The 4DEE (Four Dimensional Ecology Education) framework integrates ecological knowledge across four dimensions: concepts, crosscutting themes, the human dimension, and skills/practices. Coverage of the human dimension with its consideration of dependence, management, and anthropogenic-driven climate change is often minimalized. I have expanded the crosstown walk exercise (TIEE 2005) to include this dimension. For a number of years, my class has walked a transect in an area of Washington, DC undergoing economic development and demographic change. Historically, students examined environmental conditions along a socioeconomic gradient, but more recently, they decided to examine air quality by measuring levels of particulate matter (PM) typically associated with respiratory irritation and chronic asthma. While most often associated with mining dust inhalation, PM in cities is increasingly recognized as an urban health issue. Students hypothesized that PM levels would vary with the density of vehicular traffic and might link to socioeconomic conditions, especially those associated with tree and vegetation coverage. Typically, areas with higher valued housing have more vegetation. As part of a two-month long class exercise, they measured PM along four streets and collected information on traffic volume, housing value and tree cover along the crosstown transect.
Results/Conclusions
Students found that PM levels directly related to traffic volume with areas closer to major thoroughfares exhibiting higher levels compared to those in less trafficked streets. Streets with greater tree density showed reduced PM levels, especially those with larger, older trees typically found in more affluent neighborhoods. Interestingly, some of the ambiguity in the relationship of PM with trees and socioeconomic condition may result from recent environmental and social change. Over the last decade Casey Trees planted hundreds of trees in empty tree boxes and housing values increased as a result of gentrification in historically African American neighborhoods. While I provided the initial outline for the exercise, the methods, data collection, and analyses were all products of student decisions. Hypotheses were grounded in student observations of current environmental conditions coupled with an historical frame of reference. Their interest in the project resulted in a level of participation higher than anticipated—and led five students to continue the investigation into the following semester and three presentations (on-campus, regional and national). This same group of students is currently looking leaf surface structure as a mechanism by which vegetation density might affect PM levels.