Environmental Recovery after the Dust Bowl: Implications of Land Policies in the Great Plains
研究了美国1930年代以来的农田保护项目，发现政策使县级草地恢复每年增加2%-8%，且初始土地转换对土壤侵蚀有长期影响。
Land conservation policies, especially land restoration, take significant time to reveal any detectable effects on environmental quality. This study evaluates farmland conservation programs in the United States from their introduction in the 1930s to recent years and captures the short- and long-term effects on environmental outcomes, such as grassland restoration and soil erosion. Using spatial and temporal variation in the policy, I use a difference-in-difference model and identify that the conservation policy exposure has increased county-level grassland restoration annually on average by 2%–8%. The treatment effect varies with initial farm size, tenancy rate, and access to irrigation. Next, I use county-level spatial variation in initial funding to examine the long-term persistent effect on cropland erosion. Using the political economy behind the funding allocation as an instrumental variable, I show that the initial conversion of land had persistent effects on county-level soil erosion in the Great Plains, even in the long term.