The Four Pests campaign and China's Great Famine

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China's Great Famine of 1959–1961 is the deadliest in recorded history, claiming an estimated 30 to 40 million lives. In this episode of VoxDevTalks, Shaoda Wang discusses new research examining one underexplored contributor to that catastrophe: the mass extermination of sparrows under Mao Zedong's Four Pests campaign. Using historical ecological data and bottom-up crop yield records, his research offers the first rigorous causal estimate of how the loss of a single bird species helped tip a food crisis into a humanitarian catastrophe.

The case against sparrows

Launched in 1958 as part of the Great Leap Forward, the Four Pests campaign called on the Chinese population to eradicate rats, flies, mosquitoes, and sparrows. The inclusion of sparrows was driven by complaints from farmers who had observed the birds feeding on grain. The logic seemed straightforward: fewer sparrows meant more food. What it ignored was the ecological role sparrows played in controlling crop pests, particularly locusts.

Scientists at the time were not silent on the matter. Several prominent researchers warned that sparrows also consumed large quantities of insects, and that without this natural pest control, agricultural yields could actually fall. Their warnings went unheeded.

"It is true that sparrows eat crops, but sparrows also eat crop pests, especially locusts. So historically, without chemical pesticide, sparrows were relied on as a very important source of natural pest control."

How millions of people killed billions of birds

Mobilising a population to eliminate a species on this scale required extraordinary effort. Citizens deployed a range of methods – shooting, nest destruction, trapping – but one of the most striking tactics involved noise. By creating continuous, loud disturbances, people prevented sparrows from landing, forcing them to keep flying until they fell from exhaustion.

The scale of the effort produced one of the more surreal episodes of the period. In Beijing, people were making so much noise that flocks of sparrows sought refuge inside the Polish Embassy. The building was surrounded, the racket continued, and the birds died of exhaustion within the compound walls. Central government records eventually claimed that two billion sparrows had been killed – though these figures, tied to political incentives for local officials, are treated with considerable scepticism by researchers.

Measuring the impact

Quantifying the effect of sparrow eradication on agricultural output is complicated by the same political dynamics that shaped the famine itself. Local officials inflated crop yield reports sent to Beijing, which meant the central government continued exporting food even as the country starved.

To work around this, the researchers use two alternative data sources. Rather than relying on reported sparrow kills, they construct a sparrow habitat suitability index – a measure of how climatically and environmentally suitable each county was for sparrow populations before the campaign began. Counties with higher suitability were more exposed to the shock of eradication. For crop yields, they turn to county gazetteers: records compiled by local elites in a bottom-up process with no link to central reporting incentives, and which diverge sharply from the inflated official figures.

"These gazetteers, they're not government official data. Instead, they are compiled by local elites in a bottom up fashion, and this number was never linked to any political incentives."

Establishing a causal link between sparrows and crop failure

The core of the research rests on a difference-in-differences framework. Counties with high sparrow habitat suitability are compared to those with low suitability, tracking agricultural yields before and after the eradication campaign. The two groups followed similar trajectories prior to 1958. After the campaign, counties where sparrows had been most prevalent saw a significantly sharper decline in yields – a divergence the researchers attribute to the loss of natural pest control.

A key concern in any such analysis is confounding: might the counties that lost more sparrows also have experienced more intense implementation of other Great Leap Forward policies? The researchers address this directly, collecting data on a range of contemporaneous policy measures and checking whether these correlate with their sparrow suitability index. Finding no strong relationship, and observing that controlling for these factors does not materially alter their results, they conclude that the yield declines they identify are driven by sparrow eradication specifically.

"There's no obvious reason why this should be correlated with the incentives of local officials or the implementation of other Great Leap Forward policies."

How much did sparrow eradication contribute to the famine?

The estimates are stark. According to the research, the eradication of sparrows reduced China's crop yields by approximately 8–9% relative to the baseline – accounting for around 20% of the total agricultural decline during the Great Famine. Applying the same county-level comparison to mortality and fertility data, the researchers estimate that more than two million deaths can be attributed directly to the eradication of sparrows, representing roughly 6% of the total death toll.

"More than 2 million deaths can be attributed to the eradication of spirals. That's roughly 6% of the total death count during the Great Famine."

Lessons for environmental policy and political economy today

The researchers are careful to note that no government today is pursuing anything like the Four Pests campaign. But they argue that the history carries three layers of contemporary relevance. First, species are being lost every day to forces less visible than a state campaign, and for many of them, humanity has a poor understanding of the ecological functions they perform. The Great Famine illustrates what can be lost when that balance is disturbed.

Second, large-scale human interventions in natural systems – solar geoengineering, carbon capture, ecosystem management – are increasingly under discussion. The apparent logic behind the sparrow campaign was not irrational on its face. The catastrophe lay in the failure to anticipate second-order effects.

Third, and most broadly, the episode is a cautionary tale about campaign-style governance that overrides scientific consensus. The parallel drawn in recent Chinese public discourse – between the zero-sparrow campaign and the zero-covid policy – captures something the researchers find instructive: in both cases, an extreme, top-down intervention, resistant to expert dissent, produced outcomes far worse than anticipated.

Reference

Frank, E, Q Wang, S Wang, X Wang, and Y You (2025), "Campaigning for extinction: Eradication of sparrows and the Great Famine in China," Unpublished manuscript.