Urban Forest Change on the Ursinus College Campus

An urban forest is a community ecosystem consisting of a variety of trees and shrubs that benefit both people and wildlife residing in cities, suburbs, and exurbs (Nowak et al 2010). Proper maintenance of the urban forest, particularly in terms of maintaining sufficient canopy and leaf area, optimizes ecosystem services (Nowak et al. 2016), such as climate regulation, reduction of energy usage, improving air quality, and reduction of stormwater impacts as well as the potential to address food in security (Clark and Nicholas 2013) and provide important mental health benefits (Rajoo et al. 2020), including for students (Rajoo et al. 2018). The removal and addition of trees and shrubs throughout the city can alter the composition of the urban forest. Drivers of tree loss are often related to he health of trees, safety concerns about diseased trees, and the impact of these to community community members (Roman et al. 2022).

This project examines how urban forest composition on the Ursinus College campus has changed in the past five years. 

In the first stage of the analysis, we mapped areas where trees have been removed from campus (Figure 1). We looked at the frequency of species removals, the reasons for these removals, and areas where trees have been removed. As part of this review, we also sought to estimate the cost of lost ecosystem services.

Analysis of tree removals on the Ursinus campus over the past five years reveals that 73 trees have been removed and that health issues are the primary reason for these removals (Figure 2).

The most frequently removed tree species are ash (Fraxinus spp.), which is a direct result of the infestation of emerald ash borers, while oak trees (Quercus spp.) are the second most frequently removed species (Figure 3).

Oak removals are also due to the effects of the oak root fungus and the close proximity of many older oaks. Tree removals has impacted areas distributed widely across campus (Figures 1, 4). Still, there were many removals concentrated in specific areas due to construction projects, such as those with the IDC, The Commons, and during the Winter break of 2022-2023 the Wellness expansion (i.e. more trees are scheduled to be removed with the creation of a new parking lot ). Interestingly, despite the removals due to construction being so dense, three times more trees were removed due to health reasons overall. Construction and health issues are likely to continue changing the composition of Ursinus College’s urban forest in the future.

In addition to the data collected on site and reasons for tree removal we can analyze the potential ecosystem services lost. Of the thirteen species removed, nine of them were native and four of were non-native (Figure 5). This greatly impacts native wildlife that depend on the native tree species for food and habitats. However, the majority of exotic species still add benefits to the ecosystem. For example, the newly planted Chinese elm (Ulmus parvifolia) trees, a non-native species, may be able to occupy the same niches as native elm trees due to their genetic similarity while not being resistant to Dutch elm disease. A greater biodiversity of trees has the potential to attract a greater biodiversity of wildlife, including birds. Birds improve the value of an ecosystem by providing services such as insect control and providing people mental health benefits through their songs (Begum). 

Many values associated with quantifiable ecosystem services have been lost from campus (Figure 6). Urban trees are necessary to both plant and upkeep in a stable amount because they can provide valuable ecosystem services by insulating buildings and effectively decreasing energy costs. Additionally, they can also absorb and clean stormwater, lessen soil erosion, buffer pollution, and both store and sequester carbon dioxide. From the tree removals documented on campus, we can conclude that energy usage will be the most impacted due to these combined factors and the recent and constant removal of trees on campus. 

In the second stage of the analysis, we considered which species of trees have been planted to replace lost trees, which species were most frequently planted, and where these replacement trees have been planted. The Ursinus College Tree Care Committee has a policy that requires two trees to be planted for each tree that is removed, so we considered how well the College is doing with its efforts here by comparing the number of replanted trees with those that have been removed. Further, in an attempt to understand how these replacement trees might influence the ways tree lost have impacted ecosystem service provision, we also compared the size classes of replacement trees (at maturity) with general information about the trees we have removed. We also consider how some of these newly planted trees might provide for Non-Timber Forest Products (NTFPs).

As part of the second stage, we walked the campus with Facilities Ground Supervisor Neil Tyson to locate and document all new plantings during the same period of time. Over the course of the past five years, Ursinus Facilities staff (Figure 8) and contractors associated with the construction of new buildings have planted have planted 71 trees.

Of these trees, the majority were maple trees (Acer spp.), although many of the plantings included different species which provide different ecological benefits to offset the loss of the many trees removed (Figure 8).

Compared to the species removed, these newly planted trees will be shorter at maturity that removed species and change the canopy cover on the campus (Figure 9). While most planted species were native, five were non-native species and, of these species, the majority will reach 40-60 feet at maturity (Figure 10).

Despite this difference in species provenance and size, many of these planted trees will provide other benefits, such as NTFPs, which can be used for a variety of reasons as well as provide multiple educational experiences and opportunities (Figure 11).

When looking to complete future plantings, we hope that the composition of the Ursinus College Urban Forest will emphasize planting a variety of native species with greater heights that will further bolster lost ecosystem services.

In the final stage of our analysis, we considered areas of the campus where we might continue planting new replacement trees to offset what we identified as a deficit in the number of replacement trees. While this analysis was based on a walk with Campus Facilities staff, we recognize that these are only preliminary suggestions and would need to be further assessed for their viability as planting sites.

During walks with Neil Tyson, Campus Groundskeeper, we also recorded and discussed potential sites for planting additional new trees. Our discussions focused on areas (polygons in the map above) where multiple trees might be added as well as specific locations for the planting of a single tree (individual pin points on the map above).

The Urban Forest on the Ursinus College campus has undergone noticeable change over the past years regarding the tree canopy, forest composition, and ecosystem service interactions. We have reached less than half of our replanting requirement, with future removals planned for the next year. Yet we're reminded that maintaining and increasing tree canopy, even on college campuses, reguires "generational time scales" (Roman et al. 2017). With increased effort and understanding of how our Urban Forest has changed, we hope to positively impact both the natural community on campus and residential for students and Faculty.

In the process of this project, a significant tree on the campus was identified for removal. The Olin Oak, nestled outside Olin Hall, brought joy to many generations of students, faculty, and wildlife throughout its life. It is with great sadness that we watch it go. Still, we hope to preserve the memory of its impact on our lives and use this opportunity to spread awareness regarding urban forestry and promote sustainability in its upcoming absence. Student support is so vast we now have an email address to show our appreciation ( olinoak@ursinus.edu ). We will miss it dearly but carry its spirit with us.

Works Cited

Begum, T. (2020, October 8). How listening to birdsong can transform our mental health. Natural History Museum.  https://www.nhm.ac.uk/discover/how-listening-to-bird-song-can-transform-our-mental-health.html 

Nowak, D. J. (2010). Sustaining America's urban trees and forests (No. 62). United States Department of Agriculture, Forest Service, Northern Research Station.

Nowak, D. J., Bodine, A. R., Hoehn, R., Ellis, A., Low, S. C., Roman, L. A., ... & Endreny, T. (2016). The urban forests of Philadelphia. Resource Bulletin NRS-106. Newtown Square, PA: US Department of Agriculture, Forest Service, Northern Research Station. 80 p., 106, 1-80.

Rajoo, K. S., Karam, D. S., & Abdullah, M. Z. (2020). The physiological and psychosocial effects of forest therapy: A systematic review. Urban Forestry & Urban Greening, 54, 126744.

Roman, L. A., Fristensky, J. P., Eisenman, T. S., Greenfield, E. J., Lundgren, R. E., Cerwinka, C. E., ... & Welsh, C. C. (2017). Growing canopy on a college campus: understanding urban forest change through archival records and aerial photography. Environmental management, 60(6), 1042-10.

Roman, L. A., Fristensky, J. P., Lundgren, R. E., Cerwinka, C. E., & Lubar, J. E. (2022). Construction and Proactive Management Led to Tree Removals on an Urban College Campus. Forests, 13(6), 871. MDPI AG. Retrieved from  http://dx.doi.org/10.3390/f13060871