Beyond the obvious impact of domestic livestock grazing on temperate forest vegetation - A global review

Large herbivores have a keystone role in many forest ecosystems. There is widespread recognition that undesirable changes may be caused by the complete removal of grazing-related disturbances, whereas there can be benefits from properly managed, targeted livestock grazing, both from a forest management and biodiversity perspectives. However, there are also many contradictory statements and results about forest grazing. We summarize the main scientific evidence and knowledge gaps on forest livestock grazing through a global review of the literature for the temperate region. We analysed 71 publications discussing the impact of livestock grazing on vegetation in forests. Grazing reduces vegetation biomass, but less obvious effects relevant to conservation include increased habitat diversity and increased regeneration of selected canopy tree species. Moreover, detailed guidance on how grazing should be carried out for conservation purposes is limited because the results are strongly context dependent. The direction and amplitude of effects can be influenced not only by forest type and stocking levels, but by foraging preferences of livestock, availability of alternative forage, grazing season and herder activity. We stress the need for well-planned real-world experiments and observations, and for more quantitative studies to foster evidence-based conservation management. Grazing differences between wild ungulates and livestock should be better studied, because the effects are often overlapping. We suggest widening the temporal and spatial scales of case studies and stress the need to create space and openness for interdisciplinary and participatory research and conservation approaches, initiating knowledge co-production on the benefits and dis-benefits of grazing in forests.