Optimizing Native Pollinator Habitat Design for UrbanBotanical Gardens Evaluation

Thesis Abstract

Urban botanical gardens increasingly rely on designed pollinator habitats to sustain native bee and butterfly communities, enhance plant-pollinator networks, and improve ecosystem services within metropolitan landscapes. However, practical guidance on how to optimize habitat design for urban contexts remains fragmented, risking suboptimal biodiversity gains and wasted management resources. This study aims to optimize native pollinator habitat design for urban botanical gardens through an integrated design–implementation–evaluation approach, with specific objectives to (i) identify habitat configurations that maximize pollinator richness and visitation rates, (ii) evaluate plant-pollinator interaction networks under different design prescriptions, (iii) assess maintenance requirements and cost-effectiveness of each design, and (iv) develop an evidence-based decision-support framework for garden managers. The theoretical basis integrates the habitat suitability theory and network resilience theory to explain how plant assemblages and spatial arrangement influence pollinator community structure and ecosystem stability in urban mosaics. A mixed-methods design combines quantitative experimental trials with qualitative stakeholder insights. The study adopts a quasi-experimental, multi-site field trial conducted in four metropolitan botanical gardens, each implementing three distinct habitat designs (A) high-flower density with continuous forage, native plant guilds grouped by phenology, and structural diversity; (B) modular microhabitats emphasizing nectar-providing forbs and larval host plants distributed along pollinator corridors; and (C) minimal intervention with naturalistic succession and adaptive planting. Over two growing seasons, 12 experimental plots (each 20 m × 20 m) per site will be established, yielding 144 plots in total. Pollinator activity will be monitored using standardized transect observations and pan-trapping, with weekly counts across peak foraging months (April–October). Plant-pollinator interactions will be mapped through direct observation and validated with DNA metabarcoding of pollen on captured bees, enabling construction of interaction networks. Vegetation metrics (species richness, functional trait composition, ontogenetic stage), abiotic variables (soil moisture, light availability), and maintenance costs will be recorded monthly. Local beekeeper and horticultural staff interviews will elicit governance, maintenance feasibility, and perception of sustainability. Data will be analyzed using generalized linear mixed models (GLMMs) to test effects of design on pollinator richness and visitation rates, multivariate analyses (PERMANOVA, NMDS) to compare interaction networks, and cost-effectiveness analysis to evaluate economic feasibility. Structural equation modeling will evaluate mediating pathways among plant traits, habitat configuration, pollinator responses, and network robustness. A thematic analysis of stakeholder interviews will identify implementation barriers and enablers, triangulated with observational data. The study will test hypotheses grounded in habitat suitability theory predicting higher pollinator metrics where plant guilds provide continuous floral resources, and network resilience theory predicting more robust networks with functional complementarity and spatially diverse provisioning. Key expected findings include (i) design A yielding the greatest pollinator richness and visitation rates during peak forage periods, (ii) more modular and temporally diverse interaction networks in design B, indicating enhanced resilience to phenological mismatches, and (iii) design C providing acceptable ecological gains at lower maintenance cost, informing trade-offs. The research is anticipated to contribute to knowledge by integrating urban habitat design with empirical pollinator ecology, refining design guidelines for urban botanical gardens, and delivering a replicable evaluation framework adaptable to other urban green spaces. The main conclusion will articulate a validated evidence-base for prioritizing habitat features (plant phenology, structural heterogeneity, and corridor connectivity) that maximize pollinator support while remaining cost-effective for garden managers. Recommendations will address scalable implementation strategies, standardized monitoring protocols, and policy implications for urban biodiversity planning.