The Earth is hurtling towards disaster and up to half of all species on the planet may be extinct in 100 years' time, a leading biologist has warned.

Stuart Pimm, a Professor of Conservation Ecology at Duke University, USA, has conducted research into major extinction events throughout history, including the last great extinction 65 million years ago when a huge asteroid wiped out the dinosaurs.

"When you look at the range of unsustainable things that we are doing to the planet," Professor Pimm told Reuters, "changing the atmosphere, global warming, massively depleting fisheries, driving species to extinction, we realise that we have a decade or two. If we keep on doing what we are doing, by the end of the century our planet will really be a pretty horrendous place."

Pimm remains cautiously optimistic that mankind can help solve many of the problems we create Duke University

Pimm's report, co-authored by Clinton Jenkins from the Institute of Ecological Research in Brazil, calculates the "death rate" every year per million species. Previously it was thought the rate before humans emerged was 1 per million, but the study analysed samples from every region of the Earth, both on land and in the seas and found the actual rate before man was just 0.1 per million. It is now between 100 and 1,000 per million per year, up to 10,000 times the natural rate. This could mean the Earth is on the brink of a sixth great extinction. If that happens, the consequences will be almost unimaginable.

"We lost the dinosaurs and a third to a half of all of the species," says Pimm. "If we continue on the present course, that is how much we will lose, how many species we will lose. And we know after the last time that it took 5-10 million years to recover. So if we destroy this beautiful planet that we have it isn't going to come back overnight."

However, Pimm remains cautiously optimistic that mankind can solve many of the problems we create.As we become more aware of our environment and technology improves, there is still time to save the world: "When combined with data on land-use change and the species observations of millions of amateur citizen scientists, technology is increasingly allowing scientists and policymakers to more closely monitor the planet's biodiversity and threats to it. For our success to continue, however, we need to support the expansion of these technologies and the development of even more powerful technologies to come."