In a recently published article in the journal Nature, scientists report that the most widely used methods for calculating species extinction rates are “fundamentally flawed” and overestimate extinction rates by as much as 160 percent. Nevertheless, the global species extinction crisis caused by habitat loss is real and a growing threat.
This warning by scientists who just stated that extinction rates are overestimated must not be disregarded. Hopefully, politicians and the public in general will take notice of the warning of these critical scientists. Their warning is much more important than their message that when better methods will be applied the extinction rates will not be overestimated anymore. When no steps will be taken to preserve habitats, and thereby preserve animals and plants, they will be lost and gone forever.
Habitat loss is widely regarded as the main driving force for species extinction. Therefore conservation efforts are directed at the prevention of this habitat loss, which is paramount. Though there is agreement within the research and conservation community about the importance of extinction, the rates of this phenomenon are still highly uncertain. As no proven direct methods or reliable data exist for verifying extinctions. The indirect method scientists and conservationists have used until now is called a “species-area relationship”. This method starts with the number of species found in a given area and then estimates how the number of species grows as the area expands. Using that information, scientists and conservationists did backward extrapolations to estimate how many species will remain when the amount of land decreases due to habitat loss. Dr. Hubbell, one of the authors, says: “In the Nature paper, we show that this surrogate measure is fundamentally flawed. The species-area curve has been around for more than a century, but you can’t just turn it around to calculate how many species should be left when the area is reduced; the area you need to sample to first locate a species is always less than the area you have to sample to eliminate the last member of the species”.
The warning of the scientists regarding the effect of habitat loss has been articulated on UCLA’s website where Hubbell says: “There have been five mass extinctions in the history of the Earth, and we could be entering the sixth mass extinction. Humans are already using 40 percent of all the “plant biomass” produced by photosynthesis on the planet, a disturbing statistic because most life on Earth depends on plants. Some three-quarters of all species thought to reside on Earth live in rain forests, and they are being cut down at the substantial rate of about half a percent per year”.
(Sources: Nature, 19.05.2011; UCLA newsroom, 18.05.2011)
