Mankind is the 'Earth's biggest threat'

Researchers who analysed 30,000 academic studies dating back to 1970 said man was responsible for changes that ranged from the loss of ice sheets to the collapse in numbers of many species of wildlife.

"Humans are influencing climate through increasing greenhouse gas emissions, and the warming world is causing impacts on physical and biological systems," said Cynthia Rosenzweig, at the Nasa Goddard Institute for Space Studies.

The effects on living things include the earlier appearance of leaves on trees and plants; the movement of animals and birds to more northerly latitudes and to higher altitudes in the northern hemisphere; rapid advances in flowering time and earlier egg-laying in Britain; and changes in bird migrations in Europe, North America and Australia.

On a planetary scale the changes include the melting of glaciers on all continents; earlier spring river run-off; and the warming of oceans, lakes and rivers.

The study's conclusions go further than the most recent report by the Intergovernmental Panel on Climate Change, which concluded last year that man-made climate change was "likely" to have had a discernible effect on the planet.

It says natural climate variations cannot explain the changes to the Earth's natural systems.

In the study, published in the journal Nature, Miss Rosenzweig and researchers from 10 institutions across the world analysed data from published papers on 829 physical systems – such as glaciers and ice sheets – and 28,800 plant and animal systems. They produced a picture of the changes to each continent. The changes were most marked in North America, Asia and Europe but mainly because far more studies had been carried out there.

The authors said there was an urgent need to study environmental systems in South America, Australia and Africa, especially in tropical and subtropical areas.

In North America, the researchers found that 89 species of plants were flowering earlier, such as the American holly and box elder maple; a decline in the population of polar bears; and the rapid melting of Alaskan glaciers.

In Europe, they found evidence of glaciers melting in the Alps; earlier pollen release in the Netherlands; and apple trees producing leaves 35 days earlier in Spain.

In Asia they reported a change in the freeze depth of permafrost in Russia; and the earlier flowering of ginkgo in Japan.

In Antarctica, the population of emperor penguins had declined by 50 per cent. In South America, the melting of the Patagonia ice-fields were contributing to a rise in sea levels.

Prof Barry Brook, of the University of Adelaide, described the evidence that mankind was altering the world as "overwhelming".

He said: "These changes are only a minor portent of what is likely to come."

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