A growing body of literature emphasizes the need for novel, process-oriented approaches to restoring ecosystems in our rapidly changing world. Dynamic and process-oriented approaches focus on the adaptive capacity of ecosystems and the restoration of ecosystem processes promoting biodiversity, rather than aiming to maintain or restore particular ecosystem states characterized by predefined species compositions or particular bundles of ecosystem services [Perino 2019: 1].
In contrast to other types of restoration efforts aiming to recreate the composition and appearance of an historical ecological community, rewilding focuses on ecosystem function and recognizes the dynamic and unpredictable nature of ecosystems. This article highlights three key ecological processes that rewilding aims to activate: trophic complexity, natural disturbances and dispersal.
Rewilding aims to restore these three ecological processes to foster complex and self-organizing ecosystems that require minimum human management in the long term [Perino 2019: 2].
Trophic complexity implies the presence of large vertebrates, including herbivores that modify the landscape through grazing or dam building and predators that control the herbivore populations. These keystone species can promote biodiversity in the landscapes they inhabit.
Stochastic (random) natural disturbance (such as fire or flooding) can increase ecosystem heterogeneity and complexity, allowing less competitive species to survive. Rewilding involves discontinuing both controlled anthropogenic disturbances and suppression of natural disturbances.
Rewilding actions aim to release ecosystems from continued and controlled anthropogenic disturbances to allow for natural variability and sources of stochasticity. Mowing of grassland can be reduced or replaced by natural grazing. Dams can be removed or their management modified to restore natural flood regimes. Logging can be replaced by allowing natural fire and pest regimes [Perino 2019: 4].
Dispersal – rewilding aims to remove anthropogenic barriers that limit the movement of plants and animals and thus the dispersal of their genetic material and potential for recolonization after a disturbance event. The creation of ecological corridors is an example of a rewilding activity that enhances dispersal.
The interaction of these ecological processes boosts the functioning of each. For example, the presence of larger animals facilitates seed dispersal throughout the system. High levels of dispersal, in turn, can facilitate ecosystem recovery following a disturbance.
Rewilding projects can be passive (allowing abandoned agricultural fields to recover on their own) or active (species reintroductions, for example), and are most effective when conducted in a manner that engages the local community in the process.
Perino, Andrea, et al., 2019, Rewilding complex ecosystems, Science 364, https://science.sciencemag.org/content/364/6438/eaav5570.abstract.