We studied more than 1,500 coastal ecosystems - they will drown if we let the world warm above 2C

• These ecosystems support fisheries and wildlife, absorb the impact of crashing waves and clean up pollutants.
• But these vital services are threatened by global warming and rising sea levels.
• Growing recognition of the potential for this “blue” carbon sequestration is driving mangrove and tidal marsh restoration projects.

What we did

We pulled together all the available evidence on how mangroves, tidal marshes and coral islands respond to sea level rise. That included:
Altogether, our international team assessed 190 mangroves, 477 tidal marshes and 872 coral reef islands around the world. We then used computer modelling to work out how much these coastal ecosystems would be exposed to rapid sea level rise under projected warming scenarios.

What we found

• We found most tidal marshes and mangroves are keeping pace with current rates of sea level rise, around 2–4mm per year.
• In some locations, land is sinking, so the relative rate of sea level rise is greater.
• In these situations, we found marshes failing to keep up with sea level rise.
• What’s more, these are the same rates of sea level rise under which marshes and mangrove drown in the geological record.

Let’s give coastal ecosystems a fighting chance

• But this time, they will be competing with other land uses and increasingly trapped behind coastal levees and hard barriers such as roads and buildings.
• If the global temperature rise is limited to 2℃, coastal ecosystems have a fighting chance.
• There is a role for governments in designating retreat pathways, controlling coastal development, and expanding coastal nature reserves into higher ground.