Global warming puts Madagascar's reptiles and amphibians in danger of extinction

Raxworthy has been surveying the diversity of Madagascar's herpetological assemblage since 1985 and discovered the uphill migration almost by chance while in the field. On repeated surveys of northern Madagascar's mountains, the Tsaratanana Massif, he noticed that some species were missing from camps where they'd been previously observed. Moreover, some of these "missing" species popped up at the next higher elevation surveyed. He culled elevation records and was able to compare surveys of animals over a ten-year period.

The results were dramatic. Among 30 species of geckos, skinks, chameleons, and frogs, and controlling for sampling effort, an average shift uphill of 19 to 51 meters (62 to 167 feet) was observed over the decade. When these results were compared with meteorological records and climate change simulations, the movement of animals could be linked to temperature increases of 0.1°C to 0.37°C (0.18°F to 0.67°F) over the same decade, which corresponds to an expected upslope movement of 17 to 74 meters (59 to 243 feet).

Raxworthy's results are robust because of the diversity of species included in his analyses. These animals come from five different families of amphibians and reptiles—narrow-mouthed toads, mantelline frogs, chameleons, geckos, and skinks—making it unlikely that a simple phenological change could explain the upward movement. "When you see a general trend across all these groups of organisms, it is likely to be related to a broad explanation like general temperature warming, not something more subtle such as seasonal variation," says Raxworthy.

These species, currently moving upslope to compensate for habitat lossat lower and warmer altitudes, will eventually have no place to moveto. "Two things together—highly localized distribution close to thevery highest summits, and the magnitude of these upslope shifts inresponse to ongoing warming—make a poisonous cocktail for extinction,"said Raxworthy.

The direct link between observed movement up mountains, possible extinction, and climate change has consequences for Madagascar's network of national parks. The government of Madagascar is currently planning to set aside 10 percent of its landmass for conservation purposes. "The Malagasy government is creating important new reserves and protecting forests. Sadly, however, with a phenomenon like global warming, species will move upslope, and so eventually may still lose all their habitat and go extinct," says Raxworthy. "This conservation problem thus requires a global solution."