Scientists have accumulated the most detailed data to date indicating that human activity is systematically stripping the planet of its rich biodiversity.

Nearly a third of native British plants have significantly decreased in 40 years, more than half of native birds have declined in just two decades and nearly three-quarters of British butterflies have fallen in numbers in 20 years.

The study involved about 20,000 naturalists who inspected the entire British landscape to compile three atlases of native birds, butterflies and wild plants. The information they gathered on the presence or absence of more than 1,500 species in each 10-kilometre (six-mile) square of countryside they surveyed was compared directly with similar atlases compiled 20 or 40 years previously.

In the relatively short period between the past and present surveys, the scientists found a dramatic decline of all three major groups of wildlife, with one-third of all species studied disappearing from at least one part of the UK they had occupied 20 or 40 years ago. Jeremy Thomas, the leader of the study from the Centre for Ecology and Hydrology in Dorset, said the decline in butterflies was much worse than expected and far worse than that of birds or plants. "The results are appalling," he said. "In Britain 71 per cent of all butterfly species have declined in the last 20 years.

Cretaceous-Tertiary extinction (about 65 million years ago)

The last mass extinction wiped out the dinosaurs and nearly half of the main groups of marine animals. Most likely cause was a collision with a large asteroid.

Triassic extinction (199m to 214m years ago)

Killed nearly half of the major groups of marine wildlife. Believed to have been caused by undersea volcanoes.

Permian-Triassic extinction (about 251m years ago)

The worst mass extinction, wiping out up to 95 per cent of species. Probably caused by volcanic eruptions or an asteroid.

Late Devonian extinction (about 364m years ago)

Death toll estimated to be 22 per cent of marine families and 57 per cent of marine genera. No one knows why it happened.

Ordovician-Silurian extinction (about 439m years ago)

Killed a quarter of marine families, including some bizarre creatures such as Hallucigenia (right). Believed to have been caused by a fall in sea levels as glaciers formed, then rising sea levels as glaciers melted.