Earth’s surface is so significantly shaped by human activity it is critical to understand how to preserve and promote species in human-dominated ecosystems. Although we see a rise in urban living across the globe, due to protected economic downturn and the recent foreclosure crisis, many United States cities have lost substantial population in recent decades. This has left municipalities with the task of demolishing abandoned residential structures, creating parcels of vacant land. Cleveland, Ohio which has over 20,000 vacant lots covering 1,450 hectares of land area. These greenspaces have the potential to serve multiple environmental functions including species conservation, storm water retention, and local food production. Worldwide urban agriculture has grown rapidly and requires the work of beneficial arthropods including spider predators for sustainable crop production. We quantified the current ecological value of vacant land to support spider biodiversity using pitfall trap and assessed how its conversion to support urban agriculture affected these species and their potential diet using artificial sticky webs of the sheet-web spiders (Linyphiidae) and via molecular gut contents of common linyphiid species.
Vacant lots supported high spider diversity, with 30% of genera known to occur in the state of Ohio found within them. Conversion of vacant lots to urban farms resulted in a reduction in the abundance of spiders, particularly Linyphiidae, and a significant difference in spider community composition. We found no difference in the dietary niche breadth of Linyphiidae among vacant lots and urban farms. However, across both habitats dietary breadth increased within microsites dominated by grass cover versus bare ground or mulch. Collembola, a key prey of sheet-web spiders, were significantly more abundant in sticky webs collected from vacant lots versus urban farms. Collembola were also more numerous in microsites dominated by grass versus bare ground, mulch, or flowering plants. We are currently analyzing the results of our molecular gut content analysis. We anticipate these data to provide a far greater understanding of the food web linkages among common linyphiid species and provide a study system to examine how local habitat structure and landscape variables influence niche breadth and overlap among competitors. Our findings demonstrate that greenspace design and management do influence the diversity, abundance, and composition of spider communities. Encouraging alternative prey populations in urban farms by replacing bare ground or mulched areas with vegetation may encourage spider populations and the level of biocontrol service provided.