The gigantic Three Gorges Dam project and global warming could
be to blame for the recent rodent outbreak in central China's Hunan Province.
The rodent scourge surrounding Dongting Lake, China's
second-largest freshwater lake, had been for the most part
controlled. In a recent two-week mouse offensive, residents of the
22 counties encircling the lake eradicated some 2.3 million of the
estimated 2 billion rodents.
The rodents were driven out into populated areas when
floodwaters burst out in late June.
Shi Dazhao, director of the Chinese Agricultural University's
laboratory on the prevention and control of rodents, and a
consultant to the Chinese Association for the Control of Rodents
and Sanitary Insects (CPCA), attributed the magnitude of this
year's rat pest problem to the gigantic dam project and global
warming.
His assessment was partially echoed by Wu Chenghe, chief of the
plantation protection station for Datong Lake, a sub-lake of
Dongting Lake. Wu argued that interception of the upper watershed
had lowered water levels and created ideal conditions for a rodent
outbreak.
The fact that water levels did not rise during last year's flood
season also helped boost rat numbers, he said.
But while the media have called it the region's most severe rat
infestation in the past decade, Deng Zhi, a senior researcher with
the Academy of Military Medical Sciences, told China Daily
that rodent outbreaks were a natural annual event during flood
seasons.
"Running for their lives, the rodents always come and go during
flood seasons and there's hardly a way to stop them," he said. The
root cause of this year's particularly massive rat attack was
ongoing human polderization, he added.
"Polderization violates the laws of ecology," he said.
"It not only facilitates floods, but also creates an ideal
condition for rodent reproduction."
Another reason is nearby counties' reliance on reeds for paper
production, and a source of food of rodents.
"The more reeds people grow, the more rodents and paper
factories there are, the more pollution there is, and the more
serious the rat problem becomes," Yang Hualin, director of the
CPCA, said.
Experts believe Hunan's rat control campaign was tricky to
solve.
Shi said: "It's not that we can't kill all the rodents, but that
it's not worth doing. Just how much money, time and effort ought
the government to spend in trying to protect each hectare of
farmland?
"But if we were to let the rats run wild, the crops would be
ruined. And if we were to truly resolve the issue through lake
restoration, where should all the surrounding residents be
relocated and how will they live?" Shi proposed several immediate
and long-term solutions to the problem. For instance, the
government should try to control rodent reproduction before each
flood summer, and farmers should avoid growing crops during the
period.
Monitoring stations with an organized and trained workforce
should also be established immediately, because "prevention is key
to everything", he said.
In the long run, coordinated development and supervision at all
levels for a national preventive scheme was a must, he said, adding
that a disease prevention fund may be useful.
The Ministry of Health launched its first strategic national
scheme on the prevention and control of emerging infectious
diseases on June 20. But a comprehensive project to facilitate
inter-departmental prevention and control efforts was still
unavailable.
(China Daily July 16, 2007)