Scientists, who also noted that people were mowing their lawns earlier, have concluded that spring now arrives ahead of schedule.

The findings were submitted to scientists at the UK Phenology Network by hundreds of paid observers across the country and have been combined with environmental data over three centuries. The study is bound to intensify calls for tighter controls on environmental pollution linked to climate change.

The report, published yesterday in the BBC Wildlife Magazine, provides startling evidence of how nature is reacting to rising temperatures and changing rainfall patterns. Authors of the report have calculated that spring starts around six days earlier for every 1C temperature rise but not all species are affected in the same way.

For example for every 1C temperature rise, oak trees come into leaf 10 days earlier compared to four days earlier for the ash, its main competitor for space.

In an example of the ecological balance being upset, these changes also affect caterpillars, which are developing earlier to meet the need to feed on the trees' young leaves. This may also have an effect on the migratory patterns of birds that feed on the insects, which can more readily adapt to climate change.

"The findings suggest that there won't be a smooth progression towards a warmer climate, with all species advancing in unison, but rather that different responses may disrupt the complex linkages in nature," said Tim Sparks, one of the report's authors.

The authors predict more drastic changes if, as expected, global temperatures rise between 2C and 6C.

It is now warmer than at any point in the past 1,000 years and nine of the 10 warmest years have occurred in the past decade.

England's beech woods may disappear along with animals such as Scotland's capercaillie and snow bunting - both birds which prefer a cold environment.

The landscape may also change because of shifting rainfall patterns, more extreme weather and rising sea levels, the report predicts. Arable farming may migrate to the west as parts of East Anglia become too dry to cultivate.

"Climate change will affect our wildlife but nature is difficult to predict" said Mr Sparks. "What is clear is that we need to act now if we are able to help the natural world to survive and adapt to future change."

Under a warming climate, Britain may be invaded by new animals and plants. Among birds, the candidates include the black kite, cattle egret and hoopoe. There may also be new moths and butterflies, including the mazarine blue butterfly and the black-veined white butterfly.

More evidence of change

CRICKETS

The long-winged conehead, formerly restricted to the south coast, has moved 60 miles north.

RED ADMIRAL BUTTERFLY

A migrating species that is now spending the winter in the UK.

FROGS

Spawning has occurred before Christmas for several years in milder parts of Cornwall. Researchers have discovered dozens of cases in October and as far north as Northern Ireland.

BUMBLEBEES

Activity in winter is aided by exotic flowers but scientists have logged 4,000 reports of bees in January in what is called a "significant change" in behaviour.

DAFFODILS

Flowering is no longer restricted to spring with it being spotted on Christmas Day. There are similar changes with the white dead-nettle.

OAK TREES

In the past 50 years the oak has come into leaf three weeks earlier. In southern England leaves now emerge in late March.

GRASS

Now grows all year with 7 per cent of respondents to the survey in Scotland cutting their grass in winter.