Coastal Communities’ Living Barriers—Mangroves and Coral Reefs—Could Soon Collapse Due to Climate Change

Mangroves and coral reefs help prevent erosion and block storm surges during extreme weather. But even they have their limits, new studies suggest.

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The mangroves in Seychelles, Aldabra Island store vast amounts of carbon but are still threatened by climate impacts. Credit: Wolfgang Kaehler/LightRocket via Getty Images

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Hundreds of thousands of “climate refugees” had to flee their homes following the devastating floods that hit the southern state of Rio Grande do Sul in Brazil at the end of April, which I covered in last week’s newsletter

Around 1,000 miles north of this region, however, conservationists in Rio de Janeiro have spent four years planting tens of thousands of mangrove trees to ensure that they don’t suffer a similar fate, reports the Associated Press.  

Research shows that these wetland forests are often the first line of defense during a severe storm, stabilizing soil and sand to prevent erosion and blocking seawater during storm surges, which are frequent in Rio de Janeiro’s Guanabara Bay. Coral reefs play a similar role for coastal communities around the world, reducing up to 97 percent of wave energy during a storm

However, these natural barriers may be faltering. A new report found that more than half of mangrove ecosystems around the world are at risk of collapse by 2050 due to human development and climate change. Meanwhile, coral reefs are in the midst of their fourth ever worldwide bleaching event, which dampens their ability to buffer coastlines. 

For today’s newsletter, I am diving into why these ecosystems are crucial for protecting communities from hurricanes and sea-level rise, and how scientists and insurers are scrambling to save them in the face of climate change. 

Nature’s Bulwarks: Mangrove forests typically grow in tropical brackish swamps near the coast in places like Florida, Colombia and Malaysia. Largely visible above the ground and in crystal clear waters, the trees’ root networks provide nurseries for fish and crabs and dig firmly into the soil, forming a living wall for coastal communities. 

A 2020 study found that these trees prevent more than $65 billion in property damages around the world each year. Along with providing productive fishing waters for local communities, mangroves also act as massive carbon sinks, storing almost three times the carbon as tropical forests, helping to slow climate change. 

But even these natural coastal barriers have their limits. Mangroves are being increasingly threatened by deforestation, development, pollution, dam construction and climate impacts such as rising sea levels and hurricanes. Though the trees are saltwater tolerant, too much seawater can be toxic; in 2017, Hurricane Irma killed more than 10,000 hectares of mangrove forest—equivalent to nearly 25,000 football fields—in southwest Florida, many of which died because seawater was trapped around their roots, according to NASA

Losing more than half the world’s mangroves could also mean the loss of $36 billion worth of coastal flood protection, and 17 million days of fishing effort—which represent the total amount fishing activity in a given region—per year, according to the new mangrove report, published by the nonprofit International Union for Conservation of Nature (IUCN).

“Mangrove ecosystems are exceptional in their ability to provide essential services to people, including coastal disaster risk reduction, carbon storage and sequestration, and support for fisheries,” Angela Andrade, chair of the IUCN Commission on Ecosystem Management, said in a statement. “Their loss stands to be disastrous for nature and people across the globe.” 

Coral reefs are in similarly dire straits as climate change accelerates. Fueled by warming temperatures, Hurricane Maria and Irma damaged more than 11 percent of Puerto Rico’s reefs, a trend seen in other storm-prone regions around the world. In April, my colleague Bob Berwyn wrote about how prolonged ocean heat waves are disrupting the symbiosis of corals and algae, resulting in bleaching events that disrupt the reefs’ overall health and, in turn, its services for people. 

“During big storms, the waves are 10 meters outside the reef, but the corals break the waves and they’re only 3 meters when they reach the shore,” Brigitta van Tussenbroek, who studies coastal ecology in Puerto Morelos, Mexico, told Berwyn. 

“But that barrier doesn’t exist anymore,” she said. “I’m really afraid of what will happen during the next big hurricane. I don’t see how these coastal developments will survive.”

Nature and Insurance: If given enough time and space, mangroves and coral reefs can both restore naturally after extreme weather events. However, in some places such as Hawaii and Florida, climate-fueled storms and heat waves are putting these ecosystems through nine rounds without so much as a water break in between

Now, conservationists, governments and even insurance companies are stepping up to lend a helping hand for restoration. In February, the nonprofit Nature Conservancy announced the purchase of a new insurance policy with insurance company Munich Re for Hawaii’s coral reefs, to replace a plan that was first launched last year. The policy offers a maximum payout of $2 million over the year-long policy, which is triggered when winds reach 50 knots or more during a storm in the region, and funds go toward restoration. 

French insurance company AXA and environmental consultant ClimateSeed introduced a similar climate insurance policy in November for mangrove forests in San Crisanto, on Mexico’s Yucatán Peninsula, providing compensation of up to $100,000 to respond to damages from hurricanes, reports Green Queen. Experts say this type of “parametric” policy—in which payouts are agreed upon before a weather event, rather than assessed after—is promising, but assessing risk and supplying prompt payouts will become increasingly complex due to climate change. 

At a government level, officials in some areas are working to formally integrate mangrove and coral reef restoration into their flood mitigation plans. Recently, Miami-Dade County, Florida, and the U.S. Army Corps of Engineers drafted a $2.7 billion plan to protect the region from storm surges, which includes millions of dollars to research the effectiveness of reefs and mangroves to buffer coastlines, reports Tampa NPR affiliate WUSF.

Near Panama City, Florida, the U.S. Fish & Wildlife Service has been restoring dunes, oyster reefs and pine forests to fortify Tyndall Air Force Base, which suffered major damages during Hurricane Michael in 2018. The Department of Defense has even gotten involved, investing millions of dollars to develop “self-healing, hybrid biological and engineered reef-mimicking structures” made with concrete and coral to buffer coastlines, according to the Defense Advanced Research Projects Agency

In any case, scientists agree that protecting the world’s “living walls” is going to become increasingly important as climate impacts unfold. 

More Top Climate News

It’s been a big week for carbon offsets, which theoretically allow companies and governments to purchase emissions reductions in one area to compensate for their own greenhouse gas pollution. 

Today, the Biden Administration announced a set of government guidelines for the use of “high-integrity” carbon credits to help bolster a credible carbon market, reports The New York Times. Carbon offsets have faced intense scrutiny in the past few years because studies and investigations find that they often do not provide the emissions reductions that they claim to or can hurt local communities, which writers Sam Schramski and Cícero Pedrosa Neto covered for Inside Climate News in November. However, some environmental groups and analysts say that offsets could help support local communities for restoration projects. 

Similarly, a group of companies, including Google, Meta, Microsoft and Salesforce, announced last week their own coalition to purchase credits from “high-impact, science-based restoration projects.” Dubbed the “Symbiosis Coalition,” they plan to contract for up to 20 million tons of carbon credits by 2030, though the Verge writer Justine Calma pointed out that these efforts “still add up to a small fraction of the emissions these companies produce.”

Meanwhile, climate activists have been spray-painting mega-yachts in the Marina Port Vell in Barcelona (with biodegradable paint) to protest luxury tourism’s links with fossil fuels. Organized by the Extinction Rebellion and Scientist Rebellion, this protest is part of a broader “Week of Revolt” throughout the European country, so more could come soon. 

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