Ecological impacts and management of wild boar rooting in forest ecosystems

Wild boar (Sus scrofa) is one of the most widely distributed wild ungulates, and its populations are increasing and expanding globally due to socioeconomic change, reduced predator pressure, and climate warming. Rooting, a characteristic foraging behavior in which wild boars overturn litter, vegetation, and soil, is a major disturbance in forest ecosystems and can alter soil properties, biotic communities, ecosystem processes, and ecosystem services. In this literature review, we synthesize current knowledge of wild boar rooting in forest ecosystems. We first summarize the drivers of rooting regimes. We then review rooting-induced changes in soil physical and chemical properties, the community structure of soil microbes, invertebrates, and understory vegetation, as well as ecosystem processes and functions, including carbon and nitrogen dynamics and forest regeneration. We also discuss methodological challenges in quantifying rooting and their implications for cross-study comparisons. By reviewing previous studies, we found that both rooting regimes and their ecological impacts are highly context dependent. Available evidence suggests that these drivers can be structured into population-level, environmental, and temporal dimensions. Specifically, rooting regimes are influenced by factors such as population density, social structure, habitat heterogeneity, forest composition, topography, soil moisture, food availability, mast production, and seasonality. Ecological responses to rooting likewise varied considerably among studies, except for generally negative effects on understory vegetation diversity and cover, nutrient dynamics, and forest regeneration. Variation in ecological responses may be driven by differences in rooting intensity and frequency, forest type, soil characteristics, temporal scale, and survey methodology, although evidence for these mechanisms remains largely based on individual studies. Standardized assessments of rooting intensity and frequency would therefore provide a valuable framework for more robust cross-study comparisons. Based on these findings, we argue that effective management should not focus solely on rooting occurrence, but should integrate rooting regimes, ecosystem vulnerability, and local management priorities. We further identify several important knowledge gaps and research priorities, including clarifying the effects of rooting on mature trees and whole-forest carbon dynamics, testing biodiversity responses along rooting disturbance gradients, evaluating cascading effects across trophic levels, and assessing how climate change and extreme events interact with rooting to shape forest ecosystem functioning.