Tracking important site safeguard through different approaches to measuring the indicator of protected area coverage of Key Biodiversity Areas

Trends over time in the protected area coverage of Key Biodiversity Areas is an indicator to track progress for global environmental targets, including Sustainable Development Goals 14 and 15, and Target 3 of the Kunming-Montreal Global Biodiversity Framework. Given the key role of this indicator, it is important to understand its statistical robustness, strengths and weaknesses. Here we explore the statistical properties, sensitivity to change, strengths and weaknesses of five potential formulations of the indicator. The most widely used formulation is the mean coverage of KBAs by protected areas and other effective area-based conservation measures (OECMs). We also consider: the median coverage of KBAs; the percentage of the total KBA area covered; the percentage of KBAs covered completely; and the completeness of KBA coverage. We found that no single formulation stands out in terms of performance and strengths. We therefore recommend the reporting of multiple formulations each time the indicator is updated, for example completeness of KBA coverage, percent of KBAs covered completely, and mean percentage coverage of KBAs, as a complementary set of formulations of an important site safeguard index reflecting the progress in safeguarding sites of biodiversity importance.