Living lab for sustainable cities.

• Author: Barton, Erin
• Position: FRONTIER HORIZONS

A NEW DAY DAWNS, and morning light filters through the towering stems of an ocotillo, casting striped shadows on the ground. Although the thorny plant looks a bit lackluster, it provides an adequate perch for a zealously chirping curve-billed thrasher. An abundance of black widow spiders lurk unseen in the cracks and crevices below. By all appearances, this is a typical morning in Arizona's Sonoran Desert. In some ways it is but, in many ways, it is not.

Many residential yards in Arizona are designed with xeric landscaping, which requires little water and looks like the wild desert surrounding the city. Ecologically speaking, however, these yards are "functionally not at all like the desert," according to Nancy Grimm, professor in the School of Life Sciences at Arizona State University. That ocotillo, for instance, is drowning. Homeowners tend to shower too much water on their yards even when they mimic an arid landscape. Desert birds like the curve-billed thrasher seem to exhibit more aggressive territorial behavior in the city than those living out in the desert. What about the black widows? To homeowners' distress and exterminators' delight, their populations are denser in urban areas than in rural ones, nourished by the insects that swarm to the oasis of the city.

Less visible changes are occurring as well. Biogeochemical cycles in the soil, water, and air are all different between residential yards and wild Sonoran sites. These are just a few of the findings from ASU's Central Arizona-Phoenix Long-Term Ecological Research (CAP LTER) program, funded by the National Science Foundation since 1997. The NSF supports 26 LTER sites across the U.S., but only two focus on urban environments: the Baltimore Ecosystem Study and CAP LTER.

"Phoenix, and cities in general, are microcosms for the kinds of changes that are happening globally," notes Grimm, the CAP LTER principal investigator and project director. "In biogeochemical cycles, for example, they show symptoms of the imbalances in nitrogen, carbon dioxide, ozone, and other chemicals that they help to create globally."

Human activities create these changes, which, in turn, affect humans. As people adapt to the altered environment, they change the natural world further. This circular relationship within the urban socio- ecosystem is the basis of CAP LTER's overarching research question: how do the services provided by evolving urban ecosystems affect human outcomes and behavior, and how does...