A half-million-year record of some deep-water cousins of crabs called ostracodes provides some of the strongest evidence yet that global climate change can reduce the variety of life forms on Earth, according to a report released Thursday (Feb. 13, 1997).
"For the first time, we have been able to plot the ups and downs in biodiversity in a particular group of animals through 11 complete periods of drastic global climate change," said Dr. Thomas M. Cronin, research geologist with the U.S. Geological Survey. "The rise and fall in the number of species of ostracodes during 11 glacial cycles suggests that the effects of any future global climate change-whether natural or manmade-could further affect the richness of life on Earth beyond the risk already posed by habitat degradation and other environmental effects."
Cronin and coauthor Dr. Maureen E. Raymo, Associate Professor at Massachusetts Institute of Technology, reported in the February 13, 1997, issue of Nature that the biodiversity of bottom-dwelling communities living in the abyssal North Atlantic Ocean has been unstable in the face of past global climatic changes.
They measured how trends in the biodiversity of fossilized ostracodes varied over a half-million year interval of alternating cold (glacial) and warm (interglacial) climates. The microscopic fossil shells were preserved in deep-sea sediment cores recovered from the North Atlantic Ocean by the Ocean Drilling Program.
By comparing the trends in biodiversity with global climate change
as determined from the chemistry of the shells, the authors were able to
establish a statistical correspondence between diversity and climate
changes that were caused by cycles of the Earth's orbit relative to the
sun. The astronomical or orbital theory of climate holds that changes in
the seasonal and geographical distribution of the sun's energy reaching the
upper atmosphere strongly influence Earth's climat
Contact: Donovan Kelly
United States Geological Survey