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Were there Modern-Day Dust Bowls? Evidence Suggests that Recent Extreme Droughts Contributed to Cropland Conversion in the United States Phu V. Le1 (Author and Presenter) Abstract Climate and weather extremes have always been a critical problem for the sustainability of US agriculture. In this study, we focus on the single most destructive event - extreme droughts. We present the first evidence of the effect of severe drought condition on farmland loss trend in the US in late twentieth century. By incorporating extreme drought into the total productivity factor, we model the cropland conversion as a consequence of weather shocks that produced permanent damages to the productive capacity of the soil, such as losses of the topsoil from extreme drought events like the Dust Bowl. The result indicates that extreme droughts and uncertainty regarding their long lasting effect on soil productivity discourage sustainable agricultural use and accelerate irreversible conversion out of agricultural production. This result also highlights a major threat to US agriculture arising from climate change that may introduce significant agricultural regions to extreme dry condition. The threat could be worse if future yield growth cannot keep up with observed historical pattern. In addition, we suggest a potential mechanism in which Ricardian approach [1,2] to estimating the impact of climate change, by assuming full adaptation, may have underreported actual damages from the extremes. And we consider a fat-tail climate change scenario that disproportionately increases the frequency or intensity of extreme drought events could be particularly damaging to the US agricultural landscape. The ultimate concern is that even with a projected increase in precipitation in all global warming scenarios, drought affected areas have also been on the rise since the Dust Bowl, and extreme droughts may experience a large percentage change. A very large population in the US will be severely affected following dire prediction for drought and increased aridity in the coming decades. This is especially problematic for studies using mean shift to project long-term climate change impact. Such assumption on mean shift doesn’t account for a possible scenario, one that has just grasped much attention recently, that more drying condition may become prevalent even in as soon as 2030s, especially for most of the western US [3,4]. Extreme drought damages soil, lowers productivity, reduces farming profit and accelerate permanent farmland conversion to urban use. Facing highly anticipated drought condition in the coming decades, the prospect of the US’ future agricultural landscape rests squarely on the capability to spur higher agricultural productivity to compensate possible damage from extreme droughts. The threat of yield plateau, or yield leveling out, could be dramatic on agricultural sector. Reference: [1] Mendelsohn, Robert, William D. Nordhaus, and Daigee Shaw (1994), "The Impact of Global Warming on Agriculture: A Ricardian Analysis," American Economic Review, Vol. 84(4), pp. 753-771. 1 Department of Agricultural and Resource Economics, University of California at Berkeley. A full paper is available upon request at [email protected]. [2] Schlenker, Wolfram, Michael W. Hanemann, and Anthony C. Fisher (2005), “Will U.S. Agriculture Really Benefit from Global Warming? Accounting for Irrigation in the Hedonic Approach,” American Economic Review, Vol. 95(1), pp. 395–406. [3] Dai, Aiguo (2011), “Drought under Global Warming: a Review,” Wiley Interdisciplinary Reviews: Climate Change, Vol. 2, pp. 45-65. [4] Dai, Aiguo (2011), “Characteristics and Trends in Various Forms of the Palmer Drought Severity Index during 1900–2008,” Journal of Geophysical Research, Vol. 16, D12115, 2011.