by Dan McCabe
Sustainable urban planning aims to ensure that urban development patterns do as little ecological harm as possible, but new research suggests that conventional planning approaches neglect a significant contributor to urban environmental health. Mathey et al. (2015) studied the effects of urban brownfields, formerly developed sites that have been abandoned and remain underused, and found that vegetation-rich “green” brownfields provide a variety of valuable ecological services to their areas. The benefits of these services depend on the type and amount of vegetation at a particular site, its location, and human intervention, but green urban brownfields overall show a large potential to aid the goals of sustainable development. Specifically, brownfields provide habitats that support enhanced biological diversity, aid microclimate by cooling the unnaturally warm urban environment, and provide local residents with recreational opportunities. These findings were obtained via a literature review, climate modeling, and a survey of local residents. The authors concluded that green urban brownfields should receive more credit for their ecosystem services and the most effective way to reap their benefits is to leave them mostly wild, while possibly converting some area to recreational spaces.
Green urban brownfields have a particularly large potential to promote sustainable urbanism because of their prevalence; they are extremely common in cities that have transitioned from industrial economies or undergone population decreases. Over time, abandoned sites are colonized by plant life that expands and attracts an array of animal species, which can sometimes be threatened or endangered. Conventionally, brownfield are seen as potential locations for urban redevelopment, but the authors considered the implications of either converting them to more conventional green spaces or leaving them essentially wild. A review of case studies of the ecology of green urban brownfields in Germany was used to assess the habitat services provided by brownfields of different vegetation levels. The authors found that species diversity tended to increase along with the age of the site and the structural complexity of its plant life.
In an effort to quantify the microclimate services of brownfields, the authors used climate modeling software to evaluate surface temperature in the area surrounding these sites. Green spaces tend to provide a cooler environment than built areas, and vegetated brownfields are apparently no exception. While densely wooded areas may cause cooling of up to 2.1 K, the effects of brownfields are substantial but slightly less pronounced, ranging from 1.4 K to 1.7 K depending on vegetation level.
The final part of this study consisted of a survey given to residents of Dresden, Germany, on their use and perception of brownfields in the area. Respondents shared that they tend to use brownfields for walking, meeting places, experiencing nature, and more. They also expressed, however, a strong preference for traditional well-maintained urban parks as a location for recreational activities. Thus, while brownfields do appear to provide some recreational services to residents, the benefits are limited.
The results of this study were largely qualitative, but the authors were still able to draw some valuable conclusions. To examine the implications of different planning policies, they applied the knowledge obtained to two different scenarios in a brownfield-rich area in Dresden. In the first scenario, large-scale rebuilding took place; in the second, green brownfields were left relatively wild or converted to conventional maintained green spaces. The second scenario resulted in cooler temperatures, greater ecological diversity, and more recreational opportunities for residents. While the authors did not provide concrete advice for urban planning strategies regarding brownfields, their research illustrates the undervaluation of these green spaces in conventional urban planning and reveals the benefits they provide. More research is needed to investigate the ideal planning strategies regarding brownfields, but this paper lays the groundwork for a more comprehensive planning approach that takes full advantage of these unique and valuable spaces. Because brownfields are often the only green spaces available in urban areas, properly exploiting their ecosystem services can have tremendous benefits for local ecology.
Mathey, J., Robler, S., Banse, J., Lehmann, I., Brauer, A., 2015. Brownfields as an Element of Green Infrastructure for Implementing Ecosystem Services into Urban Areas. Journal of Urban Planning and Development, ahead of print.