As ocean temperatures rise because of climate change, corals and other sensitive organisms survive where temperatures are less extreme. But a new study from researchers at Florida Tech, published this month in the journal Communications Earth & Environment, found that local land and sea use have suppressed the benefits of these potential safe havens in some places.
Extended periods of unusually warm water temperatures, known as marine heatwaves, drive deadly mass-bleaching events on coral reefs, like those seen in the Florida Keys in 2023 and the Great Barrier Reef in 2024 that made headlines globally. These mass-bleaching events can cause cascading effects that disrupt the rest of the ecosystem.
“Identifying locations where coral reefs have been least impacted by marine heatwaves and where the environment is most favorable for the survival of corals, known as climate refugia, is critical for protecting these complex ecosystems and the benefits humans gain from them,” explained Andrew Walker, a Ph.D. candidate at Florida Tech and lead author of the new paper.
Yet marine heatwaves are not the only threat coral reefs face globally. Though scientists and researchers have warned for decades that human-caused disturbances, such as sewer discharge, excess fertilizer use, and overfishing negatively impact coral reefs on a local scale, the new study broadens the view of these impacts.
“The ecological impacts of local disturbances have been difficult to detect on a global scale, making the scope and impact of the issue difficult to determine,” said co-author Rob van Woesik, professor and director of the Institute for Global Ecology at Florida Tech and co-author of the paper. “Our study sheds light on the prevalence of both local impacts and marine heatwave impacts on stony corals, revealing where these local-scale effects are likely suppressing otherwise viable climate refugia,” continued van Woesik.
In addition to mapping the impacts of marine heatwaves and local disturbances globally, the Florida Tech team also examined different environments that have been hypothesized to act as climate refugia: high-latitude reefs, deep reefs, remote, offshore reefs, and turbid reefs. The Florida Tech team found that turbid reefs showed the most potential to act as climate-change refugia. “While turbid reefs are not as visually stunning as clear-water reefs, more and more studies, ours included, have found that turbid reefs may be some of the best locations for corals to survive climate change,” says Walker.
But the frequent nearshore location of these reefs means they are more exposed to the negative impacts of local land and sea use, suppressing their potential to act as climate refugia. “Reducing the impacts of local disturbances on these reefs can provide corals with more climate refugia than researchers had previously anticipated,” van Woesik said.
Walker added, “These findings should empower regional and local governments, management, and local organizers to protect their coral reefs from climate change through reducing the stress corals face from other, more localized disturbances.”
The findings from Walker and van Woesik were published ion the article, “Local human disturbances on coral reefs negate potential climate refugia,” on Feb. 6 in the journal Communications Earth & Environment.
