USA (10 Nov 2001) -- Only 5 percent of the coral in the Carysfort Reef, the largest reef in the Florida Keys, is left alive, according to new research based on images from NASA's Landsat 7 spacecraft. In 1975, more than half the Carysfort Reef was live coral. For the first time, the structure and extent of coral reefs can be monitored globally with new observations from Landsat 7. Detailed images of reefs from nearly 900 locations around the world have been collected in the first year of the Landsat 7 mission. "Landsat 7's ability to see land features as small as 100 feet across and to repeatedly observe coral reefs worldwide makes this archive of images a unique and valuable scientific resource," said Landsat project scientist Darrel Williams of NASA's Goddard Space Flight Center in Greenbelt, Md. "No one else has been willing or able to acquire and archive this type of high-resolution global data for use by the scientific community," he said. Scientists at the University of South Florida (USF) in collaboration with colleagues at the College of Charleston and at Dalhousie University in Halifax, Nova Scotia, have completed initial tests of Landsat 7's ability to study coral reefs. They presented their results at the Ninth International Coral Reef Symposium in Bali, Indonesia, Oct. 23-27. Nearly 1,500 scientists are attended the meeting, which is held only once every four years. "Reefs around the world are in ecological collapse, especially in the Florida Keys," said Phil Dustan of the College of Charleston. "We need to use remote sensing to help fight for their conservation." The research includes a Landsat 7 inventory of the extensive coral atolls in French Polynesia in the South Pacific using 22 separate scenes, each covering about 12,000 square miles. The study shows coral reef scientists how to do a large-scale reef inventory anywhere around the world. "With the Landsat 7 data, we can rigorously test hypotheses about how entire reef ecosystems form," said coral reef ecologist Bruce Hatcher of Dalhousie University. "We no longer are limited to the observations we can collect by wandering around in small boats and sampling individual reefs to infer large-scale processes from a few samples." Hatcher and doctoral student Abdulla Naseer from the Maldives Ministry of Fisheries are using Landsat 7 data to understand how wind, waves, and sea level have shaped the coral-reef nation of the Maldives, south of India. By combining weather and tidal records with a catalog of the physical features of the 2,800 reefs derived from Landsat 7 images, they can identify patterns of reef growth and erosion caused by monsoons and the ocean's waves and currents. A detailed understanding of how these climate forces shape coral reefs will enable scientists to better predict how reefs will respond to future climate changes. | |
Scientists estimate that 10 percent of the world's coral reefs have already been seriously degraded and a much greater percentage is currently threatened. Overfishing, destructive fishing practices, pollution, siltation, and global climate change are all seen as threats to the beauty of coral reefs and to their services to this and future generations of humans. In recognition of the dire outlook for coral reefs, the International Coral Reef Initiative (ICRI), a partnership among governments, international organizations, and nongovernment organizations, was created in 1995 to preserve coral reefs and related ecosystems. With the Landsat 7 image archive, physical damage to reefs can now be monitored in near real-time, said Hatcher. "With Landsat 7's repeated coverage of coral reefs throughout the year and its fine-scale imaging capability, we will be able to see damage to reef structure caused by hurricanes." More than 5,000 coral reef images have been collected to date by the Landsat 7 mission. Many reefs have been imaged several times, providing a glimpse of seasonal changes in reef structure and biology. Landsat 7 was launched by NASA in April 1999 and began routine science observations in June 1999. Images are archived, processed, and distributed by the U.S. Geological Survey, which also assumed responsibility for daily operations of Landsat 7 in October. SOURCE - ENN |
