China is trying to feed 20% of the world's population on 7% of the world's arable land. And a third of the world uses water from China's rivers.

Rapid industrialisation and climate change, however, have led to bad air, polluted rivers and drought. And rather than clamping down on polluters, local government often protects local industries.

Along the Huai river's main tributary, 50,000 people suffer from cancer and in one village alone, 118 people have died.

In this episode we see shocking images from "cancer villages", and hear from green activists, Party officials, academics and scientists as they wrestle with environmental damage.