In 1958, China launched the Four Pests Campaign, targeting sparrows for eating too much grain. Despite warnings from scientists, officials pushed forward. A recent study examines what happened next using farm records and ecological models. The research shows that removing sparrows disturbed ecosystems and harmed crops. In areas where sparrows were common, rice output fell about 5.3% more and wheat dropped 8.7% more compared to places with fewer sparrows. Sparrows had eaten insects that damaged these crops, but when the birds disappeared, insect numbers rose. Interestingly, sweet potatoes, which grow underground, did not suffer and sometimes grew better. This suggests insects affected only above-ground crops. The study also found that grain collection demands increased, though production often fell. In counties with many sparrows, death rates rose by 9.6%, with 1960 being the deadliest year. Researchers estimate that nearly 20% of crop losses during the famine could be linked directly or indirectly to the sparrow eradication. The Great Chinese Famine caused tens of millions of deaths due to weather, policy, and economics. This study adds that ecological disruption from killing sparrows played a significant role. Sparrows kept insect populations in check, and their removal upset the balance, leading to a food shortage and higher mortalities. The findings warn about the risks of disturbing natural systems, as effects may appear later and be severe. Simply put, removing one element like sparrows can cause unexpected and deadly consequences.