Stochastically modeling the projected impacts of climate change on rainfed and irrigated US crop yields

Abstract

Food demands are rising due to an increasing population with changing food preferences, placing pressure on agricultural production. Additionally, climate extremes have recently highlighted the vulnerability of the agricultural system to climate variability. This study seeks to fill two important gaps in current knowledge: how irrigation impacts the large-scale response of crops to varying climate conditions and how we can explicitly account for uncertainty in yield response to climate. To address these, we developed a statistical model to quantitatively estimate historical and future impacts of climate change and irrigation on US county-level crop yields with uncertainty explicitly treated. Historical climate and crop yield data for 1970-2009 were used over different growing regions to fit the model, and five CMIP5 climate projections were applied to simulate future crop yield response to climate. Maize and spring wheat yields are projected to experience decreasing trends with all models in agreement. Winter wheat yields in the Northwest will see an increasing trend. Results for soybean and winter wheat in the South are more complicated, as irrigation can change the trend in projected yields. The comparison between projected crop yield time series for rainfed and irrigated cases indicates that irrigation can buffer against climate variability that could lead to negative yield anomalies. Through trend analysis of the predictors, the trend in crop yield is mainly driven by projected trends in temperature-related indices, and county-level trend analysis shows regional differences are negligible. This framework provides estimates of the impact of climate and irrigation on US crop yields for the 21st century that account for the full uncertainty of climate variables and the range of crop response. The results of this study can contribute to decision making about crop choice and water use in an uncertain future climate.

Resilience of food sufficiency to future climate and societal changes

“…Our tree-based statistical modeling approach 14 performed well on unseen data (R 2 = 0.95; our model error is~15% of current yield, in line with previous work 11 reporting RMSE of 9 to 20% of current yields across different crops; see also Methods). Our findings fall within the range of existing projections, which vary substantially: comparable forward-looking studies project changes in global yield within this timeframe of -5% to +13% 16 , -5% to +47% 17 ,~+1% 18 , ±20% 19 . Some studies focused on climate change find consistent declines (-10% 20,21 to almost -30% 11 ).…”

“…We propose a new approach consistent across scenarios that embeds the crop mix adaptation assumption by considering total caloric yield. This approach innovates beyond past modeling approaches of crop-specific responses to climate change 11,[16][17][18][19][20][21][22] by predicting total caloric yields, aggregating across all crop types from the outset, which sidesteps the need to predict exact crop mixes, implicitly assuming upfront some degree of crop mix adaptation. This study does not explore potential more complex behavioral responses, economic or environmental feedbacks, or likelihood of farmers to adapt to future conditions.…”

Climate adaptation by crop migration

“…Future increases in temperature may open up new agriculturally suitable areas 1 , and crops in some locations will benefit from increases in temperature 9 . However, yield responses to temperature generally increase up to a point past which they decrease rapidly 7,10,11 , and on average across the globe, temperature increases are expected to have a damaging impact in the absence of compensatory management responses 4,[11][12][13] . Yet agricultural systems will inevitably respond to these changing conditions and therefore actual losses will thus depend on the efficacy of adaptive responses by farmers 6,[14][15][16][17] .…”

Shifts in Hydroclimatology of U.S. Croplands

“…Another important question that should be addressed here is how much irrigation requirement would change in response to hydroclimatic change for maintaining current crop yields. Irrigation has been commonly used as an adaptation tool to increase crop yields and decrease the impacts of climate changes [31][32][33]. Considerable research has investigated the effects of climate variability on crop yield [34].…”