However, eutrophication is accelerated by human activities and is the main problem facing New Zealand lakes. Most eutrophic lakes are found in the North Island, on land dominated by pasture.
Lakes receive nutrients from fertilisers added to pastures to increase their production.
Nutrients are vital for plant and animal growth. New Zealand lakes are monitored for a number of variables. These variables are combined to produce a Trophic Level Index, which tells us the overall condition of a lake. The individual variables and the Index are presented on this web site.