The Kill Sparrows Campaign was an effort created by Mao Zedong (leader of the Communist Party of China) to protect farms. The campaign was part of the Four Pests Campaign, an initiative to eradicate rats, sparrows, mosquitoes, and flies to improve people's health and hygiene. The goal of the Kill Sparrows Campaign was to improve crops, which people thought were being depleted by sparrows feeding on them. However, this led to a domino effect of destruction.
The Great Leap Forward
The Four Pests Campaign was part of a project called the Great Leap Forward, which aimed to improve China's industrial and agricultural industries. Farming was turned into a state-sponsored activity, and Zedong aimed to increase the efficiency and yield of crops.
Sparrows didn't just eat grains -- they also ate insects. Insect populations spiked as there were no remaining sparrows. Locusts, in particular, bred rapidly and swarmed across China, eating all the crops they could find. Ornithologists began pointing out that the diet of sparrows is about 75% insects and 25% grain, though it was too late. Citizens ran out of food quickly, and the lack of crops combined with an increased use of pesticides aiming to reduce the sparrow population combined to create a devastating famine. The estimated death count is approximately 45 million.
In 1958, Zedong famously said "Make the high mountain bow its head, make the river yield the way." -- and soon came to realize his mistake. The campaign and famine have shown that nature is not something to be conquered, and ecosystems are not to be disrupted without serious consequences.