What's happening?
Unfortunately, although people have added to nature' s diversity, it is our more destructive behaviour that is now hitting the headlines.
Growing populations, pollution, over-use of natural resources like fish and timber, the conversion of wild habitats into farmland and the increased mechanization of farming, expanding cities, and industrial areas - all are working to drive many plant and animal species to the brink of extinction.
A key problem is that one-half of the world is much richer than the other. These wealthy industrialized countries use far more than their fair share of resources - with only a quarter of the world' s population, they burn 70% of the worldÕs fossil fuels. Many of the natural resources the industrialized nations consume are found in poorer countries, whose economies depend on exports. The tropical timber trade, which has led to so much deforestation in Southeast Asia, has grown largely as a result of demand from affluent customers in Europe and Japan.
Wealth and land are unevenly distributed within countries too. In Brazil, the richest 2% own more than half the land; in South Africa, the most prosperous 15% possess over three-quarters. Meanwhile millions of rural people have no land at all and struggle to survive. All too often they are driven to over-exploit any natural area they can.
Every year, people clear about 17 million hectares of tropical forest. Estimates suggest that, if this continues, up to 60,000 plants, and even larger numbers of animals could die out over the next 30 years.
Coastal and marine habitats such as mangroves and coral reefs are also suffering. Over-fishing is one culprit, as it upsets the balance of fish populations - over-fishing on the Great Barrier Reef was partly responsible for an outbreak of crown-of-thorns starfish. Without predators, the starfish proliferated and preyed on corals, reducing reefs to a mass of dead skeletons which were rapidly overgrown with algae.
Industrial pollution, sewage, and soil washing down from inland hillsides that have been stripped of their protective forests, also take their toll. In 1920, the Philippines had 500,000 hectares of mangroves - today, fewer than 40,000 hectares remain. And only about 10% of the archipelagoÕs coral reefs are still healthy.
Freshwater ecosystems - rivers and streams, lakes and wetlands - are being destroyed too. In Sweden, 4,000 lakes are so acidified that no fish can live in them.
The now widespread planting of highly productive, uniform crop strains has driven many varieties out of existence. Today, farmers in the USA cultivate one-fifth of the vegetable varieties they grew 100 years ago. Such losses reduce the gene pool available for cross-breeding, and create farming systems that can be very vulnerable to pests and diseases.
Even the diversity of human communities is at risk. It is thought that 92 Brazilian tribes have disappeared this century, taking all their traditional knowledge with them. As more and more habitats are destroyed, indigenous peoples all round the world are threatened with extinction. By the end of the 21st century, the number of languages spoken in the world could have fallen from 6,000 to 3,000.
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