Summary

The Four Pests Campaign was a mass mobilization campaign in China from 1958 to 1962. The campaign aimed to eradicate the four pests, which were rats, sparrows, flies, and mosquitoes, as well as to promote hygiene and public health.

Intended Positives

The campaign aimed to improve public health by reducing the spread of disease and to increase agricultural production by reducing crop damage caused by the targeted pests.
The "Four Pests" campaign was introduced in 1958 as a hygiene campaign aimed to eradicate the pests responsible for the transmission of pestilence and disease:
-the mosquitos responsible for malaria
-the rodents that spread the plague
-the pervasive airborne flies
-the sparrows—specifically the Eurasian tree sparrow—which ate grain seed and fruit[1]

Known or Announced Negatives

-The campaign led to the destruction of large numbers of sparrows, which led to a population explosion of insects that damage crops and spread disease. This had a negative impact on agricultural production and public health. The failure of cops because of insects led to a famine that killed an estimated 10 million people.

Observed Positives

The campaign did lead to a reduction in the population of rats, flies, mosquitoes, and other pests.

Observed Negatives

The campaign also led to the destruction of large numbers of sparrows, which had a negative impact on agricultural production and public health.
While the campaign was meant to increase agricultural yields, concurrent droughts and floods as well as the lacking sparrow population decreased rice yields. In the same month, Mao Zedong ordered the campaign against sparrows to end. Sparrows were replaced with bed bugs, as the extermination of sparrows had upset the ecological balance, which subsequently resulted in surging locust and insect populations that destroyed crops due to a lack of a natural predator.

With no sparrows to eat them, locust populations ballooned, swarming the country and compounding the ecological problems already caused by the Great Leap Forward, including widespread deforestation and misuse of poisons and pesticides. Ecological imbalance is credited with exacerbating the Great Chinese Famine-which led to the starvation and death of between 20 to 43 million people.
The Chinese government eventually resorted to importing 250,000 sparrows from the Soviet Union to replenish their population.