They can stink like fish and rotten eggs, breed swarms of mosquitos and lack the glamour of coral reefs. But mangroves, with other coastal habitats, are vitally important to our climate — and they’re under threat.In just the past decade, scientists have discovered that some of our underappreciated coastal habitats — called “blue carbon ecosystems” — play a huge role in tackling CO2 emissions.But human activities such as burning fossil fuels and coastal development have already caused half of them to disappear.”They’re like the armpits of our coastline, but they are really important,” said Deakin University marine ecologist Peter Macreadie.What is blue carbon?Blue carbon coastal ecosystems — such as mangroves, seagrass meadows and tidal wetlands — are named for their place at the boundary between land and sea, and their unmatched ability to suck CO2 out of the atmosphere and store it in the ground below.
This process is called carbon sequestration.Capturing carbonCoastal plants capture CO2 through photosynthesis and land-based carbon sourcesCarbon can be stored in the soil of blue carbon habitats for thousands of yearsWhen these habitats are damaged or destroyed the carbon can be released as CO2 back into the atmosphereIt was intense carbon sequestration by ancient forests and algae millions of years ago that helped create the very deposits of coal and oil we tap into for fossil fuels today.
Nearby on the ecology colour palette are the better-known green carbon systems of trees and forests. While important, they aren’t nearly as efficient at storing carbon as their blue counterparts.
“We know that forests are pretty good at [carbon sequestration], but their carbon stores are bound to the lifetime of the trees, for only 100 or so years, and then it is released back into the atmosphere,” Dr Macreadie said.
As well as being a temporary carbon store, trees can only soak up so much carbon before they become “saturated”.