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Naturalization – Bringing More Nature to the City – or Not?

Naturalization is a term that Edmontonians are hearing a lot these days, especially now as the City of Edmonton launches its new Naturalization, Reclamation and Restoration Plan (NRRP). The term naturalization has passed into common usage over the years as municipalities have grown to indicate a type of civic landscaping that steers away from intensive management and aims to “make more natural.” (Hence it is not being used in its original technical sense of an organism becoming established in a foreign land.) The City is now saying the Plan will “provide processes and best practices to bring maintained turf and depleted land areas back to a more natural state of vegetation and ecological function,” as well as to “expand the urban tree canopy by identifying locations for park, boulevard and other open space opportunities to plant new trees and implement naturalization.” (Among other things citizens are invited to nominate sites for tree planting and can leave their comments on the Engaged Edmonton page at https://

Naturalization sounds like something the ENPS would support, and in fact it once called itself the Edmonton Naturalization Group as it participated in some of the City’s initiatives in the early 2000s. But while the City’s ideas about naturalization have been evolving, there are ecological flaws in its conceptualizing.

Considerable emphasis has been placed on the idea of passive naturalization, i.e., simply stopping mowing in its green spaces, which theoretically would allow native flora to passively infiltrate, although it also recognizes that in some circumstances deliberate planting of native species may be necessary (active naturalization). Economic savings would be the main driver in the case of passive naturalization through reduced horticultural management, although increases in native biodiversity are anticipated in both instances.

However, the notion that natural biodiversity will increase by passive naturalization (simply by stopping mowing) contradicts ecological principles. In civic environments there is no source of native plant propagules (except possibly in parts of the river valley and some natural areas). On the other hand, there are plenty of weeds, and existing or planted natives will struggle to compete against them; remember, weeds are naturally super-adapted to the modified, disturbed environments in which naturalization would be slated to occur; conversely, natives thrive in long-established, natural, consolidated and cooperatively evolved communities. The City will either take on a bigger bill for weed control or citizens will have to learn to tolerate a much weedier city – without an increase in natives. This may to some extent be alleviated if native trees and shrubs are planted densely and adequate after-care reduces a traditionally high mortality, but all this will be costly, and will surely offset any cost savings that might be realized from ceased mowing. Is the City prepared to invest the necessary resources to do a proper job? Another question arises: will the City commission the growing of sufficient native material, or will it forge ahead unprepared, relying on nursery-grown cultivars of ‘native’ species? Anyone wishing to see an example of the City’s previous naturalization handiwork in a natural area should take a look at Schonsee Natural Area in the northeast, a completely ploughed-up and re-contoured wetland area. It was inadequately re-planted and since appears to have been abandoned, resulting in a wasteland of weeds.

How the City proceeds with its NRRP will be interesting to watch.


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