Coral reefs cover a larger area than previously thought – 02/19/2024 – Science

The total area of ​​the planet covered by coral reefs is larger than previously thought, according to the most comprehensive, high-resolution assessment ever made.

Shallow coral reefs cover around 348,000 square kilometers of the globe’s surface — an area equivalent to the state of Goiás —, according to research led by the University of Queensland, in Australia. Previous estimates indicated an area of ​​154,000 square kilometers to 301,000 square kilometers.

“This is the first accurate representation of the distribution and composition of the world’s coral reefs, with clear and consistent terminology,” said Mitchell Lyons, a researcher at the University of Queensland and lead author of the study. “This data will allow scientists, conservationists and policymakers to better understand and manage reef systems.”

Coral reefs are home to around a quarter of all marine life on the planet and are essential for the livelihoods of around a billion people.

These ecosystems are extremely vulnerable to climate change, which is leading to rising ocean temperatures and increasing water acidification.

At several points, they are being decimated by mass bleaching events and disease, which are expected to become more intense and frequent as the Earth warms.

Accurately mapping corals is a necessary step toward protecting them, researchers say. The research published in Cell Reports Sustainability last Tuesday (13) used more than 100 trillion pixels of detailed images from Planet’s Sentinel-2 satellites and Dove CubeSat constellation, in addition to a set of data provided by 480 different sources. This information was then used to train a machine capable of classifying the presence of reefs at different depths.

Scientists have mapped a total of 348,361 square kilometers of coral reefs down to about 15 meters of water depth. This area includes hard surfaces like coral and rock, as well as soft surfaces like sand, rubble, mud, or seagrass.

About a quarter of the total area has been classified as coral habitat, where high-density stony coral is found. Seagrass meadows, which play an important role in marine ecosystems, cover 67,236 square kilometers.

Scientists now want to improve the tool’s ability to distinguish species. This is necessary to assess a reef’s resilience to climate change and its impacts, said Helen Fox, director of conservation science at the US-based Coral Reef Alliance and co-author of the paper.

“It’s important to preserve genetic diversity,” Fox said. “The more diversity you have, the greater the chance of having different species that can survive.”

Previous efforts to map coral reefs on a global scale were undertaken before high-resolution satellites could photograph the entire surface of the world. This meant that this type of map was only available at local or regional scales. The new map is publicly available through the Allen Coral Atlas and Google Earth Engine.

“The main question is whether these results can help us understand what is happening on small scales, contributing to decision-making at the local level,” said Fox.

The data is already being used to support conservation efforts, restore coral reefs and identify sensitive areas.

Projects using the tool are underway in more than a dozen countries, including Indonesia, Vanuatu, Belize, Kenya, Australia and Micronesia.

The Fijian government is using the maps as a data source to identify areas of coral that need to be rehabilitated after cyclones.

“It’s more than a map,” Lyons said. “It is a tool for positive change for reefs and coastal and marine environments in general.”