China's massive seawalls decimate godwit populations
New Zealand's bar-tailed godwit population is predicted to halve in the next 10 years with research pointing to China's massive habitat destruction along its coastline as a cause.
To fuel its rapidly growing economy China is building seawalls and reclaiming wetland and coastal estuarine environments at the rate of 600,000 hectares a year.
Thousands of kilometres of seawall now cover at least 60 per cent of mainland China's coastline.
A paper in last November's Science magazine said the growing seawall has caused a dramatic decline in internationally shared bio-diversity and ecosystems. It warned the wall will threaten China's regional ecological security and sustainable development.
Co-author and Nelson ecologist and ornothologist David Melville said the NZ Ornithological Society and the Pukorokoro Miranda Trust, in the Firth of Thames, have been banding the site-faithful godwits in New Zealand for the past decade.
"Annual survival rates are going down," he said of the research results. "At the current rate of survival the New Zealand population will halve in the next 10 years."
NZ godwits' migratory path is through China's Yellow Sea, into Alaska and directly back to New Zealand.
The north-west Australian godwit population was worse off. Bird numbers were predicted to halve in five years, Melville said.
North-west Australian godwits migrated through the Yellow Sea to Alaska and back through the Yellow Sea to Australia.
Melville said analysis of migration survival studies of godwits, and other international shorebirds, suggested there was a problem with what was happening in the Yellow Sea, which is between mainland China and the Korean Peninsula.
The growth in reclamation along the coastline for land for housing, ports, industrial development, farming, transport and general urban sprawl was dramatic, rapid and outstripped Google Earth imagery.
"And in areas where there are still mudflats they are all subject to severe pollution and exploitation of any animals, worms or seaweed farming. There is a whole raft of things going on. The mudflats are under severe stress."
Melville witnesses the change on the ground having worked periodically in China over the past 30 years and more recently assisted with the field studies of students from a Shanghai university.
There was a chance some migratory birds could change their feeding habitat in response to the stresses on China's coastal margin, he said.
Research around the extensive reduction of food for migratory shorebirds at Yalujiang Reserve noted no Australian godwits arrived this year.
"It will be interesting to see if there is a massive reduction in birds returning to north-western Australia, or if they have found another food source."How much flexibility the birds have in changing their migratory pattern and how quickly that adaption can happen we do not know."The big crunch is how much habitat will be left at the end of the day."
A statement from China's central government in April on how it would look after its environment focussed on solving air and water pollution. Ecology did not get the same traction, he said.
"It did talk about the need to control reclamation and by 2020 35 per cent of China's coastline would remain in a natural condition - but are we talking about rocky coastline, or some soft shores as well."
However, Melville said it was pointless to criticise other countries until New Zealand communities started to look after their own migratory shoreline bird habitats, like the Motueka sandspit, which were a focus of conflicting demands.
Motueka's annual Welcome to the Godwits Festival had raised awarenesss, but he wanted to see the Department of Conservation, Tasman District Council and the community work together to recognise the international importance of the shorebird site as well as other recreational and community values.
Melville said witnessing the coastal degradation on such a massive scale as in China was depressing, but the situation also presented the opportunity to study how birds responded to such a massive habitat change.