Islands of Green

Site: 
An old community garden plot in an inner block in west Baltimore. Uncultivated at the time of the photo, annual and short lived perennial colonizing plants are predominant.
BES LTER photo

Urban ecosystems offer fundamentally new habitat for both animal and plant species. While originally viewed as largely disturbed environments, urban places are emerging not as ecological disasters, but rich environments where humans interact strongly with organisms, generating new habitat and assembling new ecological communities.

In Baltimore, green space is now known to harbor many species of plants, soil invertebrates, and birds. New species of soil invertebrates have been discovered in urban ecosystems. Furthermore, there are "hotspots" of urban biodiversity now known to harbor rare plant species. While non-native species, such as the European starling, House sparrow and House finch, are well-known to proliferate in the urban environment, there exists high spatial variation in the levels of biodiversity. This is, in part, due to how humans view and alter the environment to maintain "natural" areas, restore habitat and design the urban landscape. Such natural areas are now fundamental to the development of the sustainability plans for Baltimore County and Baltimore City.

New research by BES investigators into the mechanisms generating and maintaining biodiversity in urban ecosystems is being guided by a new conceptual framework built on findings by collaborations between ecologists and social scientists. For example, BES scientists have learned that the socioeconomic and lifestyle factors, such as household income, ethnicity and education are significantly related to vegetation factors such as herbaceous vegetation coverage. Furthermore, levels of plant species diversity were found to be maintained along an urban to rural gradient. These prime examples showing that there exists significant biodiversity in urban ecosystems are driving new hypotheses as to why, given the urban environment is viewed as such an ecologically-degraded ecosystems.

BES researchers are continuing their efforts to understand how people view and value nature, and what social factors drive decisions about which species are maintained at a location. One way to understand this is by revising traditional ecological theory to include new mechanisms of species associations. For example, while remnant habitats can largely be driven by larger scale habitat alteration and disturbance, people are strong contributors to actively maintaining species associations. People circumvent some key ecological factors that organisms experience in "pristine" systems by facilitating dispersal (e.g., planting gardens), eliminating undesirable species (e.g., weeding), and relaxing important ecological interactions (e.g., eliminating herbivory with pesticides). The next step in understanding how biodiversity is maintained in the urban environment will explicitly include the socioeconomic factors involved.

Detailed summary of plant biodiversity along both a urban to rural and soil fertility gradients at the Baltimore Ecosystem Study LTER. Contrary to the initial expectations, urban ecosystems harbor significant biodiversity of plants and, in some cases, higher numbers of plant species than in rural habitats.
Groffman et al. 2006
For further reading: 
Boone, C.G., M.L. Cadenasso, J.M. Grove, K. Schwarz, G.L. Buckley. 2010. Landscape, vegetation characteristics, and group identity in an urban and suburban watershed: why the 60s matter. Urban Ecosystems 13:255-271.
Davis CA. 1999. Plant Surveys and Searches for Rare Vascular Plant Species at Two Pilot Areas: Gwynns Falls/Leakin Park, Baltimore City, MD. Baltimore: Natural History Society of Maryland.
Groffman PM, Pouyat RV, Cadenasso ML, Zipperer WC, Szlavecz K, Yesilonis IC, Band LE, Brush GS. 2006. Land use context and natural soil controls on plant community composition and soil nitrogen and carbon dynamics in urban and rural forests. Forest Ecology and Management 236: 177 -- 192.
For further information: 
Holly Beyar, Project Facilitator, Baltimore Ecosystem Study LTER
Contact email: 
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