Conditions in streams and rivers vary widely across New Zealand’s diverse landscapes. Even in streams and rivers not impacted by humans, stream conditions and the types of animals present can vary a lot.
The invertebrates living in streams and rivers, such as snails and insect larvae (referred to as macroinvertebrates), have different levels of tolerance to pollution and damage to habitat. This allows freshwater scientists and managers to use measures of stream macroinvertebrates as indicators of ecosystem health in our waterways.
When doing this, it is important to compare to a reference state, or what the stream would be like without any negative impacts from human activity. The reference state can vary a lot between stream types. Not all stream types have an unimpacted example for comparison, so we need models to predict what the reference state would look like.
This report develops a model predicting the reference state for stream macroinvertebrates across New Zealand. It builds upon initial work to develop a proof-of-concept for this technique in 2017 (see Macroinvertebrate metrics for the National Policy Statement for Freshwater Management). This will help freshwater scientists and managers understand the potential reference or unmodified condition in different stream and river types. This will improve the information gained from stream macroinvertebrates and help inform assessment and restoration.