Friday, May 14, 2010
Goodbye to 20 % of all lizards by 2080?
An interesting, but depressing study was published in Science this Friday. A research team lead by Barry Sinervo, and also including my colleagues Donald Miles (University of Ohio) and Jean Clobert (CNRS, France) have shown an alarming high rate of local population extinctions in Mexico over the last 35 years. Based on these observed real-time extinctions and biophysical modelling of lizard body temperatures in the field (based on experiments), they conclude that the rate of climate change and increasing temperatures are too high for the lizards to have time to adapt.
Lizards and other ectotherms are constrained in their foraging time in hot climates because they must avoid overheating. In particular, viviparous lizards suffer, since pregnant females are especially sensitive: they carry embryos in their bodies which easily die at high temperatures. It is therefore not surprising that most viviparous lizard populations are found at higher latitudes and altitudes, i. e. in colder climates. As temperatures increase dramatically in these environments, these viviparous lizards face a significantly higher extinction risk compared to oviparous lizards, largely because their foraging time becomes drastically reduced and they have to spend a larger part of the day in the shade, to avoid overheating.
The research team estimate, conservatively, that about 20 % of all lizard species on Earth run a significant and serious risk of becoming extinct before 2080, unless the current global warming trend is reversed. This is rather alarming, as lizards is only one of several organismal groups that are likely to have passed the "extinction" threshold determined by anthroprogenic global warming. Other groups that have been discussed are amphibians.
Perhaps we are now entering the next (the sixth) massextinction, which will also drag humans away from this planet? Keep in mind that one of the most famous massextinctions about 251 milllion years ago (The Perman-Triassic massextinction event) killed between 70 and 96 % of all living species, and happened after a global temperature increase of about 6 degrees. Incidentally, a six-degree temperature increase is one of the scenarios outlined by UN:s intergovernmental panel IPCC in their most pessimistic scenario over the coming 100 years (although some climate scientists consider this a rather realistic scenario). If so, Homo sapiens might not have long time left on this planet.
You can read more about this lizard study here, and do not forget to watch the video, where Jean Clobert and Barry Sinervo discuss their findings.