As sea level rises, wetlands crank up their carbon storage

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  1. Rogers et al. Wetland carbon storage controlled by millennial-scale variation in relative sea-level riseNature, 2019 DOI: 10.1038/s41586-019-0951-7

Some wetlands perform better under pressure. A new study revealed that when faced with sea-level rise, coastal wetlands respond by burying even more carbon in their soils. Coastal wetlands, which include marshes, mangroves and seagrasses, already store carbon more efficiently than any other natural ecosystem, including forests….

For wetlands that had faced rising seas, carbon concentrations doubled or nearly quadrupled in just the top 20 centimeters of soil. When the scientists looked deeper, at 50 to 100 centimeters beneath the surface, the difference hit five to nine times higher.

The extra boost comes because the carbon added to wetland soils by plant growth and sediment is buried faster as wetlands become wetter. Trapped underwater with little to no oxygen, the organic detritus does not decompose and release carbon dioxide as quickly. And the higher the waters rise, the more underwater storage space exists for the carbon to get buried.

….The trick, of course, is to ensure wetlands do not drown and disappear if waters rise too quickly. “Preservation of coastal wetlands is critical if they are to play a role in sequestering carbon and mitigating climate change,” Rogers said. For coastal wetlands to survive, they need space to migrate inland….