Changes in Coral Reefs May Be Sign of Global Warming
Upsurges in water temperature are primarily responsible for outbreaks of bleaching in the world’s coral reefs and may signal global changes from a magnified greenhouse effect, scientists said Thursday.
“The first proof of global warming may well come from the bleaching of the fragile and highly sensitive coral reef system,” Ernest H. Williams of the University of Puerto Rico’s Caribbean Aquatic Animal Health Project told the subcommittee on science, technology and space of the Senate Commerce, Science and Transportation Committee.
“Unfortunately, we do not have sufficient data to fully evaluate this intriguing suggestion,” he said, “because this gigantic series of disturbances have been understudied and virtually ignored.”
As far back as 1911, scientists have studied episodes in which coral lost its normal yellow and brown color and took on an appearance of tan or brilliant bone-white, but the outbreaks have attracted mounting attention since severe cases in 1987. Similar outbreaks are expected this year.
Although the loss of color indicates that coral is under great stress, it recovers. But the researchers warned Thursday that episodes of increasing frequency and severity could lead to destruction of reefs, which some call the tropical rain forests of the ocean.
Bleaching occurs when algae, which provide sustenance for the thin veneer of living cells covering the coral skeletons, withdraw or are expelled from the coral colonies. In the absence of algae, the outer coral tissue becomes transparent and the organism takes on the color of its skeleton.
Across the Caribbean--in reefs off Florida, Jamaica, the Bahamas and elsewhere--bleaching has been observed at water depths from four feet to 200 feet.
A notable spread of bleaching was observed in the Caribbean in 1979 and 1980. It was observed in Australia and the eastern Pacific in the next two years and has recently intensified around Puerto Rico, Jamaica, the Florida Keys, Okinawa and Hawaii, Williams said.
Although pollution is known to cause stress in coral colonies and lead to bleaching, Williams and five other scientists appearing before the Senate panel Thursday agreed that elevated water temperatures are the most prevalent cause.
Outbreaks studied during the 1980s consistently coincided with record water temperatures, Thomas J. Goreau, a research scientist at the Discovery Bay Marine Laboratory in Jamaica, told the panel.
The conclusions of the coral experts were substantiated by data on global atmospheric temperatures gathered by satellite. Roy Spencer of the National Aeronautics and Space Administration and John Christy of the University of Alabama at Huntsville said that the bleaching coincided with readings of elevated temperatures in the lower and middle levels of the atmosphere.
Unless there is a dramatic turnabout in the remaining weeks of the year, 1990 will be the warmest year on record, British climatologist P. D. Jones of the University of East Anglia told the panel.
Worldwide, the month of March was the warmest month ever recorded. In Siberia, Jones said, the temperature was an astonishing 18 degrees above the average of the preceding decades.
The reports were issued as climate scientists and environmental ministers from around the world prepare to meet in Geneva for the second World Climate Conference, setting the stage for the opening round of negotiations on a global warming treaty.
Sen. Albert Gore Jr. (D-Tenn.), chairman of the hearing, charged that the Bush Administration has already set out to sabotage the conference by preventing the scientific conclusions from being made a part of a declaration by environmental ministers.
