Hurricanes' impact on wildlife worsens
December 10, 1998
By Environmental News Network staff
When large tropical storms course across the Caribbean and the Gulf of Mexico, their damaging effects are often magnified by ongoing, human-caused disturbances to coastal and island ecosystems, according to U.S. Geological Survey scientists who study the biological and environmental legacy of storms like Hurricane Georges.
Particularly vulnerable are already stressed ecosystems, such as coral reefs, and rare species such as the red-cockaded woodpecker, sea turtles and the highly endangered Puerto Rican parrot, for which the combination of increasing human pressures and the natural cycle of hurricane disturbance can be devastating.
It is still too early to determine what the lasting effects of Hurricane Georges will be on the parrot, but when the storm hit on Sept. 21, there were less than 43 species left in the wild. When Hugo hit in 1989 the population was about the same size and it was reduced to less than half.
Preliminary reports indicate that most of the wild parrots survived the storm this time around, said Dr. Jaime Collazo, a federal geologist working on the recovery effort of this highly-endangered species.
"To date, 36 of 40 birds have been counted during preliminary surveys," he said.
The birds were most likely spared due to Georges path which had a minimal impact on the low valleys where the parrots nest and breed.
Biologists caution, however, that the detrimental effects of hurricanes are often indirect, and not felt immediately. Dr. J. Michael Meyers, a wildlife research biologist at the USGS Patuxent Wildlife Research Center, who has been involved in the parrot recovery effort, says the experience of Hurricane Hugo demonstrated a variety of ways in which the birds can be affected.
"Food may not be available, and the parrots will have to travel farther," he said. "Cover is less, and so predation on the parrots will be higher."
Once numbering in the tens or even hundreds of thousands, the wild population of Puerto Rican parrots reached an all-time low of 13 in 1975.
Scientists believe that extensive deforestation in Puerto Rico is the main cause of the decline, along with hunting and the collection of parrots for pets.
In the wake of Georges, researchers will monitor such things as survival and movement patterns of the parrots, as well as try to assess how habitat changes as a result of the hurricane may affect the ability of the wild parrots to elude predators.
Dr. James Wiley, leader of the USGS Grambling Cooperative Wildlife Project in Mississippi, has studied hurricane effects on wildlife in Puerto Rico and on other islands in the Caribbean. In addition to the parrot, Wiley says, people should be concerned about the recent storm's impact on other threatened wildlife.
Both of these species are critically endangered, with populations numbering in the hundreds. Like the Puerto Rican parrot, the endemic pigeon and blackbird have been reduced from large to remnant populations through loss of habitat and, in the case of the plain pigeon, hunting.
Wiley says he has received one report of plain pigeons coming into urban areas to feed on royal palm trees after the hurricane. "That is abnormal behavior, and suggests that food resources in normal foraging areas are a problem," he said.
Both Wiley and Collazo say that a small population size and limited range can make any species extremely vulnerable to chance events such as hurricanes.
Many Caribbean species have adapted to take advantage of the changing patchwork of habitats created by these disturbances. But this evolutionary dynamic is upset when there is no acceptable habitat for individuals driven out of one area to move into, or when there is no larger population to recolonize disturbed regions.
As well, coral reefs, though not hit as hard as they were by Hugo, were disturbed by Georges. Like other species, corals normally benefit from hurricanes, but because of poor land-use practices they are more vulnerable to sediment and rampant algal growth.
"Reefs have persisted for thousands of years and can usually regenerate after hurricanes," said Dr. Caroline Rogers, a U.S. Geological Survey biologist. "However, reefs which are subject to a combination of natural stresses and harmful human activities may not be able to bounce back."
Dr. Thomas Doyle, an ecologist at the USGS National Wetlands Research Center, said that while scientists have no sure way of predicting hurricane patterns in the future, they do know that hurricanes will have a greater harmful impact on more species and ecosystems as long as current land-use trends continue to fragment habitats and disrupt natural processes.
"Parceling conservation areas into smaller non-contiguous land units makes them more susceptible to greater hurricane damage," he said. Rare and narrowly distributed species like the Puerto Rican parrot are already experiencing the implications of this basic ecological lesson.
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