Incorporating anthropogenic effects into trophic ecology: predator-prey interactions in a human-dominated landscape.
Apex predators perform important functions that regulate ecosystems worldwide. However, little is known about how ecosystem regulation by predators is influenced by human activities. In particular, how important are top-down effects of predators relative to direct and indirect human-mediated bottom-up and top-down processes? Combining data on species' occurrence from camera traps and hunting records, we aimed to quantify the relative effects of top-down and bottom-up processes in shaping predator and prey distributions in a human-dominated landscape in Transylvania, Romania. By global standards this system is diverse, including apex predators (brown bear and wolf), mesopredators (red fox) and large herbivores (roe and red deer). Humans and free-ranging dogs represent additional predators in the system. Using structural equation modelling, we found that apex predators suppress lower trophic levels, especially herbivores. However, direct and indirect top-down effects of humans affected the ecosystem more strongly, influencing species at all trophic levels. Our study highlights the need to explicitly embed humans and their influences within trophic cascade theory. This will greatly expand our understanding of species interactions in human-modified landscapes, which compose the majority of the Earth's terrestrial surface.
Faculty of Sustainability, Leuphana University Lüneburg, Rotenbleicher Weg 67, 21335 Lüneburg, Germany ine.dorresteijn@gmail.com.
Ine
I
Dorresteijn
Faculty of Sustainability, Leuphana University Lüneburg, Rotenbleicher Weg 67, 21335 Lüneburg, Germany.
Jannik
J
Schultner
Institute for Land, Water and Society, Charles Sturt University, Albury 2640, Australia.
Dale G
DG
Nimmo
Faculty of Sustainability, Leuphana University Lüneburg, Rotenbleicher Weg 67, 21335 Lüneburg, Germany.
Joern
J
Fischer
Faculty of Sustainability, Leuphana University Lüneburg, Rotenbleicher Weg 67, 21335 Lüneburg, Germany.
Jan
J
Hanspach
Geography Department, Humboldt-University Berlin, Unter den Linden 6, 10099 Berlin, Germany Integrative Research Institute on Transformations in Human-Environment Systems (IRI THESys), Humboldt-University Berlin, Unter den Linden 6, 10099 Berlin, Germany.
Tobias
T
Kuemmerle
Geography Department, Humboldt-University Berlin, Unter den Linden 6, 10099 Berlin, Germany.
Laura
L
Kehoe
Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia.
Euan G
EG
Ritchie
D000818:Animals; D003670:Deer; D004285:Dogs; D020387:Food Chain; D005589:Foxes; D006802:Human Activities; D008962:Models, Theoretical; D011157:Population Dynamics; D011235:Predatory Behavior; D012383:Romania; D001503:Ursidae; D019596:Wolves
apex predators; habitat modification; large herbivores; mesopredators; top-down versus bottom-up; trophic cascade