Essays on climate change interactions with agricultural land and water use

Abstract

Agriculture and climate change are closely connected as climate change impacts agriculture through crop yield loss, reduction in area harvested and increase in irrigation water use. Agriculture plays both roles in the emission and sequestration of greenhouse gases. This dissertation is divided into two main parts. The first part has two essays that examine the impacts of climate change on winter wheat production and irrigation water use. The second part examines the cost–effectiveness of using lands under the Conservation Reserve Program (CRP) to sequester carbon through tree planting program. This dissertation contributes to the literature by showing how crop yield variability is not the same as production variability. The total impact of climate change is underestimated if climate change impact on yield alone is used. Another contribution to the literature is the modeling of crop abandonment in relation to climate change using correlated random effects fractional probit model. My work also illustrates how irrigation water use will change and how this change will impact the level of water in the aquifer by mid–century. In my first essay, I examine the impact of climate change on winter wheat production in Kansas. I decompose the total impact of weather variables on wheat production in Kansas through crop abandonment and yield. Using yield impacts alone to measure the climate change impact on production underestimates the total impact of climate change on production. I use the correlated random effects fractional probit model to estimate crop abandonment and account for unobserved heterogeneity between time–invariant variables and yield. The result projects a 16.3% decrease in winter wheat production by mid–century under the Representative Concentration Pathway (RCP) 4.5. I find that 86.72% of the projected decrease in production is due to the reduction in yield while crop abandonment is projected to decrease production by 13.17%. Yield is projected to decrease by 14.12% while crop abandonment is expected to increase by 18% by mid–century. Majority of damages from climate change are explained by an increase in temperature. In the second essay, I examine the impact of climate change on groundwater extraction for corn production in Kansas. Using a 24–year panel data of irrigation water use, weather and soil data, I estimate the impact of weather variability on irrigation water use for corn. I include the field–level fixed effects and a quadratic time trend to control for time invariant– variables and technological progress over time. I provide new evidence that shows farmers are less responsive to changing irrigation water use than an irrigation schedule would predict due to changes in weather. The result indicates 9% and 12% increase in irrigation water use by mid–century under RCP 4.5 and 8.5 respectively. The number of water rights that exceed their authorized water quantity will increase by 18.1% on average across different climate models under RCP 4.5. The effect of an increase in irrigation water use on the water level in the aquifer is spatial different. In Southwest Kansas, the historical rate of depletion is 2.05ft/year and by mid-century, the rate of depletion is projected to increase to 2.43 ft/year. In South Central Kansas, historical depletion is around 0.19 ft/year and the rate of depletion is predicted to increase to 1 ft/year by mid-century. In the third essay, I analyze the cost–effectiveness of carbon sequestration through the afforestation of the Conservation Reserve Program (CRP). I use the correlated random effects probit model (CRE) to estimate the impact of an increase in the Conservation Reserve Program (CRP) payments on land use change. The CRE model allows me to control for unobserved heterogeneity and exploit variation in returns to land over time. Estimation without control for unobserved heterogeneity produces biased estimates with coefficients with the wrong sign. My estimates are used to simulate land use change, carbon sequestered and the marginal cost of carbon at different levels of CRP rent (i.e., the supply curve for carbon sequestration). At the average CRP rent rate of $71.21, 118,046 acres is gained by CRP and 2.1 million tons of carbon is sequestered per year at a marginal cost of $24.6. Increasing the average rent by 30% will add additional 159,736 acres and 0.24 million tons of carbon per year.