The mismeasure of conservation.

One of the basic purposes of protected areas and other effective area-based conservation interventions is to achieve conservation impact, the sum of avoided biodiversity loss and promoted recovery relative to outcomes without protection. In the context of the Convention on Biological Diversity's negotiations on the post-2020 Global Biodiversity Framework, we find that targets for area-based interventions are framed overwhelmingly with measures that fail to inform decision-makers about impact and that risk diverting limited resources away from achieving it. We show that predicting impact in space and time is feasible and can provide the basis for global guidance for jurisdictions to develop targets for conservation impact and shift investment priorities to areas where impact can be most effectively achieved.