Researchers have developed a new way to map coral reefs accurately and have produced the first-ever global coral reef atlas. The maps contain over 65,000 square kilometers (25,097 square miles) of coral reefs and their habitats.
A 10-year Global Reef Expedition
The novel detailed maps have been designed using a combination of Earth-orbiting satellites and field observations. They are the result of a 10-year Global Reef Expedition.
The expedition surveyed over 1,000 remote coral reefs in 15 countries, many of which had never been studied before. The scientists used data collected from extensive SCUBA surveys.
They then extrapolated that information across the entire reef using ultra-high-resolution satellite imagery. To check the accuracy of their new mapping method, the scientists compared the maps with video footage from cameras along the reef. The effort is part of an attempt to conserve the world's coral reefs.
"In order to conserve something, it's imperative to know where it is located and how much of it you have," said Sam Purkis, professor and chair of the UM Rosenstiel School Department of Marine Geosciences.
"Developing such an understanding for coral reefs is especially challenging because they are submerged underwater and therefore obscured from casual view. With this study, we demonstrate the potential to use satellite images to make coral reef maps at global scale."
More cost-effective and practical
This new method of surveying coral reefs is more cost-effective and practical than traditional ones. Conventional coral reef surveys are expensive since they require hours of underwater surveys conducted by highly-trained scientific divers.
"Satellite, aircraft, and drone imaging will become an increasingly important tool for addressing the coral reef crisis at the global scale at which it's occurring," said Purkis, also the interim chief scientist for the Living Oceans Foundation.
The maps made for this study can be found on an interactive coral reef atlas called the World Reef Map. The atlas also provides baseline data of coral reef health before the 2017 mass bleaching event.
The scientists have made the resource available to the public to promote coral reef conservation and restoration efforts. It is estimated that over 50 percent of coral reefs worldwide have been lost in the past 40 years due to climate change and other human-caused activity.
"Benthic habitat maps are an essential tool in coral reef conservation as they provide a snapshot of where reefs are located and the status of their health," said Alexandra Dempsey, the director of science management for the Khaled bin Sultan Living Oceans Foundation and a co-author of the paper.
"Scientists will use these habitat maps as baseline data to help track changes in reef composition and structure over time."
The maps are published in the journal Coral Reefs.