Most coral reefs in the Caribbean could stop growing, and even start eroding, by 2040 if global warming continues unchecked, a new study finds.
Coral reefs, especially those near shores, protect valuable coastlines from flooding during cyclones and storm surges by breaking up wave energy. For the reefs to continue to act as natural wave barriers, they need to grow fast enough to keep up with sea level rise. However, coral growth is increasingly under threat from diseases, pollution and the effects of climate change.
Climate change, in particular, is causing a decline in reefs worldwide. Rising ocean temperatures are causing corals to bleach and die, making reefs more vulnerable to other threats. Meanwhile, higher carbon dioxide levels are making seawater more acidic, making it harder for corals to build their skeletons.
Researchers who monitor coral reefs in the tropical western Atlantic or the Caribbean — including the Florida Keys, Mexico’s Caribbean coast and the Caribbean island of Bonaire — have observed the progressive decline in reef health due to diseases and extreme ocean heat over the last several decades, said Chris Perry, the study’s lead author and a professor at the University of Exeter, U.K.
So, the researchers set out to find out how well reefs in the region will continue to grow as the climate warms. They first examined vertical sections of ancient fossil reefs, exposed by coastal uplifting. This allowed them to understand how different coral communities built reefs over time in the past, Perry said.
They combined this understanding with ecological data from more than 400 modern reef sites to calculate how fast these reefs grow today. Further, they used climate models to predict how the reefs’ current growth rates might change by 2100 under different global warming scenarios.
The researchers found that by 2040, more than 70% of coral reefs in the Caribbean region could stop growing and start eroding. By 2100, nearly all the reefs could be eroded, if warming reaches 2° Celsius (3.6° Fahrenheit) above pre-industrial levels. Under current climate policies, temperatures globally are projected to rise by 2.7°C (4.86°F) by 2100.
The analysis also projects that coral growth is unlikely to keep pace with sea level rise. In some areas, reefs could face 0.3-0.5 meters (about 1-1.6 feet) of additional water over them by 2060, and about 0.7-1.2 m (2.3-3.9 ft) by 2100.
Coral reefs not only protect shorelines, they are also an essential sheltering habitat for marine life and sustain important fisheries that communities globally depend on. If coral growth can’t keep pace with sea level rise, the reefs’ ability to reduce coastal wave energy will be diminished, increasing the risk of coastal erosion, flooding and disruption of ecosystems like seagrass meadows, Perry said.
Actions that keep global warming to below 2°C will be critical to limiting the worst effects of future sea level rise, he added.
Banner image: Leonoras reef in Klein Bonaire. Image by EdFladung via Flickr (CC BY-ND 2.0).
