Iconic red cedars — known as the “Tree of Life” — in the Pacific Northwest have been dying because of climate-induced drought. Deep inside a forest in Oregon’s Willamette Valley stands a dead “Tree of Life.” Its foliage, normally soft and green, is tough and brown or missing altogether. Nonetheless, the tree’s reddish bark, swooping branches and thick, conical base identify it as the Pacific Northwest’s iconic western red cedar. The rings become thinner over time, indicating the tree’s growth slowed before the tree finally died, a sign that this red cedar died from drought. “That’s why it’s the canary,”...