|
| Landsat
7 Shows Global Trove of Coral |
Allen Kenitzer
October 25,2000
Goddard Space Flight Center, Greenbelt, Md.
Tel. 301/286-2806
Colette Glover-Hannah
University of South Florida, Tampa
Tel. 813/974-6996
Release No. 00-127
GLOBAL CORAL REEF MONITORING NOW FEASIBLE
WITH NEW LANDSAT 7 DATA ARCHIVE
The structure and extent of coral reefs can now, for the first
time, be monitored globally, thanks to new observations from
NASA's Landsat 7 spacecraft. 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
(30 meters) 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."
Scientists at the University of South Florida, in collaboration
with colleagues at the College of Charleston and Dalhousie University
(Halifax, Nova Scotia), have completed initial tests of Landsat
7's ability to study coral reefs and are presenting their results
at the 9th International Coral Reef Symposium in Bali this week.
Nearly 1500 scientists are expected to attend the quadrennial
meeting.
Landsat 7 measurements of live coral in the Carysfort Reef,
the largest reef in the Florida Keys, matches detailed surveys
taken on the ground, according to a joint study by Frank Muller-Karger,
Serge Andrefouet, and Dave Palandro of the University of South
Florida's College of Marine Science and Phil Dustan of the College
of Charleston. The surface area of live coral in this reef has
declined from more than 50 percent to less than 5 percent since
1975.
"Reefs around the world are in ecological collapse, especially
in the Florida Keys," says Dustan. "We need to use remote sensing
to help fight for their conservation."
Andrefouet has also completed 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.
He was able to identify and map many different types of reef
formations, from entire atolls covering hundreds of square miles
to individual marine habitats. "This study shows coral reef
scientists how to do a large-scale reef inventory anywhere around
the world," says Andrefouet, a remote-sensing scientist who
was raised in French Polynesia.
"With the Landsat 7 data we can rigorously test hypotheses about
how entire reef ecosystems form," says 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 2800
reefs derived from Landsat 7 images, the scientists 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.
With the Landsat 7 image archive, physical damage to reefs can
now be monitored in near real-time, says 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."
Over 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 day-to-day operations of Landsat 7 this month.
-end-
download the MS Word document of this press release here |
|
