Reclaiming urban vacant land to manage stormwater and support insect habitat

Urban green spaces can provide important wildlife habitat and ecosystem
services. In legacy cities, built structures are demolished as populations
dwindle, resulting in vacant land. Vacant land constitutes an opportunity
to establish green infrastructure that provides multiple ecosystem
services. Our objective was to determine whether establishing green
infrastructure on vacant land to manage stormwater could provide insect
habitat in the legacy city of Cleveland, Ohio, U.S.A. Two green
infrastructure treatments were implemented on vacant land in the historic
Slavic Village neighborhood in 2014 and 2015: rain gardens (lower cost)
and bioswales (higher cost). We hypothesized that rain gardens and
bioswales would support more abundant, species rich insect communities
compared to unaltered vacant lots. Wild bees (Hymenoptera: Aculeata) and
lady beetles (Coleoptera: Coccinellidae), two insect groups of
conservation concern, were sampled during the summer (June–August) from
2014 to 2016 using pan traps and yellow sticky card traps. Local
vegetation and temporal variables were measured. Generalized linear mixed
effects models evaluated whether insect biodiversity varied with
treatment, habitat variables, site, and time. We collected 3,004 bees from
pan traps and 5,438 lady beetles from yellow sticky card traps during this
study. Bee biodiversity was similar among treatments. In 2014, alien
Coccinellidae abundance was higher in vacant lots compared to rain
gardens. In 2015 and 2016, alien Coccinellidae were marginally more
abundant in rain gardens compared to vacant lots and bioswales, while
native Coccinellidae abundance was significantly higher in vacant lots. In
the short term, establishing green infrastructure on vacant land can
improve stormwater management without compromising the quality of vacant
land as insect habitat.