linked to global warming is another threat to biodiversity. It has been implicated in the bleaching of coral reefs and the decline of amphibians in tropical montane forests. Pollution, damming and disasters like oil spills have also taken a toll on wildlife, while over-hunting, over-fishing and the trade in animal body parts have had devastating consequences. North America\'s bison herds which once numbered millions were all but killed off by white settlers in the 19th century. The northern right whale was hunted to near extinction by commercial whalers and now number only around 300. Numerous fisheries collapsed during the later part of the 20th century, including Canada\'s Grand Banks cod fishery, which closed a decade ago with the loss of 40,000 jobs. Africa\'s elephant populations were significantly depleted by poachers involved in the global ivory trade, which was banned in 1989, stemming the slaughter of the majestic beasts. Currently, the illicit \"bushmeat\" trade and illegal logging activities in central and west Africa are pushing many primates to the brink of extinction, including humanity\'s closest living relatives, the gorillas and chimpanzees. Some animals have benefited from human activity. Coyotes, confined originally to the grasslands of western North America, rushed to fill the niche opened up by the slaughter of wolves by livestock farmers. They have spread out and \"colonised\" virtually the whole continent south of the Arctic tree line. A SIXTH EXTNCTION? Many scientists believe we are witnessing the first mass extinction since the dinosaurs were killed off 65 million years ago and the sixth in the four-billion-year history of life. The estimates vary. Some studies suggest that the extinction rate of vertebrate groups globally could be 15-20 percent over the next 100 years. Others have said 50 percent of species on the planet could be wiped out over the next century because of human activities. Bjorn Lomborg argues in his controversial recent book \"The Sceptical Environmentalist\" that we could lose just 0.7 percent of the planet\'s species over the next five decades -- an estimate hotly disputed by many biologists. REUTERS NEWS SERVICE