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Seagrass meadows have joined the endangered list of ecosystems, along with tropical rainforests, coral reefs and mangroves.

A new study, co-authored by marine biologist Professor Gary Kendrick in the School of Plant Biology, has shown that seagrass loss rates around the world are comparable to those reported for coral reefs, tropical rainforests and mangroves – with potential negative impacts for the more than one billion people who live within 50km of them.

The first global study of its kind, Accelerating loss of seagrasses across the globe threatens coastal ecosystems , was published in the prestigious journal Proceedings of the National Academy of Sciences of the United States of America last week.

By assessing more than 200 studies carried out on seagrass around the world, the authors found that seagrasses had been vanishing at the rate of about 110 square kilometres a year since 1980, and that 29 per cent of the known meadows had disappeared since seagrass areas were initially recorded in 1879.

Professor Kendrick said the loss of seagrass had a negative affect on fisheries and human health through degradation of the ecosystem.

“Seagrass fixes as much carbon dioxide as tropical forests,” Professor Kendrick said. “It buffers coastal areas from damaging waves, expected to increase with rising seas, and acts as a filter for toxic materials released into the ocean from industry.”

He blames nutrients in sewage and run-off from agriculture and industry for most of the seagrass death.

“These nutrients trigger the growth of algae that grows above or on the seagrass and stops it from getting the sunlight it needs to survive,” he said.

“Our report of mounting seagrass loss reveals a major global environmental crisis in coastal ecosystems, for which seagrasses are sentinels of change,” he and his co-authors wrote. “More importantly, in contrast to coral reefs, which also herald environmental changebut occupy a relatively small portion of the world’s oceans, seagrasses are lobal in extent except for the highest polar regions. Coastal ecosystems are under pressure from coastal development, growing human populations, climate change and ecological degradation.

“Seagrass meadows provide important ecosystem services, including an estimated US $1.9 trillion a year in the form of nutrient cycling, enhancement of coral reef fish productivity, a habitat for thousands of fish, bird and invertebrate species, and a major food source for endangered dugong, manatee and green turtle,” they wrote.

The study argues that coastal ecosystems have recognised ecological and economic values. For example, seagrass meadows support commercial fisheries, subsistence fisheries that ensure the livelihood of entire communities, nutrient cycling, sediment stabilisation, and globally significant carbon sequestration. They also provide links to other marine habitats.

“The bad news locally is that, in Cockburn Sound, we have lost about 80 per cent of our seagrasses,” Professor Kendrick said. “But the good news is that in the areas between Fremantle and Cockburn, the seagrass has recovered.

“We cleaned up our activities south of Fremantle harbour in the late 1970s and the seagrass has grown back. We hope this might be a model for future seagrass recovery.”