Fig. 1: Modes of agricultural adaptation.

(a–e) represent theoretical gridded maps of crop harvested area. Dark green grid cells have the largest fraction of harvested area, decreasing as the shade gets lighter. Map (a) represents the initial time period (t₁), while maps (b–e) represent theoretical scenarios at a later time (t₂). As temperatures change (contours), the geographical distribution of harvested areas may or may not shift relative to a, the initial distribution. We compare observed changes in growing season temperatures of harvested areas to a counterfactual in which harvested areas remain constant (b). For the warm bound (95th percentile), no significant difference between the experienced temperature trend and the counterfactual temperature trend (c, f) would indicate no adaptive migration in response to warming; an experienced temperature trend that is significantly less than the counterfactual temperature trend suggests adaptation by crop migration to cooler areas (d, g); and an experienced temperature trend greater than the counterfactual temperature trend would suggest that crops are not only coping with temperature changes but expanding into even warmer areas (e, h).