In humid uplands landsliding is the dominant mass wasting process. In the western Southern Alps of New Zealand landslides are scale invariant and have a power-law magnitude frequency distribution. Independent studies from other regions suggest that this is a general property of landsliding. This observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution. It is particularly useful when estimating regional geomorphic rates, because it constrains the frequency and overall significance of extreme events, which cannot otherwise be evaluated. By integrating the complete response of the system, we estimate the regional denudation rate due to landsliding to be 9 ± 4 mm yr −1. Sediment discharge from the western Southern Alps is dominated by landslide-derived material.