Biological Journal of The Linnean Society

Recently, two articles were published in leading scientific journals, each calling attention to an emerging mass extinction. The two are complementary in that they reached the same conclusion by using data from contrasting environments. But, the important question in each case is, can the beginning of a mass extinction be confidently predicted from the evidence presented? The two articles are the latest of several publications that have stated the Earth is in the beginning of a great extinction episode that will eventually result in the loss of at about 75% of all living species. The most recent extinction of this magnitude occurred at the close of the Cretaceous about 65 million years ago. The new mass extinction prognosis began about 22 years ago and was based on estimates of species extinction, due to human activities, that had reached thousands of species per year. Although such unsupported estimates soon gave way to more realistic approximations based on documented records, the spectre of a mass extinction has remained. However, I have found evidence that human-caused extinctions have amounted to only about 1.5 species per year for the last 500 years and that these losses have probably been equalled or surpassed by species born (speciation) during that time. Without evidence of substantial net species loss, mass extinction becomes a speculation without substance. The world’s greatest conservation problem is not species extinction but population decline to the point where many species exist only as remnants of their former abundance.

Emergence of a sixth mass extinction?