Saving coral reefs from space

An ambitious project aims to completely map all the coral reefs on the planet by 2020 using the world’s largest fleet of Earth-observing satellites.

A satellite photo of a section of the Great Barrier Reef in Australia

One of the most well-known and cited facts about the Great Barrier Reef is that it is so large it can be seen from space. But it turns out that using satellites every coral reef can actually be seen from space, including the ones we haven’t even found yet. That is the goal of a group of major organisations who have teamed up to map every coral reef in the world by 2020. Coral reefs are extremely important biodiversity hotspots providing a home to around a quarter of all marine species. They are also equally important to humans supporting over half a billion people worldwide with food, storm protection and income. Unfortunately they are also one of the most threatened marine ecosystems facing multiple man made pressures including overfishing, coastal development and most notably coral bleaching from rising sea temperatures. It is therefore very important that we are able to monitor the health and abundance of reefs around the world. However this is no easy task because the world’s oceans are so vast and mapping coral reefs is expensive and time consuming. Therefore the solution may just be to look up in order to look back down.

The mission

The challenge of creating a map of coral reefs was started and funded by philanthropist and co-founder of Microsoft Paul G. Allen. He decided to take action after learning that one of his favourite dive spots had been decimated by coral bleaching. So he assembled some of the best scientists, advocates and remote sensing technologists to build a tool that would do three things. Firstly improve global understanding of our coral ecosystems, secondly drive better policies to help protect them and finally to encourage others to take action. Unfortunately he would never live to see these goals become a reality after he suddenly died from Non-Hodgkin lymphoma on October 15th 2018. But because of his insight and backing the aptly named Allen Coral Atlas is already well under way.

Paul G. Allen both created and funded the project before his death

The Atlas aims to use high-resolution and up-to-date satellite image of the world’s coral reefs to create a detailed map highlighting their composition and structure. It is a massive undertaking and includes partners from Planet aerospace, University of Queensland, Carnegie Institution for Science, Hawaii Institute of Marine Biology, and National Geographic. Between them they have the particular expertise and assets necessary to complete the challenge set forth by Allen, including the world’s largest fleet of over 150 Earth-orbiting satellites. The Allen Coral Atlas is already live having successfully mapped six initial sites including Heron Island, Mo’orea, Karimunjawa and West Hawaii. But they plan to have mapped every tropical coral reef above 30 metres depth, including those we may not have even found yet, by the fall of 2020.

Making the map

The mapping process begins in space using the satellites, provided by Planet, that orbit the Earth’s poles. As the Earth rotates beneath them the fleet acts like a line scanner, capturing images of the planet’s surface strip by strip in incredible detail. The images are then sent to the Carnegie Institute for Science where a team led by Greg Asner clean them up removing visual obstructions such as the atmosphere, clouds and light reflection from the sea. It is also at this point that images from multiple satellites are cross referenced to create the most accurate dimensions possible. Asner has stated that “at one of our test sites, we had 132 different Planet satellites pass over” which makes the images they produce as detailed as possible as they cover almost every angle.

From there the polished images are handed over to a team from the University of Queensland, led by Stuart Phinn and Chris Roelfsema, who go over every pixel and classify it as coral, rock, algae or sand as well as calculating other features such as depth. This is cutting edge technology for ocean mapping as, “It is just mind-blowing that we’re able to now do this” said Phinn.  A team of divers are then sent to the location to double check how accurate the process is, although this will eventually be phased out once the method is perfected. The finished images are finally uploaded to the Allen Coral Atlas which is available online for anyone to access.

What does it look like?

allen coral atlas - moorea
One of the first examples of a completed map

The end product is a global photomosaic of Earth’s coral reefs available in a Google Earth style viewer. Each pixel represents four metres squared of reef, which is a remarkably high resolution when you consider the images were captured from space. The pixels are then colour coded, based on the classification done by Phinn and Roelfsema, highlighting their composition. The result is a brightly coloured representation of the features of each reef. So not only can you find the exact locations of each reef you can also tell the depth, size, shape and most importantly the ratio of healthy to dead corals. This allows scientists to determine the status of a coral reef and look for patterns between different locations across the globe all from the comfort of their deckchair. The database is then continually updated based on new incoming images allowing for a real time image that can show any changes as they happen. Have a look for yourself here.

How will it help?

When it is completed the Allen Coral Atlas will be used by experts, such as the Hawaii Institute for Marine Biology who specialise in coral science, as a way of tracking the health of coral reefs. It will act as an early warning system and monitor reefs for any flashes of colour change that will indicate stressors. For example if a large percentage of pixels become lighter then it may indicate significant bleaching or loss of corals to destructive practices such as blast fishing. Whereas a darker colour would suggest an increase of algae due to loss of herbivorous fish from overfishing. But most importantly it will highlight which reefs remain healthy despite factors such as rising sea temperatures. Greg Asner explains “those are key, not just because they’re sitting there now alive, but that’s the future genetic base for what is going to survive in frequently warmer seas”. This will help people such as the Hawaii Institute in their search for ‘super corals’ that are resilient for bleaching and could be the key to saving other species.

Another great loss

Unfortunately Paul G. Allen was not the only major influential member of the Atlas Team that was lost last year. Legendary coral scientist and director of the Hawaii Institute of Marine Biology Ruth Gates lost her battle with brain cancer on October 26th 2018, less than two weeks after Allen. She was described by Andrew Zolli, the vice president of global impact initiatives at Planet, as “one of the world’s most visionary, passionate and committed voices for science, conservation and coral reefs”. But despite the tragic loss of both Gates and Allen the team is determined to finish the work they were so passionate about and will use it to motivate the project. “It has been really hard, but the important thing is how we deliver on the mission” was the message of the Vulcan company that oversees Allen’s philanthropic ventures.

Ruth Gates was a key part of the Allen Coral Atlas

To sum up

Coral reefs are facing a serious fight for their survival in the face of human driven factors and if current trends continue it is a fight they are likely to lose. Therefore the need to monitor these marine ecosystems and the effects we are having on them is greater than ever. The Allen Coral Atlas is already well underway and will hopefully deliver on their goal to finish by the fall of 2020. Once completed it will be an indispensable tool in the fight to protect coral reefs and the vibrant ecosystems they support. But perhaps the most important thing about the project is that it symbolises the legacies and beliefs of people like Paul Allen and Ruth Bates who were willing to stand up and take responsibility for protecting our planet.


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