Think invasive exotics are responsible for the extinction of local species? Think again, reports Fred Pearce in NewScientist (5 September 2015, paywall):
The UK government’s Non-native Species Secretariat (NNSS) declares that invasive species have “contributed to 40 per cent of the animal extinctions that have occurred in the last 400 years“. Its source is the Global Biodiversity Outlook 2 report, published in 2006 by the secretariat of the UN Convention on Biological Diversity (CBD).
They, in turn, say the stat came from a 2005 paper by Cornell ecologist David Pimentel, who was in turn drawing on a 1998 paper by David Wilcove, now at Princeton University.
As is clear from the paper’s title, “Quantifying threats to imperiled species in the US”, Wilcove was not talking about actual extinctions but an extinction threat, and in the context of the US (in fact, his data largely related to Hawaii). Wilcove told me his paper was being misused. Although informed of this, the NNSS has kept the claim on its website. …
Uh oh. Eventually we reach this juicy detail:
The report cites a 2005 paper in the journal Trends in Ecology & Evolution, by Miguel Clavero and Emili Garcia-Berthou of the University of Girona, Spain. But that turns out to be just four paragraphs long.
It reports, but gives no details of, an analysis of a quarter of the 680 extinct species in an International Union for Conservation of Nature (IUCN) database. The authors told me they had not kept the details of their analysis, nor notes on which species they had included.
Ya gotta be kidding me. They sound as bad as … myself. And that’s bad. The reason for this dubious paper?
This work was a riposte to a rather longer paper by Jessica Gurevitch and Dianna Padilla of Stony Brook University in New York, who looked at the same IUCN database and concluded that just 2 per cent of all extinctions had alien species listed as a cause.
Especially for a rebuttal, failing to keep your notes, or the details of the analysis, is inexcusable – thus, Fred’s turn of phrase, “Chinese Whispers”. And it turns out many citations and conclusions come to rest on this report. While no one’s denying there must be concerns about invasive species – whether we’re talking the zebra mussels in Minnesota’s lakes or the rather more exotic pythons in the Everglades of Florida – understanding the true numbers is key to the proper allocation of resources towards the problem, as the magnitude of the problem is unquestionably the key. In fact, here’s a chilling example of a failure to defend against an invasive species properly:
(Image courtesy Imgur)
