Stream restoration in Christchurch
Things have come a long way in the Garden City since the days when meandering streams were channelled and boxed, creating poor habitat for native plants and animals. The Christchurch City Council has been actively involved in stream restoration for more than a decade, conducting extensive riparian planting and reinstating natural stream banks.
Scientists from NIWA, EOS Ecology, and the council have recently published the results of a long-term study of the effects of the restoration work in five urban streams. Riparian planting improved in-stream habitat conditions, resulting in higher fish densities in some streams. Desirable invertebrate communities, such as caddisflies and mayflies, however, did not come back. NIWA and EOS Ecology are investigating the continued absence of these ‘good’ invertebrates. Preliminary results suggest high sedimentation and heavy metal contamination may be compromising their survival.