The controversial culling of black swans looks likely to be stepped up after it was revealed they were responsible for the loss of 15 per cent of Tauranga Harbour's ecologically important seagrass meadows.
"These are unwanted Australians," Bay of Plenty Regional councillor Ian Noble declared after the lid was lifted on the impact grazing black swans were having on the harbour environment.
A PhD research project by Virginie Dos Santos has for the first time quantified the impact of black swan grazing. She found it took at least three years for seagrass to recover in the most heavily grazed areas.
Her 2007-10 study looked at the effects of grazing and defecation on the health of the meadows. Dr Dos Santos' findings have joined the growing list of problems caused by the graceful bird, which is an emblem of Western Australia.
Fish and Game already authorises an annual cull because of complaints the swans are eating crops, defecating on mud flats and beaches, and endangering aircraft flying in and out of Tauranga Airport.