Coral reefs are 25% larger than we thought, revealed by Satellite Imagery

We have recently discovered that the world’s coral reefs are actually 25% larger than we previously thought. By using satellite images, machine learning, and on-ground knowledge from a global network of people living and working on coral reefs, we have identified an extra 64,000 square kilometers (24,700 square miles) of coral reefs – an area equivalent to the size of Ireland.

In total, the planet’s shallow reefs, which means reefs that are between 0-20 meters deep, now amount to 348,000 square kilometers, which is the size of Germany. This figure includes entire coral reef ecosystems, ranging from sandy-bottomed lagoons with a little coral to coral rubble flats and living walls of coral.
Within this 348,000 km² of coral, 80,000 km² is home to a hard bottom – rocks instead of sand. These areas are most likely to be home to significant amounts of coral – the places that snorkelers and scuba divers prefer to visit.

Previously, it was challenging to determine the exact extent of coral reefs as we had to gather information from various sources. But now, with high-resolution satellite data covering the entire world, we can see reefs as deep as 30 meters down. Together with direct observations and records of coral reefs from over 400 individuals and organizations across countries with coral reefs from all regions, such as the Maldives, Cuba, and Australia, we were able to produce the world’s first comprehensive map of coral reefs and their composition, called the Allen Coral Atlas.

To create these maps, we used machine learning techniques to analyze 100 trillion pixels from the Sentinel-2 and Planet Dove CubeSat satellites to make accurate predictions about where coral is and is not. The team worked with almost 500 researchers and collaborators to make the maps.

The maps are already being used by reef management agencies worldwide to plan and assess conservation efforts and threats to reefs. The Tongue Reef, off Port Douglas in Far North Queensland, is an excellent example of the new detail we now have for previously undetected coral.

Our maps have three levels of detail, the first being the most expansive – the entire coral reef ecosystem, seen from space as light areas of coral fringed by darker deeper water. Then we have geomorphic detail, which shows what areas within the reef look like, including sandy lagoons, reef crests exposed to the air at low tide, sloping areas going into deeper water, and so on. And finally, we have fine detail of the benthic substrates, showing where coral is most likely to be and the substrates (seafloor) available to the polyps, such as existing coral, sand, rubble, or seagrass.

Coral cannot grow on sand and must attach to a hard surface like rock before expanding the reef out of their limestone-secreting bodies. Our maps include fine detail of benthic substrates, which helps identify where coral is most likely to be found and the available substrates to the polyps.
Despite these exciting discoveries, coral reefs are in danger due to climate change, which is heating up the sea and making it more acidic. Coral polyps cannot handle too much heat, and these ecosystems are home to a quarter of the ocean’s species.

On a brighter note, these maps are already leading to real-world change, as we have seen new efforts to conserve coral reefs in Indonesia, several Pacific island nations, Panama, Belize, Kenya, and Australia, among others.

This news is a creative derivative product from articles published in famous peer-reviewed journals and Govt reports:

Reference:
1. Lyons, M., & Phinn, S. (2024, February 14). The world’s coral reefs are bigger than we thought – but it took satellites, snorkels and machine learning to see them. The Conversation. https://theconversation.com/the-worlds-coral-reefs-are-bigger-than-we-thought-but-it-took-satellites-snorkels-and-machine-learning-to-see-them-223322

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