Trophic control of mesopredators in terrestrial ecosystems: top-down or bottom-up?
It has been argued that widespread extinctions of top predators have changed terrestrial ecosystem structures through mesopredator release, where increased abundances of medium-sized predators have detrimental effects on prey communities. This top-down concept has received much attention within conservation biology, but few studies have demonstrated the phenomenon. The concept has been criticized since alternative explanations involving bottom-up impacts from bioclimatic effects on ecosystem productivity and from anthropogenic habitat change are rarely considered. We analyse the response of a mesopredator (the red fox) to declines in top predators (wolf and Eurasian lynx) and agricultural expansion over 90 years in Sweden, taking bioclimatic effects into account. We show a top-down mesopredator release effect, but ecosystem productivity determined its strength. The impacts of agricultural activity were mediated by their effects on top predator populations. Thus, both top-down and bottom-up processes need to be understood for effective preservation of biodiversity in anthropogenically transformed ecosystems.
Elmhagen
Bodil
B
School of Biology, University of Newcastle upon Tyne, Devonshire Building NE1 7RU, UK.
Rushton
Stephen P
SP
D000383:Agriculture; D000818:Animals; D005075:Biological Evolution; D002980:Climate; D004777:Environment; D020387:Food Chain; D005589:Foxes; D046008:Lynx; D011157:Population Dynamics; D011235:Predatory Behavior; D013548:Sweden; D019596:Wolves