TreesCount! 2015 is the third citizen participatory inventory of street trees in New York City. Every ten years, NYC Parks has worked with volunteers to record the location, size, species, and condition of all public curbside trees. Volunteer street tree inventories promote increased awareness of the importance of the urban forest and support municipal urban forest management. New York City’s prior street tree inventories in 1995 and 2005 led to advances in customer service, funding for routine street tree pruning, the quantification of the ecological and economic benefits of trees, and a major urban greening campaign called MillionTreesNYC.

From May 2015 to October 2016, over 2,200 citizen mappers spent almost 12,000 hours using high tech mapping tools with survey wheels, tape measures, and tree identification keys to create a spatially accurate digital inventory of NYC’s street trees. The simple and intuitive mapping method was designed by a local non-profit, TreeKIT. The mapping technique leveraged a municipal geospatial dataset of curb edges to solve urban locational accuracy issues. The data collection method was integrated by the software company Azavea into a web application featuring online training modules, event management and community engagement tools to provide a seamless volunteer experience. The TreesCount! user experience was designed to scale for thousands of non-technical volunteers to collect standardized and consistent data with minimal training. To inspire public engagement, the web app featured real-time inventory metrics for individuals as well as partner community groups, and a progress map on the status of the data collection campaign. Powered by the public, TreesCount!2015 demonstrated that citizen science can support the collection of high quality spatial data for municipal urban forest management and ongoing citizen engagement.

Data collectors recorded eleven variables on each tree which included biological, structural, and infrastructural information. To learn more about each variable collected in the census, click here.

TreesCount! 2015 was the third decadal street tree census, and largest citizen science initiative in NYC Parks’ history. The 2015 census attracted 2,241 active volunteers, more than doubling involvement from the 2005 census; with the largest increases in participation seen in Brooklyn and the Bronx. The results of the census show that there are 666,134 trees planted along NYC’s streets, of which volunteers mapped and surveyed 225,595 (34%).

One of the recruitment strategies employed by NYC Parks in 2015 was to leverage existing relationships and build new ones with partner groups to reach individual volunteers. This strategy resulted in the involvement of 64 community groups who collectively mapped over 15% of block edges in the city. These groups ranged in size from large groups like the Prospect Park Alliance and the Lower East Side Ecology Center, to smaller groups like the Sunset Park Block Association and the Jackson Heights Beautification Project. The ten community groups with the most participants are noted in figure below:

NYC Parks also worked with US Forest Service social scientists at the NYC Urban Field station to survey volunteer census participants. Just over 27% of volunteers responded to the survey. The survey indicated that volunteers were students, retirees, tourists, taxi drivers, artists, and engineers, among many other backgrounds. For many respondents, volunteering provided them with a link to nature, taught them a new skill, or gave them a chance to explore their neighborhood and their city. Additionally, 59.6% of the volunteers that responded to the survey had never volunteered with NYC Parks before, and 46.9% had never worked with trees. We also learned from the survey that at least 11 participants in 2015 also volunteered in the first census in 1995.

NYC Parks also studied the quality of the data collected by different categories of census participants. The emphasis of the volunteer training was for participants to feel comfortable using their training and survey resources to make their best educated guess. Volunteers were also reminded that NYC Parks had a data quality process in place to identify spatial inaccuracies. In addition to volunteers, NYC Parks also hired and trained data collection staff in order to complete the census. To learn more about the data quality assurance process, and how volunteer-collected data compared to data collected by dedicated NYC Parks staff, check out this report.

Click here to read more about volunteer training events, which took place throughout the course of the census.

Check out what motivated volunteers to count trees.

The 2015 Street Tree Census showcases technological advances across several dimensions, emblematic of a forward-thinking, transparent and community-oriented Parks department. The most notable differences from past efforts involved the baseline geospatial data, methods for mapping trees, and techniques for mobilizing volunteers and tracking progress. We also used technology to check the data for accuracy after it was collected. And the final deliverable of the census— the web map giving the data back to the public and updated daily for education, stewardship, and general awareness—is the enduring product of this high-tech vision for urban forestry in NYC. We also shared all of our datasets—from 1995, 2005 and 2015—with the public through the NYC OpenData portal so that anybody can analyze and learn about changes in the street tree population over time. Together, these technologies facilitated an enormous citizen science engagement project, a spatially precise street tree map, a living web application for public engagement in the urban forest, and a comprehensive dataset for anybody to download.