Monitoring Young Tree Survival with Citizen Scientists: The Evolving Tree Checkers Program in Philadelphia, PA

Citizen science programs are not static; they change over time in response to new program priorities and emerging technologies, as well as to improve work flow for program staff and volunteers. In this article, the authors present a case study of an evolving urban forestry citizen science program at the Pennsylvania Horticultural Society, a nonprofit organization in Philadelphia, Pennsylvania, U.S. The Tree Checkers program involves tree stewards recording data each summer about recently planted tree survival, growth, crown vigor, and maintenance, while also engaging their neighbors to encourage proper tree care. The program began in 2011, but changed in 2016 to use a new online data collection tool that was integrated into a larger tree data management system. Tree Checkers has also shifted to be more focused on rigorous data to report program performance and share information with researchers, whereas the earlier years of Tree Checkers were centered on enabling and encouraging neighborhood tree stewards to plan for tree care. A recent data quality evaluation showed that volunteer data was reasonably consistent with data reported by more experienced interns for tree survival, vigor, and trunk measurements, but stewardship variables were not interpreted and recorded consistently. By making rigorous data more central to Tree Checkers, program staff also sought to institutionalize monitoring within the organization, allowing for direct comparisons of outcomes year-to-year. The authors close with lessons learned that are relevant to other organizations seeking to create or enhance outcomes monitoring programs with citizen scientists.