As our planet warms, thousands of species will struggle to adapt, becoming confined to smaller spaces or dying out altogether. One group of life on Earth already feeling the heat, and projected to decline severely in the years to come, is corals. New research, presented at the 2020 Ocean Sciences Meeting, predicts that coral reef habitats may have disappeared almost entirely by 2100.
The key contributors, the researchers say, are warming waters and ocean acidification, both the result of human-driven climate change. The team believes that in the next two decades, we could lose between 70 and 90 percent of the world’s coral reefs, an alarming statistic.
Corals are teeny marine creatures belonging to the same phylum as anemones and jellyfish. Some corals produce calcium carbonate, forming a hard, protective outer skeleton in which to live – this is what creates the stunning coral reefs we see in tropical oceans. Vast numbers of identical coral polyps can be found together, and most species form a symbiotic relationship with algae that provide them with important nutrients. Coral reefs provide food and homes for an enormous array of life; without these underwater rainforests, many reef-dwelling species could disappear.
The team behind the new research wanted to determine where coral restoration projects could have the most success. Restoration involves growing corals in a lab and then transplanting them into the ocean where they can grow and thrive. Adding fresh young corals to a struggling reef can help it recover to its original state.
However, when the researchers tried to map where best to focus these efforts, they reached a depressing conclusion. By the end of the century, close to zero suitable coral habitats will be left for conservationists to restore.
"By 2100, it's looking quite grim," said Renee Setter, a biogeographer at the University of Hawaii Manoa, in a statement. Her team found that by 2045, most parts of the ocean where reefs dwell won’t be suitable for coral restoration. By 2100, only a handful of locations will be viable options, including pockets of Baja California and the Red Sea.
"Trying to clean up the beaches is great and trying to combat pollution is fantastic. We need to continue those efforts,” Setter added. “But at the end of the day, fighting climate change is really what we need to be advocating for in order to protect corals and avoid compounded stressors."
When the water surrounding a reef heats up, the corals become stressed and eject their symbiotic algae, which removes their color and makes them much more susceptible to death. This process is known as bleaching and can turn entire communities of pink and orange corals a ghostly white.
While many factors affect the health of corals, the researchers believe that increasing acidity and temperature are the biggest contributors to their demise. They note that pollution has already impacted most reefs around the world, so it won’t have such a significant impact in future when compared to the effects of global warming, which is projected to get worse.
To mitigate climate change, we must drastically reduce the amount of greenhouse gases like carbon dioxide that we pump into the atmosphere. Otherwise, iconic aspects of the natural world, such as vibrant coral reefs and their inhabitants, will be lost forever.