Vacant land in cities can comprise a substantial fraction of the total land area, from 5 to 11% in just the cities we are focusing on. This land can vary widely in its land cover or use- e.g. bare soil or abandoned buildings to fields or community gardens. This variability in cover or use can lead to a correspondingly wide range in potential ecosystem services or disservices, such as stormwater retention or exacerbation of the urban heat island effect. Our objective is to assess spatial distribution and land cover of vacant properties in multiple cities across the United States, and use this data on land cover and other landscape properties to assess the impacts of these vacant lots on ecosystem services and disservices. The cities examined represent a range in biophysical and geographic settings and include Baltimore MD, Miami FL, New York NY, Phoenix AZ and Portland OR. Specifically, we are assessing land cover using high-resolution land cover rasters derived from satellite imagery, as well as Google Street View imagery, in conjunction with city property databases that identify vacant lots. We are evaluating stormwater absorption using the NRCS Curve Number method to model runoff based off of land cover and soils data, and are also doing field surveys of soil infiltration rates across the city of Phoenix.
Results/Conclusions
Examining vacant lot land cover, we find variability between our cities according to biophysical setting and age. In Phoenix, a desert city where rapid development has occurred recently, the majority of vacant parcels are bare earth which has been passed over by development. In our several humid cities, we find a mix of vacant properties dominated by vegetation as well as impervious surfaces such as abandoned buildings or pavement. We expect ongoing Google StreetView analysis to provide additional insight to more specific uses of vacant land, such as community gardens or parking lots. Stormwater retention across these lots is strongly controlled by infiltration capacity of these land covers and underlying soils, and we expect ongoing field surveys of infiltration to highlight needs for increased resolution in spatial soils data. Stormwater modeling across the cities has identified lots which are the greatest contributors of runoff. In the future, we hope to add assessment of heat mitigation (or exacerbation) by vacant lots to this analysis. Using these results we can prioritize interventions to enhance ecosystem services such as stormwater retention via green infrastructure or other strategies.