Rising sea levels threaten migratory birds: study

(AFP) Google news 6 May 13;

SYDNEY — Millions of birds that stop at coastal wetlands during annual migrations could die as rising sea levels and land reclamation wipe out their feeding grounds, researchers warned Monday.

The study into the migratory habits of shorebirds predicted that a loss of 23 to 40 percent of their main feeding areas could lead to a 70 percent decline in their population.

Led by a team of scientists from Australia's government-backed National Environmental Research Programme, the study said some areas have already reported alarming population losses of 30-80 percent.

"Each year, millions of shorebirds stop at coastal wetlands to rest and feed as they migrate from Russia and Alaska to the coasts of Southeast Asia and Australasia," said researcher Richard Fuller.

"We've discovered that some of these wetlands are highly vulnerable to sea level rise and might be lost in the next few decades.

"If the birds can no longer stop at these areas to 'refuel', they may not be able to complete the journey to their breeding grounds."

The researchers studied wetlands along migration routes across Alaska, Russia, China, North Korea, South Korea, Japan, Philippines, Vietnam, Thailand, Malaysia, Indonesia, Papua New Guinea, Australia and New Zealand.

In many cases rapid coastal development and reclamation for agriculture were already chewing into tidal wetlands the birds use as feeding grounds on their long journeys, which sometimes extend half way around the world.

Species showing signs of being in trouble include the bar-tailed godwit, curlew sandpiper, great knot, grey-tailed tattler, lesser sand plover, and red knot, said the study, published in the Proceedings of the Royal Society journal.

The scientists used "graph theory", a mathematical approach, to estimate the impact of the loss of these wetlands on shorebirds.

It found that if a tidal wetland habitat served as an important "stepping stone" for the shorebirds, a small amount of habitat loss could trigger disproportionately large declines in bird populations.

"This is because some of these tidal wetlands are 'bottleneck' sites where the majority of the birds stop to refuel," said Takuya Iwamura, of Stanford University.

"For example, we discovered that a sea level rise of 150 centimetres (59 inches) may result in the loss of 35 percent of coastal wetlands, but it could lead to a 60 percent decline in curlew sandpipers, eastern curlews and great knots."

The scientists are embarking on a second study to identify the best ways to save the disappearing shorebirds and get a better grip on the scale of the problem.

Sea level rise threatens birds
ARC CoE for Environmental Decisions Science Alert 6 May 13;

Millions of shorebirds could be lost as sea levels rise in the coming decades, international environmental scientists have warned.

World-first research predicts that a loss of 23 to 40 per cent of the birds’ main feeding grounds could lead to a 70 per cent decline in their population.

This places some of the world’s shorebirds at greater risk as some areas have already reported alarming population losses of 30-80 per cent.

“Each year, millions of shorebirds stop at coastal wetlands to rest and feed as they migrate from Russia and Alaska to the coasts of Southeast Asia and Australasia,” says Dr Richard Fuller of the National Environmental Research Program’s (NERP) Environmental Decisions Hub and The University of Queensland (UQ).

“We’ve discovered that some of these wetlands are highly vulnerable to sea level rise and might be lost in the next few decades. If the birds can no longer stop at these areas to ‘refuel’, they may not be able to complete the journey to their breeding grounds.”

The NERP researchers studied wetlands along the shorebirds’ migration route across coastal Alaska, Russia, China, North Korea, South Korea, Japan, Philippines, Vietnam, Thailand, Malaysia, Indonesia, Papua New Guinea, Australia and New Zealand.

In many cases rapid coastal development and reclamation are already chewing into the tidal wetlands the birds use as feeding grounds on their long journeys, which sometimes extend halfway round the world. Species already showing signs of being in trouble include the bar-tailed godwit, curlew sandpiper, eastern curlew, great knot, grey-tailed tattler, lesser sand plover, red knot and terek sandpiper.

The scientists used “graph theory”, a mathematical approach to estimate the impact of the loss of these wetlands on shorebirds.

“We found that if a tidal wetland habitat serves as an important ‘stepping stone’ for the shorebirds, a small amount of habitat loss can trigger disproportionally large declines in the population,” says Dr Takuya Iwamura of Stanford University, who conducted the research at NERP. “This is because some of these tidal wetlands are ‘bottleneck’ sites where the majority of the birds stop to refuel.

“For example, we discovered that a sea level rise of 150 centimetres may result in the loss of 35 per cent of coastal wetlands, but it could lead to a 60 per cent decline in curlew sandpipers, eastern curlews and great knots.”

NERP scientists are also embarking on a second international study to identify the best ways to save the disappearing shorebirds. This research is crucial for federal policy because Australia has signed migratory bird agreements with China, Japan and South Korea.

“We’re aware that some shorebird species have declined in the past few decades, but we still know very little about all the causes for these declines or the scale of the problem,” says Mr Rob Clemens of NERP and UQ.

“Our studies attempt to piece together what is happening throughout the entire migration journey of these birds,” he says. “We can then determine which species should be protected, how best we can monitor the birds, and where and how we should act to save them.

“But while more knowledge would be useful, it’s important that we start protecting the birds based on what we already know, such as halting the reclamation of coastal wetlands in the vulnerable regions.”

Dr Richard Fuller explains that huge areas of the world’s coastal wetlands have been reclaimed for urbanisation and agriculture in recent years, reducing the size of the wetlands available for migratory birds.

While some existing wetlands can shift inland as sea levels rise, sites along highly developed coastlines, for example in Japan, China and the Republic of Korea, cannot move at all because of the scale of human development close to the coast.

“While we can build sea walls to defend ourselves against rising sea levels, the cost of this will only increase as time goes by,” Dr Fuller says. “We could instead be looking for opportunities to return our coastlines to a more natural state.

“We must act now to protect these crucial ‘stepping stones’ for migratory shorebirds – if you lose one critical site, you risk losing the entire population of a species that stops there.”

The study “Migratory connectivity magnifies the consequences of habitat loss from sea-level rise for shorebird populations” by Takuya Iwamura, Hugh P. Possingham, Iadine Chadès, Clive Minton, Nicholas J. Murray, Danny I. Rogers, Eric Treml and Richard A. Fuller appears in the latest issue of Proceedings of The Royal Society B.