Tropical plants help identify lags between abrupt climate and vegetation shifts

05/28/04

Clues to the timing and cause of abrupt climate changes in the past may lie in ocean floor sediments, according to a study by scientists at Woods Hole Oceanographic Institution (WHOI).

In a paper published May 21 in the journal Science through its Science Express web site, Konrad Hughen, Timothy Eglinton, Li Xu and Matthew Makou used multiple records of climatic and terrestrial vegetation change preserved in ocean floor sediments in the Cariaco Basin in Northern Venezuela. The sediment cores revealed rapid changes during the last deglaciation 15,000 to 10,000 years ago.

"Our data record rapid climate changes, as well as rapid vegetation changes," said Hughen, an associate scientist in the WHOI Marine Chemistry and Geochemistry Department and lead author of the report. While abrupt climate shifts occurred simultaneously in the high latitudes of the North Atlantic and in tropical South America, the WHOI researchers found that abrupt changes in tropical vegetation lagged the abrupt climate shifts by 25 to 50 years.

Previous studies of methane concentrations, a recorder of tropical wetland formation, in Greenland ice cores and temperature changes over Greenland were used to infer that tropical climate change may have lagged high-latitude changes, favoring a high-latitude trigger for abrupt shifts. In today's study, however, the team's findings provide evidence that tropical vegetation change lagged local tropical climate, and climate shifts at high and low latitudes were simultaneous. Thus the trigger for climate change may be in either or both the tropics or high-latitudes.

The reasons for a delayed response time for vegetation changes following abrupt climate shifts are unknown. "It takes a while for trees and plants to be impacted by climate shifts," Hughen said. "Some plants may be able to adapt for a longer period of time than others when faced with gradual rather than rapid climate changes."

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