Coastal habitats may sequester 50 times more carbon than tropical forests by area

"I took a journalist interested in mangroves into a small lagoon where juvenile sharks could be found. Instead of finding sharks, we found a backhoe dredging a large sand spit across the lagoon. The work was being done without sediment traps and as we later found out, without permits. One mangrove shoot stood in the eventual path of the backhoe and I decided to get a shot of it standing tall - both condemned and yet defiant to the bitter end." Photo and explanation by Matthew D Potenski, MDP Photography/Marine Photobank.

From an article by Jeremy Hance on Mongabay.com:

Highly endangered coastal habitats are incredibly effective in sequestering carbon and locking it away in soil, according to a new paper in a report by the IUCN. The paper attests that coastal habitats—such as mangroves, sea grasses, and salt marhses—sequester as much as 50 times the amount of carbon in their soil per hectare as tropical forest.

"The key difference between these coastal habitats and forests is that mangroves, seagrasses and the plants in salt marshes are extremely efficient at burying carbon in the sediment below them where it can stay for centuries or even millennia. Tropical forests are not as effective at transferring carbon into the soil below them, instead storing most carbon in the living plants and litter," explains the paper's author and Conservation International’s Marine Climate Change Director, Dr. Emily Pidgeon. "But coastal ecosystems keep sequestering large amounts of carbon throughout their life cycle. Equally, the majority of carbon stays locked away in the soil rather than the plant, so only a relatively small amount is released when the plant dies."

This capacity for coastal environments to lock away carbon for thousands of years has largely been ignored in accounts of the global carbon cycle, according to the paper, even though the amount of carbon they are responsible for storing is very high.

Coastal habitats with vegetation "[contribute] about half of the total carbon sequestration in ocean sediments even though they account for less than 2 percent of the ocean surface,” Pidgeon writes, explaining that much of this is capacity is due to the fact that coastal vegetation usually spreads deeper below ground than it grows above with some plants going as deep as eight meters.