In-stream habitat unit additions: If you build it, will they stay?

Abstract

River restoration in New Zealand is often focussed on riparian planting, hoping water quality improvements will improve overall ecosystem health. These interventions are important, but successful community recovery requires additional steps to improve aquatic habitat. We trialled the addition of simple, instream habitat units as a practicable restoration tool and opportunity to investigate community recovery mechanisms. Habitat units were designed to be simple to construct using sustainable, readily available materials, and optimised to create heterogeneous habitat and refugia for invertebrates. Here, we present the outcome of three trials: (1) a preliminary trial as a proof of concept that habitat addition can facilitate establishment of drifting colonists; (2) a trial in streams with varying physical characteristics to identify methodological constraints; and (3) a project co developed with local iwi (indigenous people) in NZ, demonstrating the value of indigenous knowledge in restoration.