Ian McIvor

By Ian McIvor, Grant Douglas, John Dymond, Garth Eyles and Michael Marden

Part of the book: Soil Erosion Issues in Agriculture

By Ian McIvor, Thomas Mackay-Smith and Raphael Spiekermann

Increases in the magnitude and frequency of rainfall events in New Zealand due to climate change, coupled with existing concerns about sediment and nutrient contamination of waterways, are changing policy and practice around erosion management and land use. We describe the challenges around slope erosion reduction, cover current legislation and management practices, illustrate how modeling can inform erosion management and describe new opportunities, whereby native species can become a new active management tool for erosion control. Passive erosion management depending on natural revegetation by slow growing woody species is used on land retired from grazing but is much less effective than active erosion management in reducing shallow slope erosion. Active erosion management using exotic fast-growing poplar and willow trees strategically placed on hillslopes is effective in reducing erosion, but these trees can be hard to establish on drier upper slopes. An endemic woody tree, Kanuka, grows on drier slopes and is being tested as an erosion control tool. Kanuka seedlings have been successfully established on pastoral slopes, including drier slopes. A spatial decision support tool developed to identify pastoral hillslopes at high risk of erosion has improved decision-making when positioning appropriate trees on these slopes.

Part of the book: Soil Erosion