The short answer, no. Urban rewilding encapsulates a far more nuanced debate surrounding this complex and relatively less-studied process.
The term 'rewilding' holds various interpretations in different applications, yet has gained notable traction in academia over the last 20 years. For cities, 'rewilding' mainly describes "opportunities to increase nature's presence in urban settings" - a broad concept encompassing everything from increasing greenspace access, conserving native fauna, to (yes) planting more trees. We shall critically examine the case for urban rewilding and discuss why urban rewilding is not as straightforward as it seems.
Benefits of Urban Rewilding
Besides the direct benefit of biodiversity conservation, proponents of urban rewilding including the IUCN often highlight the wide range of ecosystem services offered by urban biodiversity to justify the need for rewilding in cities for explicit human benefit.
Health Benefits
Numerous studies associate improved physical and mental health with rewilding. While evidence linking the availability of urban greenspace to outdoor exercise participation and obesity remains mixed, there are consistent findings correlating lower mortality, improved cardiovascular health and heightened moods with higher greenspace exposure.
The benefits of greener cities on psychological wellbeing are well-documented and less contentious than those on physical health. Studies in Australian, European and American cities show urban greenspace correlating with lower stress and anxiety levels. Increasingly, studies also reveal improved mental wellbeing from transient human-wildlife interactions in cities, especially from songbirds and 'wildlife gardening'.
These health benefits might even be evident on much smaller scales. Biologists from the University of Adelaide formulated the Microbiome Rewilding Hypothesis, proposing that richer urban biodiversity can also 'rewild' urban microbiota. Higher exposure to diverse microbial stimuli, usually limited to well-vegetated rural environments, may lead to stronger immune systems and lower risks of conditions like asthma, allergies and inflammatory diseases.
A short clip summarizing the possibilities and controversies surrounding the global rewilding movement and in particular, rewilding in cities (Source: BBC)
Social benefits
Besides tangible health benefits, urban rewilding can also strengthen our social capital. A review by RMIT University revealed robust evidence of urban nature encouraging stronger communal bonds and a greater sense of identity. This is especially prevalent in private and community gardens, where residents derive satisfaction and a sense of belonging from cultivating nature within their neighbourhoods. This strengthens an ethic of communal responsibility and environmental stewardship built over shared experiences and newfound friendships.
Environmental benefits
Urban rewilding provides crucial environmental regulatory functions, mostly from increased plant biomass. More vegetation reduce the Urban Heat Island effect by covering impermeable heat-absorbing surfaces with vegetation, where cooling effects can be felt up to 1km beyond greenspace boundaries. Urban forests also act as carbon sinks to absorb atmospheric CO2 and mitigate global warming - an increasingly important feature given the reduction of natural forest from urbanization. Urban vegetation also creates natural buffers for noise pollution while improving air quality by lowering concentrations of air pollutants.
Increased vegetation also provides natural flood-risk management in flood-prone areas. The London Wildlife Trust launched an innovative project in Brixton that encouraged rain gardens, specially designed greenspaces that captures rainwater piped down from rooftops, preventing excess runoff onto the roads.
Animals also provide specialized ecosystem services. Many urban predators provide effective pest control, while scavengers like hyenas and vultures are crucial waste disposal agents in developing countries. Pollinators play instrumental roles in pollinating crops and safeguarding food security, prompting conservationists to create 'bee corridors' in London to reverse the decline in British honeybees.
Does Urban Rewilding always work?
Not all greenspace is equal
The broad umbrella of urban rewilding does not always reconcile the ideals of expanding greenspace area and boosting urban biodiversity - the former does not necessarily lead to the latter.
Referring back to honeybee conservation in London, a survey by the London Beekeepers Association reveal that most of London's greenspace comprises mown grass and plane trees which are not suitable foraging habitats for honeybees due to low wildflower diversity. Simply increasing vegetation cover without adequate considerations for species assemblages will lead to suboptimal restorative effects. Likewise, planting trees in isolated pockets does not enhance the connectivity of urban forests as discussed in my previous post - as fragmented greenspaces acting as biogeographical islands exhibit lower insect diversity.
Even when planners carefully curate floral diversity in cities to enhance faunal and microbial diversity, these desired effects cannot be guaranteed. Studies on urban ecology reveal that while humans can actively manipulate the abundance and species richness of plants, such direct control is rarely replicable for other organisms. Conservationists can only rely on indirect ecological responses to illicit desired faunal and microbial assemblages, but efforts may be hindered by abiotic factors.
Model of how humans can only indirectly control non-plant populations through plants (Source: Faeth et al. 2011)
Not all animals are equal
Encouraging urban biodiversity inevitably brings wildlife much closer to our doorsteps, which may sometimes be too close for comfort. For conservationists and residents alike, some species might be more desirable than others.
Human-wildlife conflicts are spotlighted as prominent arguments against faunal rewilding. In the UK, property and infrastructural damage by badgers, a species protected by law, is a recurring issue with no long-term solution to date. For cities with roaming deer populations like Iowa, wildlife-vehicle collisions account for an increasing proportion of road accidents, which may reflect unplanned repercussions of rewilding efforts.
Other species may even turn up 'uninvited'. Cormorants have populated the Walthamstow Wetlands in northeast London in a unique process called auto-rewilding, where a species voluntarily relocates to areas it previously uninhabited due to human disturbance. Cormorants were attracted to Walthamstow's abundant fish stocks but now come into conflict with local fishermen who view them as invasive nuisance species. This phenomenon questions whether auto-rewilded species should be framed as 'invasive' or celebrated as conservation achievements.
Considerations moving forward
Urban rewilding treads the delicate human-nature interface within a complex web of social and ecological relations. With most attention devoted to the benefits of rewilding, adequate consideration should also be placed on the practical challenges and possible 'ecosystem disservices' that rewilding brings. Conservationists must appreciate these embedded nuances to weigh both human and environmental concerns.
A robust debate on rewilding should therefore consider the question:
'Who is rewilding for?'
Different dimensions of rewilding carry different implications and limitations - some inevitably prioritize human benefit over conservation objectives. Each case study requires immersive contextualization to develop appropriate localized strategies sensitive to prevailing socio-environmental conditions.
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