When California’s historic five-year drought finally relented a few years ago the tally of dead trees in the Sierra Nevada was higher than almost anyone expected: 129 million. Most are still standing, the dry patches dotting the mountainsides.

But some trees did survive the test of heat and drought. Now, scientists are racing to collect them, and other species around the globe, in the hope that these “climate survivors” have a natural advantage that will allow them to better cope with a warming world.