Rimu, tōwai forest ecosystem (MF24)

About this ecosystem

This ecosystem is restricted to areas over 450m above sea level with high levels of rainfall, wind and cloud cover.

Primary formed by volcanic activity, the major factors that influence the composition and structure of this ecosystem are:

  • altitude
  • the landforms it occupies
  • soil drainage.

In Auckland, this ecosystem only exists in the Hunua Ranges.

Bird's eye view of vast rimu and tōwai forest.
Forest near Kohukohunui summit of the Hunua Ranges.
Photo credit: Jason Hosking

Flora and fauna in this ecosystem

Canopy species such as rimu and northern rata are common. Submontane species which are naturally uncommon in Auckland but occur in the Hunua Ranges include:

  • mountain cabbage tree
  • mountain horopito
  • hutu.

This ecosystem also supports species such as:

  • kokako
  • kākā
  • kererū
  • pepeketua (Hochstetter's frog).
Grouping of small fern plants.
Forest understorey beside the Kohukohunui Track, Hunua Ranges.
Photo credit: Jason Hosking

Threats to this ecosystem

This ecosystem is critically endangered and under conservation management. 

Pest mammals, like goats, possums and rats, are the main threat in this forest, as they eat plant leaves and shoots. This can destroy the trees resulting in regeneration failure and species loss. 

Extensive dieback of northern rātā has also been attributed to possums.