Global biodiversity is being lost rapidly, and the recovery of threatened species faces many challenges. Looming large are the anthropogenic causes of population declines, including habitat loss, invasive species, and overexploitation. Genetic threats exacerbate the problem: Population declines erode genetic variation and mating of close relatives in small populations causes inbreeding, together harming the long- and short-term viability of a population. On page 635 of this issue, Robinson et al. (1) report using genomic data from the vaquita porpoise (Phocoena sinus) from Mexico—which has suffered a recent severe population decline as a result of incidental mortality through fishery operations (bycatch)—to examine genetic diversity and anticipate its likely effects on future population trends. They conclude that, provided bycatch is reduced, the species shows promising potential to overcome genetic threats. The analysis exemplifies some of the ways that genomics can inform conservation policy and practice.