85-90% of New Zealand was covered with forest. Only 15% of the South Island and 1.5% of the North Island lay above the timberline. Grassland or shrubland occurred on river terraces subject to regular flooding, frost-prone valley floors, steep cliffs, active sand dunes, leached shallow soils, ultramafic soils, and recently disturbed areas that were normally in forest. Wetlands with sedge, rush or shrub land cover were common, but forested wetlands may have been as abundant. But outside these limited areas the forest cover was unbroken.