On an ecological level, most of the animal translocations (mudfish, crayfish, mayflies) when introduced had high initial survival, however after six months or less the numbers of each dropped dramatically. Limited colonist organisms and lack of physical habitat are both factors preventing population growth; however ecosystem recovery is also dependant on catchment and long-term processes such as, but not limited to:
- storm water
- contaminated sediment
- pests and predators
- climate change
- campus and suburban expansion and development
Introduced species are sourced from the Christchurch City outskirts, so once biodiversity ‘hotspot’s are established and city planning allows, translocations may have greater success.
While the Okeover Stream has been improved readily due to recognition of its potential to be effectively rehabilitated and its span mainly on campus, work on the Avon requires significantly more effort and hence is slower to occur.
Pre-Europeans– Waitaha settle the Avon (Otakaro) River catchment using it for transport and fishing for eels, whitebait, flounder and collecting pipi.
Pre 1900s– European settlers arrive and import their own native flora to revegetate sections of the plains; small fishing trades set up
1900-1990– Wetlands drained, increasing development of Christchurch city degrades land farmed extensively around the Avon
1970s– University construction begins on Ilam site; extensive use of Avon as drain for high groundwater runoff
1996 – Student initiative leads replantation of mown banks of Avon on campus, restoration process of Okeover Stream on University of Canterbury campus
1998 – Riparian plantings in the upper reaches of Okeover to reduce run-off and increase stream shading; 10 individual planting events
1999 – Pool and riffle sequences created to increase habitat diversity by oxygenating the water and flushing fine sediment
2000 – In-stream habitat improved involving boulder addition and plantings for flow and habitat heterogeneity and to establish wetland
2001 – Sediment traps constructed to disperse sediments and increase riffles; wetland and forest plantings added along Okeover
2003 – Mayflies population trialled and headwaters rehabilitation begun; riffle-pool sequences created using plantings and stone placements; headwaters rehabilitation begun
2004 – Gold Award for sustainable headwaters design (NZILA); mudfish and crayfish introduced
2005 – Eel housing, harakeke softening, and meanders rehabilitation projects
2006+ - Stormwater investigations at depth by university
University of Canterbury: current and future Goals
The University of Canterbury Waterways Plan (2006) expresses the university’s intention to continue protecting these “self-sustaining ecosystems, which have a natural physical character and function”, so that they might support indigenous plant and animal species found in a lowland South Island tributary. It also asserts that the waterways will be incorporated as “an integral part of the University’s programme of research and teaching”, and that the contribution of sustained wildlife by means of the streams is highly considered and greatly appreciated.
As well as these ecological goals, social implications for the urban waterways management are to raise waterway awareness both in the University and local communities, improve peoples understanding of stream ecosystem functions, inhabitants and requirements, and to increase participation in the waterways vision.
Information sourced from the University of Canterbury website, www.canterbury.ac.nz, and the Sustainability Department of UoC, www.sustain.canterbury.ac.nz