Mammalian herbivores are major drivers of terrestrial ecosystems worldwide and changes in their abundance can have strong ecological and socio-economic consequences. With my research program I aim to provide governments, industries and NGO's with the necessary scientific basis to deal with these consequences. I study the mechanisms that drive herbivore abundance, community assemblages and their role in ecosystem functioning. Changes in herbivore numbers are often mediated by changes in their food resource. This relation between herbivores and their resources is not passive, but includes a range of positive as well as negative feedback interactions at individual, population and community scale. I study these interactions and the factors that modify them, specifically the role of top-down (herbivores, carnivores) versus bottom-up (abiotic) factors. Hence, my work includes herbivore-plant, herbivore-herbivore and herbivore-carnivore interactions within the abiotic setting of the ecosystem. I am currently exploring the (dis)similarities between herbivore-resource interactions in browsing and grazing systems in Africa and Europe, including Swedish boreal and temperate forests. Moreover, I recently started studying how predation risk affects the impact of herbivores on the functioning of terrestrial ecosystems.