Green infrastructure has the potential to play an increasing role in conserving biodiversity as urbanization increases in the United States and internationally. Green infrastructure can be broadly defined as an inter-connected system of natural areas and open spaces that conserves the values and functions of natural ecosystems, promotes clean water and air, and provides an array of ecosystem services to both people and wildlife. Previous studies indicate that green infrastructure can either promote or inhibit biodiversity, but more research is needed to understand and quantify the benefits of green infrastructure. The purpose of this study is to investigate and quantify plant biodiversity patterns and ecosystem functioning relationships within various types of green infrastructure in Portland, Oregon. Results will be used to explore potential tradeoffs between use of green infrastructure for water-related ecosystem services and biodiversity conservation. Select green infrastructure sites will be analyzed based on geographic location and across a range of site sizes. Total number of genera and abundance data will be collected to calculate plant biodiversity, which will then be used to explore species-area relationships and conservation value of sites of different sizes in various contexts. Additionally, interviews will inform our understanding of public perceptions of green infrastructure.
Using City of Portland geospatial data on street trees, the results indicate that of the 218,491 surveyed street trees, there are 146 street tree genera. The most common genera is Acer with 57,755 trees (26.5 percent of total), then Prunus with 25,816 street trees (12 percent), and Pyrus with 11,699 street trees (5 percent). In terms of street tree condition, 55.4 percent are classified as “fair”, 35.3 percent as “good”, 8.4 percent as “poor”, and 0.85 percent as “dead”. A variety of figures were created to show the number of genera and frequency of street trees per 500 m2 grid cell and for each of Portland’s neighborhoods. The results indicate that street trees biodiversity and density are not equally distributed within Portland. As this research continues, the results will help inform land managers about best practices for promoting plant biodiversity and ecosystem functioning within various types of green infrastructure. This project is a new research effort that is being conducted in addition to and in conjunction with the Urban Water Innovation Network (UWIN) National Science Foundation Grant Award #1444758, a nationwide consortium of universities and partners that seeks to address various challenges to urban water systems and urban water sustainability.