We first review, in five sections, the external perturbations and their associated processes which can lead to landslide failure: i) increase of slope angle, ii) increase of load applied to the slope, iii) rise of groundwater level and pore pressure, iv) frost weathering processes and v) earthquake loading. Second, we analyse the New Zealand landslide catalogue, including all landslides recorded in New Zealand between 1996 and 2004, in time and rate and find a strong correlation in landslide occurrences. The time correlation between landslide occurrences for events occurring more than 10 days apart is not driven by earthquake-landslide nor landslide-landslide interactions. We suggest the climate-landslide interactions drive most of New Zealand landslide dynamics, non-linearly and beyond the empirically reported daily correlation. Third, we compare the occurrence of landslides in time, space and rate of New Zealand.