Understanding the differences between single‐ and multiobjective optimization for the conservation of multiple species.

The purpose of this study is to understand how solutions from single‐ and multiobjective optimization for the conservation of multiple species are different and what impacts these differences. We identify optimal conservation investment allocations maximizing expected species' habitat ranges for multiple pairs of species using two approaches in the central and southern Appalachian region. We find that disparities between the two approaches are affected by differences in the involved species' expected habitat ranges (i.e., contrasting and similar) and their correlation pattern (i.e., positive, negative, and insignificant). Using a single metric by aggregating species' habitats for multiple species to carry out single‐objective optimization is shown to favor the species with a larger habitat distribution more if the involved species' expected habitat distributions are negatively correlated and their distribution difference is larger. Framing multiple metrics of species' habitats separately using multiobjective optimization for the same set of multiple species, in contrast, does not show such a drastic disparity. Recommendations for resource managers: Our findings help conservation organizations choose an optimization approach that fits a specific purpose related to the conservation of multiple species. Using a single metric by aggregating multiple species' habitats to carry out single‐objective optimization is shown to favor the species with a larger habitat distribution clearly if the involved species' expected habitat distributions are negatively correlated and their distribution difference is substantial. Selecting an appropriate optimization mechanism for multiple species with similar and positively correlated habitat distributions is not critical since both methods produce similar results. If solutions based on single‐objective optimization are chosen, a conservation organization's goals may not align well with equity concerns regarding ecological protection and restoration. As climate change progresses, conservation organizations may need to be extra cautious about relying on patterns of historical species occurrence when applying an appropriate optimization approach. [ABSTRACT FROM AUTHOR]