Naturalized cities or urban ecosystems.

Oliver López-Corona & Elvia Ramírez-Carrillo

To cope the global loss of wildlife, the cities of everyone is trying to create open areas and re-naturalize their neighborhoods, in what many understand as an effort to return a region to its natural and uncultivated form, while also including new architectural and landscape design components.

In general, the practice of naturalization or “rewilding” in English, when carried out in natural environments, is traditionally understood as restoring the original biodiversity in an ecosystem, generally through the return of higher-order animal species, which in turn stabilizes those of higher order. lower, with the 1995 reintroduction of wolves to Yellowstone National Park being one of the best known and most successful examples. During the first 15 years after the reintroduction of the wolf, trophic waterfall studies revealed that there are indeed initial signs of ecosystem recovery in both plants and animals.

However, it is implausible to assume this approach rigorously in urban areas, that is, although naturalization in natural areas may have the objective of returning the ecosystem to states that are as close to pristine, this is clearly not feasible in an urban environment. , where the objective would have to be another. But which?

We think that the answer to this question passes first through the recognition that it is necessary to stop conceiving of cities only as degraded ecosystems, but as a new type, urban ecosystems.

In an article that we have under review on how to evaluate the planetary capacity to respond to disturbances, including anthropogenic ones, we have proposed a new definition of ecosystem:

An ecosystem is an open thermodynamic system constituted by a community of living organisms in conjunction with the nonliving components of their environment that through its interactions and evolutionary processes, constrained by the external conditions, self-organised in a maximum solar photon flux dissipation, in which the system is at criticality, with maximum computational and inferential capabilities that allow it to respond and thrive under uncertainty, stressors, perturbations and ultimately time, in a well-defined geographic context.

Under this proposed definition of ecosystem, then the objective of naturalizing a city translates into creating a configuration of natural and non-natural elements that satisfy ecosystem functions such as thermal regulation (avoiding, for example, heat islands), regulation of the hydrological cycle (adequate capture and filtration to avoid flooding), regulation and fixation of carbon, pollination, filtration and buffering of pollutants in the soil, among others. A healthy urban ecosystem should then function close to optimal values ​​for water quality, air and ambient temperature; It should produce a good part or ideally all of the food required by the different species that inhabit it, including, in an important way, Homo Sapiens. In this state of urban ecosystem health, cities would also be not only resilient but even antifragile.

In this way, on the one hand, we do need to conserve in a standard sense of the term the protected natural areas that are around or within cities, but also through processes that we could understand as niche construction, to generate the necessary conditions to establish or maintain the urban ecosystem functions for example establishing networks of urban gardens, pollinator gardens, water catchment systems, etc. The latter is being done, for example, with the generation of artificial elements such as the “super trees” of the Gardens by the Bay in Singapore. In the same way, it would not make sense to remove all the jacarandas from Mexico City because they are exotic species, but rather to make a naturalization effort in another sense of the word in the sense of “making an animal or plant species acquire the necessary conditions to live and perpetuate itself in an environment different from the one from which it comes ”.

We believe that thinking of cities as urban ecosystems positions us on the right path to have greener, more biodiverse, productive, healthy and anti-fragile urban spaces.