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Weighing values and risks of beloved invasive species: The case of the survivor tree and conflict management in urban green infrastructure

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Urban Forestry & Urban Greening


A critical aspect of urban green infrastructure management hinges on the treatment of native and invasive species. Invasive species are widely seen as a major threat, yet the context-specific values people have for some of these species pose challenges for their management. Here, we offer a case study of the 9/11 survivor tree, a Callery pear (Pyrus calleryana Decne.) that survived the terrorist attack on September 11, 2001 at the World Trade Center in New York City and has since become a symbol of resilience. That individual tree and its progeny are beloved and they are also characterized as invasive. As part of the longitudinal research of the US Forest Service Living Memorials Project, we report findings from semi-structured interviews conducted with eight stewards from six living memorial sites that have survivor trees and with five individuals who have expert knowledge of the survivor tree, its propagation and dissemination. We find that some people see the tree primarily as a heroic symbol of hope and resilience, others see it primarily a threat to personal property, safety, and to biodiversity, which overshadow its social value. We conclude that Callery pears are associated with multiple, conflicting values, having the power to both unite and divide around issues of recovery and resilience in social and ecological spheres. Whereas managers and policy makers tend to have absolute views of invasive species as negative, living memorial stewards and others affected by tragedies have personal relationships that significantly influence their attitudes and practices toward a line of Callery pears. We conclude that urban green infrastructure management might best be seen as a highly contingent and value-driven practice, and that understanding these social meanings may lead to better stewardship of the whole social-ecological system.


Invasive trees; Living memorial; Callery pear; Pyrus calleryana Decne.; Resilience; Urban social-ecological system


McMillen, Heather; Campbell, Lindsay K.; Svendsen, Erika S. 2019. Weighing values and risks of beloved invasive species: The case of the survivor tree and conflict management in urban green infrastructure. Urban Forestry & Urban Greening. 40: 44-52.

Last updated on: January 7, 2020