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Coral reefs cover more of Earth’s surface than realised, new estimates reveal
There’s much more coral in the world than previously thought.
Satellite images have revealed a missing 64,000 square kilometres of coral cover, an area similar to the size of Ireland.
The world’s coral reefs cover an astounding 348,000 square kilometres of our planet, a new paper has revealed.
While this may represent just 0.1% of the Earth’s oceans, these reefs are a vital marine habitat. They’re estimated to support anywhere from 25-40% of all marine species, as well as protecting coastlines and providing income for millions of people.
While coral reefs are at risk from threats such as climate change, overfishing and pollution, the researchers are hopeful that by knowing their full extent we’ll be better able to protect them.
Dr Mitchell Lyons, the lead author from the University of Queensland, says, ‘This is the first accurate depiction of the distribution and composition of the world’s coral reefs, with clear and consistent terminology.’
‘It’s more than just a map, however - it’s a tool for positive change for reefs and coastal and marine environments at large. This data will allow scientists, conservationists, and policymakers to better understand and manage reef systems.’
The findings of the study were published in the journal Cell Reports Sustainability.
The coral atlas used satellite imagery to identify suitable coral reef habitat. Public domain image © NASA/JSC via NASA image library.
How much coral is there in the world?
The mapping of the world’s coral reefs is part of a wider project known as the Allen Coral Atlas, which aims to collate a wealth of data to help protect these ecosystems.
Advances in satellite technology means that global estimates of coral cover have only become a reality within the recent years, with the atlas using data from a constellation of satellites known as Dove CubeSats.
Hundreds of these are currently orbiting the Earth, sending back high-resolution pictures that can be used to see how our planet’s surface is changing.
The researchers then combined these with photos from the European Space Agency’s Sentinel-2 satellites to map out the Earth’s coral reefs in unprecedented detail. In total, they mapped 348,361 square kilometres of shallow coral reefs, an area around 1.5 times the size of the UK.
However, of this only around 80,000 square kilometres or so is home to coral itself. The rest consists of environments which are classed as parts of coral reefs, and could be suitable for coral, but are currently either empty or lived in by other important reef organisms such as algae and seagrass.
The maps have also fully documented the coral-rich seas around Indonesia and Australia for the first time. This revealed that Indonesia is as the most coral-rich country on Earth, having about twice as much as Australia.
Coral bleaching occurs when the coral's symbiotic algae are ejected from its body in times of stress. Image © Ethan Daniels/Shutterstock.
Following the completion of the map, the challenge now is to keep the coral atlas current.
The team hope to keep updating and refining their data to demonstrate how coral reefs are changing over time, as the threats to corals become increasingly pronounced. It is also integrating data from other sources to track these threats.
Records of bleaching, for instance, can reveal which areas are at higher risk of being affected by heat, allowing automatic alerts to be issued within days of temperatures rising.
Previous research has suggested that responding rapidly to bleaching, such as putting at-risk corals in the shade, can aid their recovery. This means that early alerts can give nations a better chance of protecting corals during warm conditions.
Rising temperatures in the oceans are also contributing to more powerful tropical cyclones which can devastate fragile coral reefs. In turn, the loss of these reefs can have knock on effects for people who rely on them for their income, be it for tourism or fishing.
As a result, countries are using the coral atlas to plan recovery and restoration efforts. For example, while Vanuatu is set to be hit by increasingly unpredictable coral-damaging cyclones as climate change continues, the map can provide valuable information as to which areas should be prioritised for restoration.
Meanwhile, over in the Seychelles, coral mapping has been used to assess the value of the coral reefs to the country’s tourism industry which is helping them plan for the future.
With these tools in hand, the researchers hope that the corals can survive what the twenty-first century has in store for them.
