Acore contributor to the degradation of water quality has been the growth of intensive dairy farming over three decades which has left many South Island rivers with deficient streamflows and problematic nitratebased eutrophication. Between 1990 and 2020, the number of dairy cattle in the Canterbury region increased from 113,000 to over 1.2 million. Included in that number are Ngāi Tahu's own cattle; the business arm of the iwi has a substantial farming investment.
