Mangroves show surprising resilience to storms in a changing climate

(Press-News.org) Dense, spindly mangrove forests line the coast of tropical regions, buffering coastal flooding and providing a valuable sink for carbon, but there is concern that more intense and frequent storms due to climate change could have prolonged impacts on these ecosystems. A new study by Yale School of Environment scientists, however, suggests that these systems may be more resilient than expected.

The team calculated the “recovery debt” of mangroves in Everglades National Park after hurricanes Wilma and Irma, showing that all the carbon lost during the storms was recovered within four years. (Wilma hit South Florida in 2005 and Irma hit in the region in 2017.) This relatively fast turnaround suggests that these ecosystems will remain strong carbon sinks. The calculations also provide a rough estimate of how many years mangroves need between storms to recover adequately — a vital threshold to understand as storms increase in frequency and intensity, the scientists note.

The findings, recently published in Global Change Biology, help illuminate the complex process of ecosystem recovery after climate-driven shocks and the value of long-term ecological monitoring.

“Mangroves have the capacity to capture carbon lost due to hurricanes relatively quickly,” said Sparkle Malone, assistant professor of ecosystem carbon capture and research scientist with the Yale Center for Natural Carbon Capture, who led the study. “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.”

Previous research has focused on the magnitude of individual storms’ impact on mangroves or examined the recovery of individual aspects of the ecosystem. Few studies have unraveled all of the ecological processes at play in recovery.

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

To that end, the researchers used the novel measure of recovery debt, which reflects the total carbon lost during each storm and how long it would take to get it back.

Reed likened it to an unexpected financial expense. If one’s budget is tight, the debt from the surprising expense could take a long time to pay off, but if one is financially stable, it is less of a burden. 

Biweekly, we highlight three news and research stories about the work we’re doing at Yale School of the Environment.

To calculate recovery debt, the team needed to analyze several years of data both before and after storms. In partnership with Florida International University, they tapped into the Florida Coastal Everglades Long Term Ecological Research program, which provides information on forest structure, soil biogeochemistry, and other data, as far back as 2004 at some sites. The team used observations from two monitoring tower sites and satellite imagery to establish landscape-wide patterns.

“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 said.

The findings reflect a surprising — and reassuring — degree of resilience that underlines the value of restoration efforts, she said.

“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.”

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