The Earth is en route to its sixth mass extinction, say a group of paleobiologists in the latest edition of Nature.

Such events are characterised by very rapid and widespread loss of biodiversity and over three-quarters of all species dying out in a geologically very short time span. After previous episodes it took life on Earth millions of years to recover.

The recorded catastrophes in Earth’s ancient history were caused by external forces, like massive meteorites, but the sixth mass extinction, dubbed the Holocene Extinction, would be the direct result of human influence on the ecological world around us, through climate change, pollution, overfishing and intensive land use. It is an insight that led Nobel laureate Paul Crutzen to state the Holocene is actually over – and that we now live in the Anthropocene, the geological period that will even have its fossil record directly influenced by the dominance of humans.

Mammal extinction rate increased more than 80,000-fold

The researchers studied fossil records of the last 65 million years and found the ‘natural’ extinction rates among mammals are actually as low as ‘less than 2 species’ dying out in one million years. In the past 500 years however this increased sharply, with at least 80 of the total of 5570 mammal species going extinct.

Extrapolating trends of endangered species the researchers conclude that 75% of the remaining mammals will have died out in 334 years from now.

Comparing fossil records to present data the researchers find a similar speed up of extinction rates for amphibians, reptiles, birds, plants, mollusks, and other forms of life. The authors state their study highlights the need for effective conservation measures.

© Rolf Schuttenhelm | www.bitsofscience.org