for National Geographic News
For the past two weeks residents living around China's second largest lake have been able to smell a rat—make that two billion rats.
When the Yangtze River flooded on June 23, the water level rose in Dongting Lake, which sits along the river south of Wuhan in central China's Hunan Province (see a China map).
The flooding began flushing out rat holes around the lake, triggering a literal rat race for higher ground.
Since then farming communities in more than 20 counties near Dongting have been overrun, observers say.
"For the past week, the situation has been very serious," Tan Lulu, who works for the international conservation group WWF, told National Geographic News from WWF's Hunan office in Changsha.
Farmers are using everything from poison to hammers—and even their bare hands—to kill the rodents, Lulu noted.
"There are so many rats that you can kill three of them with one [strike]," she said, adding that the banks of the lake are carpeted with dead rats.
About two billion rodents have been coursing through the region, according to Chinese media reports, although it's not clear how this number was determined.
The rats have ravaged at least 4 million acres (1.6 million hectares) of farmland by eating the roots and stems of crops, the state-run China Daily newspaper reported.
In response, several news reports note, residents in the district of Dahu have killed more than 2.3 million rats—or 90 tons of the rodents—since the invasion began.
To combat the problem, local authorities have distributed rat poison in the affected areas.
Sanitation staff has also been dispatched to prevent disease outbreaks.
In some places around Dongting Lake, 2-foot-tall (0.6-meter-tall) concrete walls have been hastily built to keep the rodents away from farms.
"The current focus is on educating the villagers in protecting themselves while killing the rats, and supervising the local health situation," Peng Zaizhi, director of the emergency control division of the Hunan provincial disease prevention and control center, told the China Daily.
Dongting Lake is officially considered to be 1,058 square miles (2,740 square kilometers). But the lake is a flood basin of the Yangtze River, and its actual size fluctuates with seasonal rains.
Lulu, of the WWF, said a drought preceding the recent flooding exacerbated the rat problem.
"The drought exposed land that used to be the lake, and the rodents took up residence there," she said.
"When that land became submerged, the rats fled to higher ground."
The region has also been affected by the cutting and replanting of trees for two paper mills near the lake.
"Dongting Lake used to be a beautiful place," Lulu said, "but it has become very polluted."
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