Assessing impacts of different development policies on the city and its "ecological footprint."

Wil Orr's research group at Prescott College in Arizona is trying to make the connection between present-day patterns of consumption and the build up of greenhouse gases in the upper atmosphere. Their efforts have attracted funding from NASA, among other sources. Orr's computer model, U-Grow, shows the impacts of different urban development scenarios on a region's "ecological footprint." This term relates the land area of hinterland required to support all the resource needs of a community. This includes not only the land people live on but also land needed for water collection, growing of crops, the mining of metal, extraction of oil and so on.

The model tracks development trends from 1950 to the present and allows adjustment of variables from the present day forward. For example, one can see the effect over time caused by changing the size of new houses or the land allotted per house. Outcomes range from the amount of driving per person to the total land area consumed in a given period. U-Grow allows users to run a number of scenarios and stop the model at any future year to obtain a snapshot of the community and the size of its ecological footprint.

The first image on the right shows linear graph projections of present trends. By changing variables, one can see additional graph lines showing the effects of different policy changes over time. 2- and 3-D map views depict the varying amounts of land consumed by development under each of the policy scenarios.

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