Three Essays on the Impact of Climate Change and Weather Extremes on the United States' Agriculture.

摘要

This dissertation incorporates three independent essays on the impact of climate change on the United States' agriculture, with each explores a different facet of climate change. In the first essay, using historical crop yield reports paired with high-resolution climate data, I discovered a small and positive effect of a decreasing diurnal temperature range on yields of five major crops including corns, wheat, cotton, soybeans, and sorghum. The asymmetric increases in observed maximum and minimum temperature have resulted in a falling diurnal temperature range across the United States. This effect could help mitigate some potential harmful impacts of climate change in the future, averaging up to a two percent yield offset for summer crops. Meanwhile, little impact on winter crops is expected. Moreover, the overall impact of climate change from a rising mean temperature and less fluctuations is dominantly harmful for most crops.;The second essay presents a structural model of cropland conversions with an application to the impact of extreme droughts. Droughts are perhaps the most destructive events to the US agriculture. Extended periods of severe droughts in the late 20th century caused widespread economic damages comparable to that of the Dust Bowl in 1930s. I showed that those events contributed to converting lands from agricultural production to urban uses by damaging soil productivity and lowering farming profits. I concluded the Ricardian approach to estimating climate change impacts is insufficient. Specifically, the Ricardian method works well for equilibrium adjustments by assuming that farm owners are able to make complete adaptations to a changing environment. However, the Ricardian approach fails to take into account the presence of climate extremes whose adaptations are neither possible nor costless. As a consequence, this method may underestimate the true cost of transient events related to climate change such as extreme droughts. This finding carries a significant implication for the future of the US' private croplands. As the US is predicted to experience more precipitations in the future with climate change, it seems that there would be a beneficial impact of more water for crops. It may not necessarily be the case, however. Even with increased precipitations, drought conditions may occur more frequently and intensively. Damages from potentially extreme drought events were not considered in the Ricardian estimates.;In the third essay, I examined the impact of extreme heating conditions on prime farmland conversions in California using the hedonic regression technique with a spatial dataset. I focused on the number of extreme heating days, defined as day with the recorded maximum temperature rises above 90 degree Fahrenheit. I found a small but significant nonlinear impact of extreme heating days on farmland conversions. A mild increase in the number of extreme heating days may be good for crops, thus helps keep farmlands in agricultural production. However, too excessive heating is harmful and accelerates conversions out of farming. (Abstract shortened by UMI.).