Thousands of infant sequoia and coastal redwood saplings, each the size of a thumb, sprout beneath grey foil and growing lamps in bus-size greenhouses. In the next room are their juvenile siblings, five to eight inches tall: sequoias, coastal redwoods, oaks and a hundred other tree species form the Archangel Ancient Tree Archive (AATA), a living library of the world's mightiest trees. These are not just any saplings " they all are descendants of so-called champion trees, specimens of exceptional size, age and resilience. At 75, David Milarch is trying to save the world's last old-growth forests from extinction " by using their DNA to help reverse climate change. The need, Milarch notes, is urgent: "Ninety-eight percent of the old-growth forest has been logged," he explains. "We have to save the remaining two percent." Unlike with other tree planting initiatives, Milarch puts plans in place to nurture the saplings for generations to come. To make this possible, he and Arboretum Detroit work with schools. "We empower the kids. We teach them, we give them the materials, and we check in on them," Milarch explains. "We're propagating the propagators. That's the paradigm shift." Each child gets to name a sapling, "because kids need to connect with nature," Milarch says. And later on, when the kids face hardship, Milarch points out, "they can always run to their tree and get some solace."