In an effort to halt the loss of plant species to habitat loss, climate change, and other threats, the 1992 global Convention on Biological Diversity calls for at least 75 percent of the known threatened species to be conserved by 2020. But once you’ve identified a plant as threatened, what’s the best strategy for protecting it? How do you prevent plants in small populations from inbreeding with siblings? And what happens when what was identified as an endangered species turns out to be a subspecies of an organism that’s doing fine?

Conservation geneticist Christy Edwards, of the Missouri Botanical Garden, grinds up leaves of threatened species to extract their DNA, then analyzes millions of fragments to inspect important traits, such as how closely related various individuals are. Her work has led to some surprises: endangered plants that aren’t in danger in reality, and seemingly “safe” populations that need more protection.

Her work also guides reintroduction and captive breeding programs for the most rare species. In this live interview at the Sheldon Concert Hall in St. Louis, Edwards explains the big decisions that stem from studying some of the most minute parts of a plant.