Mangrove Forests Demonstrate Surprising Storm Resilience in Changing Climate: Study

Mangrove forests buffer coastlines from flooding while acting as valuable carbon sinks, but scientists are concerned about the impacts that more extreme and frequent storms caused by climate change are having on these ecosystems.

In a new study, scientists from Yale School of the Environment discovered that mangrove forests could actually be more resilient to these more intense storms than had previously been thought.

“Mangrove forests are strong carbon sinks. In addition to their potential for carbon storage in both vegetation (above- and belowground) and the soil, anoxic conditions dampen aerobic respiration, increasing the capacity for carbon sequestration,” the authors wrote in the findings of the study. “Consisting of only 0.5% of the coastal area, mangroves contribute 10%–15% of total coastal sediment carbon storage globally and 10%–11% of total particulate carbon export to the marine environment. Thus, mangrove forests are critical to the global carbon cycle.”

The research team determined the “recovery debt” of Everglades National Park mangroves in the aftermath of hurricanes Irma in 2017 and Wilma in 2005, a press release from Yale School of the Environment said. The recovery debt is the total amount of carbon lost during a storm and the amount of time it takes to get it back. The results showed that the mangroves recovered all the carbon that was lost during the storms within four years.

The relatively fast turnaround of south Florida mangroves suggested that the ecosystems will continue to be strong carbon sinks.

“Although important for their capacity to capture and sequester carbon, mangroves are among the most threatened and rapidly disappearing coastal environments worldwide. More than 35% of mangrove forests have been degraded or lost over the past two decades due to anthropogenic activities,” the authors wrote in the findings. “Occurring in regions with a high frequency of tropical storms and hurricanes, mangrove-dominated ecosystems exist across subtropical to tropical coastlines, including South Florida, the Gulf of Mexico, and within the Caribbean.”

The team’s calculations gave an approximation of the amount of time mangroves need to recover adequately between storms, which the scientists said is essential information as storms increase in intensity and frequency.

“Mangroves have the capacity to capture carbon lost due to hurricanes relatively quickly,” said Sparkle Malone, a research scientist and assistant professor of ecosystem carbon capture with the Yale Center for Natural Carbon Capture, in the press release. “It’s a good sign that mangroves in the Everglades are and will continue to be relatively resilient to the types of disturbances we know they’re going to experience in the future.”

Earlier research focused on how the magnitude of individual storms impacted mangroves or the recovery of individual features of the ecosystem.

The recent findings help shed light on the complex processes involved in ecosystem recovery following climate shocks, as well as the importance of long-term ecological monitoring.

“Many people frame disturbance research in terms of how much initial loss there was,” said lead author of the study David Reed, an associate research scientist at Yale School of the Environment. “That’s part of the story, but it’s really about how long it takes to recover from that loss.”

Reed compared the recovery debt of the mangroves to an unexpected expense. If someone’s budget is small, it could take a significant amount of time to pay off a surprising expense, whereas if one’s finances are stable, it’s less of a burden.

To calculate the mangroves’ recovery debt, the researchers analyzed years of data from before and after storms. To establish landscape-wide patterns, the team examined observations from satellite imagery and monitoring towers.

“There have been a lot of resources and instrumentation put in this area, and so you can study processes that you can’t do on the landscape scale anywhere else in the world,” Malone explained.

Malone said the findings reflect a reassuring and surprising degree of resilience that underscores the importance of restoration efforts.

“We know that it’s in the millions, maybe even billions, of dollars of resource protection that mangrove forests provide, and so this confirms with all of the funding and effort put into Everglades restoration, that it’s worth it,” Malone said. “We will likely continue to reap the benefits of those investments for a long time into the future.”