Destruction of seagrass on a par with loss of rainforests and coral reefs

Vital marine habitat under threat
Daniel Cressey, Nature 29 Jun 09;

While the world has focused on the destruction mankind has brought to coral reefs, the massive loss of an equally important ecosystem has been widely ignored.

Now the first comprehensive assessment of the state of seagrass meadows around the world has revealed the damage that human activities have wrought on these economically and biologically essential areas.

A synthesis of quantitative data from 215 sites suggests that the world has lost more than a quarter of its meadows in the past 130 years, since records began, and that the rate of that decline has grown from less than 1% per year before 1940 to 7% per year since 1990.

"Seagrass loss rates are comparable to those reported for mangroves, coral reefs and tropical rainforests, and place seagrass meadows among the most threatened ecosystems on earth," write the authors of the synthesis, which is published this week in the Proceedings of the National Academy of Sciences1. "Our report of mounting seagrass losses reveals a major global environmental crisis in coastal ecosystems, for which seagrasses are sentinels of change."

As well as supporting unique wildlife such as green turtles (Chelonia mydas) and dugong (Dugong dugon), seagrass meadows also serve as a vital nursery for fish, supporting populations for coral reefs and commercial fisheries. They also serve to stabilize sediment and provide coastal protection, as well as trapping carbon and helping in nutrient transportation.

Suffering sentinels

For the global survey, the researchers compiled a database of all data on changes in the extent of seagrass cover spanning at least two years. They included published studies, online databases and unpublished but audited research.

Their synthesis shows that since 1980 seagrasses have been destroyed at the rate of 110 square kilometres per year. While 25% of sites increased in size and 17% showed no detectable change, 58% declined.

Overall, the measured area of loss between 1879 and 2006 was 3,370 square kilometres from the total of 11,592 for which suitable records were available — a loss of 29%. Extrapolating this to a global scale suggests 51,000 square kilometres of seagrass meadows have been lost since records began.

Study author Frederick Short, a researcher at the University of New Hampshire, Durham, admits that there is "not that much data" available on seagrass, so the total loss is difficult to pin down exactly.

Still, he says, "It is looking quite bleak for many parts … we are abusing our coastal systems."

The vast majority of this decline, say Short and other experts, is attributable to human activity. Nutrient and sediment pollution from nearby human activities and the introduction of invasive species are both contributing to their decline.

Seagrasses — flowering plants that evolved from terrestrial plants — are also likely to be affected by climate change, the authors note. And while the world focuses on photogenic coral, seagrass loss is just as worrying, perhaps more so as they are more widely distributed.

"The seagrass ecosystem in general is quite unacknowledged," says Short.

Uncertain fate

Giuseppe DiCarlo, marine climate change manager at Conservation International and a member of the steering committee of the World Seagrass Association, told Nature News that even where seagrass meadows have been lost there is the opportunity for recovery if protection via the designation of Marine Protected Areas can be brought in.

"It's nice to finally have some global numbers that can be used when advocating for the protection of seagrass," he says. "If you look at a regional scale, like in the Caribbean, we're going to lose the seagrass beds altogether [if something isn't done]."

Susanne Livingstone, programme officer on the International Union for Conservation of Nature (IUCN) Global Marine Species Assessment, says experts wouldn't be surprised to hear a 30% figure for losses, but despite these losses seagrass rarely makes it into the public consciousness. "It's probably because they're not as sexy [as corals], they're not as attractive," she says. "They're just as ecologically important if not more so."

Livingstone has been working on the forthcoming assessment of seagrass from the IUCN's Red List of the world's most threatened species. While the results of this are not yet available, she confirms that it will take the newly published research into account.

References
1. Waycott, M. et al. Proc. Acad. Natl Sci. USA advance online publication doi:10.1073/pnas.0905620106 (2009).

Loss Of Coastal Seagrass Habitat Accelerating Globally
ScienceDaily 29 Jun 09;

An international team of scientists warns that accelerating losses of seagrasses across the globe threaten the immediate health and long-term sustainability of coastal ecosystems. The team has compiled and analyzed the first comprehensive global assessment of seagrass observations and found that 58 percent of world's seagrass meadows are currently declining.

The assessment, published in the Proceedings of the National Academy of Sciences, shows an acceleration of annual seagrass loss from less than 1 percent per year before 1940 to 7 percent per year since 1990. Based on more than 215 studies and 1,800 observations dating back to 1879, the assessment shows that seagrasses are disappearing at rates similar to coral reefs and tropical rainforests.

The team estimates that seagrasses have been disappearing at the rate of 110 square-kilometers (42.4 square-miles) per year since 1980 and cites two primary causes for the decline: direct impacts from coastal development and dredging activities, and indirect impacts of declining water quality.

"A recurring case of 'coastal syndrome' is causing the loss of seagrasses worldwide," said co-author Dr. William Dennison of the University of Maryland Center for Environmental Science. "The combination of growing urban centers, artificially hardened shorelines and declining natural resources has pushed coastal ecosystems out of balance. Globally, we lose a seagrass meadow the size of a soccer field every thirty minutes."

"While the loss of seagrasses in coastal ecosystems is daunting, the rate of this loss is even more so," said co-author Dr. Robert Orth of the Virginia Institute of Marine Science of the College of William and Mary. "With the loss of each meadow, we also lose the ecosystem services they provide to the fish and shellfish relying on these areas for nursery habitat. The consequences of continuing losses also extend far beyond the areas where seagrasses grow, as they export energy in the form of biomass and animals to other ecosystems including marshes and coral reefs."

"With 45 percent of the world's population living on the 5 percent of land adjacent to the coast, pressures on remaining coastal seagrass meadows are extremely intense," said co-author Dr. Tim Carruthers of the University of Maryland Center for Environmental Science. "As more and more people move to coastal areas, conditions only get tougher for seagrass meadows that remain."

Seagrasses profoundly influence the physical, chemical and biological environments of coastal waters. A unique group of submerged flowering plants, seagrasses provide critical habitat for aquatic life, alter water flow and can help mitigate the impact of nutrient and sediment pollution.

The article "Accelerating loss of seagrasses across the globe threatens coastal ecosystems," appears in the Proceedings of the National Academy of Sciences Early Edition on June 29. The article was authors by 14 scientists from the United States, Australia and Spain, including Drs. Michelle Waycott (lead author), Carlos Duarte, Tim Carruthers, Bob Orth, Bill Dennison, Suzanne Olyarnik, Ainsley Calladine, Jim Fourqurean, Ken Heck, Randall Hughes, Gary Kendrick, Jud Kenworthy, Fred Short, and Susan Williams.

The assessment was conducted as a part of the Global Seagrass Trajectories Working Group, supported by the National Center for Ecological Analysis and Synthesis (NCEAS) in Santa Barbara, California, through the National Science Foundation.
Adapted from materials provided by University of Maryland Center for Environmental Science, via EurekAlert!, a service of AAAS.

Study: Coastal seagrass increasingly being lost
Yahoo News 29 Jun 09;

WASHINGTON – Coastal development and declining water quality are threatening seagrasses worldwide, researchers report. A study of coastal grasses around the world shows that 58 percent of the seagrass meadows are in decline, according to a report in Tuesday's edition of Proceedings of the National Academy of Sciences.

Seagrass provides habitat for coastal life and helps reduce the impact of sediment and nutrient pollution.

"The combination of growing urban centers, artificially hardened shorelines and declining natural resources has pushed coastal ecosystems out of balance. Globally, we lose a seagrass meadow the size of a soccer field every thirty minutes," co-author William Dennison of the University of Maryland Center for Environmental Science said in a statement.

"With the loss of each meadow, we also lose the ecosystem services they provide to the fish and shellfish relying on these areas for nursery habitat. The consequences of continuing losses also extend far beyond the areas where seagrasses grow, as they export energy in the form of biomass and animals to other ecosystems including marshes and coral reefs," Robert Orth of the Virginia Institute of Marine Science of the College of William and Mary added.

The researchers said that since 1990 there has been about a 7 percent loss of seagrass per year, with the major impacts coming from coastal development and dredging and reductions in water quality.

The research was supported by the National Center for Ecological Analysis and Synthesis (NCEAS) in Santa Barbara, California, through the National Science Foundation.

PNAS: http://www.pnas.org

Loss of seagrasses 'accelerating'
Anna Salleh, ABC 30 Jun 09;

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.

In the largest study of its kind, Kendrick and colleagues analysed 215 studies of seagrass beds in shallow coastal waters from around the world.

They found seagrass is being lost from east and west North America, the Caribbean, Mediterranean, Europe, parts of East Asia, Southeast Asia, as well as tropical and temperate Australasia.
Nutrient culprit

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.

"In Western Australia, in Cockburn Sound, we've lost 80% of our seagrasses. Over 1200 hectares of seagrasses have been lost in the last four decades," says Kendrick.

"The loss of seagrass there can be tied directly to nutrient input in the form of nitrogen."
Lungs of the ocean

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."
Impacts

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.

While seagrass beds off undeveloped parts of Australia, such as much of Queensland, remain healthy, most of the seagrass elsewhere in Australia is suffering, says Kendrick.

"Australia wide, seagrass has a problem anywhere there are port developments, harbours and urban development," he says.

But, there are some good news stories.

Kendrick says seagrass between the port of Fremantle and the port of Cockburn in Western Australia has recovered.

"Basically we cleaned up our activities south of Fremantle harbour in the late 1970s," says Kendrick, wondering if it might be a model for future seagrass recovery.

"Can we replicate what's happening there?"

Seagrass losses reveal global coastal crisis
Michael Perry, Reuters 29 Jun 09;

SYDNEY (Reuters) - Mounting loss of seagrass in the world's oceans, vital for the survival of endangered marine life, commercial fisheries and the fight against climate change, reveals a major crisis in coastal ecosystems, a report says.

A global study of seagrass, which can absorb large amounts of planet-warming carbon dioxide, found that 29 percent of the world's known seagrass had disappeared since 1879 and the losses were accelerating.

Seagrasses are flowering plants found in shallow waters. They were vanishing at the rate of about 110 sq km (42 sq miles) a year since 1980, said the study to be published in the U.S. journal Proceedings of the National Academy of Sciences.

The study by Australian and American scientists found seagrass meadows were "among the most threatened ecosystems on earth" due to population growth, development, climate change and ecological degradation.

It said there were only about 177,000 sq km left globally.

"Seagrass meadows are negatively affected by impacts accruing from the billion or more people who live within 50 km (30 miles) of them," said the report received by Reuters on Tuesday.

The study said the loss of seagrass was comparable to losses in coral reefs, tropical rainforests and mangroves.

"Seagrasses are sentinels of change" and the loss of seagrass was an indicator of a deteriorating global marine ecosystem. "Mounting seagrass loss reveals a major global environmental crisis in coastal ecosystems," it said.

ECONOMIC LOSSES

It is estimated that 70 percent of all marine life in the ocean is directly dependent upon seagrass, according to U.S.-based Seagrass Recovery (www.seagrassrecovery.com).

Seagrasses are the only flowering plants that can live entirely in water. They are most closely related to lilies and are very different to seaweeds, which are algae.

Seagrass meadows provide important ecosystem services, said the study, citing an estimated US$1.9 trillion a year in nutrient cycling, enhancement of coral reef fish productivity, habitats for thousands of fish, bird and invertebrate species and a major food source for endangered dugong and turtles.

Seagrass beds are believed to rival rice paddies in their photosynthetic productivity or the ability to extract greenhouse gas CO2 and convert it into oxygen and stored carbon matter.

One acre of seagrass can lock away nearly 8 metric tonnes of carbon per year, which equals the CO2 emissions from a car traveling more than 3,500 miles, says Seagrass Recovery.

The study said more than 51,000 sq km (19,700 sq miles) of grass had been lost in the past 127 years, with largest losses (35 percent) occurring after 1980.

"Seagrass losses decrease primary production, carbon sequestration and nutrient cycling in the coastal zone. If the current rate of seagrass loss is sustained or continues to accelerate, the ecological losses will also increase, causing even greater ill-afforded economic losses," said the study.

Vanishing Seagrass: as Important as Coral Reefs (But Way Less Sexy)
Discover Magazine 30 Jun 09;

Human beings are increasingly making their homes on the coasts of continents, but this demographic shift is taking a toll on a sensitive coastal ecosystem that is often overlooked: seagrass meadows. A new analysis of seagrass abundance around the world found that 27 percent of these meadows have disappeared since 1879, and the rate of loss is accelerating. The study’s authors write: “Seagrass loss rates are comparable to those reported for mangroves, coral reefs and tropical rainforests, and place seagrass meadows among the most threatened ecosystems on earth….. Our report of mounting seagrass losses reveals a major global environmental crisis in coastal ecosystems, for which seagrasses are sentinels of change” [Nature News].

Endangered species expert Susanne Livingstone notes that despite these losses seagrass rarely makes it into the public consciousness. “It’s probably because they’re not as sexy [as corals], they’re not as attractive,” she says. “They’re just as ecologically important if not more so” [Nature News]. Seagrass meadows provide grazing for a variety of marine animals, including the green turtle and the manatee-like dugong. The coastal areas also serve as nurseries for fish; both coral reefs and commercial fisheries would feel the impact if seagrass meadows vanish.

In the study, which will be published in the Proceedings of the National Academy of Sciences, researchers say that nutrients in sewage and run-off from agriculture and industry are the major cause of seagrass death…. 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 [Australian Broadcasting Corporation].

Seagrasses, which evolved from terrestrial plants, are the only flowering plants that can live entirely in water. They are most closely related to lilies and are very different to seaweeds, which are algae…. Seagrass beds are believed to rival rice paddies in their photosynthetic productivity or the ability to extract greenhouse gas CO2 and convert it into oxygen and stored carbon matter [Reuters]. If seagrass meadows continue to shrink in shallow coastal waters around the world, it will accelerate the pace of global warming, researchers say.

Loss of world's seagrass beds seen accelerating
Jim Loney, Reuters 2 Jul 09;

MIAMI (Reuters) - The world's seagrass meadows, a critical habitat for marine life and profit-maker for the fishing industry, are in decline due to coastal development and the losses are accelerating, according to a new study.

Billed as the first comprehensive global assessment of seagrass losses, the study found 58 percent of seagrass meadows are declining and the rate of annual loss has accelerated from about 1 percent per year before 1940 to 7 percent per year since 1990.

Published this week in the Proceedings of the National Academy of Sciences, the study, based on more than 200 surveys and 1,800 observations dating back to 1879, found that seagrasses are disappearing at rates similar to coral reefs and tropical rainforests.

"Seagrasses are disappearing because they live in the same kind of environments that attract people," James Fourqurean, a professor at Florida International University and a co-author of the study, said in an e-mailed response to questions.

"They live in shallow areas protected from large storm waves, and they are especially prevalent in bays and around river mouths."

Scientists say seagrass processes waste dumped into the sea, helps stabilize ocean-bottom sediments in coastal areas to reduce erosion, provide nurseries for fish and shellfish and feeding grounds for larger marine creatures, including those that live in coral reefs.

But the grasses can be damaged by polluted water from coastal development, decreasing water clarity, and by dredging and filling of meadows.

The scientists also said global climate change "is predicted to have deleterious effects on seagrasses." Many scientists believe greenhouse gases are causing the world to warm, leading to a host of environmental effects including warming and rising oceans.

'ECONOMICALLY AND ECOLOGICALLY IMPORTANT'

Seagrass meadows are important food fisheries and host gamefish like tarpon, permit and bonefish.

A recent study estimated the annual economic value of seagrass at $3,500 per hectare (2.5 acres), Fourqurean said.

"Seagrass beds are at least as economically and ecologically important as tropical forests or coral reefs," he said.

The study, by a team of scientists from the United States, Australia and Spain, found that 29 percent of known seagrass meadows have disappeared since 1879. Over the entire 130-year period, seagrass was lost at a rate of 1.5 percent per year.

An estimated 19,690 square miles (51,000 square km) of seagrass has been lost since 1879 of a total estimated area of 68,350 square miles (177,000 square km), the researchers said.

"Globally, we lose a seagrass meadow the size of a soccer field every thirty minutes," said co-author William Dennison of the University of Maryland.

The scientists said 45 percent of the world's population lives on 5 percent of its land adjacent to the coast.

In the early 20th century, heavy seagrass losses were noted in North America and Europe, where the industrial revolution led to rapid coastal development.

Today, population growth in the regions bordering the Pacific and Indian Oceans are likely leading to the heaviest losses of seagrass, but those regions lack the scientific infrastructure to assess the loss, Fourqurean said.

He said mitigation efforts have had some success in saving and restoring seagrass. For example, in Florida, where treated sewage water is often dumped in the ocean, water managers in Tampa changed their method of treating wastewater and failing seagrasses rebounded.

(Editing by Mohammad Zargham)

Meadows of the sea in 'shocking' decline
MacGregor Campbell, New Scientist 3 Jul 09;

Seagrass meadows are disappearing at an accelerating pace, according to a new report, which is the first to look at the problem on a global scale.

Seagrass meadows, along with coral reefs, mangrove forests, and salt-marshes, provide valuable ecosystem services like nutrient cycling. They also protect edible crustaceans, like shrimps and crabs, and juvenile fish such as salmon. In addition, seagrass meadows provide habitats for endangered species like dugongs, manatees, and sea turtles.

While marine ecologists have been measuring localized seagrass loss for decades, they had never before pooled their information to get a global perspective. So a team led by

Michelle Waycott of James Cook University in Townsville, Queensland, Australia pooled data from 215 regional studies, from 1879 to 2006.

They found that the total area of known seagrass meadow had decreased by 29 per cent over the 127 years. They also found that the rate of loss had accelerated, from less than 1 per cent per year in the 1940s to 7 per cent per year since the 1990s.
Sediment dump

"We put tremendous pressure on sea grass beds, but we get a lot of benefits from them," says Susan Williams of the Bodega Marine Laboratory, one of the report's co-authors.

The study points to sediment dumping from coastal development projects, pollution, and agricultural nutrient runoff as major causes of the decline. All three can decrease water quality, starving the plants of the sunlight they need to grow.

Natural disruptions like hurricanes accounted for a small proportion of losses.

According to Williams, the numbers translate to losing a football pitch's worth of seagrass every thirty minutes.
Shocking loss

Overall, the rate of loss is comparable to that for tropical rainforests and coral reefs.

However, seagrass meadows exist in both tropical and temperate zones, and are more widespread than either rainforests or reefs. Their loss has the potential to affect coastal communities all over the world.

"Those numbers are pretty shocking," says Ben Halpern, a marine ecologist with the National Center for Ecological Analysis and Synthesis.

Although not involved with this study, Halpern and colleagues released a map last yearMovie Camera of human impacts on marine habitats.

"Marine ecosystems have a lot more opportunity to bounce back than ecosystems on land," he says. "We do need to act quickly, but there is real hope that our actions can be effective."
Watershed moment

Not all areas of the globe decreased. Of the 51 sites that showed increases, 11 were attributable to improved water quality and restored habitat, showing that human efforts can bring the grasses back.

The report notes that transplantation efforts have generally failed, but watershed management and habitat remediation are effective.

One notable example is Tampa Bay, Florida, US, where efforts to reduce nutrient runoff have resulted in 50 per cent clearer water, and a recovery of 27 square kilometres of seagrass beds in the last 25 years.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0905620106

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