Doctoral Dissertation Research: Modeling the Impact of Urbanization on Ecosystem Services in the Twin Cities of Minnesota

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Urban growth generates many benefits such as housing and employment opportunities, but also affects the environment's ability to provide ecosystem services including clean air and water. While knowing how urbanization impacts ecosystem services at multiple spatial scales over time is a critical step in the development of sustainable cities, inadequate scientific understanding remains a primary obstacle to this goal. Doctoral student Adam Berland at the University of Minnesota Twin Cities, under the supervision of Dr. Steven Manson, will explore the spatial and temporal dynamics of urbanization's effects on ecosystem services for an urban core in downtown Minneapolis, MN. The study will take place along a transect that extends from the urban core in downtown Minneapolis through the suburbs to the peri-urban fringe, thus capturing a general gradient of urbanization. The research focuses on the urban forest, a collective term for all trees within the urban area, to determine how previous land cover change has affected the urban forest along an urban-rural gradient, how ecosystem services are associated with the urban forest currently distributed along an urban-rural gradient, and how projected urban expansion will affect ecosystem services in the coming decades. Aerial photographs will be used to document forest canopy change in the transect over the past 70 years with respect to land cover transitions. Regression analyses will assess the relationships among tree canopy cover, land cover type, and distance from the urban core to demonstrate how urban forest cover has fluctuated with land use changes over several decades, thus providing a context for understanding current and future urban forest ecosystem service prospects. Then current ecosystem services in the study transect will be characterized based on detailed vegetation and land cover surveys of 300 field sites. Several modeling approaches will approximate current urban forest provision of services such as air pollution removal, stormwater interception, and carbon storage. Finally, future ecosystem service distributions will be estimated for 50 years under a range of possible land cover change scenarios. Using tree rings and municipal planting records to develop species-level age-to-size relationships for the most common trees in the transect, the study will project tree growth and associated changes in ecosystem service provision. Together, these efforts will highlight past, present, and future ecosystem service distributions along the study transect. This research will address a key gap in scientific knowledge by demonstrating the distribution of ecosystem services along an urban-rural gradient at multiple spatial scales over time. Given recent increases in regional-scale planning, the study is timely because it analyzes scenarios across several municipalities. Project findings will be directly applicable to regional land managers and urban foresters by highlighting areas of historic gains and losses in ecosystem services, projecting the effects of future land cover change scenarios and urban forest management strategies, and projecting the impacts of future pest outbreaks and natural disasters. Together, the findings will guide local professionals in their short- and long-term efforts to improve urban forest ecosystem service provision in the Twin Cities Metropolitan Area.