Posts Tagged ‘habitat loss’

Overestimating biodiversity loss?

Thursday, June 2nd, 2011

Earlier this May, Fangliang He and Stephen Hubbell made headline news by publishing, in Nature, a study that demonstrates that usual estimates of species extinction rates are actually overestimates. Their argument is basically as follows:

Estimates of biodiversity loss from habitat loss are generally based on a relationship between the number of species in an area and that area’s surface. This relationship is known as the species-area curve. It is based on surveys that count species inside a survey area. The bigger the area, the more species there are. Of course, it makes sense to say that the bigger the area lost, the more species are lost.

What He and Hubbell explain is that in establishing the species – area curves, species are added to the count as they are encountered. The survey area necessary for a first encounter with a species is necessarily smaller than the area that encompasses 100% of that species (except in the trivial case of there being only one single individual of the species).

This larger area, which harbours 100% of the species, is the one which should be used for calculating species extinction from habitat loss. As a result, the species – area relationship gives less species going extinct for a given area of habitat loss… Makes sense doesn’t it?

The authors insist that their point does not mean that biodiversity is not being lost at an alarming rate. That also makes sense of course.