Seagrass is important to capture carbon. ASU study just mapped it globally for 1st time

Seagrass is an aquatic plant that grows in shallow ocean waters and provides support to ecosystems near coastlines. But until now, it hasn’t been monitored consistently.

As part of a new study, researchers with Arizona State University have mapped out seagrass fields around the world.

While seaweed is an algae, seagrass has roots and other traits very similar to plants on land. It also helps prevent coastline erosion, filters water and stores carbon.

Researchers say mapping can help provide insight into coastal restoration efforts and how seagrass loss contributes to climate change.

They say some coastlines with seagrass are like a rainforest underwater, but one that hasn’t been studied in depth.

“There's a missing piece for that. So people pay attention a lot on coral reefs, but seagrass is actually very, very important. It can cohabitate with coral reefs, building the food chains,” said Jiwei Li, ASU professor and study author.

That has created gaps in understanding the whole picture of how carbon is cycled through the ocean.

But like other plants, seagrass helps absorb carbon and prevents it from spreading in ecosystems. And it’s not just the grass itself that stores carbon.

“The sediment of seagrass stores much more carbon than the seagrass itself,” Li said.

The sediment below seagrass plains in the ocean behaves similarly to soil on land. But by mapping out where seagrass is around the earth, scientists can estimate how much carbon is stored in the grass and the land below it.

The new map shows that global seagrass fields store about as much carbon as could be emitted by 500 million cars in just one year. But considering the limitations of their observations, that’s likely a conservative estimate.

“We know the height of forests, we know the biomass of forests, we know how many species,” Li said. “But for seagrass, we actually just know how many seagrass meadows are actually there”

Li says future research could help dig down into not just where the seagrass meadows are, but the different types of plants and their density that lie within, which would help get an even better understanding of how seagrass ecosystems interact with carbon stores.

The researchers say mapping can help provide insight into coastal restoration efforts and how seagrass loss contributes to climate change.