Coral reefs don’t just harbor unique ecosystems that take millennia to grow. According to new research, they also protect vulnerable coasts from crashing waves, since their nooks and crannies dissipate much of each wave’s energy before it makes landfall — and as they’re killed off by the warming ocean, the ocean could buffet coastlines like never before.
"What we found was that if you lost the health of your coral reef, if it lost its structural integrity and its live coral cover, you could get waves that were larger than what were predicted due to high sea levels," said Daniel Harris, a geomorphologist at the Australian University of Queensland and the lead author of a new paper that describes the findings in Science Advances. “That means you don’t need to wait for rising sea levels to have bad outcomes.”
The results are particularly grim because of their relationship to climate change. Stress from warmer water temperatures cause coral to expel the symbiotic algae that live in their tissues, leading them to turn white and become susceptible to disease and storm damage. That phenomenon, known as "coral bleaching," has killed off reefs across the world.
To study the effect of bleaching on wave height, Harris and his collaborators collected wave energy data from island reefs in French Polynesia. Then they used that data to model what future waves will look like as the coral continues to degrade. What they found was grim: as the reefs die, the waves that hit the shore could more than double in height, which could erode beaches, threaten coastal infrastructure and compound the damage of rising sea levels.
If Harris’s findings are accurate, he believes, island nations could start to feel the brunt of the super-powered waves in just five or ten years, as cyclones and storm surges break down what remains of dead and dying reefs.