U.S. winter wheat: How is terrain elevation shaping yield response to climate change?

Wheat plays a critical role in global food security; however, its vulnerability to rising temperatures introduces significant uncertainty about future yields in a changing climate. Although earlier studies have linked higher temperatures to yield reductions, the moderating influence of terrain elevation on crop-climate interactions remains insufficiently explored. We combine 42 years of county-level yield data (1982-2023) with phenology-specific climate exposures to evaluate how terrain elevation shapes U.S. winter wheat responses to extreme heat and precipitation. Using an econometric framework with county-specific temperature thresholds for extreme degree days, we identify a critical elevation cutoff at 350 meters that delineates two distinct yield-climate regimes. Low-elevation counties exhibit faster long-term yield growth but greater vulnerability to late season heat stress compared to high-elevation counties. Indeed, the late season coincides with the grain-filling stage, which is critical for winter wheat yield outcomes. Rolling-window estimates further reveal that heat-related yield losses have intensified since the 1980s, with late season penalties nearly doubling. Trends also indicate stronger vulnerability among low-elevation counties, especially in the recent period (2004-2023). These findings demonstrate that topography fundamentally mediates climate risks to wheat production. Adaptation may therefore require not only a latitudinal but also an elevational redistribution of wheat cultivation, reshaping the geography of U.S. production under climate change. More broadly, the results underscore the importance of integrating terrain elevation into climate-crop assessments to improve yield projections and inform adaptation strategies across diverse agricultural systems.