Sustainable Catchment Management: Thresholds for Ecological Sustainability

The majority of New Zealanders live in urban environments, and national and regional community surveys have shown that improving the state of our urban waterways and environment are high priorities. An understanding of the real and perceived driving forces and pressures contributing to the sustainability of the natural resources of urban (including peri-urban) catchments, and the thresholds at which development is no longer sustainable are necessary if management goals are to be met. The points or zones of change from one ecological condition to another, usually resulting from a change in ‘pressure’ or ‘development’ are key ‘thresholds’ of change in ecosystems. In this paper we present the results of reviews and investigations that consider threshold values for aquatic ecosystem sustainability in urban and peri-urban environments as measured by indicators of the state of stream health at the catchment level. In particular our focus is on connectivity and fragmentation of biophysical stream and catchment attributes. Threshold values can be used in sustainable catchment management planning or as goals for enhancement and restoration.