Contrasting long-term temperature trends reveal minor changes in projected potential evapotranspiration in the US Midwest

Bruno Basso,Joe T Ritchie,Rafael A Martinez-Feria,Lydia Rill

doi:10.1038/s41467-021-21763-7

Bruno Basso, Joe T Ritchie + Show 2 more

Open Access

https://doi.org/10.1038/s41467-021-21763-7

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Journal: Nature Communications	Publication Date: Mar 5, 2021
Citations: 42	License type: open-access

Affiliation: Michigan State University

Abstract

Warming generally leads to increased evaporative demand, altering the amount of water needed for growing crops. For the Midwest, some studies have suggested that reaching yield targets by 2050 will not be possible without additional precipitation or large expansion of irrigation. Here, we show that this claim is not supported by the historical summer climate trends, which indicate that the warming of daily average temperatures is largely driven by increases in minimum temperatures, while maximum temperatures have decreased. This has translated into a net decrease in vapor pressure deficit (VPD) and potential evapotranspiration (PET). With the increasing rainfall, this suggests that crop water deficits have likely become less frequent in the region despite the warming climate. By projecting these trends into 2050 and ancillary use of a crop model, we estimate minor changes in PET that would have minimal effects on corn yields (<6%) under persistence of these trends.

Highlights

Warming generally leads to increased evaporative demand, altering the amount of water needed for growing crops
The 60-year cooling trend in Tx was not generalizable to the whole region, it did exhibit a spatial gradient, with the majority of stations with a strong cooling trend clustering within the north–western quadrant of the study region (i.e., Iowa, Nebraska, South Dakota, and Minnesota; Fig. 2). This suggests that the decline in Tx in the western plains is driven by more recent changes, whereas it may have softened in the eastern portion of the study region
This points to the potential inadequacy of short-term climate records (

Summary

Introduction

Warming generally leads to increased evaporative demand, altering the amount of water needed for growing crops. Some studies have suggested that corn in the Midwest will require ~35% more water inputs to reach yield targets by 205020,21, arguing that sustaining yield gains will not be feasible without widespread expansion of irrigation infrastructure[22] This claim is questionable, in part due to evidence showing that large differences in crop biomass and yield can be achieved with the same amount of ET, both within and across species with similar growing-season length[14,23]. Midwestern summer climate, has seen a long-term decline in Tx and increasing precipitation has been observed despite moderate warming of daily average temperatures (Ta)[25,26,27] It is unclear how these historical temperature trends have affected growing-season VPD and PET in the Midwest, and how future changes in atmospheric water demand under the persistence of these trends could impact crop yields. We projected the temperature trends into 2050 to calculate the expected PET changes in the region under current climate trajectories and predicted the potential impacts on corn water stress and yields with ancillary use of the SALUS (systems approach to land-use sustainability) crop model[28,29]

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