PS 20-28 - Socio-economic diversity of orchards' settings in an urban environment

Abstract: The world is rapidly becoming urbanized, and this represents a major threat to biodiversity. Thus, how green spaces are managed will influence biodiversity as well as ecosystem services. Urban agriculture has emerged in the last couple of decades as a possible way to manage urban green areas and provide habitat for a diverse range of insect pollinators. A more recent trend is the increased use of fruiting trees as part of a broad range of crops grown in cities. Unlike community gardens, which can result in a quick return on investment, orchards require a greater investment and take longer to produce. Another counter point is that urban orchards tends to have greater inter-year variability in yield. We hypothesized that orchard floral diversity will correlate with socio-economic diversity across St. Louis metro region.

We partnered with a local agriculture non-profit, Seed St. Louis, and identified 52 orchards throughout the city of St. Louis. Of those, we selected nine orchards to represent the urban gradient across the metropolitan area (three in each urban, suburban and exurban). Selected orchards are at least 1 kilometer apart from each other. All trees were marked with a unique number and identified to species or variety. Environmental and demographic data was extracted via GIS at 500 and 1000m scales.

We identified a total of 171 trees across the nine focal orchards (mean = 19 ± 5.6). The largest orchard had 50 trees, while the smallest had seven. All orchards had a variety of tree species. The most common trees were apples (n = 41), followed by pears (n=32) and peaches (n=27). Other fruits included plums, apricots, and cherries. The native fruit paw paw (Asimina triloba) was recorded in three orchards (n=5). We also recorded several nut trees, almonds (4), Chinese chestnut (1) and walnuts (1). Most orchards are less than five years old and a majority are located in areas of the city considered food desserts. There was a weak but significant positive correlation between income and the number of trees per orchard. There was also a weak correlation between impervious area and tree abundance. We will continue this work over the next two years and expand the number of orchards included in the research.