Global Loss of Seagrasses 29% and Accelerating

Loss of Seagrasses 'Accelerating'

~Rate of seagrass loss comparable to the loss of tropical rainforest~

Nearly 30% of global seagrass beds have been lost since records began, and the rate of loss is accelerating, according to a new study.

Marine biologist Professor Gary Kendrick, of the University of Western Australia in Perth, and colleagues report their findings this week in the Proceedings of the National Academy of Sciences.

"The losses have been quite substantial," says Kendrick. "Every year we're losing about 110 square kilometres of seagrasses globally."

He and colleagues found that since 1980, 29% of seagrass has disappeared and the overall rate of loss has accelerated from 0.9% a year, before 1940, to 7% a year, since 1990...

...Nutrients in sewage and run-off from agriculture and industry are the major cause of seagrass death, says Kendrick.

These nutrients trigger the growth of algae, plants and animals that grow above or on seagrass, and stop it from getting the sunlight it needs...


Impacts

Kendrick says the rate of seagrass loss is comparable to the loss of tropical rainforest.

He says studies have found seagrass fixes as much carbon dioxide as tropical forests, and is also a crucial part of the ocean food chain.

About 75% of seagrass feeds bacteria, which are the bottom of the ocean food chain, says Kendrick: "They actually feed the whole food web."

He says the other 25% of seagrass is eaten directly by animals such as dugongs, green turtles, fish, snails and crustaceans, as well as birds like geese and swans.

Seagrass meadows are also crucial to the survival of fish that live in coral reefs, says Kendrick: "So there's a very close connection between reef systems and seagrass systems in the tropics."

...The loss of seagrass negatively affects fisheries and human health through degradation of the ecosystem, says Kendrick.

He says seagrass buffers coastal areas from damaging waves, expected to increase with rising seas, and also acts as a filter for toxic materials released into the ocean from industry...


for complete news article:
2009-06-30
http://www.abc.net.au/science/articles/2009/06/30/2611630.htm


for complete journal article:
http://www.pnas.org/