A FOOTBALL pitch-sized chunk of undersea meadow is vanishing every 30 minutes, according to the first global assessment of the problem.
Seagrass meadows are found in shallow coastal waters around the world. Along with coral reefs, mangrove forests and salt-marshes, they play an important role in nutrient cycling, while also providing a refuge for crustaceans, juvenile fish and endangered species such as dugongs, manatees and sea turtles.
Although marine ecologists have been measuring local seagrass loss for decades, they had never before pooled their information to get a global perspective. So a team led by of James Cook University in Townsville, Queensland, Australia, did just that, combining 215 regional studies from 1879 to 2006.
Advertisement
They found that the total area of known seagrass meadows decreased by 29 per cent between 1879 and 2006, and that the rate of this loss is accelerating (Proceedings of the National Academy of Sciences, ).
鈥淲e put tremendous pressure on seagrass beds, but we get a lot of benefits from them,鈥� says of the Bodega Marine Laboratory in Bodega Bay, California, one of the report鈥檚 authors. For example, they provide a nursery habitat for edible shrimp, crab and fish.
The team place much of the blame on sediment dumped by coastal development projects, pollution and nutrient run-off 鈥� all of which decrease water quality, starving the plants of the sunlight they need to grow.
Overall, the rate of loss is comparable to that for tropical rainforests and coral reefs. But since seagrass meadows are more widely distributed, existing in both tropical and temperate zones, the effect of this loss is more widespread.
鈥淭hose numbers are pretty shocking,鈥� says Ben Halpern, a marine ecologist with the National Center for Ecological Analysis and Synthesis in California. But marine ecosystems are more able to bounce back than those on land, he says. 鈥淲e do need to act quickly, but there is real hope that our actions can be effective.鈥�