Animals and plants have suffered a drop of more than 30 per cent in their global abundance in forests, freshwaters and the seas, WWF said, unveiling a Living Planet Index, which it hopes will become the Dow Jones or the Footsie of the world's environmental health.
The index resembles a bear market lasting a whole generation. Put together with virtually all the available data on declining species, and taking 1970 as a baseline year and giving it a value of 100, it had dropped to 68 by 1995 and is still dropping.
Although there are several detailed status reports on world resources, produced by the United Nations and other agencies, this is the first time an attempt has been made to measure the change over time of the global environment as a whole.
"In spite of the uncertainties, it is safe to say that the period since 1970 has been the most destructive in the history of the natural world since the great extinction 65 million years ago, when the meteor hit the Caribbean and wiped out the dinosaurs," said Jorgen Randers, deputy director of WWF International.
The index, which the World Conservation Monitoring Centre in Cambridge and the New Economics Foundation helped WWF to compile, is an aggregate figure of deterioration in world forests and marine and freshwater ecosystems.
Forest decline has been measured by loss of forest cover; the deterioration in oceans, lakes and rivers measured by declines in the species they support.
The index shows loss of abundance in existing species rather than extinctions, because the true number of species in the world is not accurately known. Data for nearly 350 kinds of mammals, birds, reptiles and fish have been used.
The index for forests shows a fall of about 10 per cent in the period 1970-1995, that for oceans about 30 per cent, and surprisingly, that for freshwater ecosystems the worst fall of all, at about 50 per cent.
"We wanted to know how fast nature is disappearing from the globe, in spite of our efforts to the contrary," Mr Randers said. The 32 per cent decline in a single generation was "chilling", he added.
WWF freely admits that there is an uncertainty range of 10 to 15 per cent either side in their figures, but believes this will diminish as more data become available. In future the index will be published every year.
The figure for forests may hide a steeper decline in environmental quality, as loss of forest area is not necessarily proportional to loss of forest wildlife. Furthermore, the temperate forests of Europe and North America have stayed stable during the period, or even increased in some areas with planting, while tropical rainforests have suffered severely.
"We have lost about 45 per cent of the world's tropical forest, probably nearly 50 per cent," said Sir Ghillean Prance, director of the Royal Botanic Gardens at Kew, west London, who welcomed the publication of the index yesterday.
"The figure of 30 per cent decline for the world as a whole is truly frightening," he added.
The Living Planet Index also attempts to measure the pressure of human consumption of natural resources which is the cause of environmental decline. Consumption has gone up even more than nature has gone down: using 1970 once again as a baseline year, with a value of 100, global consumption stood at 163 by 1995.
More vividly, the index establishes a country-by-country "consumption pressure rating" for 152 nations. "We wanted to show in just one number what a country's burden on the environment per person is," said Jonathan Loh, one of the authors of the report.
The rating is based on six factors: a country's consumption of grain, fish and wood; its consumption of cement (indicating growing urbanisation); its emissions of carbon dioxide from industry and motor vehicles; and its use of fresh water.
Some surprising results are thrown up: on a per capita basis, Norway is shown as having the heaviest consumption "footprint" on the globe, while Britain is shown as having the lightest among the nations of Western Europe.
These are anomalies caused by the use of only six sectors (the only ones in which data for all countries were available). Norway has a low population, an enormous oil industry and a big fish catch; Britain is an established nation with its infrastructure largely built, which uses less cement than others.
WWF is confident, however, that as more data are included, the results will be less anomalous, and says that the broad outlines of the consumption index are robust: the consumption footprint of Western Europe is more than three times that of Africa and more than twice that of Asia.