Trophic rewilding: impact on ecosystems under global change.

Abstract

Human-induced global change is increasingly affecting life on our planet, including living conditions for humans themselves as well as the resources we depend on [1,2]. As a result, species diversity is strongly declining [3–5]. The Living Planet Index shows a 58% global decline in populations of amphibians, fish, reptiles, mammals and birds between 1970 and 2012, varying from 36 to 38% in terrestrial and marine ecosystems to 81% in freshwater habitat [6]. Habitat loss or degradation and overexploitation are the main causes of these steep declines. Since the worldwide expansion of modern humans ( Homo sapiens ) began, humans have overexploited vertebrates, with a bias to the largest animals being extirpated first, from the Late Pleistocene extinctions of terrestrial megafauna to the ongoing declines of terrestrial, marine and freshwater large-bodied animals [7–11]. There is increasing evidence that this global wildlife loss, or defaunation, does not only imply the loss of charismatic animals but also the functions they have in ecosystems [12–16]. To restore these missing functions, a novel ecological restoration technique has emerged, referred to as rewilding [17]. Rewilding aims to restore natural processes in ecosystems in general, and often focuses on re-introduction of missing large wildlife species or, in case these went extinct, their proxies [18]. Rewilding is increasingly implemented in practice globally, with a strong emphasis on Europe and the re-introduction of large herbivores [19,20]. Rewilding has recently been described as ‘a captivating, controversial, twenty-first century concept to address ecological degradation’ [20]. Most rewilding initiatives fit the concept of trophic rewilding, defined as an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote …