phenology

 The study of the timing of recurring natural events — when the cherry trees bloom, when the first frost arrives, when the geese fly south, when the salmon run begins. Phenology tracks the calendar that the living world keeps for itself, independent of human schedules. It is the oldest science, practiced by every agricultural and Indigenous culture that ever watched the sky and the soil for signals of what was coming next. In an era of climate change, phenological records have become some of the most valuable data on earth — they show, in accumulated observations stretching back centuries, that spring is arriving earlier and autumn later than it used to.