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Lessons from Landslides

Pastoral farming on very steep land may not be economically sustainable, according to a study carried out in the lower North Island following the wet winter of 1993. The Landcare Research study concludes that hill country steeper than 35o is too erosion-prone to be viable.

The wet winter of 1993 saw more than twice the average rainfall produce extensive landslides and an estimated $9 million in damage. Some hill slopes lost 25% of their pasture through erosion.

Scientist Ross Fletcher says that there are various land management options for erosion-prone hill slopes, ranging from the spaced planting of trees in pasture and farm woodlots to oversowing, retention of indigenous vegetation and reversion of very steep slopes to scrub.

Aerial photographs showed that there was less erosion under trees. Poplar trees planted in pasture for soil conservation purposes reduced erosion by 62%, and pinus radiata woodlots reduced erosion by 90% compared to similar unplanted slopes.