Green menace

While extensive planting changed the farmers' lives, it also led to environmental problems.

Pesticides used to help produce bumper crops of oranges leached chemicals into the soil, and in the rainy season, these chemicals were washed into streams, rivers, and eventually, a nearby reservoir. When the temperatures climbed in the hot season, blue-green algae started to appear in the water.

Blue-green algae is a cyanobacteria that thrives in warm, nutrientrich water. As more chemicals emptied into the reservoir, the bacteria grew quickly, forming "blooms", which produced cyanotoxins that can make humans and animals sick.

In 2012, hydrology experts found the bacteria was being produced on a massive scale and contaminating Xunwu's water supply. The local government took drastic measures. Farmers were forced to stop planting new orange trees and ordered to chop down all the citrus trees close to the reservoir.

"I knew the bacteria was harmful, but once you have a better life it is really hard to go back and find yourself in financial dire straits," said Huang, adding he had no choice but to cut down all his "money trees".

But the problems created by the contaminated reservoir not only posed a threat to the health of locals, but also to tens of thousands of people 450 kilometers away.