INCREDIBLE SATELLITE IMAGES, COMBINED WITH MACHINE LEARNING AND THE DIRECT KNOWLEDGE OF EXPERTS FROM ALL OVER THE WORLD, HAVE REVEALED ANOTHER 64,000 km² OF CORAL REEFS, AN AREA AS LARGE AS IRELAND, WHICH WAS NOT KNOWN TO EXIST
Journey among the incredible coral reefs
The incredible coral reefs, among the ecosystems richest in biodiversity, host a vast range of animal and plant species. Among these, the red coralonce abundant also in Italy, today increasingly rare in the Mediterranean.
Well, these formations, typical of tropical seas and oceans, are much larger than we ever imagined.
Another 64,000 km² of barriers were discovered. This brings the total size of the planet’s shallow coral reefs (0-20 meters deep) to 348,000 km² – the size of Germany.
But there’s more.
Within these 348,000 km² of coral, 80,000 km² have a rocky rather than sandy bottom. A perfect ecosystem for coral, since it cannot grow on sand. The polyps must attach themselves to a hard surface such as rock before they can begin to expand the reef from their limestone-secreting bodies.
In short, a real attraction for snorkelers and underwater fishing enthusiasts.
But why have the true dimensions of the barriers only been discovered today?
From the human eye to the triumph of technology
In the past, collecting data on coral reefs required Herculean efforts.
In fact, it was necessary to combine a series of information from sources scattered all over the world.
Now, thanks to modern high-resolution satellite technologies, machine learning and field data to produce benthic and geomorphic maps (processed by the Allen Coral Atlas system), it has been possible to map coral reefs up to 30 meters deep.
Previously it had not been possible to descend beyond 25 metres.
Result?
It was possible to obtain the first complete map in the world of the extent of coral reefs and their composition.
The painstaking work is due to over four hundred scholars and organizations spread throughout the world, from the Maldives to Cuba to Australia.
Let’s try to understand how we came to process the incredible images.
Focus on machine learning mapping. In search of lost coral
Machine learning techniques analyzed as many as 100 trillion pixels from the Sentinel-2 and Planet Dove CubeSat satellites. The goal? Accurately predict where the coral was located. A challenging task made possible only by the unwavering commitment of the team made up of researchers and collaborators from every corner of the world.
The result is a digital work of art that reveals the intricate contours of these underwater ecosystems, giving us an unprecedented glimpse into the fascinating world of coral.
The maps of the Allen Coral Atlas have in fact offered a complete vision of the coral reefs.
Three incredible mappings
An initial mapping showed the entire coral reef ecosystem, with its light areas of coral surrounded by darker, deeper waters.
The second examined the geomorphic characteristics (landforms in their genesis and evolution) that make up coral reefs: from sandy lagoons to ridges exposed during low tide.
Finally, the third explored the benthic substrates, i.e. composed of those aquatic, animal and plant organisms which, during a continuous and important period of their life, maintain a relationship with the bottom.
The images were breathtaking: they revealed the areas where coral can grow and thrive, and those where the ocean cannot accommodate these spectacular limestone formations.
A precious conservation tool
But the Allen Coral Atlas maps didn’t just serve to show the beauty of the reefs.
Above all, they are a vital tool for the conservation of our precious marine heritage. Coral reef management agencies around the world use them to plan and evaluate conservation work, as well as address growing threats to coral reef life.
From Indonesia to Panama, Belize to Australia, communities are coming together to protect these ocean wonders.
Some curiosities
In 1842, the biologist and naturalist Charles Darwin proposed a classification of coral reefs into three main categories: coral reefs surrounding islands, coral reefs, and atolls. Darwin also observed that over time one type of coral reef could evolve into another.
Importance of coral reefs
Coral reefs are of fundamental importance and must be defended for several reasons. First, in recent decades, we have seen a significant increase in coral bleaching, the so-calledbleaching”.
It is caused by the death of polyps, which can be caused by diseases or changes in environmental conditions such as temperature and salinity, phenomena often related to ongoing climate changes.
Furthermore, the excessive spread of coral predators, such as starfish “crown of thorns” Acanthaster placi (Linnaeus, 1758) threatens the ecosystem and the colonies of these very small octopuses.
Coral reefs not only provide vital habitats for a wide range of marine species, but are also of great value to humans. For example, Mediterranean red coral, once highly prized by the Greeks, Romans and Persians, not only for ornamental purposes but also for its medicinal properties, was used in the treatment of colic and kidney stones.
To tell it, Pliny the Elder (23 AD), in his Natural History.
And it was the Roman naturalist who was the first to identify the presence of corals also in our Mediterranean sea, around Naples, Trapani and along France almost two millennia ago.
Today, unfortunately, overfishing and other human activities have made corals increasingly rare and difficult to find.
Therefore, the protection of coral reefs is essential not only to preserve marine biodiversity, but also to safeguard the resources they provide for human well-being.
Source
Mitchell Lyons, Postdoctoral Researcher, University of Queensland and Stuart Phinn, Professor of Geography, Director – Remote Sensing Research Centre, Chair – Earth Observations Australia, University of Queensland
Creative Commons.