The Waikaia eco-region is a cool temperate area defined by its two ecological districts, Nokomai and Umbrella. Both districts are characterised by a block-faulted landscape of broad plateaux, hills, and ranges, with a geology dominated by schist and greywacke. The vegetation is primarily modified tussockland, with extensive areas of exotic pasture and limited remnants of beech forests. These remnants, particularly in the Waikaia catchment and on the Umbrella Range, are vital habitats for isolated populations of forest birds, including the yellowhead, yellow-crowned parakeet, and robin. The eco-region also marks the eastern limit for several alpine species, and its upland areas contain extensive bogs and unique insect and snail populations