Projected changes in cold hardiness zones and suitable overwinter ranges of perennial crops over the United States

Abstract

Average annual absolute minimum temperatures (TNn) provide a means of delineating agriculturally relevant climate zones and are used to define cold hardiness zones (CHZ) by the United States Department of Agriculture. Projected changes in TNn, mean winter minimum temperatures, and CHZs over the conterminous United States (CONUS) were assessed using an ensemble of statistically downscaled daily climate model output through the mid 21st century (2041-2070). Warming of TNn is on average ∼40% greater than that of mean winter minimum temperatures across CONUS with an average climate velocity of 21.4 km decade-1 resulting in widespread shifts in CHZs. These changes enable a geographic expansion of thermally suitable areas for the cultivation of cold-intolerant perennial agriculture including almond, kiwi, and orange crops. Beyond these crops, warming of TNn has broad implications for food security and biotic interactions.