Pakihi are confined to the west of the South Island where they are widely scattered, particularly on old outwash gravels. Pakihi are a type of wet heath, characterised by very infertile soils with an impervious horizon and little or no peat. In South Westland, pakihi have developed as a result of natural processes of inundation of soils where there is impeded drainage combined with soils becoming very infertile as a consequence of developing in areas of very high rainfall. Pakihi-type vegetation in northern Westland is the result of human-induced fire.

Pakihi share both environmental and vegetation features with North Island gumlands. Characteristic species are mānuka, wire rush, Centrolepis pallida and tangle fern.

The expected natural range* of pakihi across Aotearoa is 310,716 hectares.

*area this ecosystem could occupy without the presence of people.