Final Report Summary - HOTSPOT (Resource hotspots and the role of apex predators in terrestrial ecosystems)
Apex consumers are major ecological drivers and strongly influence ecosystem functioning because they are at the top of their food chain. Most work on apex consumers involves the effects of apex predators. However, one could also consider megaherbivores as apex consumers. Megaherbivores are plant-eating animals with a minimum adult body mass of 1,000 kgs. Because of this size they escape predation and thus control their food chain. The HOTSPOT program studied the effects of both types of apex consumer, apex carnivores and megaherbivores, on lower trophic levels and ecosystem functioning in South African savannas (Hluhluwe-iMfolozi Park, looking at effect of megaherbivores and apex carnivores) and Swedish boreal and nemoral forests (looking only at effects of apex carnivores). The work in South Africa was done in close collaboration with the center for African Conservation Ecology of Nelson Mandela Metropolitan University in Port Elizabeth. Using observational and experimental studies, which involved 4 different PhD projects and > 10 different MSc thesis studies, the program delivered many new insights in the mechanisms through which apex consumers influence ecosystem functioning. For example, in our savanna work we showed that megaherbivores may modify the predation risk induced effects of apex carnivores on lower trophic levels because they are not affected by predation risk. We also showed a variety of ways in which megaherbivores, white rhino and elephant, shape the structure of savanna systems. This work is now especially important because poaching is severely threatening both rhino and elephant populations globally. In Sweden, the project has started to deliver new insights in the way Scandinavian carnivores, brown bear specifically, is influencing behavior of ungulates and if these behavioral changes affect lower trophic levels. HOTSPOT is thus playing an important role in advancing the field of apex consumer impact on ecosystem structure and functioning in European as well as South African ecosystems. As such, HOTSPOT results contribute to understanding what it means to lose apex consumers, large carnivores as well as megaherbivores, but also what it means to regain their control, e.g. with the return of large carnivores in Europe. During the four years of the project, the fellow hugely strengthened his CV, in terms of publication output, supervising doctoral students as main and co-supervisor (now 6 in total), examining doctoral dissertations, increasing his teaching experience and many other aspects (e.g. responsibility as departmental coordinator of PhD studies). Up to now the program has resulted in 12 journal publications, with more to come. As a result, the HOTSPOT project has been extremely successful in terms of enforcing the long-term professional integration of the fellow as he now holds a permanent position as a senior lecturer at the Swedish University of Agricultural Sciences.