Department News

2011-05-18

Professor Steve Hubbell Published In Nature and Featured in the UCLA Newsroom

Professor Steve Hubbell has been recently published in Nature, "Species-area relationships always overestimate extinction rates from habitat loss". The point that Professor Hubbell's paper makes is: Extinction due to habitat loss is the signature conservatrion problem of the 21 century Despite its importance, estimating extinction rates is problematic because there are no proven direct methods for estimating extinction. So conservation biologists typically use and indirect method based on the species-area relationship to estimate future extinction rates from projected habitat loss. However, we show in our paper that this is fundamentally flawed logically. The species- area relationship is a a species accumulation curve that describes how the number of species increases with sample area. Since species do not occur everywhere, by adding more sample area, the number of species always increases with larger areas sampled. The idea has been that one can simply reverse the species- accumulation curve, reducing the area, and calculate how many species should be left after a certain amount of habitat has been lost. The problem with this method is that the sampling problems when constructing a species-area curve are completely different than when reducing area to calculate species extinction. When one constructs a species-area curve, one adds a new species to the count of species already found as soon as one individual of the new species is encountered. However, to case a species to go extinction, one must remove area until the last individual of a species is included in the sample area. We prove a theorem in our paper that the area needed to find the first individual of a species is always less than the area required to encounter the last individual of a species. We then give some examples of the extent of overestimate of extinction rates, which range up to at leas 160%. However, we go to great pains to say that our findings should not lead to complacency about extinction due to habitat loss, which is a real and growing problem.This article is featured in an interview of Professor Hubbell in the UCLA Newsroom.