Soil erosion, sediment and nutrient run-off to water, pests and weeds, and loss of soil structure are some of the adverse environmental effects associated with land use. Parts of the South Island High Country are affected by ecological decline and loss of biodiversity. Depletion of ground cover has reduced site productivity and increased vulnerability to weeds and wind erosion. Storm events such as Cyclone Bola have worsened the problem. Soil loss from erosion has reduced flood capacity downstream and deposits of sediment have affected the ferile flats and inshore fisheries.
Erosion is also a problem in the hard North Island hill country.
Approximately 10 million hectares are at risk. Erosion affects farm viability. Each individual slip scar requires about 20 years to return to near its original productivity. Pollution of streams, lakes and groundwater results from nutrient and sediment run off in parts of New Zealand. The Waikato, Canterbury and Southland are some of the areas at risk.