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Title: Uncertainty of climate change impacts on soil erosion from cropland in central Oklahoma

Author
item Garbrecht, Jurgen
item Nearing, Mark
item Zhang, Xunchang
item Steiner, Jean

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2016
Publication Date: 5/15/2016
Citation: Garbrecht, J.D., Nearing, M.A., Zhang, X.J., Steiner, J.L. 2016. Uncertainty of climate change impacts on soil erosion from cropland in central Oklahoma. Applied Engineering in Agriculture. 32(6):823-836.

Interpretive Summary: Soil erosion on cropland over the next half century may increase due to climate change and may require additional soil conservation actions to maintain today’s erosion levels. Climate models are typically used to project the future climate. Hydrologic and soil erosion models are then used to estimate the climate impact on soil erosion. However, projecting future climate conditions involves uncertainty that, in turn, lead to uncertainty in estimated future soil erosion rates. Awareness of these uncertainties is essential to the development of flexible conservation and adaptation measures that remain effective over a broad range of projected climates. In this study, three climate-associated sources of uncertainties were selected for examination of their effect on future soil erosion rates for winter-wheat cropland in central Oklahoma. The uncertainty due to imperfect climate projection models and storm intensification was found to be sizably larger than the inherent uncertainty associated with the realization of a future outcome. Thus, it is recommended that projected soil erosion rates and their uncertainty be an integral part of the conservation planning process. This can be accomplished by using a probabilistic approach to express the uncertainty of projected soil erosion rates as a distribution of potential outcomes. This distribution and a target threshold soil erosion rate are used to determine the risk of exceeding the target threshold. If the risk is too high, additional conservation actions are required to lower future soil erosion rates.

Technical Abstract: Impacts of climate change on soil erosion and the potential need for additional conservation actions are typically estimated by applying a hydrologic and soil erosion model under present and future climate conditions defined by an emission scenario. Projecting future climate conditions harbors several sources of uncertainty that, in turn, lead to uncertainty in projected soil erosion rates. Awareness of these uncertainties is essential to the development of flexible conservation and adaptation measures that remain effective over the broad range of climate projections. In this study, three climate-associated sources of uncertainties were selected to examine their effect on projected soil erosion for winter-wheat cropland in central Oklahoma. Forty soil erosion distributions representing various combinations of two emission scenarios, ten climate projection models, and two storm intensification alternatives were developed and evaluated. The total uncertainty range of 40 projected soil erosion distributions was 2.1 to 18.2 Mg/ha/yr at the median, and 25.0 to 114.0 Mg/ha/yr at the 10% Probability of Exceedance level. The uncertainty due to imperfect prediction tools (climate models) and model choices (storm intensification) was found to be sizably larger than the inherent uncertainty associated with the realization of a future outcome (emission scenario). It was concluded that uncertainties in projected soil erosion rates are potentially large and should be considered in planning future conservation needs. This can be accomplished by using a probabilistic approach to express the uncertainty of projected soil erosion rates as a distribution of potential outcomes. This distribution and a target threshold soil erosion rate determine the risk of exceeding the threshold. If the risk is too high, additional conservation actions are required to lower future soil erosion rates and their uncertainty range.