How to make wild and autonomous nature
An international team of researchers have worked to clarify what rewilding actually is, and how best to design and implement rewilding as a practical tool to reverse the global losses of biodiversity.
Since it was introduced almost 30 years ago, the idea of rewilding has met both enthusiasm and criticism. Some have called for a strict definition of the concept of rewilding or pointed to the need for improved knowledge on the wider implications of using rewilding as a tool in nature management, e.g., regarding the effects of reintroducing large carnivores and herbivores into ecosystems. There has also been criticism related to value differences and societal involvement.
Now, a group of researchers from 19 universities in Europe and Canada, including Aarhus University, have proposed an updated definition of rewilding that broadly covers how rewilding has been discussed and implemented in reality, published in Science magazine.
Their article, Rewilding complex ecosystems, also proposes a theoretical framework that researchers and managers can use for guidance when designing and implementing rewilding. A core point in the methodology is societal involvement.
Wildness rather than wilderness
The researchers start by clarifying that rewilding should be seen as an approach to ecosystem restoration that aims to restore self-sustaining and complex ecosystems, with interlinked ecological processes that promote and support one another while minimizing or gradually reducing human interventions.
Importantly, the general aim is not to recreate pristine wilderness, but to restore wildness, i.e., i.e., the autonomy of natural processes. Therefore, rewilding is not reserved for large natural areas, but can also be applied even to small urban green spaces or abandoned farmland, using the framework described by the researchers.
They see rewilding with its focus on natural processes and self-managing ecosystems as a powerful tool in future nature restoration for benefitting biodiversity and society.
Complex food chains with room for disturbance
"We’ve identified three core ecological elements that promote an ecosystem’s robustness and ability to maintain its biodiversity, and incorporated these into a framework for designing and implementing rewilding," explains one of the authors of the article, Professor Jens-Christian Svenning, director for Center for Biodiversity Dynamics in a Changing World (BIOCHANGE) at Aarhus University.
The three core elements are:
- Trophic complexity, and not least the top-down trophic effects of large herbivores and carnivores, which overall is expected to promote biodiversity maintenance through a range of mechanisms. This specific aspect of rewilding is the focus of trophic rewilding, as explained in a 2016 paper by Svenning and collaborators (http://bit.ly/rewildingPNAS).
- Natural disturbances such as flooding, insect infestations and fires. Such disturbances often occur in a more or less stochastic manner, enhancing spatial and temporal environmental heterogeneity and increasing ecosystem complexity, and thereby promote biodiversity.
- Dispersal. Improvement of connectivity within and among ecosystems to promote dispersal, aiding biodiversity mainatance, e.g., by facilitating recovery of ecosystems after disturbance events.
Specific projects require specific assessments
The new framework is general, and specific rewilding projects will require more detailed assessments.
"Our general framework is meant to help design the specific initiatives to be implemented for a specific focal ecosystem. The actions to be taken may range from merely stopping human interventions to active restoration of e.g., fauna and hydrology before ecosystems are ‘let loose’," says Jens-Christian Svenning.
Because rewilding always takes place in a societal context, it is important to involve local communities and consider the socio-economic setting, when designing a rewilding initiative. Such a participatory approach to rewilding is important to ensure that all stakeholders have a clear understanding of goals, management options, desirable outcomes, and associated risks. This in turn requires interdisciplinary training for researchers and practitioners.
The researchers also stress the need for objective, evidence-based assessments of rewilding initiatives so science and society can learn from the projects as well as for the accountability of the projects.
Chernobyl as a shining example
As suggested above, rewilding does not necessarily entail releasing new species. In general, it is possible to come a long way by doing nothing and letting nature take its course (passive rewilding).
An example of abandoned farmland used for passive rewilding is the almost 1,500 km2 of land in Ukraine and Belarus, which was evacuated after the Chernobyl nuclear power plant meltdown in 1986. Since then, the zone has been extended to a coherent rewilded natural area of almost 5,000 km2. Targeted reintroductions of European bison (Bison bonasus) and Przewalski’s horses (Equus ferus przewalskii) to restore trophic interactions (trophic rewilding) have been exceptions to this passive approach, and after being released, horses and bison are now thriving along with a diverse fauna and flora with minimal human intervention.
Rewilding and the new UN Decade on Ecosystem Restoration
The focus on rewilding is highly topical, as the UN General Assembly on 1 March this year declared the period 2021-2030 as the UN Decade on Ecosystem Restoration.
During this period, the United Nations Environment Programme (UNEP) and the Food and Agriculture Organization of the United Nations (FAO) will be restoring 350 million hectares of degraded natural areas to create ecosystem services for up to USD 9 trillion and for additional sequestration of up to 26 gigatonnes of greenhouse gases from the atmosphere.
"Successful and large-scale future initiatives for nature restoration are essential for countering the global biodiversity crisis, where the biggest problem is the loss and degradation of natural areas," explains Jens-Christian Svenning.
Professor Jens-Christian Svenning,
Center for Biodiversity Dynamics in a Changing World (BIOCHANGE),
Department ofr Bioscience, Aarhus University
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