Fig. 4: Hotter-drought fingerprint by Whittaker biome type.

The 3-year window, centered on the mortality start year, is displayed for each biome. Above each biome triptych the number of sites included is listed (Woodland/Shrubland n = 355, Temperate Seasonal Forest n = 99, Tropical Seasonal Forest/Savanna n = 81, Subtropical Desert n = 64, Temperate Grassland n = 53, Tropical Rain Forest n = 19, and Boreal Forest n = 18). Points represent the mean z-score for each variable, and whiskers are the 95% confidence interval in that mean. Strong signals appear in woodland/shrubland, temperate grassland/desert, both temperate seasonal forests, and tropical seasonal forests/savannas, and even boreal forests (with a small sample) show significant indicators of hotter drought. Tropical rainforests do not show this particular hotter-drought signal in our present analyses—highlighting that a combination of data scarcity and diverse responses of various forest types in the tropics will need further investigation, as outlined in point (5) of the future research opportunities listed in the main text.