Urban Growth and Ecological Density

An often neglected part of how we develop urban areas in our the quest for infill and density is the importance of green space. Not only do green spaces provide vital place for recreation, but they also help improve water quality, air quality, and reduce the heat island effect. In addition, they can create important refuges and corridors for wildlife.

In the rural area, species diversity is an important sign of ecological health. Nonetheless a healthy forest may contain only a handful of different tree species over ten acres. In a city, the pressures from pollution and use are much higher, and there may only be a half acre of green space. As we densify neighborhoods, we can create ecological density to offset these pressures (to borrow a phrase coined by Lucia Phinney). Having artificially higher species diversity intentionally designed habitats is a way that we could create more resilient green space. In addition, someone hiking in the national forest may cover several miles. In an urban area where that experience may not always be possible, creating ecological density can create a greater feeling of experiencing nature in a smaller place. In many ways, this is the same thing zoos and wildlife centers do for urban residents. It makes it possible for people who may not have the opportunity to go to Africa or hike through Yellowstone to have an encounter with wildlife in an urban setting. So where someone might hike for an hour in the national forest to come to a location with trilliums, in an urban area potential trillium habitat could be identified and created within a smaller area.

By no means is ecological density meant to replace natural ecosystems. In fact, Natural ecosystems are the blueprint that we need to create quality green space and urban habitat. By understanding the concepts that make habitats work in rural areas, we can then apply those concepts in new ways in urban areas. For example, we might observe that a rooftop is a similar habitat in many ways to a granite rock outcrop, and then use that knowledge in our design of green roofs and in our selection of species. By extrapolating these concepts, we can create more diverse habitats in smaller spaces, and by doing this we can make growth areas more livable for urban residents.

In short, as our community continues to push for greater residential and commercial density in our growth areas, we should put an equivalent effort into pursuing ecological density and creating high quality green spaces.