Lizard researcher dusts off 30-year-old field notes that formed foundation of the study
This article originally appeared on BYU News.
Utah – When Brigham Young University biology professor Jack Sites spent
summers in the late 1970s collecting lizards in Mexico, he had no idea
his field notes would one day help form the foundation for a worldwide
study that attributes local lizard extinctions to climate change.
is the senior author on the paper published in this week’s issue of Science.
Led by Barry Sinervo, professor of ecology and evolutionary biology at
the University of California, Santa Cruz, the study reports a global
pattern of lizard die-offs in habitats unchanged except for rising
The researchers surveyed lizard populations,
studied the effects of rising temperatures on lizards, and used their
findings to develop a predictive model of extinction risk. Their model
accurately predicted specific locations on five continents (North and
South America, Europe, Africa, and Australia) where previously studied
lizard populations have already gone locally extinct. According to the
model, if current trends continue, 20 percent of lizard species could go
extinct by 2080.
The disappearance of lizard populations
is likely to have repercussions up and down the food chain. Lizards are
important prey for many birds, snakes, and other animals, and they are
important predators of insects.
The study began when
Sinervo noticed local lizard extinctions, one of which was among the
lizards studied by Sites between 1977 and 1991.
provided a baseline data set with precise localities where the lizards
were common,” Sites explained. “But Mexican ecologists were going back
every few years, and pretty soon the lizards were hard to find, and then
they weren’t seeing any. These are protected areas, so the habitat’s
still there. So you start to think there is something else going on.”
Sites’ field notes for comparison, Sinervo and collaborators resurveyed
48 species of spiny lizards (Sceloporus) at 200 sites in Mexico where
the lizards had been studied between 1975 and 1995. They found that 12
percent of the local populations had gone extinct.
later connected the lizards’ decline to climate records and studied the
effect of rising temperatures on lizard physiology and behavior. For
example, cold-blooded lizards can’t forage for food when their bodies
get too hot – they must seek shade because they can’t regulate their own
temperature. The researchers found that the hours per day when the
temperature allowed foraging dropped significantly.
said that when the temperature increase hits during a critical month of
the reproductive cycle, the lizards 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,” said Sites, who earned BYU's
highest honor for faculty, the Maeser Distinguished Faculty Award, in
2002. “It doesn’t take too much of that and the population starts to
But for the phenomenon to be linked to climate
change, the pattern would need to be seen globally. Sites connected
Sinervo with researchers in Chile and Argentina, where Sites
has been working for a decade. Sinervo also worked with researchers
who documented lizard declines in Africa, Australia, and Europe.
get this kind of pattern, on five continents in 34 different groups of
lizards, that’s not random, that’s a correlated response to something
big,” Sites said, adding that the effect appears to be happening too
fast for the lizards to adapt.
Sites finds no joy in being
part of such a significant study. “It’s a terrible sinking feeling –
when I first saw the data, I thought, ‘Can this really be happening?’
It’s important to point out, but it sure is depressing.”
says the model now needs detailed testing on all five continents, with a
standardized protocol on lizard species that are widespread.
more about Sites' exploits with reptiles in this BYU
Portions of a UC-Santa
Cruz news release are used here with permission.