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A new way to map and monitor the world’s coral reefs

The Allen Coral Atlas is an ambitious project led by Vulcan Inc. to map and monitor coral reefs worldwide in unprecedented detail by 2021. The project includes scientists from ASU GDCS, the University of Queensland, and Planet as well as a field engagement team from National Geographic Society. Our team has been developing key components of the technology that powers the Allen Coral Atlas.

Why is a map of the world’s coral reefs needed?

Nearly 75% of the world’s coral reefs are threatened by a combination of global stressors such as climate change and local stressors such as overfishing and coastal development. That number is expected to rise to nearly 100% by 2050 if action isn’t taken now.

Why care about saving coral reefs? To begin with, they are some of the most biologically diverse ecosystems on our planet, supporting more species per unit area than any other marine environment. These biodiversity hotspots have provided the material for making a host of life-saving drugs to treat diseases including cancer and HIV— and they are rife with the potential for sourcing countless new medications. Along with their biological value, coral reefs also provide economic value. They protect coastal communities from storms by diffusing the energy of powerful waves and preventing property damage and coastal erosion in the process. Reefs also yield an estimated $375 billion per year globally in goods and services such as fishing and tourism.

For all these reasons, protecting and conserving our planet’s reefs is something everyone should care about. The first step in doing so is understanding exactly where coral reefs are located. Before the Allen Coral Atlas, scientists had a very broad idea about the global distribution of coral reefs but with very little accuracy. Now, scientists can pinpoint the exact location of reefs and also discern meaningful differences between reefs and adjacent features such as sand and seagrass.

These side-by-side maps of Heron Island before the Allen Coral Atlas mapping (left) and after (right) illustrate this advancement. On the left, the coral reef appears as a large turquoise-colored mass. After the same location was mapped with the Allen Coral Atlas, an astonishing amount of detail appears. The coral reef is represented by the thin outline in purple, circling an assemblage of sand, rubble, rock, and other non-coral features.

Maps of Heron Island before the Allen Coral Atlas mapping (left) and after (right).

While these improvements to mapping corals are significant, they make up just half of the bigger picture. To effectively improve conservation and management outcomes for reef ecosystems, reefs need to be monitored for major environmental changes such as bleaching events or damage from a typhoon. GDCS scientists developed the algorithms that make detailed maps like the one above possible. With that accomplishment behind them, they’ve shifted focus to developing a system to monitor changes to reefs in real-time using machine learning.

How does GDCS science and technology contribute to mapping the world’s coral reefs?

Operating the largest constellation of satellites currently in low Earth orbit, Planet acquires daily global coverage of the entire landmass of our planet and its coral reefs at 3.7-meter resolution. Many of these satellites are as small as a loaf of bread but, operating together, they collect over 11 terabytes of data every single day.

For the Allen Coral Atlas, GDCS scientists analyze and process thousands of Planet satellite images covering regions of shallow water such as coastlines where coral reefs are known to exist or where they would likely be found. GDCS analytics are then applied to the mosaics to remove “noise” such as clouds, waves, sediments, and sunlight glint on the surface of the water. Their methods also provide the water’s depth and the reflectance of the seafloor beneath the water. The corrected mosaics are then ready for further analysis by partners at the University of Queensland.

The side-by-side images below show a Planet mosaic of a coral reef before GDCS processing. On the right, GDCS algorithms have removed the noise and created one seamless image.

The image on the left shows a Planet mosaic of a coral reef before GDCS processing. On the right, our algorithms have removed the noise and created one seamless image.

How does GDCS technology detect coral reef bleaching?

Planet’s continuous stream of daily imagery of coral reefs worldwide yields a massive amount of data—too much for even a large team of scientists to manually sort through. Luckily, advanced artificial intelligence, or AI, can accomplish this otherwise impossible task. GDCS AI is can automatically compare thousands of images at a time to hunt for differences between them over timescales of days to weeks to months and even years. Subtle differences between images point to changes to coral reefs such as large-scale bleaching and storm damage.

For instance, the side-by-side images below show the same location in Moorea in French Polynesia before and after a suspected bleaching event. The area in the green square is brighter on the right than on the left, indicating coral reef bleaching.

GDCS monitoring at work: A portion of reef on Moorea Island, French Polynesia on April 15th 2019 before (left) and on May 17th during (right) a bleaching event.

Our team is continuing to refine these algorithms to render even greater detail and locate the exact areas where coral reefs are actively changing.

In the next article, we’ll explain how an early version of GDCS monitoring technology was used to track coral bleaching during Hawaii’s 2019 marine heatwave while providing real-time updates to the Hawaiian government and its citizens to drive conservation action.