Planted Riparian Buffer Zones in New Zealand: Do They Live Up to Expectations?

• Published in: Restoration ecology Vol. 11; no. 4; pp. 436 - 447
• Main Authors: Parkyn, Stephanie M., Davies-Colley, Rob J., Halliday, N. Jane, Costley, Kerry J., Croker, Glenys F.
• Format: Journal Article
• Language: English
• Published: Boston, MA, USA Blackwell Science Inc 01.12.2003; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Conservation, protection and management of environment and wildlife; Environmental degradation: ecosystems survey and restoration; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; habitat; invertebrates; rehabilitation; riparian; stream; Synecology; temperature; water quality; New Zealand; Oceania; New Zealand, North I; Buffer zone; Plant; Green area; Riparian; Water quality; Ecological recovery; Rehabilitation; Invertebrata
• ISSN: 1061-2971; 1526-100X
• DOI: 10.1046/j.1526-100X.2003.rec0260.x

River and stream rehabilitation projects are increasing in number, but the success or failure of these projects has rarely been evaluated, and the extent to which buffers can restore riparian and stream function and species composition is not well understood. In New Zealand the widespread conversion of forest to agricultural land has caused degradation of streams and riparian ecosystems. We assessed nine riparian buffer zone schemes in North Island, New Zealand that had been fenced and planted (age range from 2 to 24 years) and compared them with unbuffered control reaches upstream or nearby. Macroinvertebrate community composition was our prime indicator of water and habitat quality and ecological functioning, but we also assessed a range of physical and water quality variables within the stream and in the riparian zone. Generally, streams within buffer zones showed rapid improvements in visual water clarity and channel stability, but nutrient and fecal contamination responses were variable. Significant changes in macroinvertebrate communities toward “clean water” or native forest communities did not occur at most of the study sites. Improvement in invertebrate communities appeared to be most strongly linked to decreases in water temperature, suggesting that restoration of in‐stream communities would only be achieved after canopy closure, with long buffer lengths, and protection of headwater tributaries. Expectations of riparian restoration efforts should be tempered by (1) time scales and (2) spatial arrangement of planted reaches, either within a catchment or with consideration of their proximity to source areas of recolonists.