Category Wild Urban Woodlands

The “four natures approach”: A non-scientific approach to urban nature

In contrast to the two natural-science perspectives presented above, the understanding of “naturalness” and “wilderness” for the general public, but also for local stakeholders, is generally broader, but also individually very different, as studies by Rink (2005) and Bauer (2005) show. This runs the risk that significant qualitative differences between the different types of urban forests may not be appropriately realized and included in decision­making processes, and that nature and wilderness attributes will be used with less comprehensibility...


Naturalness from a prospective perspective

The retrospective approaches, which evaluate the naturalness of areas by comparing them with conditions that haven’t been influenced by humans, have a long tradition. This is due to the fact that the specific natural devel­opment of urban-industrial sites was recognized in ecological research relatively late. There are, however, a few authors, little-recognized today, that early on suggested a second perspective for evaluating naturalness. Bernatsky (1904) wrote that anthropogenically shaped vegetation types could regenerate themselves to an “Urformation” (a virginal or primeval condition), but that a development to a “natural condition” was also possi­ble when the earlier cultural influences continued to have an effect...


Scientific approaches to naturalness

For about one hundred years, numerous approaches for scientifically clas­sifying the naturalness of vegetation types and ecosystems have been de­veloped. They share the fact that they evaluate varying degrees of natural­ness or, reciprocally, they evaluate the extent of human influence. They share the further characteristic that a defined reference point of maximum naturalness is often missing or at least remains undetermined. Two perspe­ctives on naturalness can be fundamentally differentiated: naturalness from a retrospective or a prospective perspective (Kowarik 1988, 1999). Table 5 illustrates this concept through the assignment of existing classification approaches to both perspectives. The deciding factor is the reference point...


Are urban-industrial woodlands natural?

The question of the naturalness of urban woodland types leads, undeniab­ly, to starkly varying answers. The differences have to do with the differ­ent histories of the stands (Table 2), and also with differences in percep­tions of naturalness, which vary dramatically across different geographic reference areas and between different social groups (e. g. Henderson 1992; Ewert 1998; Lutz et al. 1999; Bauer 2005). How the characteristic double nature of urban-industrial woodlands as a product of both nature and cul­ture should therefore be classified remains an open question because tradi­tional scientific approaches to the classification of ecosystem types are usually oriented toward pristine ecosystems...


Species pool

A fundamental feature of the urban species pool is the prevalence of non­native species that were introduced accidentally to urban habitats or that escaped from cultivation (Kowarik 1995). As a consequence, non-native species play a large role in reforestation processes on urban abandoned ar­eas, but are significantly less important on peri-urban sites, for example, during succession on surface mines (Prach and Pysek 1994; Tischew and Lorenz 2005). Table 4 illustrates the significance of non-native species with the example of woody species that are dispersed in different habitats of Berlin.

The dispersal processes that lead to the colonization of abandoned areas are determined culturally as the choice of species planted in the surround­ings of the site that then serve as sources for furt...


Agency of natural mechanisms

The leeway for the agency of natural mechanisms is significantly greater in urban-industrial woodlands than in woodlands used for forestry or in those resulting from urban greening. The latter two are usually heavily influ­enced by the initial plantings, and by use and maintenance. On urban – industrial abandoned areas, in contrast, the ecosystem dynamics are mainly influenced by natural processes through population dynamics, succession and soil formation (Table 3; right column). In this way – depending on the extent of the changes caused by earlier uses – primary or secondary suc­cession as well as intermediate degrees can be induced (Rebele 2003)...


Urban-industrial woodlands: a new woodland type emerges on specific urban sites

As post-industrial uses are often not possible in the areas affected by struc­tural change, the abandonment of sites is a signal for the development of a new type of urban-industrial forest by natural colonization processes. In the German Ruhr, this new forest type is widely dispersed across sites of the iron and steel industries and across mining areas (Dettmar 1992; Weiss et al. 2005). New urban woodlands can emerge on other types of sites as well, for example, on old, less-maintained cemeteries (e. g. Zisenis 1996), on the rubble of former buildings (Kohler and Sukopp 1964; Kowarik 1992a; Fig. 1-5) and on rail yards that have fallen into neglect (e. g. Reidl and Dettmar 1993; Kowarik and Langer 1994; Burckhardt et al. 2003).

A few peri-urban woodlands can be equivalent to urban-industr...


Woodlands that result from urban greening

Stands of trees that present forest characteristics can develop from large – scale planting of trees in park areas, but also from street trees and restora­tion plantings. Because such stands are determined based on functional goals and are often designed and maintained from artistic-aesthetic per­spectives, woodlands resulting from urban greening are heavily culturally influenced.

An additional feature that differentiates this type of woodland from the two previous types is the high species diversity and the large role of non­native species in urban greenery (Ringenberg 1994; Freedman et al. 1996; Jim and Liu 2001; Kowarik 2005)...


Woodlands as a part of the traditional cultural landscape

Virgin, natural woodlands were transformed into elements of the tradi­tional cultural landscape when their structure and species composition were heavily influenced by historical or modern silvicultural uses (e. g. woodland pastures, reforestation partly with non-native species; Pott and Huppe 1991; Zerbe 2004). The habitat continuity of such woodlands can still be quite high when it is a question of transformed, pristine forests. The continuity on reforested former agricultural land, however, is comparably
low. For parts of Europe, more recent reforestations have been differenti­ated from old-growth forests through landscape historical methods (Peter – ken and Game 1984; Peterken 1994; Wulf and Kelm 1994; Verheyen et al. 2003)...


Remnants of pristine forests

Remnants of pristine forests are usually understood to be non-urban for­ests, far outside the impact area of cities. They can, however, occur as peri­urban woodlands and even as isolated urban woodlands in the centers of cities. An example of the latter is the oak-hemlock forest that today lies in the middle of the Bronx as a part of the New York Botanical Garden; it represents a remnant of the vast forests that once covered the East Coast of North America (McDonnell and Rudnicky 1989).

In the middle of urban areas, and farther away as well, such remnants of pristine forests are not usually free from human influences. As a rule they are affected by anthropogenic depositions, by at least minor historic or
contemporary forestry uses or by recreation activities...