Protected areas are central to global biodiversity conservation strategies, yet their effectiveness is often evaluated only within their formal boundaries. In increasingly fragmented landscapes, long term biodiversity persistence depends on the degree to which protected areas remain ecologically connected to surrounding habitats.
Conservation policies frequently assume that protected areas generate positive ecological effects beyond their borders, but empirical evidence for the extent, consistency, and drivers of these effects remains limited. This uncertainty constrains the ability of planners to design protected area networks that explicitly support connectivity.
Cumming, G. S. 2025. Protected area management has significant spillover effects on vegetation. Nature. DOI: 10.1038/s41586-025-09837-8.
A new study addresses this gap by examining whether protected areas influence vegetation structure in adjacent landscapes and how management type shapes these spillover effects. The research analyzed vegetation patterns inside and around more than 12,000 terrestrial protected areas across Australia using continent scale land cover data spanning 1988 to 2020. Vegetation spillover was defined as a difference between vegetation in a near boundary zone and vegetation in comparable areas farther from protected area influence.
The analysis contrasted three spatial zones: the protected area interior, a spillover zone extending up to 5 km beyond the boundary, and an independent zone more distant from protection. Ten classes of woody and herbaceous vegetation were evaluated, with comparisons designed to account for local biophysical conditions and landscape context.
The results indicate that vegetation spillovers are widespread and persistent. In 2020, 71% of the 3,063 protected areas with sufficient data exhibited a positive spillover effect greater than 0.1 for at least one vegetation class, a proportion similar to that observed in 1988. Model based estimates suggest that up to 82% of all candidate protected areas may generate positive spillovers. Woody vegetation showed particularly strong patterns, with forest cover disproportionately represented inside protected areas and detectable increases in forest and woodland extending into adjacent lands.
Protected area management designation emerged as an important predictor of spillover magnitude. Management type and its interactions with environmental and contextual variables explained approximately 16% of the variation in spillover effects, indicating that internal management practices can influence ecological conditions beyond protected area boundaries.
Overall, the findings support the view that protected areas function as integral components of broader habitat networks rather than isolated conservation units. By moderating vegetation patterns in surrounding landscapes, protected areas can contribute to structural connectivity and potentially facilitate species movement across fragmented regions.
From a conservation planning perspective, explicitly accounting for spillover effects could improve the design and evaluation of protected area networks. Incorporating these cross boundary influences into connectivity assessments and policy frameworks may enhance the effectiveness of protected areas in maintaining biodiversity and ecosystem function across working landscapes.
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