Rewilding needs a conceptual framework. Is the adaptive cycle the answer?

Johan T. du Toit and Nathalie Pettorelli explore the differences between rewilding and restoration.

The authors have adapted this post from an article originally shared by ZSL.

Rewilding means different things to different people but in applied ecology it is now broadly agreed that the concept means reorganizing, retooling, or regenerating wildness in a degraded ecosystem. Contrary to what many seem to think, rewilding is different from restoring, which by common definition means returning something to its former condition – think of a revered cathedral, classic car, or desired landscape. If restoration is not possible for a disturbed ecosystem in an irreversibly changed environment, then rewilding is the adaptive tactic for regaining and maintaining functionality, perhaps with introduced components. Rewilding is a novel and developing approach but it attracts controversy because of its inherent unpredictability and emphasis on function over species composition.

In most general discussions, talking about rewilding as the process of bringing some wildness back to an area, whether rural or urban, in a way that conflates rewilding with restoration, is probably fine. Nobody really cares about semantics in such discussions. But in conservation science it is a different matter. Any stand-alone scientific concept needs a clear definition and has to fit within a coherent conceptual framework. Happily, a conceptual framework for rewilding already exists in the form of the adaptive cycle, conceived by Buzz Holling and his colleagues from the Resilience Alliance.

Adaptive cycle - Holling and Gunderson
The adaptive cycle of Holling and Gunderson with arrows added for the stewardship options of rewilding and restoring, which draw from different loops of the cycle.

Ecosystems are complex and dynamic, continually changing and adapting through time (see above).  Following a major disturbance, ecosystems generally recover with species reassembling and biomass growing (r phase, lower left panel). Newly available resources become exploited with succession leading to an increasingly connected system with more potential for niches to be occupied. This leads to the accumulation and conservation of resources in a climax state (K phase, upper right panel), with the transition from exploitation to conservation being referred to as the ‘foreloop’ of the cycle.

Then with the next fire, hurricane, drought, outbreak, or over harvest, the ecosystem releases its potential and connectedness (omega phase, lower right panel), and cycles back – somewhat unpredictably – into the alpha phase (upper left panel) of reorganization by way of the ‘backloop’. This allows a new assemblage of species to begin exploiting freed resources while developing along a new trajectory governed by new conditions. Restoration is concerned with fasttracking the foreloop and shortcutting the backloop, to return the system to its former condition of high connectedness as quickly and predictably as possible after a disturbance. In contrast, rewilding draws from the backloop, facilitating reorganization so that the system can adapt to changed conditions, obviating the need for continual management.

Managers can facilitate reorganisation to lead to two different rewilding outcomes: (i) a change in composition and/or structure that doesn’t affect the overall nature of the ecosystem and fosters resilience (rewilding arrow to the right); or (ii) a transformation from the historic ecosystem to a novel one (rewilding arrow to the left). The latter is characteristic of situations where environmental conditions change so significantly that a regime shift is inevitable. In these situations, managers can either take a ‘wait-and-see’ approach (passive rewilding) as a novel ecosystem develops on its own, or they can intervene with species introductions and/or engineering works (active rewilding) to generate a novel ecosystem that can sustain the provision of ecosystem services under projected environmental conditions.

Rewilding can operate at multiple levels from genes to ecosystems, and managers can facilitate rewilding in many ways from translocations to mechanical engineering projects. It is a concept that embraces new opportunities and provides a way forward for ecosystems where restoration is not an option. Because rewilding focuses on processes and functions, the approach requires thinking outside the box and stimulates managers to consider why a functional type of organism is important rather than which species should or should not be present. Interestingly, this type of thinking is also developing in theoretical ecology, with a growing number of studies highlighting the importance of functional trait distribution for ecosystem processes and ecosystem services delivery.

Admittedly, rewilding jabs into the comfort zone occupied by many conservation biologists and environmental managers. The concept forces us to understand functional interactions within ecosystems, thereby highlighting our knowledge gaps, challenging us to recognize the dynamic nature of biological systems, factoring in change instead of fearing it. Ultimately, the rise of the rewilding concept is a sign that new approaches are urgently needed to conserve biodiversity and maintain ecosystem services under increasingly unpredictable global conditions, as traditional approaches on their own are demonstrably unfit for the challenges ahead.

Read the full Commentary, The differences between rewilding and restoring an ecologically degraded landscape in Journal of Applied Ecology.

Take a look at this series on rewilding covered earlier this year in partnership with People and Nature.

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