THE WORLD’S MIGRATORY BIRD FLYWAYS
INTHE 10YEARS leading to 2013, seawalls destroyed 51 per cent – or 13,600sq. km – of coastal wetland habitats in China, and losses similar to this have been experienced elsewhere. On the other side of the sea, South Korea has lost 60 per cent. Of all the problems along the flyway, it is habitat loss on the Yellow Sea In th Ique sum aspitiori sant that poses the greatest threat to shorebirds. It is also politically intractable: while the Yellow Sea laps against the shores of South pa imil ius apedi offiori sant
Korea, North Korea and China, land reclamation is governed by individual nations.
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“Nationally there is a very strict regulation on land use [in China],” says Professor Lei Guanchun, dean of the School of Nature Conservation at Beijing Forestry University. “If you want to convert farmland into a construction area or urban development area, you need to have another piece of land to compensate.”
This so-called red line law was intended to protect against famine by maintaining the amount of farmland in China, but has had the unintended effect of devastating the intertidal zones.
In the past, this effect has been multiplied – government bonuses were awarded for GDP growth, providing an incentive for reclamation and construction. Worse still, much of the reclaimed shorebird habitat sits unused. For developers, it’s just a column to be filled in a ledger. Presently, almost 70 per cent (11,000km) of China’s coastline is walled.
Coastal reclamation in the Yellow Sea eats the mudflat layer by layer, reaching further and further into the sea. Humans have been doing this for thousands of years – it’s only the pace that has changed. China’s economic boom, and the shoreline reclamation that has gone along with it, has proved disastrous for shorebirds such as the bar-tailed godwit.
In a 2008 study, satellite-tagged godwits from Australia were recorded stopping at Rudong, in the Jiangsu Province north of Shanghai. By 2015, 90 per cent of sites the godwits used in 2008 had been reclaimed. It’s not known exactly what happened to the birds, but since then both subspecies of bar-tailed godwits have been upgraded on the Commonwealth Threatened Species List.
It’s not just birds that need this area to survive: local wormpickers now use seawalls, some of which extend for kilometres, to access what’s left of the mudflats.The worms they collect are sold as fish food in Japan, but workers say that they too have felt the effect of reclamation and development.
The seawalls change the way the tides work; the mudflats can be deprived of nutrients.
The seawalls change the way the tides work; the mudflats and the organisms that live in them can be deprived of the nutrients and silt they need to survive. Meanwhile, fertiliser and pharmaceutical factories sit along the shoreline, emitting the stench of rotten meat. A link between the rise of heavy industry and the decline in bird numbers has not been proven. The worm-pickers say worms are also in decline.The fish die, the worms die and the clams disappear.The birds stand, wings drooping, unable to fly. They either fall over dead or drown in the oncoming tide.
The next wave of seawall building will embrace 60,000ha of mudflats. It will be the largest reclamation in the world, and will envelop the intertidal zone around Tiaozini. This whole area would become dry land – no worms, no tides and no shorebirds. This process has already happened: in 2006, on the other side of the Yellow Sea.
SOUTH KOREA’S SAEMANGEUM SEAWALL project cut off an estuarine tidal flat supporting an estimated 400,000 birds as well as at least 25,000 local people. The 33km seawall at Saemangeum isolated a section of land more than five times the size of Sydney Harbour for industrial and agricultural development.
At first there was an overabundance of food, as invertebrates opened their shells and died on the drying mud. But soon there was nothing, dead or alive, for the birds to eat.The reclaimed land remains largely undeveloped. “To see it trashed for no reason is like sitting next to someone you love who is dying. It’s devastating,” says Dr Nial Moores, director of Birds Korea. “The vast majority of birds simply ceased to exist,” he says.
The devastation was felt in Australia too: after the reclamation, the great knot population was reduced by 20 per cent in a single stroke.The knots never made it back. But elsewhere on
the Korean peninsula, shorebirds have found an unlikely sanctuary.
North Korea’s comparative lack of development has been a boon for the birds and for the researchers who track them. “There’s far less industrial pollution because there is far less industry along these rivers,” says Adrian Riegen. Adrian is a builder and birdwatcher from Auckland who has devoted much of his life to shorebirds at New Zealand’s Pukorokoro Miranda Naturalists’ Trust.
After working with Chinese officials to survey bird numbers at Yalu Jiang, Adrian and a small group from the trust approached the North Korean government to ask if they could assess habitat over the border.As unlikely as it seems, the government welcomed the birders. “New Zealand is not seen as much of a threat to anyone,” Adrian says, by way of explanation.
The trust has been working to find out more about the shorebird population in North Korea. They have identified several internationally significant shorebird sites, each hosting more than 1 per cent of a given species.
“Most of the coastal strip along that western side of North Korea is farmland,” he says. “There’s not a lot of chemicals used, because there’s bans on importing, or the West isn’t supplying fertilisers… It’s probably the biggest organic farm in the world.”
For Adrian, the importance of North Korea to the fragile flyway ecosystem isn’t really acknowledged. “It’s something they should be proud of – they’ve actually got sites they haven’t destroyed,” he says. “If we get in early, before they do get enough money to destroy them, maybe we can make a difference.”
In other words, Adrian says, North Korea acts as a safety valve for the entire flyway. But North Korea is only a stopover: the final destination is further north, in the breeding grounds of the Arctic Circle.
THAT SHOREBIRDS WOULD fly to the remote reaches of the world – to Siberia, Alaska and Mongolia – to breed seems counterintuitive.Yet their strategy is sound.When they arrive in spring, the winter’s snow and ice are melting, forming pools of water that attract mosquitoes and other insects.
At this time of year in Siberia, mosquitoes can mass in clouds that turn the sky grey, forcing residents and researchers to wear protective clothing. “When spring is coming, it is a spring of light and of sound,” says Dr Evgeny Syroechkovskiy, Birds Russia CEO.
The insects are a perfect food source for the newly arrived shorebirds that need all the energy they can get after their long journey.The insects also provide a perfect banquet for when the chicks hatch several weeks later, sporting short, soft bills.
Shorebirds time their arrival in the Arctic perfectly: their breeding plumage helps them blend in among the low sedge and mosses of the thaw, and they aim to hatch their eggs at the height of the insect boom. But that boom is changing.
“Climate change is a pervasive problem that is pretty much affecting all the species on Earth,” says Dr Nick Murray, a biologist at the University of New South Wales. “As snow is melting in the Arctic areas earlier each year, there is a timing mismatch with food resources. Chicks hatching from their eggs are missing the peak time of food abundance – they’re growing much smaller
Shorebirds also appear to be able to predict weather over the Pacific, days in advance.
than they otherwise would, including having a smaller bill length. That has consequences throughout the first years of their life.
“What we are seeing is that these birds are not surviving as much as they used to,” he adds. The chicks, which hatch from eggs laid directly on the ground, emerge small but fully formed.
“They weigh maybe five grams, like a little bumblebee with huge feet,” says Roland Digby, who breeds spoon-billed sandpipers at the the Wildfowl and Wetland trust in the UK. “By the time they are 20 to 21 days old they are fully fledged. From 23 to 25 days old these birds start their incredible migration,” Roland says.
The juveniles are not guided by adults for the first migration of their lives. They simply know the right direction, and take to the sky. “These birds cannot land on water. They have to be incredibly sure of what they’re doing,” says Richard Fuller.
How exactly they do this is still something of a mystery to scientists. They may navigate by the stars and Sun, but the shorebirds also have the ability to sense magnetic fields, thanks to a chemical contained in their heads.
“How can they behave as if they’ve got a GPS on board?” marvels Theunis Piersma, professor of Global Flyway Ecology at the University of Groningen in the Netherlands. “The birds very often seem to know exactly where they are, whether this is in a landscape with features, or over the ocean, which is a featureless landscape. Incredible.”
Shorebirds also appear to be able to predict weather over the Pacific, days in advance. They use low-pressure systems like a slingshot, flinging themselves towards their destination. Some birds, like the Alaskan bar-tailed godwits, fly directly south in one hop. Other birds stop off at the Yellow Sea before flying further south to their overwintering grounds.The flights take up to 10 days. Even with all the fat they’ve stored, how do they survive?
“What they can do is slow everything down, so they slow down non-essential systems, non-muscular systems that they don’t need for their powered flight,” says Richard. “They can actually shut down half of their brain at a time and essentially fall half asleep, and get sort of cognitive rest.” Despite this physiological adaptation, migration is difficult: typhoons, cyclones and even just stormy nights deplete the energy of the tiny birds. None are bigger than 2kg, and some weigh as little as 50g.
Home is everywhere when you are a migratory bird. But it’s hard not to imagine that they feel relief when the muddy shores of New Zealand, or Broome, or Botany Bay appear.
“Sometimes you see a little flock of birds land and you just know that these are birds that have literally just arrived,” says Adrian Riegen. Often, the birds fall over – exhausted – as soon as they land in Australia. Their legs have been tucked tight beneath them for over a week. Their wings have been locked in position for flight. They can’t hold themselves up.
But only a few hours later the waders – the snipes, the curlews, the godwits, the stilts, the stints, the knots, the turnstones – pick themselves up and start eating. They’ve survived this time and they have another journey to prepare for. They are migratory shorebirds, and it’s a long way north.
ANN JONES spent six months recording the sounds of shorebirds along the flyway for an ABC Radio National and BBC World Service co-production. Listen to the documentary and subscribe to Off Track at: www.australiangeographic.com.au/issue137