Fumaroles near Lake Rotokawa, north of Taupo, with prostrate kanuka (Kunzea ericoides var. microflora) scrub (middle distance) and wilding pines (background) (Bruce Burns)
Fumaroles are vents or openings that issue steam and hydrogen sulphide and other gases, and are usually associated with past or current magmatic activity. Constant steam allows frost-sensitive species to survive on fumarole margins, including otherwise tropical ferns (listed below; Given 1980). The moss Campylopus pyriformis can be important close to fumaroles where soil temperatures are too hot for vascular plants. Low soil pH also limits the species that can survive in these areas.
volcanic steam vents
Where do they occur?
Fumaroles occur primarily in the Taupo Volcanic Zone on the Volcanic Plateau in central North Island.
Notable flora and fauna
Threatened plants include the nationally vulnerable Machaerina complanata, the declining native ladder fern (Nephrolepis flexuosa), the taxonomically indeterminate and declining Christella aff. dentata (‘thermal’) and the naturally uncommon Fimbristylis velata, giant hypolepis (Hypolepis dicksonioides), and Dicranopteris linearis.
Fumaroles harbour two species of macroinvertebrates confined to high-temperature, low-pH waters: Ephydrella thermarum and an endemic mosquito (Culex rotoruae).
Threat statusCritically endangered (Holdaway et al. 2012)
Wilding pines (e.g. Pinus pinaster, P. radiata) and blackberry (Rubus fruticosus) can be problematic in marginal areas where soils are sufficiently cool for their establishment, but fumaroles tend to have few naturalized species.
Geothermal areas are generally too unstable for urbanisation; however some have been used as dumping grounds. In more stable areas, stock may trample vegetation when unfenced. Rabbits and hares are present in many geothermal ecosystems.
Geothermal fluid extraction for energy can affect surface activity and change soil temperatures with consequent impacts on plant communities. Geothermal fluid extraction can also cause subsidence. Naturally occurring eruptions often destroy vegetation. There are some impacts from tourism, but usually these impacts are well controlled.
Boothroyd IKG 2009. Ecological characteristics and management of geothermal systems of the Taupo Volcanic Zone, New Zealand. Geothermics38: 200-209.
Burns BR 1993. Bryophytes and lichens of Te Kopia Scenic Reserve geothermal vegetation. New Zealand Botanical Society Newsletter 34: 8-9.
Burns BR 1994. Botanical notes on a trip to White Island (Whakaari), 27 November 1993. New Zealand Botanical Society Newsletter 35: 8-9.
Burns BR 1997. Vegetation change along a geothermal stress gradient at the Te Kopia steamfield. Journal of the Royal Society of New Zealand 27: 279-294.
Cody AD 2007. Geodiversity of geothermal fields in the Taupo Volcanic Zone DOC Research & Development Series 281. Wellington, Department of Conservation. 70 p.
Dumbleton LJ 1969. A new species of Ephydrella Tonnoir and Malloch (Diptera : Ephydridae) from hot springs and notes on other diptera from mineralised waters. New Zealand Entomologist 4: 38-46.
Given DR 1980. Vegetation on heated soils at Karapiti, central North Island, New Zealand and its relation to ground temperature. New Zealand Journal of Botany 18:1-13.
Wardle P 1991. Vegetation of New Zealand. Cambridge University Press. Pp. 400-404.
Wildland Consultants 2011. Geothermal vegetation of the Waikato Region - An update based on 2007 aerial photographs. Wildland Consultants Ltd Contract Report No. 2348. Prepared for Waikato Regional Council. 515 pp.
Geothermal resources (Environment Waikato)
Geothermal systems (New Zealand Geothermal Association)
Rotorua Geyserfields and Geothermal sites (DOC consultation on World Heritage Status)
Rotorua’s Geothermal Treasures (DOC factsheet)