Urban Green Space Configuration, Pesticide-Free Management, and Wild Bee Assemblage Recovery in City Parks: Evidence From a 5-Year Citywide Management Intervention

This study investigates effects of pesticide-free management, wildflower sowing, and connected green corridor design on wild bee species richness, abundance, and functional diversity recovery in Copenhagen city parks over 5 years within the context of urban ecology and pollinator conservation biology, an area of growing scientific importance given its implications for urban green space management policy for pollinator conservation, pesticide-free city park program design, and pollinator corridor network planning in European cities. Using randomized cluster controlled design (48 parks, 16 per arm), annual wild bee pan trap (3 colors x 12 stations/park) and timed transect surveys, bee identification to species, and functional diversity (FDis, FRic) analysis, we examine pesticide elimination removing sublethal exposure reducing bee navigation, reproduction, and immunity, combined with wildflower resources restoring forage diversity that supports specialist bee functional groups excluded from conventional low-diversity turf in 48 parks (16 per treatment arm), annual surveys 2019-2024: 5 survey years x 48 parks x 3 replicate visits = 720 survey occasions; 18,420 individual bees identified across 84 species drawn from Copenhagen municipality parks (3-28 ha) stratified by area and impervious surface fraction, minimum 500 m inter-park distance for independence. Results indicate that pesticide-free + wildflower arm shows 48.4% species richness increase and 2.84-fold abundance increase by year 3, versus 18.4% richness and 1.48-fold abundance in pesticide-free only, and 4.2% richness gain in conventional; functional diversity FDis significantly higher in wildflower arm from year 2 (p < 0.001), with 48.4% richness increase; 2.84-fold abundance in pesticide-free+wildflower arm by year 3 as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to urban ecology and pollinator conservation biology and carry actionable implications for the design of programs and policies targeting urban green space management policy for pollinator conservation, pesticide-free city park program design, and pollinator corridor network planning in European cities.