Rising Seas Threaten Coastal Wetlands — and Local Economies

Coastal wetlands, like mangroves and tidal marshes, were once seen as wastelands needing to be emptied, but in the long run that has been akin to pouring money down the drain. A 2014 study concluded these regions provide more than $190,000 in economic value ($227,000 in 2022 dollars) per hectare, making them one of the planet's most valuable ecosystems. They’re the silver lining of our shores, but the future presents some dark clouds on the horizon. 

Coastal wetlands are extremely vulnerable to climate change and rising seas. As sea levels increase and inch over our shores, the ecological balance in these regions begin to shift, including whole ecosystems. Scientists have long debated if the migration of coastal wetlands toward inland areas can compensate for the lands that could soon be flooded by saltwater. To that end, a new study of 166 estuaries in the U.S. sheds light on the topic, finding that sea-level rise will transform our coasts, and at a cost. Assuming a 1.5-meter increase in sea levels, coastal wetlands are predicted to shift toward land, but still shrink in size. 

Throughout the U.S., coastal wetlands come in different forms, ranging from salty to freshwater habitats. Due to increased sea-level rise, more coastal saline wetlands are predicted to displace coastal freshwater wetlands, leading to a net loss in wetlands overall. States lining the Atlantic Ocean and Gulf of Mexico, including Louisiana, Florida, North Carolina, Texas and South Carolina, face the greatest decrease in coastal wetlands. 

This slow migration will also damage other valuable habitats in the process. Most of this change will occur at the cost of coastal freshwater wetlands, but croplands, grasslands, pastures and forests are also at risk. For instance, the encroachment of wetlands jeopardizes pastures managed for livestock and low-lying rice fields that are also used for crawfish cultivation. Sea-level rise already threatens agriculture in low-lying areas through flooding and saltwater intrusion into groundwater, and a change within these ecosystems adds even more threats.

The loss of wetlands also harms communities and local economies, especially in an ever-hotter world. For starters, even when their area has been greatly reduced, coastal wetlands help mitigate the damage from storm surges and concurrent waves, thereby protecting the value of properties from flooding to the tune of millions of dollars. In Florida, the disappearance of coastal wetlands resulted in an estimated additional $430 million in property damage during Hurricane Irma — and more losses could occur in the coming years.

Wetlands also provide habitat for valuable fisheries like salmon, crabs and shrimp, contributing a wide range of jobs as well as hundreds of millions of dollars each year to local economies. In addition, these ecosystems slow erosion, clean water, and provide recreational opportunities like kayaking, canoeing, recreational fishing and hunting. Finally, wetlands can help fight climate change by sequestering and storing large amounts of carbon. 

Unfortunately, coastal wetlands are already being lost at a rapid clip: the equivalent of nearly seven football fields that are destroyed every hour in the continental U.S. alone. And on a global scale, the numbers become even worse, as only 0.5 meters of sea-level rise could destroy anywhere from 46 percent to 60 percent of coastal wetlands by the end of this century.

These threats do not mean all hope is lost. Society can still make efforts to restore and protect the wetlands that still exist. Ensuring that freshwater still flows to coastal wetlands keeps them healthy and may slow the effects of sea-level rise. These actions will help maintain our coastal defenses against storms, slow global warming and preserve the planet’s food supplies.

Nearly 30 percent of the U.S. population lives in coastal counties, while the population in coastal counties lining the Gulf of Mexico has soared by 150 percent in recent decades. The appeal of living with constant ocean breezes is part of this population shift. But the risks of sea-level rise, these regions’ vulnerability to tropical storms and flooding should be put into perspective by everyone. Given the massive economic and societal benefits that coastal wetlands provide, everyone benefits, and even profits, from preserving more coastal wetlands.

Image credit: Tyler Butler via Unsplash