Applying Ecosystem Management to Urban Forestry
An ecosystem is defined as a spatially and temporally explicit place that includes all the organisms, all abiotic factors in that environment, and their interactions (Likens, 1992). For an urban ecosystem, this includes the entire set of social, ecological, and physical components that define an urban area. One might ask, What is an urban ecosystem and how might it differ from other ecosystems? McIntyre et al. (1990) reviewed the concept of “urban” and concluded that no single definition exists because of the different perspectives of those who study or work in urban systems. I propose that rather than trying to define an urban area spatially, consider thinking of it as a system where ecological, physical, and social patterns and processes interact to create a unique environment. This environment represents both the green (e.g., vegetation) and gray (e.g., buildings and roads) infrastructure. In their paper on urban ecosystems, Pickett et al. (1997) presented a simple model to reveal the interconnectedness of social, ecological, and physical components. They asserted that by changing one component, the other components are directly or indirectly affected. So, from an urban forest management perspective, a manager, by altering some aspect of ecological structure (e.g., composition and diameter distribution of trees), can influence the social and physical components of the system, and all these factors (ecological, social, physical) must be taken into account when making management decisions, particularly since they will affect the extent of ecosystem services provided by the forest.
To achieve an ecosystem approach to management, the entire urban forest needs to be considered. A manager accomplishes this by looking beyond the particular management site and evaluating the effect of the site on adjacent land uses, and congruently, the effect of adjacent land uses on the site. In other words, the site should not be viewed independently of the context in which the site occurs, since context will affect the site and the site will affect its context. By viewing management activities from this broad perspective, the manager moves beyond simply planting a tree at a particular site or location, and asks how this activity affects ecosystem process and subsequent services to the site and adjacent areas. This perspective is important because an ecosystem is an open system, in which energy, materials, and organisms move into, through, and out of the system. By altering the urban forest structure or the physical environment of the site, the manager influences this movement. For example, by increasing the canopy cover by planting trees, a manager can influence the amount of particulate material and rain intercepted by the trees. A greater interception of material leads to cleaner air and less storm runoff. By taking a broad perspective, a manager can evaluate potential planting sites in the context of surrounding vegetation and ask if the proposed planting achieves the desired management goals and objectives, or if resources should be directed to other sites. So, a broad perspective enables managers to prioritize sites for planting, and this may maximize benefits while minimizing costs (also see Chapter 13).
KeywordsSeed Bank Urban Landscape Ecosystem Management Urban Forest Urban Ecosystem
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