Saving water, supporting pollinators: Greening new residential developments through soil remediation and diverse native plantings

Abstract

Pollinators provide key ecological services, but are declining worldwide, mainly due to habitat loss. Suburban development is a major land use change globally, and these landscapes can be designed and managed to support pollinator conservation. Incorporating native plants that are drought tolerant into suburban landscapes benefits pollinators and may reduce irrigation demands. However, degraded urban soils may be a barrier to native plant establishment. We conducted an experiment with 27 native plant species to test two hypotheses: a) adding compost to soils prior to planting would increase native plant growth and floral production, leading to more abundant and diverse pollinators, but b) irrigation would not have these effects because of native plants’ local adaptations. The experiment consisted of 16 plots treated with factorial irrigation (as-needed or scheduled) and compost (compost-amended or not) treatments. We examined plant-pollinator interactions across two years using visual counts of individuals visiting open flowers and recorded 4061 potential pollinators from 156 different species. Compost doubled floral abundance and greatly increased pollinator abundance and species richness. The as-needed irrigation treatment reduced water usage by 79 % relative to weekly irrigation without impacting floral or pollinator abundance. Top pollinator-attracting plants changed across seasons, supporting distinct pollinator assemblages. Our findings show that remediating soils with compost and enhancing native plant diversity in new suburban landscapes can enhance the ecological value of native plants to pollinator communities. Research fostering collaboration among ecologists, landscapers, and developers can translate into large-scale implementation of more sustainable landscape approaches that achieve multiple conservation goals.