Does vegetation encourage or suppress urban crime? Evidence from Philadelphia, PA PLG 600 - Planning Research Design
April 1, 2015
Kim Behrouzian, Derek Pokora, Rebecca Sturley, Nikolas Koschany
CONTEXT Does vegetation encourage or suppress urban crime? Evidence from Philadelphia, PA (2012) by Mary K. Wolfe and Jeremy Mennis  What is the research about? themes of landscape architecture and urban design, specifically crime prevention through environmental design explanatory study that analyzes the association between vegetation concentration and crime rates in Philadelphia, Pennsylvania What is the relationship of this research to the literature the author(s)? 2 schools of thought on this topic attempts to fill a gap in the research Trends in the literature? the study confirms the more recent school of thought: increased concentration of vegetation will be associated with lower crime rates
IMPLICATIONS
Why is this research worth doing?
If the abundance of vegetation does influence crime, city police departments and planners can work together to improve urban environmental aesthetics in concert with crime reduction.
THE STUDY
Deductive reasoning: tests the theory using empirical data Explanatory: tests and builds the theory “why does violent crime occur where it occurs?� Structural: establishes relationships between variables
Variables: vegetation concentration, poverty, education attainment, population density, crimes (robberies, burglaries, theftsthough undefined in the study)
DATA COLLECTION
What data was used in this research? Data was gathered from three public sources: Socio-economic data at the tract level (poverty, educational attainment, population density) Crime data by Census tract Vegetation data
METHOD OF STUDY
yi = b0 + b1VEGi + b2POVi + b3EDUi +b4POPDENi + εi y = crime rate, b0=constant (y-intercept), εi=error
DATA ANALYSIS
Mary K. Wolfe & Jeremy Mennis 2012
USEFULNESS How significant are the research findings in this area? generally answers the question of whether or not vegetation concentration suppresses crime, as opposed to facilitating it quantitative data substantiates that landscape designers and planners need to work with local governments, city police forces, and neighbourhood organizations to incorporate landscape design and vegetation in CPTED measures Can the research be reapplied and the findings be generalized? since the specific unit of analysis is the census tract, the research could potentially be replicated by looking at other cities, provided they have the same data sources findings can be generalized as it quantitatively verifies that vegetation concentration has a negative correlation with crime rates
LIMITATIONS Limitations of research‌ models are always approximations of reality failure to explain how the literature review informed the choice of independent variables issues with variables examination of four dependent variables: criminal typologies aerial satellite imagery/NDVI only measures concentration of vegetation failure to adequately define independent variables tracts containing less than 100 residents were excluded from the study why does the concentration of vegetation have a relationship with crime suppression? unsure if study is replicable
QUESTIONS?