I know the basic story that mismanagement caused terrible famines in Mao’s China during the Great Leap Forward.  I only learned yesterday that it was essentially caused by a War on Sparrows (the bird).  When Mao saw a sparrow eating some grain he decided they were a pest and should be eradicated to help with food production. Unfortunately sparrows also eat bugs, which are even more of a problem for food production.  The resulting ecological imbalance lead to crop failures and millions of deaths.  A cautionary tale of bad science and concentrated power.  From wiki:

The ecological repercussions translated into a humanitarian crisis of unprecedented proportions. The absence of sparrows, which traditionally kept locust populations in check, allowed swarms to ravage fields of grain and rice. The resulting agricultural failures, compounded by misguided policies of the Great Leap Forward, triggered a severe famine from 1958 to 1962. The death toll from starvation during this period reached a staggering 20 to 30 million people,[7] underscoring the high human cost of the ecological mismanagement inherent in the “Four Pests” campaign.

Four Pests campaign