A local government near Dongting Lake in central China's Hunan Province plans to build a 40-km wall to prevent further invasion by rats.

Lujiao Township in Yueyang City, northern Hubei, is ready to shell out 6 million yuan (about US$792,000) to build the one-meter-high rat-proof wall.

"Rats may invade again as the water level in Dongting keeps rising," said Zuo Shigeng, head of the Yueyang Plant Protection Bureau.

Experts estimate 10 million hectares of crops could be devoured by rats if no effective measures are taken.

Building walls and digging ditches are the main ways to keep the rodents out, but many localities do not have the funds to build them, said Wu Chenghe, a local official in Yiyang, another city troubled by a rat infestation.

The provincial government has allocated 8 million yuan (about US$1.05 million) to repair rat-proof walls.

Poison has also been widely used to kill the rats but has already had side effects. In Binhu village of Lujiao township, about one thousand cats died after eating rats killed by poison.

The rat plague began on June 23 and an estimated 2 billion rats have invaded 22 counties surrounding Dongting Lake after their homes on islands in the lake were flooded, causing over 6 million yuan in losses.

More than 2.25 million rats -- about 90 tons of rodent -- have been killed since June 21 in Yiyang, local authorities said.

Ecological damage due to intense human activity in the lake area was a factor in the rat invasion, said Zhang Chen, an official of the World Wide Fund for Nature.

Rats moved to the center of Dongting Lake in the past few years and began to breed there, with more islets appearing as water levels fell. When the floods came they were forced to swim to land.

The decreasing number of the rat's natural enemies -- such as snakes and owls -- was also blamed for the rat invasion, according to Zhang.

(Xinhua News Agency July 14, 2007)