Urban forest health: Developing a model to prioritize and inform management in New York City
Urban forest management is an emerging field with many cities in the United States engaging in large scale urban greening projects. New York City's municipal park system is home to nearly 6,000 acres of natural forest which provide incredible ecological and social benefits to over eight million people. While efforts and programs exist to restore and protect these spaces, management recommendations and priority setting is complex due to variable conditions found in an urban setting. To advance the management and understanding of the urban forest in New York City a comprehensive data driven assessment was conducted across all forest types in city owned parkland. Using a suite of ecological health and threat metrics collected during this citywide forest assessment, we created a weighted equation of forest health and threats to use in prioritizing management, setting goals and developing ecological thresholds. Using standardized z-scores for each metric, two weighted equations were developed to describe forest health and forest threats. These health and threat values for parks and forest patches can be mapped across a management matrix to serve as a customizable tool for decision making. This resulting matrix uses ecological data to advance land management and conservation in urban forests.
We show how an integrated equation can be used to help plan and prioritize management in complex urban forests. Using data collected during the New York City forest assessment we found that distance to forest edge, advanced native regeneration, and native herbaceous and seedling cover, and leaf litter depth were more important (p < 0.001) in describing forest health than native species richness or native canopy overstory. The metrics most important in describing urban forest threats included forest patch size and exotic invasive vine growth compared to human modifications to the soil and trash found within the forest. Using a forest management priority matrix that considered three main categories 1) conservation 2) management and restoration and 3) fundraising and planning, we mapped our forests based on dominant vegetation, park and patch size. Our results provide specific guidance for focusing forest management across a large metropolitan region as well as providing indicator metrics for health and threats within complex urban systems. This approach can be adapted to other forest types and cities across the nation serving as a valuable tool and approach for guiding land management and restoration decisions.