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Rising temperatures are bringing hordes of pests
Global warming blamed for proliferation of insects
Sep 17, 2007
Climate change isn't only making Hongkongers sweat. It's also making them itch.
Along with sweltering temperatures have come hordes of biting midges and blackflies that have swarmed over the New Territories and some urban areas, infuriating residents and damaging businesses.
Experts say the tiny insects favour hot and wet weather, and their proliferation is a result of global warming.
The Food and Environmental Hygiene Department refuses to admit that the biting pests - recognised as a serious nuisance to humans and other mammals in many countries - are a severe problem.
But the number of complaints it receives has grown from 15 in 2004 to 151 last year. From January to July there were 206 complaints, most from Sai Kung.
Yuen Long district councillor Chow Wing-kan said the insects had become a nuisance and urged the government to act.
At least two families of biting insects are known to be causing the nuisance. The department, which hired a Beijing expert to study the problem in 2004, identified 20 species belonging to the family of midges known as Ceratopogonidae, which generally breed under wet soil.
And Kadoorie Farm entomologist Roger Kendrick said he had witnessed an increasing number of biting blackflies, all belonging to the family Simuliidae, which cause an itchy swelling lasting three to five days. The senior conservation officer of the fauna conservation department at Kadoorie Farm said the blackflies' arrival showed that "nature is taking revenge on human beings" for environmental damage.
The FEHD noticed that the problem began in the northern districts and border villages in the early 1990s, when massive felling of trees on the mainland brought flocks of birds. The insects' eggs were spread in their droppings.
But Dr Kendrick said that the boom had more to do with global warming, which brought heat and heavy rain. "Heavy rains speed up water flow in streams and rivers and increase oxygen in water," where blackflies can thrive.
Another entomologist, Clive Lau Siu-ki, of the Agriculture, Fisheries and Conservation Department, said hot weather can also help biting midges breed much more quickly.
Cheung Ka-yun, head of the FEHD's contract management and insect control unit, said the department used the same control methods as for mosquitoes: cutting grass, clearing rubbish and spraying river channels and drains.
But both entomologists said the department was on the wrong track.
Mr Lau said biting midges lived in the soil so just cutting the grass was no use. He suggested spraying pesticides on the soil.
Dr Kendrick said blackflies did not breed abundantly in polluted water channels and it is no use spraying there. He suggested breeding natural predators such as dragonflies and damselflies and releasing the larvae in streams, marshlands, container yards and construction sites.
Mr Cheung rejected this, saying that dragonfly larvae did not breed in polluted water channels. But Mr Kendrick said that the department should simply put the larvae in clean streams.
Friends of the Earth said the FEHD shouldn't reject the advice without trying it.
The green group's director, Edwin Lau Che-feng, said that the department could start a pilot scheme to test the proposal.