Mangroves cover less than 1% of Earth's surface but store roughly 15% of all carbon held in ocean ecosystems. A new study from the University of Exeter models how sea level rise could push these forests past a tipping point. While some areas may temporarily store more carbon as water rises, the overall capacity of mangrove forests to hold carbon is likely to decline over the next century. The model links water flow, sediment transport, mangrove growth, and carbon storage. It shows that if flooding exceeds what mangrove plants can tolerate, they drown and die back. When that happens, carbon rich soils erode and release stored carbon back into the environment. Higher sea level rise scenarios produced larger carbon losses. This matters for carbon markets and climate policy because mangrove blue carbon projects are often used to generate credits. If sea level rise undermines the permanence of that stored carbon, project developers and buyers need to account for that risk. The study suggests that site level field observations may miss the forest wide trend.
