For mangroves to keep pace with rising sea levels, they rely on buildup of organic sediments, according to Jeremy Conrad of the J.N. “Ding” Darling National Wildlife Refuge. Sediment buildup is largely attributed to root growth, decomposition of leaf litter, and deposition of mineral sediments from tides and waves. To maximize the buildup of sediments, the mangrove forest must be healthy, protected, and restored wherever possible. Root production and leaf decomposition rates are altered in stressed mangrove forests, reducing the ability to build up sediments and keep pace with rising sea levels. Eventually, these stressed forests can begin to die off and result in a loss of sediment and the conversion of forest to open water.
With projected SLR, the question being asked is if mangroves will move inward if there are no barriers in the way? Or will they simply die off if the water becomes too deep or too acidic? Further study of the entire subject is needed.
Mangroves are an excellent carbon sink. Recent studies have found that the sequestration rate of carbon dioxide is several times that of terrestrial plants — as much as four times more than a tropical rainforest. Their ability to absorb carbon dioxide from the atmosphere and store it in their roots and sediment for centuries is sizable and makes mangroves important for mitigating climate change. However, when mangrove trees die, the carbon trapped in their roots and in the sediments is released back into atmosphere creating a new carbon source which has a negative impact on climate.
Mangrove forests can play an important role in carbon removals because they are among the most carbon-dense ecosystems in the world, and if kept undisturbed, mangrove forest soils act as long-term carbon sinks.
More comparative data on carbon sequestration efficiency of mangroves is essential to make the most of their important role in climate mitigation. We would do well to learn as much as possible about this scientific wonder so that we do not lose this vital coastal relationship.
Captiva resident Dr. Suri Sehgal is an India-born American philanthropist with a long career as a crop scientist, seedsman, entrepreneur and leading expert in the global hybrid seed industry. Along with his wife, Edda, he now operates two nonprofit organizations that focus on water security, food security and social justice. He is a member of the Captiva Sea Level Rise Committee and chairs the Captiva Island Yacht Club’s Environmental Awareness Committee.
Source: Sanibel Captiva https://www.captivasanibel.com/2020/09/29/mangroves-the-first-line-of-defense/