Why this could be the worst extinction event

Is the world already tumbling into a massive extinction event with thousands of species disappearing from the planet? Some scientists think so and this could become the worst mass extinction yet.

The Countdown 2010 Initiative seeks to reverse global species loss, but it faces enormous challenges. Habitat loss and degradation, over exploitation, the depredations of invasive alien species and impacts caused by climate change and disease have put tens of thousands of species under severe pressure.

Species extinction is nothing new and there have been almost two dozen major species losses in the past 550 million years, including five particularly big extinctions.

Many people are familiar with the End Cretaceous extinction, the event that wiped out the dinosaurs, leaving the way open for the spread and domination of mammal species. This extinction happened about 65 million years ago and killed off 50 per cent of all land and ocean species.

The greatest of all mass extinctions--to date--was the End Permian extinction which took place 251 million years ago. Also known as the "Great Dying" it wiped out about 96 per cent of marine species and 70 per cent of land species. The End Ordovician extinction 444 million years ago ranks as the second worst event of this kind and the Late Devonian 360 million years ago was almost as bad, eliminating about 70 per cent of all species then living on the earth. But could the worst mass extinction already be underway? We live in what is known as the Holocene Epoch, which began at about 10,000 to 12,000 years ago at the end of the last ice age.

Extinctions are an inevitable consequence of our changing Earth, with natural modifications to climate, ocean currents, global temperature which dictates ice cover, and over geological time, the movement of entire continents.

Human civilisation emerging since the beginning of the Holocene has significantly altered this picture however, accelerating change and forcing the natural pace of extinctions.

The IUCN's "Red List" of endangered and extinct species indicates that recent extinction rates far exceed species losses seen in the fossil record. Rates based on known extinctions of birds, mammals and amphibians over the past 100 years indicates that current extinction rates are 50 to 500 times higher than rates seen in the fossil record.

The figure could 100 to 1,000 times higher than the natural extinction rate if possible extinctions rather than fully confirmed extinctions are included. And this says nothing about the species which may quietly disappear from the planet unmarked by human recording.