By Dr. Jane E Heinemann Dmochowski
Teaching Faculty
Earth and Environmental Science Department, University of Pennsylvania
Cobbs Creek Park, an 851 acre park1 managed by the Philadelphia Parks & Recreation2, is a green refuge between the suburban neighborhoods of East Lansdown, Yeadon and Darby to the west and the urban Philadelphia neighborhoods of Cobbs Creek and Kingsessing to the east. It is part of the Cobbs Creek Watershed surrounding Cobbs Creek, a tributary of Darby Creek, which extends south roughly 12 miles3 from just northwest of Haverford College. But before there was Haverford College, the Cobbs Creek neighborhood, the University of Pennsylvania, and even before the Dutch and Swedish settlers arrived in the mid 1650s4 and set up the first water mill built within the limits of Pennsylvania5, the area surrounding the creek was inhabited by the Native American Lenni Lenape tribe, who called the creek “Karakung,” believed to mean “the place of the wild geese”6. The Lenni Lenape people thrived in the area for over 10,000 years7, but in the last four hundred years tremendous change has come to the area and the work to preserve its beauty and function must be taken up by a new generation of environmentalists.
Cobbs Creek Park was established in 19118. But as the population and built environment surrounding the area of Cobbs Creek Park has continued to grow, many environmental issues have ensued. Along with the everyday deterioration caused by litter and encroachment of people, buildings, roads, and machines, the impermeable surfaces surrounding the creek have multiplied. Without permeable land cover allowing rainwater and snowmelt to percolate through the soil of the land, severe run off after even mild storms can cause devastating flooding, erosion, a build-up of nutrients and pollutants in run-off water, and lead to the instability of the banks of the creek. More severe weather events, increasingly common due to climate change, can lead to more severe flooding, further impacts to the tree canopy, and wreak havoc on the plants and wildlife in the already fragile ecosystem.
Additionally, in the nearly 400 years since the arrival of Europeans in Pennsylvania, many non-native species have been transplanted and established here for their beauty, utility, or as food. Unfortunately, many of these species were chosen specifically because they were resilient to the climate and native species of our area, and thus they have thrived, in some cases devastatingly so, often outcompeting the native species9. Climbing vines such as kudzu (Pueraria montana) and porcelain berry (Ampelopsis glandulosa var. brevipedunculata) became established in Pennsylvania in the mid-to-late 1800s10 and since then have been climbing into the native tree canopies, blocking the sun, overwhelming tree saplings and adding weight to the established trees, leading to a decrease in the photosynthetic ability of the native trees, and potentially weakening them, especially when they are further burdened by the weight of snow and ice.
Surrounded by a man-made landscape, parks like Cobbs Creek also suffer from growing deer and beaver populations, and while the abundance of a wild animal population is usually celebrated, balancing these populations with the survival of the stressed and limited vegetation in these areas is difficult. As Cobbs Creek and urban parks like it are negatively impacted, the urban heat island effect11 can worsen, further stressing the park and decreasing its positive impact on the area surrounding it.
In 2021 a group from Penn’s Water Center, Earth and Environmental Science Department, Netter Center for Community Partnerships, and the School of Engineering and Applied Science, were awarded a Projects for Progress Prize12 to renovate and enhance the Cobbs Creek Community Environmental Center and its K–16+ collaborative learning opportunities. In a collaborative effort with this team and others, I hope to bring the energy, commitment, curiosity, environmentalism, and brain power of both the Philadelphia community and the Penn undergraduate student body to monitoring Philadelphia’s urban vegetation and assessing further ecosystem restoration needs. The methods of this work will include outreach, field work, classification of satellite images, determining satellite image-derived vegetation recovery metrics13 (Figure 1), taking field spectra data, conducting grid analyses, and monitoring the creek for dissolved oxygen, pH, turbidity, dissolved solids and other measures of stream health. Ultimately, community science done right is community-driven! This project (UrbVeg CBPR) will rely on local knowledge, collective action & empowerment of both the West Philadelphia community and University of Pennsylvania students.
Figure 1. The figure on the left shows an NDVI image of the Cobbs Creek Watershed, where green indicates green vegetation, and the red indicates low to unhealthy vegetation. The yellow marker in both images is the location of the Cobbs Creek Environmental Center. The image on the right, also showing the Cobbs Creek Watershed, is an example of a classification, this one done based on Modis14 imagery. The red indicates urban and built up lands; neon green, deciduous broadleaf forest; beige, shrubs and grass; black, undetermined vegetation; and brown, woody vegetation. These images were produced in Google Earth Engine15.
This work will build on Philadelphia-based remote sensing16 and geographic information system (GIS)17 projects I have done with former Penn students using satellite images, GIS, in-person surveys, and interviews to research the urban landscape of Philadelphia. In past projects we have examined how surface permeability varies with spatial and demographic factors in Philadelphia18; how income level impacts greenspace; the effects of street albedo on the urban heat island in Philadelphia; the cooling capabilities of Penn Park; the urban outdoor recreation habits of Philadelphians on the Schuylkill River; as well as modeling the potential for urban agriculture and more.
As the community of stakeholders and Penn students learn the tools of remote sensing and other research methods, they will have the opportunity to formulate their own research questions and work together to answer them. Some possibilities include exploring how decadal trends in soil exposure, erosion, and moisture have changed in Cobbs Creek Park, and determining if there are seasonal patterns, or soil composition, that may be important to understanding how to mitigate for flood surges and associated erosion. Others might explore if the deer fence, which does not encompass all of the forest in Cobbs Creek, affects the vegetation changes in the Park. There are also plans underway to restore the Cobbs Creek Golf Club19, presenting an opportunity to explore how the restoration affects the health of the creek.
As part of this project, I have been working with a Penn student, Henry Feldman, to develop lesson plans for the community, local high school students and Penn students to learn the tools available for this research, how to get involved, and most importantly how the Park’s ecosystem relates to their lives. I hope these lesson plans and the work that comes from them will empower the West Philadelphia and Penn communities to answer the many research questions that could shape the health of the Park and the community for years to come.
References
1https://www.phila.gov/programs/rebuild/project-sites/cobbs-creek-park/ 2https://www.phila.gov/departments/philadelphia-parks-recreation/ 3https://apps.nationalmap.gov/viewer/ 4http://www.celebrateboston.com/history/pa/dutch-and-swedes.htm 5http://www.phillyh2o.org/backpages/cobbs.htm#:~:text=Cobbs%20Creek%20is%20a%20major,19th%2and%20early%2020th%20century 6http://www.celebrateboston.com/history/pa/dutch-and-swedes.htm 7https://tadubois.com/US_indigenous/US_indigenous_subpage_lenni_lenape.html#:~:text=The%20Lenape%20are%20considered%20to,known%20as%20the%20Delaware%20Indians. 8https://circuittrails.org/find-trails/cobbs-creek-trail/ 9https://www.phila.gov/2020-07-29-save-bugs-save-birds-use-native-plants/ 10https://www.phila.gov/2020-07-29-save-bugs-save-birds-use-native-plants/ and https://www.nature.org/en-us/about-us/where-we-work/united-states/indiana/stories-in-indiana/kudzu-invasive-species/ 11The urban heat island effect refers to a rise of temperature in urban areas where natural land cover has been replaced with pavement, concrete, and other surfaces that absorb and retain heat. 12https://penntoday.upenn.edu/news/inaugural-projects-progress-recipients-announced 13One example includes NDVI, Normalized Difference Vegetation Index. The chlorophyll in live plants absorb light in the visible part of the EM spectrum (VIS: from 0.4 to 0.7 µm) for photosynthesis, but live plants strongly reflect near-infrared light (NIR: from 0.7 to 1.1 µm). Therefore the normalized difference ratio of the two will be nearly 1 for healthy green plants, and closer to 0 for brown or unhealthy plants. 14https://modis.gsfc.nasa.gov/data/dataprod/mod12.php 15https://earthengine.google.com/ 16The term remote sensing is used here to refer to the analysis of satellite and other aircraft images. These images are capable of detecting the physical characteristics of an area (its buildings, water, vegetation, etc.) by measuring its reflected and emitted radiation with an onboard sensor. A remote sensing analyst can monitor and better understand the landscape changes utilizing these images. 17A geographic information system (GIS) system is one that creates, manages, analyzes, and maps all types of data. 18https://presentations.curf.upenn.edu/poster/spatial-and-demographic-analysis-surface-permeability-philadelphia 19https://www.inquirer.com/news/philadelphia/cobbs-creek-golf-course-philadelphia-20220119.html
Dr. Jane E. Heinemann Dmochowski began teaching at the University of Pennsylvania in 2006 and became the Assistant Director of the Earth and Environmental Science undergraduate programs in 2008. She helped to start the Vagelos Integrated Program in Energy Research (VIPER) in 2012, has served on multiple sustainability and education committees, including the 2021 PA Academic Standards for Science and Technology, Environment and Ecology Content Committee. She is currently Teaching Faculty in the Earth and Environmental Science Department and has taught Math and Physics at high schools in California and New Jersey; and Earth Science, Environmental Chemistry, Oceanography, Environmental Case Studies, Research Methods, and Remote Sensing at four colleges and universities, including Penn.