Migrating waders flocking to West Australia’s Roebuck Bay
In the increasingly perilous world of the migratory wading bird, Roebuck Bay on Western Australia’s Kimberly Coast stands out as a rare beacon of hope.
With shorebird numbers in free-fall across the planet, it is something of a miracle that at Roebuck Bay, just south of Broome, they appear to be on the increase. (Likewise in the isolated Eighty Mile Beach area between Broome and Port Headland.)
Nigel Jackett, warden at the Broome Bird Observatory (BBO) told Natural Images 130,000 migratory waders were counted on Roebuck Bay in Nov-Dec 2016.
He says that’s around 10% more than for several years. And although some of the increment could be cancelled by the vagaries of the human counting process, it nevertheless bucks global and Australian coastal trends.
Chris Hassell, a Broome-based shorebird ecologist and Western Australia convenor of the Australasian Wader Study Group (AWSG), thinks the pristine nature of Roebuck Bay has a lot to do with its popularity with waders.
A Ramsar site (wetland of international importance) since 1990, it has extensive and highly biologically diverse intertidal mudflats. Up to 160 square km can be exposed on big tides. Dugongs, green turtles and Australian snubfin dolphins (Orcaella heinsohni) regularly feed on the bay’s extensive seagrass meadows.
Most diverse mudflats
Roebuck Bay is also a major nursery for marine fishes and crustaceans and supports an exceptionally high diversity of benthic invertebrates (est. 300 – 500 species), placing it among the most diverse mudflats in the world, according to the Netherlands Institute.
“An interesting aspect of the [November-December] count is the large number of juveniles arriving for the first time,” says Hassell. “In the case of red-necked stints there were absolute masses of them.”
An exceptional breeding season in Siberia and Western Alaska and the uncluttered expanse of Roebuck Bay could account for the unusually high ‘winter’ influx of young birds. But he says that remains conjecture.
Elsewhere, however, the scale of migratory wading bird absences from traditional feeding and wintering grounds is in many cases extreme, and there is future uncertain.
Around the southern coast of the Australian mainland and Tasmania, numbers for previously common species such as the eastern curlew and curlew sandpiper are down more than 90%. They are both now classified ‘critically endangered’.
On the East Asian-Australasian Flyway – the main migratory shorebird route from the global south to their breeding grounds in the Arctic – habitat destruction is the birds’ greatest threat.
Land reclamation for commercial development, particularly on the Yellow Sea coast, is frequently cited ahead of climate change for the disappearance of hundreds of thousands (probably millions) of waders.
And the damage has been done in a very short time.
It is only 11 years since ‘Saemangeum’ in South Korea – described by UK shorebird conservation group Wader Quest as “one of the biggest environmental tragedies of all time”.
The estuary at Saemangeum was one of the most important stopover sites for waders on north and south migrations in the Yellow Sea region. An estimated 330,000 individual waders depended on the estuary annually for food and rest.
The mudflat area hosted around 30% of the world population of great knots – about 93,000 individual birds. It was also an important site for the spoon-billed sandpiper, which has become an icon of wader conservation as it teeters on the edge of extinction.
Sterile commercial site
But everything changed when the South Korean Government built a tide barrier across the Saemangeum estuary mouth. By April 2006, the once organism-rich wetland had become a sterile commercial site.
According to Wader Quest, in two years the number of birds at Saemangeum fell by 130,000 individuals, and by 2014 there were just 5,000 birds left.
China’s critical ‘red line’
The news from neighbouring China is hardly much better, with Science magazine reporting recently that the republic’s vanishing coastal wetlands are nearing ‘critical red line’ status.
Rapid coastal development has transformed marshes and mudflats into ports and urban sprawl. A line of concrete seawalls and sandbags now stretches longer than China’s Great Wall.
Science quotes a 2015 report from Chinese and US scientists warning the decline of China’s wetlands could drive numerous migratory bird species to the brink of extinction and jeopardise nearly 20% of the world’s fisheries.
70% of mangroves gone
At about the same time, China’s central government drew a ‘line in the mud’, decreeing that 53 million ha of wetlands must be conserved. But if current and planned coastal reclamation continue unabated, by 2020 the government’s red line will be crossed.
Half of China’s coastal wetlands have reportedly disappeared over the past 50 years – enclosed by seawalls or overrun by ports and other development. In the same period, 70% of the country’s mangrove forests and 80% of near-shore coral reefs have also been lost, according to China’s State Forestry Administration.
Story ©Natural Images 2017