New urban forest research sheds light on the risk of pest invasions

Forest pest risk analysis research is often limited to natural forests. However, urban forests are highly susceptible to invasions, and often experience the most substantial impacts. To characterize forest pest threats appropriately, Forest Service scientists are working to better understand the urban distributions of their host trees.

Urban street treesDespite serving as gateways for forest pest invasions, most urban forests are not well understood. What trees are there, where are they, and how many? Characterizing urban forests is crucial in order to track pests effectively. With colleagues, Southern Research Station scientists addressed the lack of urban tree data using a three-step modeling approach. As a test, they mapped distributions of maple, ash, and oak trees in urban areas across the eastern and central U.S. They modeled relationships between tree inventories and canopy cover, climate factors, and demographic trends. This allowed them to estimate the total number of each tree type, even if an urban area had no tree inventory or an incomplete one. The results of this work were described in the journal Forest Ecology and Management. Now, the research team is adapting the model to map the distribution of street palms around the U.S. ahead of any invasion by a major pest such as the coconut rhinoceros beetle or the red palm weevil. These insects are globally important agricultural pests, but their U.S. impact would be largely constrained to urban areas where palms line the streets. The costs of removing and replacing infested palms could be substantial in places such as south Florida, where street palms are common. This ongoing research facilitates better assessment of the spread and potential impacts of invasive urban forest pests.


Pictured: Trees in urban areas lack the structural and species diversity of natural forests. This makes them ideal hosts for invasive pests, and the subsequent damage can be a major cost for cities and municipalities. Photo by Luana Vargas, courtesy of the Desert Botanical Garden and

Related publications:

Research Partners: USDA Forest Service Forest Health Monitoring (FHM) Program. 

External Partners/Collaborators: North Carolina State University, Virginia Tech, Cornell University, McGill University, Canadian Forest Service, USDA Animal and Plant Health Inspection Service (APHIS).

Contact: Frank Koch, Research Ecologist, Eastern Forest Environmental Threat Assessment Center,

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