Scientists & Staff

Current Research

My research addresses broad questions about how urban forests change over time. Urban forests are the collection of trees in cities, towns, and suburbs, including trees along streets, in residential yards and landscaped parks, as well as urban natural areas. My work primarily concerns the parts of the urban forest that are under direct human control, such as street and yard trees. The temporal dynamics of urban forest systems involve both social and ecological drivers, including decision-making by tree professionals and arborists as well as biophysical stressors at multiple scales. Studies include:

Field monitoring of tree mortality, growth and health. Through partnerships with various non-profit urban greening organizations and municipal forestry agencies, I lead and support longitudinal data collection of urban trees. This includes tracking cohorts of trees planted through particular programs as well as repeat inventories of multi-aged trees in a given landscape. Statistical analyses reveal the factors that are associated with mortality and low vigor, pointing to potential areas of intervention for managers. Past research showed the crucial role of maintenance and stewardship in young tree survival - with maintenance (or lack thereof) sometimes dominating the findings - leading to new projects to experimentally test interventions that promote stewardship behaviors among residents.

Urban tree canopy cover. Many cities have set ambitious goals to increase canopy cover levels. Because trees are fundamentally slow-growing organisms, long-term assessments (at decadal time scales) are needed to assess the impacts of various programs and events on tree cover. Using historical aerial photography, paired with archival historical research, I investigate the decision-making that impacts long-term tree cover changes.

Historical investigations of legacy effects. Urban forests are an inherited landscape, reflecting past disturbance events (e.g., storms, invasive pests and pathogens) as well as past decisions by tree professionals, residents, and other actors. The legacy effects of past phenomena shape the urban forest that we observe and experience today. I use archival records such as city park reports, newspapers, and nursery catalogues to understand how urban forests have developed over the past century.

Co-production of knowledge and citizen science. My studies take a participatory approach to the research process, involving colleagues from the professional urban forestry sector to generate new research questions, design projects, and interpret results. This kind of co-production of knowledge leads to more actionable research that addresses the real-world needs of resource managers. For example, many local urban forestry organizations have used volunteers in data collection (i.e., citizen science), and research on citizen science data quality enables program managers to decide the appropriateness of volunteer-generated data for their needs.

Research Interests

urban ecosystems; urban forests; tree demography; citizen science; participatory research; urban tree canopy cover; urban environmental history

Why This Research is Important

Cities in the United States and around the world have engaged in ambitious programs to plant trees and increase tree cover. Research about temporal dynamics in urban forests - whether field studies lasting a few years, land cover change analysis over several decades, or historical assessments stretching back over a century - allows a deeper understanding of how change happens in these deeply entwined social-ecological systems. Furthermore, the spatial patterns observed in today's urban forests - such as tree cover and species composition - can only be fully understood in light of the temporal dynamics that produced those patterns.