>>56768851>”By April 1960, Chinese communist leaders changed their opinion in part due to the influence of ornithologist Tso-hsin Cheng who pointed out that sparrows ate a large number of insects, as well as grains. While the campaign was meant to increase 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.”
https://en.wikipedia.org/wiki/Four_Pests_campaign 