Global warming may present a threat to animal and plant life even in biodiversity
hot spots once thought less likely to suffer from climate change,
according to a new study from Rice
Univ.
Research by Amy Dunham, a Rice assistant professor of ecology and
evolutionary biology, detailed for the first time a direct correlation between
the frequency of El Niño and a threat to life in Madagascar, a
tropical island that acts as a refuge for many unique species that exist
nowhere else in the world. In this case, the lemur plays the role of the canary
in the coal mine.
The study in the journal Global
Change Biology is available online and will be included in an upcoming
print issue.
Dunham said most studies of global warming focus on temperate zones.
"We all know about the polar bears and their melting sea ice," she
said. "But tropical regions are often thought of as refuges during past
climate events, so they haven’t been given as much attention until recently.
"We're starting to realize that not only are these hot spots of
biodiversity facing habitat degradation and other anthropogenic effects, but
they're also being affected by the same changes we feel in the temperate
zones."
Dunham's interest in lemurs, which began as an undergraduate student at Connecticut College, resulted in a groundbreaking
study last year that provided new insight into a long-standing mystery: Why
male and female lemurs are the same size.
This time, she set out to learn how El Niño patterns impact rainfall in
southeastern Madagascar and how El Niño and cyclones affect the reproductive
patterns of the Milne-Edwards' Sifaka lemur.
The lemur's mating habits are well-defined, which makes the animal a good
candidate for such a study. Female lemurs are sexually responsive to males for
only one day a year in the austral summer months of December or January and
give birth six months later.
Dunham's co-authors—Elizabeth Erhart and Patricia Wright—have done
behavioral studies of lemurs in Ranomafana, a national park in the southeastern
rainforest of Madagascar, for 20 years. Erhart is an associate professor and
assistant chair of the Department of Anthropology at Texas State Univ.-San
Marcos, and Wright is a professor of anthropology at Stony Brook
Univ. and director of the
Institute for the Conservation of Tropical Environments.
"There aren't many species that have such long-term demographic data
that enable us to look at these kinds of questions," Dunham said. "So
this was a unique opportunity."
The warming of global sea temperatures may "enhance" El Niño
cycles, according to the National Oceanic and Atmospheric Administration.
Dunham found that in Ranomafana, contrary to expectations, El Niño makes wet
seasons wetter. "When it rains heavily, lemurs are not active. They sit
there and wait for the rain to stop, huddling for warmth," Dunham said.
Anecdotal evidence suggested heavy rains knock fruit off the trees when
lactating lemurs need it most, and may even kill trees outright.
Dunham learned from the data that cyclones making landfall have a direct negative
effect on the fecundity—or potential reproductive capacity—of lemurs. The team
also discovered that fecundity "was negatively affected when El Niño
occurred in the period before conception, perhaps altering ovulation, or during
the second six months of life, possibly reducing infant survival during
weaning," they wrote.
"Madagascar's
biodiversity is an ecological treasure," Dunham said. "But its flora
and fauna already face extinction from rapid deforestation and exploitation of
natural resources. The additional negative effects of climate change make
conservation concerns even more urgent."
The research was funded by the David and Lucile Packard Foundation, the
Douroucouli Foundation, the Wenner-Gren Foundation, the John D. and Catherine
T. MacArthur Foundation, the National Geographic Society, the National Science
Foundation, the Earthwatch Institute, Conservation International, the Margot Marsh
Biodiversity Foundation, Stony Brook Univ.
and Rice Univ.
Read the abstract at: http://www3.interscience.wiley.com/journal/123301926/abstract.
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