Rewilding watersheds: using nature’s algorithms to fix our broken rivers

Rewilding watersheds: using nature’s algorithms to fix our broken rivers Natalie K. Rideout, Bernhard Wegscheider, Matilda Kattilakoski, Katie M. McGee, Wendy A. Monk, and Donald J. Baird Canadian Rivers Institute, Department of Biology, University of New Brunswick, 10 Bailey Drive, Fredericton, NB, E3B 5A3, Canada. Canadian Rivers Institute, Faculty of Forestry and Environmental Management, University of New Brunswick, 2 Bailey Drive, Fredericton, NB, E3B 5A3, Canada. Environment and Climate Change Canada, Canada Centre for Inland Waters, 867 Lakeshore Road, Burlington, ON, L7R 4A6, Canada. Centre for Biodiversity Genomics and Department of Integrative Biology, University of Guelph, 50 Stone Road E., Guelph, ON, N1G 2W1, Canada. Environment and Climate Change Canada @ Canadian Rivers Institute, Faculty of Forestry and Environmental Management, University of New Brunswick, 2 Bailey Drive, Fredericton, NB, E3B 5A3, Canada. Environment and Climate Change Canada @ Canadian Rivers Institute, Department of Biology, University of New Brunswick, 10 Bailey Drive, Fredericton, NB, E3B 5A3, Canada. Corresponding author. Email: nrideout@unb.ca

In this commentary, Dandy and Wynne-Jones look at rewilding forestry and explore the reasons why there is a limited amount of rewilding research in the forestry journals and call for more attention towards rewilding from forest scientists. Here, Fernández et al. argue that a rewilding approach 'focused on preserving and restoring the structural and functional complexity of degraded ecosystems must become a primary component of broad-scale and longterm visions for biodiversity conservation'. They call for unifying rewilding approaches with different restoration baselines and management intensities under one framework that could inform about the costs, benefits and risks of the different approaches. Noss, R. F. (2003). A checklist for wildlands network designs. Conservation Biology 17(5), 1270-1275 doi:10.1046/j.1523-1739.2003.02489.x. In this article Reed F. Noss presents a checklist to help in developing wildlands network designs and conservation assessments that are part of the Wildlands Project. The Wildlands Project is based on the goals of biodiversity conservation and rewilding that is defined in the article as 'restoration of wilderness qualities and intact food webs' and follows the concept of large network of connected core reserves. In this review article, Perino et al. address criticism presented towards rewilding by proposing a framework for rewilding actions to be used as a guideline in design and evaluation of rewilding projects. They suggest a structured approach to rewilding that can be applied to projects ranging from passive to trophic rewilding.
They emphasise the importance of inclusion of all stakeholders in the process for successful rewilding. They apply their framework to four ongoing rewilding projects: restoration of natural flood regime in Germany Here, Pettorelli et al. argue that for rewilding initiatives to grow they should consider the constraints and opportunities of the environmental governance policies. They also argue that the concept of rewilding needs a clear definition and more scientific research to inform the initiatives. They define rewilding as 'the reorganisation of biota and ecosystem processes to set an identified social-ecological system on a preferred trajectory, leading to the self-sustaining provision of ecosystem services with minimal ongoing management' and identify five key research areas to guide future rewilding initiatives.
This book comprises 20 chapters on the topic of rewilding, including definitions and differences between approaches. It is an interdisciplinary book, discussing current state of ecological knowledge, rewilding objectives, and the role of humans in these initiatives. Root-Bernstein, M., Gooden, J., and Boyes, A. (2018). Rewilding in practice: projects and policy. Geoforum 97, 292-304 doi:10.1016/j.geoforum.2018.09.017.
Here, Root-Bernstein et al. explore the practice and policy transformations around European rewilding. They consider European conservation policy and the context where European rewilding emerged. They use rewilding projects in the UK and the Netherlands, which they call first wave rewilding, and in Denmark, which they call second wave rewilding, as case studies to look at the visions, strategies, and validation for the projects. Soulé, M. E., and Noss, R. F. (1998). Rewilding and biodiversity: complementary goals for continental conservation. Here, van Meerbeek et al. look at rewilding and human intervention, often considered opposing management strategies and argue that these strategies can be complimentary. They propose a framework to help decide between different management strategies along the management spectrum ranging between ecosystem selfmanagement and human management.

What is rewilding?
Anderson, R. M., Buitenwerf, R., Driessen, C., Genes, L., Lorimer, J., and Svenning, J. (2019 In this commentary paper, du Toit and Pettorelli look at the similarities and differences of rewilding and restoration. To help distinguish this, they provide two metaphors. They also provide a decision pathway to help decide between restoration, active rewilding and passive rewilding of a degraded landscape. Gammon, A. R. (2018). The many meanings of rewilding: an introduction and the case for a broad conceptualisation. Here, Jørgensen looks at the history and uses of the term rewilding in the ecological scientific discourse and argues it has become 'a plastic word' since being adopted outside of science. This paper started a conversation around the meaning and plasticity of the term rewilding.
Lorimer, J., Sandom, C., Jepson, P., Doughty, C., Barua, M., and Kirby, K. J. (2015) In this review article, Andriuzzi and Wall are looking at the possible impact of rewilding on soil and its biota, and the impact of soil processes on rewilded species above-ground. They focus on trophic rewilding and look at large herbivores and their predators, and two groups of soil biota: soil microbes and macroinvertebrates.
They emphasise the importance of including soil in the planning of rewilding projects and its part in carbon sequestration. Andriuzzi and Wall bring up the possibility of rewilding soil biota, especially mycorrhizal fungi and dung beetles. Bakker, E. S., and Svenning, J. (2018). This research paper examines the impact of trophic rewilding of Tasmanian devil to Maria Island. They specifically examine how the reintroduction influences risk-sensitive foraging and behavioural responses in a major prey species, the common brushtail possum (Trichosurus vulpecula).   Here, Jarvie and Svenning discuss the applications of using species distribution models to identify suitable habitat for trophic rewilding. They look at climatic suitability of proposed reintroduction areas for 17 largebodied candidate species across different continents and habitats under current and future climates. They discuss methodological ways to include climate change scenarios in the models. Here, Venter et al. explore the roles of fire and herbivores in mid-Holocene African savannas. They discuss the possibility of changing rangelands from a fire-dominated to a herbivore-dominated stable alternative state by rewilding them with herbivory and the implications of this for ecosystem processes and services. Berti and Svenning investigated how human pressure has affected the natural movement capacity of terrestrial mammals through time and how movement capacity will respond to future extinction and rewilding scenarios.

Reintroductions, introductions and translocations
The authors found that 74% of average and 83% of maximum movement capacity of Late Pleistocene mammal assemblages has been lost due to historical extirpations and extinctions. However, models indicate  In this feature article, Escobar briefly reviews the history of Tijuca National Park in Rio de Janeiro and the implementation of the reintroductions of red-rumped agoutis and brown howler monkeys to the park. Here, Falcón and Hansen present a conceptual framework for tortoise rewilding that takes climate change into account. They discuss how climate change might affect ecological functions (herbivory, seed dispersal, nutrient cycling) facilitated by tortoises and propose strategies to secure these functions. This article presents three ways in which ecological network models can benefit rewilding projects. (1) The models could inform about how the introduced species will integrate to the community and about its role in the food web. (2) The models could determine the species that will be affected or will affect the introduced species. (3) The models can also inform about the ways in which the whole network will change enabling more efficient monitoring. This book chapter looks at the history and current state of wild in Britain and the reintroduction of wolves to restore predation to Scotland, wild boar to restore ground disturbance, and beaver to restore river channel and riparian disturbance to increase ecosystem functionality in Great Britain.

In this study, Schulze et al. look at the long-term interactions between intermediate foraging large wild
herbivores and vegetation dynamics using Döberitzer Heide, a German wilderness area as their study area.
They simulate different future landscape dynamics scenarios. Here, Tănăsescu briefly reviews the history of restorative ecological practice and the history of wisent conservation. Tănăsescu then discusses rewilding with Bison reintroduction in Romania. The authors present a conceptual framework (Spore: Spatial Planning of Rewilding Effort) using ecological functions to prioritize where rewilding should be performed. The framework presents ecological function distribution and habitat suitability of species at fine spatial scales, resulting in management units for conservation action. They use the island of Guam as a case study to apply their framework, focusing on the restoration of seed dispersal.  Koshida, C., and Katayama, N. (2018). Meta-analysis of the effects of rice-field abandonment on biodiversity in Japan.
Conservation Biology 32(6), 1392-1402 doi:10.1111/cobi.13156. In this meta-analysis, Koshida and Katayama look at the impacts of rice-field abandonment on biodiversity in Japan considering multiscale factors such as landscape context and climate. Here, Kowarik proposes a framework for viewing urban wilderness as a social-ecological system. Kowarik This 2-year study looks at tree seed dispersal from forested areas to surrounding deforested montane pastures in Cantabrian Range, Spain. Martínez and García study whether landscape context (forest cover extent, isolated trees) affect seed arrival at pasture and whether tree fruit availability, frugivorous bird activity and abundance change during the study period. Martin-Díaz, P., Cortés-Avizanda, A., Serrano, D., Arrondo, E., Sánchez-Zapata, J. A., and Donázar, J. A. (2020).
Rewilding processes shape the use of Mediterranean landscapes by an avian top scavenger. Scientific Reports 10(1), Merckx and Pereira look at the assumptions behind European Union agro-forestry subsidies supporting farming in less favoured areas, arguing for an approach that would support intensive and sustainable farming with high yields on fertile agricultural lands at local scale and at regional scale less productive lands to be 'ecologically restored into 'wild' and resiliently functioning ecosystems'. This study looks at the impact of habitat changes occurred after the ending of forest management on the species richness, abundance and composition of ground, longhorn and bark beetles. Sitzia et al. studied longhorn, ground and bark beetles in ten managed and ten abandoned forest plots in north-eastern Italy. This research article uses Pleistocene rewilding as an example to address challenges of using species distribution models for extrapolating modelled relationships outside native ranges. The species of focus were proposed proxy species Asian elephant, African cheetah and African lion and a native species Oryx gazelle.
The area of focus was the American south-west and Great Plains. This article describes the concept of dewildingstripping nature of its healthy ecosystem and its various speciesand rewilding, using the extermination and reinstitution of wolves as a case study. Specifically, the author argues that a switch in environmental and cultural politics towards demythologizing the wolf's bad reputation might help in reinstating it as an apex predator within an ecosystem. Arts et al. take a theoretical approach to look at the relationship between rewilding and animal reintroduction.

Societal perspectives on rewilding
They identify three common rewilding elements from the literature: ecological functioning, wilderness experience and natural autonomy. They use hypothetical wolf reintroduction to Scotland as their case study to look at contributions and tensions it would have in relation to each of these elements.
This paper looks at the frictions between different modes of bovine biopolitics, using the rewilding of Heck cattle at Oostvaardersplassen as a case study. They identify rewilding as a fifth mode of bovine biopolitics in addition to four prevalent modes: agriculture, conservation, welfare and biosecurity. Lorimer, J., and Driessen, C. (2016). From 'Nazi cows' to cosmopolitan 'ecological engineers': specifying rewilding through a history of Heck cattle. Annals of the Association of American Geographers 106(3), 631-652 doi:10.1080/00045608.2015.1115332.
In this article, Lorimer and Driessen review the history of Heck cattle as a part of 'genealogy of rewilding'.
They discuss what and where is considered to be wild and who has the power to decide this. Here, Takacs discusses ecological democracy, conflicts and commonalities in Biodiversity Offsetting, REDD+, and the rewilding movement. Takacs considers the roles of scientists and non-scientists and asks questions such as 'who should have the right to be heard when protecting biodiversity?'.  In this research paper, Law et al. present the results of a 12-year study monitoring the changes in vegetation after a planned beaver-assisted restoration of agriculturally degraded fen in eastern Scotland. They discuss the possibilities of using beaver to restore agriculturally degraded wetlands.