How it looked before and after greening, near the intersection of Cecil B. Moore Avenue and N. 4th Street.
plained that the dealers weren’t around to shop in their stores anymore. Even more useful to Branas than the wealth of anecdotal information were the meticulous records Grossmann had kept on 4,436 lots greened between 1999 and 2008. The data were available to researchers and in the form of GIS (geographic information systems) maps. Branas invited Grossmann to attend a small internal meeting at Penn where broad-based research on vacant space was being presented. “He’s really open to exploring things,” Grossmann says of Branas. “From the start, he was totally engaged, trying to understand every aspect of our work, seeing how it related to his own. There’s always been a good give-and-take between the practical groundwork that we do and his academic expertise.” Starting with Grossmann’s maps, Branas designed a study to measure the effect of greening on health and safety. A control group was drawn from the almost 55,000 untreated lots Philadelphia was estimated to have at the time. “It was a ‘found’ or quasi-experiment,” Branas says, “something epidemiologists are always on the lookout for.” The Cartographic Modeling Lab then gathered data from the Philadelphia Police
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Department on the exact location and nature of crimes, as well as health information from the Philadelphia Health Management Corporation, which biannually surveys Philadelphia residents about their health. “Our researchers incorporated everything into a larger mapping system,” Branas explains, “allowing us to analyze, to make maps, to make visual what had happened in and around those vacant lots before and after they were greened.” “All this,” he adds, “is part of what the CML and cartography are able to do. Without it, we wouldn’t have been able to do our analysis.” (For the roots of epidemiological mapping, see box on p. 11.) The analysis, published in the American Journal of Epidemiology in 2011, showed a significant reduction in violent crime – particularly gun crimes – around lots that had been greened. Gun-related crimes were down between 7 and 8 percent, and Branas was able to confirm that they didn’t just shift to nearby streets. (He also reported reductions in vandalism, criminal mischief, and stress, plus increases in how much people exercised.) Branas has two hypotheses for the reduction in gun-related crime. One is the widely cited “broken windows” theory proposed by political scientist James Q.
Wilson, Ph.D., and criminologist George Kelling, Ph.D., in 1982. It claims that broken windows, graffiti, trash-strewn streets, and all other visual aspects of blight actually promote crime. The opposite happens when greening replaces blight: people feel more invested in the area. They keep it clean. If anything disorderly occurs, they call the police. Criminals are less at home in the space. While Branas accepts this explanation – for him, “broken windows” is not just a theory anymore – his work is some of the first to challenge this theory in the real world and make it more than just academic. He notes, for example, that it’s really difficult to hide an illegal gun in or around a cleaned and greened lot and believes there is a physical component to reducing gun violence. Branas’s results received a lot of press coverage, and people who knew his work saw it as an extension of his gun research. “But quite frankly,” he says, “we looked at more than 20 outcomes that potentially related to health and safety.” As he points out, only two, which he had casually added into the mix, “were about guns. It just so happens that one of those gun-oriented outcomes carried the day.”