MURP Chair Presents on Green Infrastructure Research

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In early March 2017, MURP Chair and Professor Austin Troy, PhD, gave a presentation on “Research on the Benefits of Urban Green Infrastructure,” which looked at his current and past work regarding the benefits of urban trees and other vegetation for heat island mitigation, shading, increases in property values and crime reduction.

Dr. Troy discussed how in one study, he looked at the relationship between tree canopy and crime index in the greater Baltimore region, and found that a 10% increase in tree cover equates to a 11.8% decrease in crime, with the effect 37% greater for public than private land trees. While the relationship between crime and trees varied spatially—as did the relationship between private trees and crime—the relationship between crime and public trees did not. Similarly, in another study that also used Baltimore as a case study, Dr. Troy looked at the impact of residential yard landscaping practices on block level crime.

Dr. Troy also spent time discussing the idea of causality versus association in research and within green infrastructure studies. For instance, while the association between green infrastructure and crime is well-established, can it be said that vegetation’s association with crime is causal?

Given the few studies currently available on this topic, Dr. Troy conducted another study—looking at San Francisco, Washington, D.C. and New York City—to examine whether crime actually drops more than it would otherwise after green investments have already been made. The results generated, he says, are mixed but promising, with tests within each study area suggesting likely causality.

Dr. Troy also discussed green infrastructure and urban heat, including how different surfaces’ absorptivity, reflectivity, transmissivity and emissivity can generate more or less heat in an urban environment. Dr. Troy has mapped urban heat in Denver, and examined the role of trees in mitigating its effects.

The presentation concluded with Dr. Troy previewing his current work, where he is looking at planning issues related to trees and water in the Denver area. His research questions center on how climate change, water supply and urban growth are affected by the high need for irrigation in the Colorado climate.

Each year, the urban and regional planning program within the College of Architecture and Planning, alongside CU Denver’s American Planning Association Student Chapter, host numerous lectures with faculty to discuss their current research.