Sustainability and coincidence of riparian vegetation and in-stream macroinvertebrate communities in Auckland's water sensitive developments

Abstract

Water Sensitive Urban Design has much in common with the New Zealand (NZ) practice, Low Impact Urban Design and Development (LIUDD). In New Zealand, both terrestrial and aquatic ecosystem protection and re-creation are essential elements of greenfield developments that conform to LIUDD. This paper reports on investigations into stream and terrestrial riparian plant communities within gulley environments in headwater LIUDD sub-catchments in Manukau, Auckland. The monitoring of stream macro-invertebrates and riparian plant communities reveals the degree of coincidence of the health of these complimentary habitats. Additionally, the sustainability of planted riparian communities in adjacent countryside living sub-catchments was investigated. Vegetation was sampled using the NZ Vegetation Survey Recce method. Characteristics recorded included ground cover, top height, canopy-cover and species composition. Statistical methods showed how forest structure and composition changed in relation to three factors: age, by individual site, and by management. Management was assessed from landowner interviews. Results showed expected and adequate growth of planted trees, the need for further control of weeds, and very low rates of natural seedling establishment. This information is used to predict the sustainability of these plant communities and to provide advice to landowners on appropriate interventions including supplementary planting of future forest canopy species.