Soil biological responses to, and feedbacks on, trophic rewilding

Abstract

Trophic rewilding—the (re)introduction of missing large herbivores and/or their predators—is increasingly proposed to restore biodiversity and biotic interactions, but its effects on soils have been largely neglected. The high diversity of soil organisms and the ecological functions they perform mean that the full impact of rewilding on ecosystems cannot be assessed considering only above-ground food webs. Here we outline current understanding on how animal species of rewilding interest affect soil structure, processes and communities, and how in turn soil biota may affect species above ground. We highlight considerable uncertainty in soil responses to and feedbacks on above-ground consumers, with potentially large implications for rewilding interactions with global change. For example, the impact of large herbivores on soil decomposers and plant–soil interactions could lead to reduced carbon sequestration, whereas herbivore interactions with keystone biota such as mycorrhizal fungi, dung beetles and bioturbators could promote native plants and ecosystem heterogeneity. Moreover, (re)inoculation of keystone soil biota could be considered as a strategy to meet some of the objectives of trophic rewilding. Overall, we call for the rewilding research community to engage more with soil ecology experts and consider above-ground–below-ground linkages as integral to assess potential benefits as well as pitfalls. This article is part of the theme issue ‘Trophic rewilding: consequences for ecosystems under global change'.

Multi-taxon inventory reveals highly consistent biodiversity responses to ecospace variation

“…The provision of large dung and the occasional damage to live trees should be considered instrumental to the diversification of organic matter. We envision that the role of natural dynamic processes for the diversification of organic matter – not least in the soil (33) – will be a promising field of research in future conservation studies.…”

Trophic rewilding: impact on ecosystems under global change

“…Andriuzzi & Wall [45] also indicate uncertainty and major knowledge gaps about the impact of large herbivores on soil responses and feedbacks. Despite this uncertainty, rewilding the Arctic with a larger density and diversity of large herbivores may mitigate the impact of temperature rise in this region [40,41].…”

Ecology of a widespread large omnivore, Homo sapiens, and its impacts on ecosystem processes

“…Implicit in the rewilding approach is the goal or intention to establish self-managing ecosystems whose biodiversity and ecosystem processes are maintained spontaneously and endogenously by the species and abiotic elements in the ecosystem (Lorimer et al, 2015;Root-Bernstein et al, 2017;Svenning et al, 2015). Increasing recognition of ecological extinction, and attempts to reverse it through reintroductions and taxon substitutions, has contributed to a recent focus on functional ecology, and on the ecology of many extinct and endangered large and medium-sized mammals (Andriuzzi & Wall, 2018;Galetti, Pires, Brancalion, & Fernandez, 2017;Johnson et al, 2018;Naundrup & Svenning, 2015;Sanderson et al, 2008).…”

“…Pigs also eat fruits, seeds, invertebrates, eggs, reptiles, birds and mammals, carrion, roots, and grasses (Ghiglieri, Butynski, & Struhsaker, 1982;Leus & MacDonald, 1997;Skinner, Breytenbach, & Maberly, 1976). While foraging, large omnivores may dig in the soil, overturn rocks, and help to break down fallen trees, affecting soil processes for example (Andriuzzi & Wall, 2018;Ghiglieri et al, 1982;Laurie & Seidensticker, 1977;Munro et al, 2006;Skinner et al, 1976). Omnivores also provide a range of ecological disturbances.…”

“…Omnivores also provide a range of ecological disturbances. While foraging, large omnivores may dig in the soil, overturn rocks, and help to break down fallen trees, affecting soil processes for example (Andriuzzi & Wall, 2018;Ghiglieri et al, 1982;Laurie & Seidensticker, 1977;Munro et al, 2006;Skinner et al, 1976). Sus scrofa is considered an ecosystem engineer due to the impacts of its extensive disturbances created during foraging (Barrios-Garcia & Ballari, 2012).…”