Conservationists must make hard choices about where to invest limited resources for the protection of biological diversity. Numerous prioritization schemes have identified places where biodiversity is especially rich or risks are especially urgent (1). Application of return on investment (ROI) thinking promises to make conservation investments much more efficient by explicitly incorporating economic costs alongside considerations of biodiversity (2⇓⇓–5). ROI approaches can also account for uncertainty but do not consider correlations that could increase exposure to risk (6). In PNAS, the work by Ando and Mallory (7) shows how modern portfolio theory (MPT), a standard financial tool, can be applied to prioritize conservation investments in a way that explicitly accounts for correlated uncertainty and risk–reward tradeoffs associated with the potential impacts of climate change.