On this Earth Day, the 50th and by far the most surreal since the event launched on April 22, 1970, I thought it’d be appropriate to focus on a group of ecosystems that many people might take for granted but that contribute mightily to the health of our planet: coastal wetlands.
Scientists have long recognized that coastal wetlands—which include mangroves, seagrass, and salt marshes—are critical to maintaining biodiversity. These ecosystems also hold enormous value in protecting communities and the natural world from the impacts of climate change.
A huge variety of fish, bird, invertebrate, and other species use coastal wetlands as nurseries, for shelter, and to feed, breed, and rest during migrations. These areas often stimulate economic benefits through fisheries and tourism.
Regarding climate change, coastal wetlands protect shorelines from storms and rising sea levels and sequester atmospheric carbon—services that can help countries mitigate and adapt to our warming world. For example, mangrove forests along the coasts in the tropics and subtropics are powerhouses for trapping and storing carbon. Mangroves store three to five times more carbon per unit area than other tropical forests and can preserve this soil carbon pool for decades, even centuries. They also form a natural defense against storms and can prevent billions of dollars in global damages because of flooding every year.
Seagrass meadows, which are found in nearly all coastal waters around the globe, occupy less than 0.2% of the world's ocean but bury around 10% of the total estimated organic carbon sequestered in the ocean. In temperate regions, the salt marshes that thrive along sheltered coastlines provide important flood protection benefits and are also effective carbon sinks.
It should come as no surprise then that several countries are working to include coastal wetlands as part of their climate commitments to the Paris Agreement. Known as nationally determined contributions (NDCs), these commitments can include the protection of coastal wetlands to help build resilience and reduce carbon emissions. As countries begin to include coastal wetlands in their NDCs—and their domestic climate policies—the need for more robust scientific data on these ecosystems has presented research challenges and opportunities.
In order to estimate how much carbon is stored in the soils of mangroves, seagrass, and salt marshes, scientists must first map the approximate extent of each ecosystem. Submerged ecosystems such as seagrass where the habitat is not easily “visible” present a particular challenge. In fact, many countries lack data on the extent of seagrass and the species found in their waters. Even when accurate maps are available, information on the carbon stock within the ecosystem might not be. This can present a challenge in places that may not have the scientific or financial resources to conduct a carbon assessment. In such cases, governments can still account for the carbon value in their coastal wetlands using a regional average of the carbon stock found in these ecosystems.
To address these challenges and develop strong and ambitious NDCs, several countries are building the scientific baseline to better understand the climate value of their coastal wetlands. In Seychelles, a country with extensive seagrass beds that are scattered across the archipelago, researchers will undertake a collaborative seagrass mapping project using satellite imagery and in-country field teams. This research will feed directly into Seychelles’ NDCs, which the government plans to present this year.
The science on mangrove forests around the world is advancing rapidly. Researchers are producing higher-accuracy maps and creating robust datasets of carbon stock estimates. For example, in Belize, researchers plan to estimate the carbon stocks in the nation’s extensive mangroves by taking soil core samples that provide a profile of the carbon deposited over time. In nearby Costa Rica, a country with a history of forest conservation, research is also being undertaken for mangroves. This information will help inform both Belize’s and Costa Rica’s next NDCs so coastal wetlands can be protected for their mitigation value.
We all must recognize how our and nature’s fates are inextricably linked—on every day, not just Earth Day. Governments are making strides in understanding the value of coastal wetlands and integrating that worth into climate change mitigation and adaptation policies—important steps toward protecting the natural and economic services these ecosystems provide for biodiversity and human well-being.