Does vegetation encourage or suppress urban crime? Evidence from Philadelphia, PA

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?