Coral reefs, true reservoirs of biodiversity, are seriously threatened by human activities and climate change. Consequently, their extinction has often been heralded. Now, researchers are painting a less gloomy picture: the planet's reefs are not doomed to disappear. But they will be very different from the ones we presently know. A new coral fauna will emerge, coming from the species that are most resistant to temperature increases.
Some reefs are recovering
Are coral reefs condemned to disappear? During the first decade of the 21st century, the intensification of cyclones, the phenomenon of coral bleaching due to ocean warming, outbreaks of a coral-eating starfish and coral diseases left us with this fear. But today, scientists are revising their pessimistic forecasts from the previous decade. In fact, recent research works show that, while numerous coral species have indeed been declining for more than 30 years, other are holding firm or even increasing in abundance. Consequently, some reefs have recently managed to recover.
Expanding coral genera
During a vast international study over fifteen years, IRD researchers and their partners observed the ecological development of seven coral reefs throughout the world: two in the Caribbean, in Belize and in the American Virgin Islands, and five throughout the Indo-Pacific Ocean in Kenya, Taiwan, Hawaii, Moorea and the Great Barrier Reef in Australia. Consequently, the scientists have shown the increase of certain genera, like the Porites reef corals, real reef builders that can resist temperature rises well.
They have also put these recent changes into perspective with regard to past events recorded in fossil reefs, showing that the abundance and structure of coral populations have already varied greatly over the course of past millennia.
Towards new underwater landscapes
These new data have enabled them to refine their mathematical models and to revise their forecasts for the coming decades. As ocean temperatures continue to rise, a subset of "winning" species will thrive: those that have the greatest heat tolerance, the best population growth rates or the greatest longevity. These species should progressively populate the planet's reefs, until they dominate them entirely.
Consequently, the underwater landscapes of the future will be very different to the ones that have been known for millennia. However, much remains to be discovered regarding this new coral fauna and its features. One question in particular remains: will these new eco-systems continue to meet the needs of the populations who depend on them?
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