A PNAS study tracking 208 tropical tree species across South America, Southeast Asia, and Central Africa from 2001 to 2020 finds thermal safety margins shrinking at 0.4°C per decade. Researchers combined satellite-derived canopy temperatures with species distribution maps to measure the gap between maximum leaf temperature and the critical photosynthetic threshold (Tcrit), which averages 46.1°C across species. The work, led by N. van Tiel and colleagues, was edited by **Christopher B.

Field at Stanford University**.