Sixth Extinction: Will it be man-made?

The entire basis of organic evolution is underpinned by the appearance of some species and the disappearance of others; extinction is therefore a natural process.

According to the fossil record, as few as 2-4% of the species that have ever lived are believed to survive today. The remainders are extinct, the vast majority having disappeared long before the arrival of humans.

But, the rapid loss of species that we are witnessing today is estimated by some experts to be between 100 and 1,000 times higher than the “background” or expected natural extinction rate.

Unlike the mass-extinction events of geological history, the current extinction phenomenon is one for which a single species - ours - appears to be almost wholly responsible. Such a deteriorating situation is being referred to as “the sixth extinction crisis”, after the five known extinction waves in the Ordovican, Devonian, Permian, Triassic and Cretaceous Periods.

Man-made Prehistoric Extinction
Extinctions caused by humans are generally considered to be a recent, modern phenomenon. However, humanity's first significant contribution to the rate of global extinction may have occurred during the past 100,000 years, when North
and South America and Australia lost 74 to 86% of the genera of "megafauna" - mammals greater than 44 kg.

In Australia, where the earliest human remains are dated to approximately 64,000 years, the great majority of the 22 identified genera of large land animals disappeared between 30,000 and 60,000 years ago.

In the Americas, almost 80% of large-bodied genera became extinct. Extraordinary creatures, such as sabre-toothed cats, mammoths, giant armored glyptodonts and giant ground-sloths, all disappeared some time between 11,000 and 13,000 years ago, coinciding with the dates of the first clear evidence of a human presence there.

Recent Extinction
Island megafaunas - like giant birds known as moas in New Zealand, the dodo on Mauritius, giant lemurs and the extraordinary elephant bird in Madagascar, or large rodents and ground-sloths in the Caribbean - survived until much more recently than the continental faunas. All seem to have disappeared within a few hundred years after the arrival of humans - in the case of the moas within the last 300 years.

In the last 500 years, human activity has forced 844 species to extinction (or extinction in the wild).


Current Status

A total of 15,589 species of plants and animals are known to face a high risk of extinction in the near future, in almost all cases as a result of human activities. This includes 32% of amphibian species, 24% of mammal species, 12% of bird species, 25% of conifers and 52% of cycads.

Of the 129 recorded bird extinctions, 103 are known to have occurred since 1800, indicating an extinction rate 50 times that of the background rate.

The total number of threatened animal species has increased from 5,205 to 7,266 since 1996.

Habitat loss and degradation affect 86% of all threatened birds, 86% of mammals, and 88% of threatened amphibians.

Main Culprit Countries
Indonesia, India, Brazil and China are among the countries with the most threatened mammals and birds, while plant species are declining rapidly in South and Central America, Central and West Africa, and Southeast Asia.