It’s the third week of our blue carbon month, and this week, the theme is super seagrasses. These amazing ecosystems are often under-appreciated, but they are vital for people and planet – as well as being home to fantastic wildlife, from seahorses to manatees, they keep huge amounts of carbon out of the atmosphere.

Restoring and protecting seagrass meadows helps us all, but they are disappearing. Every half an hour around the world, a seagrass meadow the size of a football pitch is lost.

• Can you sign the open letter to tell world leaders to protect blue carbon environments and ecosystems like seagrasses?

Up to 18% of the world's oceanic carbon is stored in the leaves, roots and sediments of seagrass meadows. These wonder plants can absorb carbon 35 times as fast as tropical forests per square meter, and 20% of the most commercially important fish species occupy them at critical stages in their development.

But like many of our planet's fragile ecosystems, seagrass beds are at risk. Coastal development, pollution, warming seas and destructive fishing practices have left them in a perilous state.

Almost 30% of all seagrass known to exist at the start of the twentieth century has disappeared, just when we need it most.

• Our open letter campaign calls on world leaders to defend these special ecosystems: can you add your voice?

We have some social media materials you can use to encourage your friends and family to join you in calling for conservation here - on Twitter, use #KeepItInTheSea to join the conversation.

Thank you for speaking up about these unsung ocean heroes. Next week, we are going to continue travelling along the coast. Our next stop is one of the most extraordinary ecosystems of all - mangrove forests. We will be looking at their amazing benefits for wildlife, people and our shared planet, sharing amazing photography and videos, and talking about how we can all play a role in protecting them.

Header photo courtesy of Louw Claassens, via Project Seahorse.