During the late 50s and early 60s, communist China undertook what on the surface appeared to be a relatively benign ecological program to kill pests.
It was called “The four pests” campaign. The goal was to eradicate 4 pests in China that Mao Zedong considered to be an enemy of the people. These four pests were : The mosquito which spread milaria, the rat which spread plague, the fly which spread other diseases and the sparrow which ate the grain of the peasants.
Out of these four, only one campaign was totally effective in its goal of eradicating its pest : The Eurasian Tree Sparrow.
The Chinese government, at the request of chairman Mao spent a significant sum of money encouraging and advertising to the peasants that killing the pests would make the country better.
The programs overall were extraordinarily effective as it gave the people a purpose with their free time. People got caught up in the cult of communist worship and were able to kill millions of birds in short order.
The masses of China were mobilized to eradicate the birds, and citizens took to banging pots and pans or beating drums to scare the birds from landing, forcing them to fly until they fell from the sky in exhaustion. Sparrow nests were torn down, eggs were broken, and nestlings were killed. Sparrows and other birds were shot down from the sky, resulting in the near-extinction of the birds in China.
By 1960, peasants and labor were celebrating that they had followed the government’s desires and killed all the birds. Unbeknownst to them, they had created one of the worst disasters in history.
By killing sparrows, they eliminated the primary enemy predator of the locust. Without any natural predator the locust, the local populations thrived. Grain production in most rural areas collapsed and a massive famine began.
The resulting massive famine in China killed by some estimates, 20 million people total. The government quickly rushed in to cover up their massive mistake and replaced the sparrow with bedbugs as a threat. It took till 1978 for scholarly works to be done that were able to assess the massive losses of life due to the government’s program.
Source of loss and research into famine.