New study finds catastrophic loss of mangroves

Mangroves are found at the confluence of land and sea in tropical environments. They provide invaluable habitat for nesting birds, nurseries for baby fish and sanctuaries for marine mammals.

Mangroves also provide an abundance of benefits for coastal humans – they can act as speed bumps to lessen the impact of storms, help filter a wide variety of water pollutants, and trap excess sediment. They even help coastal economies by providing fish nurseries and food production.

Studies have shown that mangroves provide approximately $2.7 trillion in ecosystem services every year. Now, a new study shows mangrove value may be even higher, with much more carbon sequestered in them than originally thought.

The study finds the carbon content of mangroves (both soil and biomass) is dramatically higher than previous estimates. The carbon content of mangroves (both soil and biomass) was found to be 4.2 billion metric tonnes, a dramatic decline from the year 2000, when mangroves held approximately 6.4 billion metric tonnes. This represents a loss of nearly 1/3 of the world’s mangrove carbon sink.

The study was conducted by 21 researchers around the world and estimated soil carbon storage of mangroves based on climate, topography, and hydrologic conditions found through satellite imagery. 

Although mangroves are found only in tropical areas and cover an area less than 3% the size of the Amazon, studies show that they capture four times more carbon than rainforests can. 

Sadly mangrove deforestation has been dramatic. Studies indicate that some 35% of the world’s mangrove forests may have been lost between 1980 and 2000. Cleared to make way for their wood as well as shrimp farming and other aquaculture, they face other risks like drowning from climate change as seas rise. The mangroves in Florida Bay and the Everglades are at particular risk. 

Since 2000, mangrove deforestation has resulted in as much as 447 million tons of CO₂, more than many large countries. 

The biggest loss in this time frame came from Guatemala, which lost nearly 6.8% of its forest mangrove soil carbon over 15 years. More than three-quarter’s of soil carbon emissions came from Indonesia, Malaysia and Myanmar. 

The researchers say their results on climate and mangroves can help determine which mangroves are storing the most carbon and should therefore be protected. They have made their maps publicly available for this purpose.

Restoring and protecting mangrove habitat alone will not change the climate, but for the scientists who study them they are one of the most viable climate mitigation options we have.