Meadows of seagrass on the ocean floor are among the planet's most efficient ecosystems for absorbing and storing carbon.
Why it matters: Climate change, industrial and agricultural run-off, and development along coastlines are threatening the world's seagrass meadows.
- About 161,150 hectares of seagrass have been lost along Australia's coasts since the 1950s, releasing carbon dioxide equivalent to that from 5 million cars each year, according to new research.
What they did: Cristian Salinas of Edith Cowan University and his colleagues compared carbon stored in the sediment of seagrass meadows with areas that no longer had seagrass in western Australia's Cockburn Sound.
- A loss of seagrass by itself didn't account for the carbon dioxide emitted from the soil, the researchers report in the journal Global Change Biology.
- Waves, tides and currents disrupted the soil and sand in shallow areas without seagrass, releasing the carbon sequestered in it.
- They also found seagrass meadows in shallow water stored more carbon than those in deep water, making the nearshore an important area to preserve, Salinas notes.
The big picture: Seagrass meadows — made up of more than 70 species of the marine flowering plant — filter seawater, buffer ocean acidification, regulate carbon and are home to more than 20% of the world's largest fisheries.
- "In one square meter is the same amount of carbon that can be sequestered in 30-40 square meters of forest," says Salinas.
- About 7% of the habitat is lost each year, contributing up to 299 Tg of carbon to the atmosphere, according to a June report from the U.N. Environment Programme.
- The U.N. and others are urging countries to preserve and restore seagrass as one way to address climate change.
