Is the planet on the verge of experiencing its sixth mass extinction? Or is this notion merely “speculation without substance,” as American scientist John C. Briggs wrote a decade ago? The subject has long been a source of ongoing controversy among scientists, and it has recently resurfaced.
In April, two American researchers, John J. Wiens and Kristen E. Saban, published an article in the journal Trends in Ecology & Evolution (TEE) entitled “Questioning the sixth mass extinction.” They argued that no study has demonstrated that 75% of species could disappear within a short geological time span – the commonly accepted definition of a mass extinction. The researchers also listed seven reasons challenging this concept (less than 0.1% of known species have disappeared in five hundred years, not all species are threatened, conservation efforts are underway, threats to biodiversity may change, etc.).
The article prompted a sharp response from other researchers. Robert H. Cowie, Philippe Bouchet, and Benoît Fontaine had to tone down the first version of their reply before it was published. “Denying that we may be experiencing the start of the sixth mass extinction paves the way for it to happen,” they wrote in a letter published in mid-June in TEE. While they acknowledged that skepticism can drive scientific progress, they said Wiens and Saban had “taken it too far” and that their study is “grist to the mill” to those who wish to ignore environmental issues. In mid-July, Wiens and Saban published a response to these criticisms.
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