In October 1996, Hurricane Lili was a killer in Central America. In Cuba, it destroyed homes and cane crops. But at its final landfall, among the small islands of the central Bahamas, the great storm was a stroke of extraordinary fortune for three American scientists--a catastrophe that created in hours the natural conditions they had speculated about for 20 years.
The resulting information may answer long-standing questions about catastrophic impacts on ecosystems and could help conservationists plan better ways to preserve natural habitat.
"This was the experience, not of one lifetime, but of several lifetimes," said one of the three scientists, UC Davis ecologist Thomas Schoener.
"I think it's unique in science," Schoener continued. "You have here a very destructive event that strikes any given site very infrequently, the experimental site was very well studied for a number of years, and the investigators not only were there during and after the hurricane but also had completed their annual population censuses just hours before the storm arrived. It won't happen again in scientific research."
A description of the adventure from UC Davis ecologist David Spiller, Washington University evolutionary biologist Jonathan Losos and Schoener appeared in the July 31 issue of the journal Science.
On Oct. 18, 1996, Spiller and Losos had just returned to Great Exuma Island from surveying the spider and lizard populations on 19 smaller islands nearby. The work was part of a long-term study of the islands' food web.
Back on Great Exuma, the researchers found weather bulletins faxed from Schoener, who was in Davis, that warned of Hurricane Lili's approach. In darkness, as the winds rose to gale force, they helped their Bahamian friends board up buildings, then collected their irreplaceable notebooks and headed for a sturdy house on higher ground.
Soon, the researchers write in the Science article, "The highly improbable happened. . . . Hurricane Lili, the first major hurricane to strike anywhere in the Exumas since 1932, passed directly over our study site with sustained winds of 90 knots [about 110 miles per hour] and a storm surge of nearly five meters [about 15 feet]."
The next day, as soon as the storm subsided, and for three days thereafter, the researchers again took a census of the populations on all the islands. Both then, and in repeated observations during the next year, the researchers found evidence for a hypothesis advanced by Schoener in 1983: When Anolis lizards are missing from small Caribbean islands with lizard-friendly habitat, hurricanes are to blame.
Their unprecedented before-and-after data, the authors write, also helped them evaluate other, more general hypotheses about the ecological impact of a natural catastrophe. They concluded:
* Larger organisms were more resistant than small ones to the immediate impact of a moderate disturbance, but the more prolific organisms recovered faster.
* Local extinction risk was related to population size when the disturbance was moderate, but not when it was catastrophic.
* After a catastrophic disturbance, the organisms that could disperse the most readily recovered the fastest.
Understanding such effects is more than academically interesting, Spiller said. It could help shape programs for preserving natural communities.
Spiller and Losos will return to Great Exuma this October, in the last weeks of the 1998 hurricane season, to continue to follow the recovery of the biota on the devastated islands.
