American hemlocks are living libraries. Able to live to up to 500 years, their rings offer a record of earth’s climatic variation. A new project is asking volunteers to gather these invaluable data before the trees disappear, possibly within decades due to the dual threat from climate change and the invasive woolly adelgid insect it brings, which weaken trees by sucking them dry. The Hemlock Legacy Project, or HeLP, is enlisting volunteers to take samples with a corer (the wound heals naturally). “Our approach is that this is an archive of information that could answer many questions”—about how forests responded to the highs and lows of historical climate changes, for instance—says Amy Hessl, a cofounder of HeLP and a dendrochronologist at West Virginia University. In addition to coring, researchers are collecting ecological information they could one day use to restore hemlock should they discover an adelgid-resistant variety.