'Global warming takes toll on lizards'

Scientists on Thursday forecast a grim future for the ecologically important critters, indicating that a full 20 per cent of all lizard species – which broadly covers 40 per cent of world’s lizard population – could be extinct by 2080. And India is no exception.

“The Indian subcontinent is an extinction hot spot. In all likelihood, the lizards in India are going locally extinct,” Barry Sinervo from the University of California, Santa Cruz, principal investigator of the project, told Deccan Herald.

Sinervo and colleagues on Thursday reported in the journal Science that rising temperatures drove 12 per cent of the Mexican lizard populations to extinction between 1975 and 1995. The lizards’ future is bleak in almost all other continents.

“Of the lizard families that occur in India, the chameleons are the most likely to be affected, since they tend to have fairly low preferred body temperatures,” said Elizabeth Bastiaans, a PhD student at the UCSC.

The research based on detailed surveys of lizard populations in Mexico from 200 different sites, indicate that the temperatures in those regions have changed, too, rapidly in the last three decades for the lizards to keep pace.

Cold-blooded lizards can’t forage for food when their bodies get too hot. They seek shade because they can’t regulate their own temperature.

The temperature rise hits the lizards during a critical month of the reproductive cycle. As a result they don’t get enough energy resources to support a clutch of eggs or embryos.
“The heat doesn’t kill them, they just don’t reproduce. It doesn’t take too much of that and the population starts to crash,” said Jack Sites, a professor at Brigham Young University.

“The model predicts that, over much of India, lizard populations with a preferred body temperature between 29 and 32 degrees Celsius will have a high probability of extinction (80-90 per cent) by 2080,” said Bastiaans.

She said while the empirical observations on which the model is based were made in Mexico, the predictions can be extended to other lizards. Analyses were carried out for several lizard families which are present in India as well.

Asked if house-lizards too face the extinction risk, Bastiaans said lizards that live in people’s houses could also experience stress due to increasing average temperatures.

“Sadly, the story for India is going to be quite bad for climate-forced extinctions, right now and into the future,” said Sinervo. The disappearance of lizards was first recognised in France and then in Mexico after which Sinervo cobbled up a team of 20 researchers from as many institutes to study the pattern in other countries.