Environmental science: Rising sea levels may not drown coastal wetlands

Under certain conditions, coastal wetlands could potentially increase their global surface area by as much as 60% despite predicted sea-level rises over the coming century, reports a paper published this week in Nature.

Coastal wetlands, such as marshes and mangroves, are important ecosystems that provide natural coastal protection. Although many studies predict widespread wetland loss as sea levels rise, some assessments suggest that this threat has been overstated and that global models have failed to take into account well-documented local feedback mechanisms that could maintain wetlands.

Mark Schuerch and colleagues address these limitations by assessing the global resilience of coastal wetlands while also considering their ability to accumulate sediment and their available accommodation space (inland space for wetlands to migrate into). The authors simulated the responses of global wetlands to sea-level rises and human activity and found that global coverage could increase by 60%, provided that at least 37% of existing wetlands have sufficient accommodation space. In scenarios where adequate accommodation space is not available, coastal wetlands face projected losses overall (worsening under scenarios that assume higher sea-level rises), potentially due to increasing sediment deficiency.

The authors note that local waterway management, such as damming and dredging, may complicate these simulations. They suggest that widespread coastal management strategies that encourage inland migration may be required to safeguard coastal wetlands from rising sea levels and protect rapidly increasing global coastal populations.

doi: 10.1038/s41586-018-0476-5

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