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Satellites Update Coral Reef Maps Made by Darwin

Satellites Update Coral Reef Maps Made by Darwin

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With Earth-observing satellite data, scientists can now monitor the health of coral reefs, even in the most remote regions scattered around the globe where it is otherwise difficult to see changes.

The extensive coral reefs on the northern shore of Vanua Levu, Fiji's second largest island, can be seen on this natural color Landsat 8 image acquired on May 10, 2015. (Photo from: NASA/USGS/Landsat)

The extensive coral reefs on the northern shore of Vanua Levu, Fiji’s second largest island, can be seen on this natural color Landsat 8 image acquired on May 10, 2015.
(Photo from: NASA/USGS/Landsat)

Satellites fill a void by providing a more complete view of remote reefs. The information is monitored globally through Coral Reef Watch, an online tool that provides near real-time and long-term monitoring, forecasting and reporting of tropical coral reef conditions. Coral Reef Watch is operated by the National Oceanic and Atmospheric Administration (NOAA).

This information is being used to monitor the quality and temperature of the waters around reefs worldwide. Water temperatures that exceed certain thresholds for a period of time can lead to a loss of corals. Satellite data processed through Coral Reef Watch provides early warning of natural and human-caused pressures that result in reef decline and loss.

Until relatively recently, global maps of coral reefs hadn’t changed significantly from the maps produced by Charles Darwin in 1842. Darwin based his historic maps on observations from his expeditions around the world. Later, French scientist Louis Joubin updated those maps in 1912 using information he received through letters from people living near coral reefs around the world.

It wasn’t until about 15 years ago that coral reef mapping leapfrogged to modern times. A new global map of coral reefs was created with over a thousand Landsat 7 satellite images collected between 2000 and 2003.

“Until we made the map of coral reefs with Landsat 7, global maps of reefs had not improved a lot since the amazing maps that Darwin drafted,” said Frank Muller-Karger, professor of oceanography at the University of South Florida in St. Petersburg, Florida. Previous Landsat missions were designed to look at land and were typically “turned off” over large oceans to conserve power. Landsat is a collaborative NASA and U.S. Geological Survey mission.

The Enhanced Thematic Mapper Plus sensor, the main instrument onboard Landsat 7, led to the development of the Millennium Global Coral Reef Map, which is distributed openly and is used by researchers and coral reef managers around the world.

The Landsat 8 satellite with the Operational Land Imager (OLI) sensor offers significantly improved capabilities. “The Landsat 8 OLI is allowing us to outline the reefs around the world and measure area and estimate depth in ways never possible before,” said Muller-Karger.

Muller-Karger teamed with the NOAA Coral Reef Watch program under a 2013 NASA Applied Sciences grant to develop new products using U.S. and international satellites for a coral reef ecosystem stress alert program.

Coral is a living organism that makes rocklike deposits of their skeletons. These marine animals leave these deposits to accumulate to form reefs over hundreds to thousands of years. These reefs provide a habitat for more than 1 million species of plants and animals while also protecting coastlines from storm damage and erosion and providing a tourism destination.

Factors influencing the health of coral reefs include rising sea levels, powerful storms, pollution, coastal development, mining pressures for cement, overfishing and other human activities such as the construction of artificial islands and ports.

(Read the full report originally written by Audrey Haar in Phys.org.)

Avatar of Coral Triangle Written by Coral Triangle

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