Global patterns and potential drivers of human settlements within protected areas

Protected areas (PAs) represent one of our most important conservation strategies for halting biodiversity loss. The number of PAs has increased remarkably over the last few decades. Yet, biodiversity is still being lost at alarming rates, even within many of those PAs. Understanding the factors that influence the levels of human pressure within PAs remains a key objective. In this study, we examined the factors associated with the human settlements' levels within the world's PAs. Using the random forests technique, an ensemble machine learning method, and a vast number of PAs (81 100-137 523), we assessed the importance of nine factors, including the PAs' management objective as reflected by their International Union for Conservation of Nature (IUCN) Category. The IUCN classifies PAs into six categories ranging from strict nature reserves to areas in which multiple human uses are permitted. The prevalent but untested assumption is that human settlements' levels within PAs vary according to their management objective, with less strict PAs having higher levels. Our results, however, show that the differences between the categories were for the most part minor. The most important predictor of human settlements was accessibility measured as the time required to reach the PA from the nearest major city. These findings were consistent across all of the world's subregions. Other less important factors included the extent of croplands within PAs, elevation, and slope. Our findings suggest that PAs nearer urban centers tend to have higher human settlements' levels regardless of their other characteristics, such as management objective and year of establishment. Managing those PAs successfully will be necessary to achieve the post-2020 global biodiversity targets and will require conservation strategies that acknowledge and engage the local communities.

Automated summary

Protected areas are important conservation strategies, but biodiversity loss continues within them. Human settlement levels within PAs are influenced most by accessibility to major cities, with factors like cropland area, elevation and slope also playing a role. Management strategies that involve local communities are crucial for achieving global biodiversity targets.