The use of environmental heterogeneity as an indicator of protected area effectiveness in conserving biodiversity

Abstract Developing innovative monitoring systems for biodiversity outcomes in protected areas (PAs) are important to enable effective adaptive management. Here we show how to quantitatively detect and monitor temporal and spatial patterns in environmental heterogeneity, an important indicator of ecological integrity and biodiversity patterns. We used a 28-year time series (1991 – 2018) generated from freely available Landsat satellite imagery and Roa’s quadratic index to calculate trends in heterogeneity for 41 PAs across South Africa. We selected PAS where mega-herbivore assemblages were similar and where management objectives were broadly aligned with South African legislation to protect biodiversity. Heterogeneity decreased in 11 (32%), increased in three (7%), and remained stable in 26 (63%) PAs. In PAs where heterogeneity was decreasing, factors such as fire, precipitation, woody encroachment, and elephants may be contributing to a possible park effect where small, fenced areas are becoming more homogenized. However, our results also indicated that factors such as fire and herbivory as well as the location of roads, waterholes, and camps can be manipulated to increase PA heterogeneity. The framework presented here can be extended to include every PA nationally, or even globally, and the data product fully automated. This presents an opportunity for conservation management to incorporate this important biodiversity indicator in PA monitoring programs as well as other large-scale environmental monitoring initiatives.