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The decade from 2010 to 2019 marked a significant turning point in China’s history of environmental regulation and pollution. This article describes the recent trends in air and water quality, with a focus on the five years since China declared a “war on pollution” in 2014. It summarizes the emerging literature that has taken advantage of accompanying improvements in data availability and accuracy to document sharp improvements in environmental quality, especially local air pollution, and understand their social, economic, and health consequences. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

Massive wildlife losses over the past 50 years have brought new urgency to identifying both the drivers of population decline and potential solutions. We provide the first large-scale evidence that air pollution, specifically ozone, is associated with declines in bird abundance in the United States. We show that an air pollution regulation limiting ozone precursors emissions has delivered substantial benefits to bird conservation. Our results imply that air quality improvements over the past four decades have stemmed the decline in bird populations, averting the loss of 1.5 billion birds, approximately 20 percent of current totals. Our results highlight that in addition to protecting human health, air pollution regulations have previously unrecognized and unquantified conservation co-benefits.