Wilson et al. 2026 - Older urban forest fragments support parasitoid wasp spillover into adjacent landscapes. - Full dataset

Dataset for Wilson et al. 2026 - Older urban forest fragments support parasitoid wasp spillover into adjacent landscapes. Abstract:Urban reforestation programs seek to offset the detrimental effects of urbanization on tree cover and associated ecosystem services. One understudied ecosystem service that urban forests may provide is biological control of insect pests in adjacent managed landscapes by providing habitat for natural enemy arthropods. As forest fragments mature, ecosystem services such as biological control may accrue within fragments and in adjacent landscapes. We measured arthropod natural enemy abundance within and surrounding 20 urban forest fragments in Lexington, Kentucky, USA, that were each planted between 1999-2019, representing a 20-year chronosequence. We collected natural enemies at three locations within fragments and at 0, 5 and 10 meters away from fragment edges using pan traps. We also measured site size and impervious surface cover surrounding each fragment at a 100 m and 1000 m radius. Natural enemy spillover was higher in older forests relative to newer forests, and this effect was more negative for smaller sites relative to larger sites. Parasitoid wasp spillover was higher outside of older fragments relative to newer fragments while no other natural enemy group was affected. Finally, natural enemy abundance within fragments was positively associated with impervious surface cover at a 100 m radius. Our findings indicate that reforestation in urban areas can support natural enemy spillover to adjacent landscapes and this effect appears to increase over time since establishment. Urban forest fragments may reduce the severity of pest outbreaks in adjacent managed landscapes.