‘Blue carbon’ banks: From the Conversation.
Mangrove forests, which grow in salt water in tropical regions, are especially effective at locking up “blue carbon” – so called to distinguish it from “green” carbon storage on land. Louisiana State University scientists Robert Twilley and Andre Rovai estimate that “the wood and soil of mangrove forests along the world’s coastlines hold 3 billion metric tons of carbon – more than tropical forests.”
Coastal development is an enormous threat to mangroves, whether for vacation homes in Florida or aquaculture farms in Asia. Twilley and Rovai wanted to pinpoint what type of mangroves were the most effective at storing carbon. By comparing conditions in different settings where mangroves flourish, they determined that river deltas and estuaries offer the best conditions for mangrove growth and carbon uptake:
“Overall, mangroves in deltaic coasts such as the Mississippi River delta, the Amazon in Brazil and the Sundarbans in India and Bangladesh can sequester more carbon yearly than any other aquatic or terrestrial ecosystem on the globe. These are the world’s blue carbon hot spots.”
4. Mangroves versus marshes
Mangroves are actually benefiting from climate change in some regions, such as Florida and the Gulf of Mexico. Villanova University biologist Samantha Chapman has found that mangroves are becoming more abundant in these areas, moving into zones formerly dominated by salt marshes, which typically are found in cooler zones.
Mangroves protect coasts more effectively against large waves, so this change isn’t necessarily harmful. However, as Chapman says,
“it is important to note that marsh plants provide important habitats for numerous species of birds and fish. We don’t yet know how these animals will fare as mangroves replace marshes, nor do we yet understand other downsides of plant range shifts due to climate change.”
Moreover, she notes, mangroves are not building new shoreline quickly enough to keep up with sea level rise in all locations. As her findings show, there is still much to learn about how climate change will affect different types of wetlands in various locations.