Baltimore Field Station

The Baltimore Forest History Project -
Historical Aerial Imagery, Community Engagement and Citizen Science

We are working to understand the relationships among people, communities, and forests in Baltimore over the past 100 years. The distribution of landscapes that seem like “nature” or “wilderness” are actually the result of complex social histories. By examining urban forest environmental history we hope to gain a better understanding of historically-constituted mechanisms of racial and economic environmental inequalities. These insights will help contribute to local agency and non-profit goals for a more equitable future urban forest landscape for Baltimore City.


We are using several sources of historical aerial imagery to characterize change in the city’s forest patch ( >10,000 ft2) cover over time (1926-27, 1937-38, 1952-53, 1964, and 1972). This analysis of forest patch change allows us to determine which forest patches have been relatively stable, persisting through time, and which are much more dynamic. We have classified land use for the earliest set of images, taken between 1926-27 and covering 210 mi2 (544km2) within and surrounding Baltimore City. This set comprises 93 individual images, or “tiles” taken from a bi-plane, and capture a moment of dynamic expansion in the city, just prior to the Great Depression (left side, Figure 1). We obtained high-resolution scans of each image, which were geo-rectified to spatially align with current GIS data. This process converts the images from a disparate set of photographs into a seamless GIS dataset that can be used to observe changes in land patches over time—and ultimately to be integrated with other long-term social, economic, and ecological data (e.g. Grove et al. 2015). In 2018, the team began to georectify and classify images from 1952-1953.

[aerial  photos:]  St.  Peter’s  Cemetery,  1927  (left)  and  2010  (right).  In  1927,  land  on  the  western  border  of  the  cemetery  was  forested.  Today,  the  property  has  become  reforested,  while  lands  outside  the  cemetery’s  boundaries  have  been  cleared.
St. Peter’s Cemetery, 1927 (left) and 2010 (right). In 1927, land on the western border of the cemetery was forested. Today, the property has become reforested, while lands outside the cemetery’s boundaries have been cleared.


Classifying land use is the first step toward analyzing change in forest cover. However, classifying land use, such as identifying forest patches on these historic photographs, cannot be automated. Thus, we have developed preliminary methods for land use/land cover classification of historic imagery as part of the “Baltimore Forest History Project,” which will be a community-based collaborative research platform. Using a “crowd sourcing” approach, the Baltimore Forest History Project will aim to allow members of the community to classify the historic images through a web-based research platform.


1927 Aerial imagery of Balitmore City and part of Baltimore County (left), 1927 Land use and land cover of Baltimore City and part of Baltimore County.
Georectification of 1927 aerial imagery for Baltimore City and portions of Baltimore County surrounding the city. (left) and Land-use and land cover classification of Baltimore City and portions of Baltimore County in 1927. (right)


During the summer of 2017, we worked with Baltimore high school and college interns to develop the necessary methods for land use and land cover classification, digitization, and quality assurance and quality control protocols of this imagery. Our team, which includes the non-profit land trust Baltimore Green Space, plans to work with local community members, schools, and organizations such as TreeBaltimore to classify the images in an online GIS database. Many of these local participants are lifelong Baltimore residents and have in-depth knowledge of the green space in their neighborhoods, and how it may have changed over time. Participants will engage the scientific process while contributing their personal, in-depth knowledge of the “forest patches” that are part of their communities.


Our preliminary analysis of the historical imagery suggests that this effort will reveal important insights into the relationships between property ownership and forest patch dynamics. For example, “Jonah House Forest” is an emergent forest within the historic St. Peter’s Cemetery (Figure 1). In 1996, the Archdiocese of Baltimore leased the overgrown and neglected cemetery property to Jonah House, a social justice religious community for $1 per year. Jonah House continues to manage the 22-acre forest patch because, as one of the caretakers mentioned in an interview, they believe in fostering a place of retreat for all forms of life. Over time, the ownership and land use of properties outside the cemetery have changed, as has the forest cover on these properties, while the cemetery, whose ownership has remained constant for well over a century, has become reforested.


In the future, we will extend the historic analysis through time by analyzing satellite imagery (1970-Present), which we can use to analyze the more recent 45 years of change over time. This research will help us determine patterns of change from which we can develop hypotheses about forest patch dynamics and ownership regimes. These insights may help inform future environmental planning, conservation, management, and stewardship goals for Baltimore City forest patches, and other cities throughout the region.


Morgan Grove, Team Leader, Baltimore Field Station

Nancy Falxa Sonti, Ecologist, Baltimore Field Station



Ogden, Laura A.; Aoki, Carissa; Grove, J. Morgan; Sonti, Nancy Falxa; Hall, William; Locke, Dexter; Pickett, Steward T. A.; Avins, Miriam; Lautar, Katie; Lagrosa, John. 2019. Forest ethnography: An approach to study the environmental history and political ecology of urban forests. Urban Ecosystems. 22(1): 49-63.


Grove, J.M.; Cadenasso, M.; Pickett, S.T.; Burch, W.R.; Machlis, G.E. 2015. The Baltimore School of Urban Ecology: space, scale, and time for the study of cities. Yale University Press.

Last ModifieDecember 3, 2019->->->