The terraced fields in Yuanyang county, Yunnan province, which have a history of more than 1,300 years and have been declared a World Culture Heritage site in 2013, are being threatened by an invasion of crayfish.

The local government has allocated 1.1 million yuan ($176,880) every year since 2012 to buy pesticide to fight the invasion.

It also issued rules stating that crayfish farming is not allowed in the terraced fields, and that no crayfish should be sold in the county.

Crayfish sold in the county will be confiscated and destroyed. In 2012 about 3.7 million crayfish were killed.

Crayfish were brought to Yuanyang county by an immigrant worker. They spread rapidly in the county after other farmers started to raise crayfish in their own terraced fields.

Terraced fields damaged by the crayfish, which bury themselves in the soil more than one meter deep, leak water and cannot be used to grow crops.