Vacant lots are described as sites that have the potential to be built upon but currently sit unused or abandoned. Viewed as a social problem with associations to crime, trash, and overgrown vegetation, vacant lots are generally thought to have a negative presence in many neighborhoods. However, we suggest this perception needs to shift to locations of urban potential, because vacant lots may serve as informal greenspaces for urban biodiversity while offering important regulating and cultural ecosystem services. We asked what kind of vacant lots are present in a city and evaluated how the setting of the vacant lot shaped its biotic characteristics to assess which lots should be prioritized for management. We surveyed 150 vacant lots throughout Baltimore, Maryland for their plant and bird communities, classified the lot’s setting within the urban matrix, and surveyed nearby residents. We used vacant lot classifications from the literature as an initial guideline, then described additional settings unique to Baltimore. We conducted Bray Curtis ordinations to describe variation in tree and bird communities and single factor ANOVAs to detect differences in vegetation structure among lot types. Our goal was to assess whether vacant lots are ecologically and culturally valuable for urban greenspace management.
Baltimore’s vacant lots varied extensively in their biotic contents and setting within the urban matrix. We categorized vacant lots into the following settings: entire block, inner block, corner lot, missing tooth, suburban yard, and wayside. The settings largely depended on where the vacant lot occurred in the city, from block-grids downtown to suburban neighborhoods. Within our sites, we found 64 tree species and 60 bird species. The tree community separated out across vacant lots by exotic tree species, but had similar species composition throughout Baltimore. Bird community composition correlated with tree species richness and canopy cover, with more native bird species found in lots with greater tree cover. Wayside vacant lots and suburban yards were the only vacant lot settings that differed significantly in their bird communities. Each vacant lot setting offers its own constraints and opportunities for conservation practices. For example, vacant blocks typically offered large areas to sanction for parks, versus “missing tooth” lots between buildings that are typically small, shaded, and had fewer trees. Collectively, vacant lots can provide large areas of urban greenspace with the potential for some locations to enhance urban tree cover and bird habitat, while balancing the needs and preferences of city residents.