Threats
Orakei-korako geothermal area
Values and vulnerability
New Zealand's geothermal landscapes are important because of their scenic attraction, cultural significance, potential for scientific study and as energy sources. Yet they are far more than just visually fascinating features such as geysers and mud pools. They are outstanding natural ecosystems comprising native thermal vegetation, formations and the features themselves. The nature conservation values of these systems are highly significant, but often overlooked. Traditionally they have not been highly valued by New Zealanders because they are not well understood and because local residents are used to the landscapes as part of their lives.
The plant life associated with geothermal features is special because it is unique to the harsh geothermal environment and vulnerable to human interference. The risk of weed infestation is high if geothermal vegetation is disturbed. Few people know of the rare thermal orchids and mistletoe, or that the dark orange coloration commonly seen on geothermal vegetation is a fungus. On a national botanical conservation values ranking system, Whakarewarewa's geothermal vegetation rates the highest-ranking possible. The vegetation at Silica Flats rates the third highest. Similarly, wildlife habitat values at Silica Flats reach the second highest possible ranking, while at the Motutara Point wildlife refuge and sanctuary, wildlife habitat values are the highest.
At the Motutara Point refuge, the warmth of the water and environmental conditions create a bird spa. The adjoining Sulphur Point Wildlife Sanctuary is an outstanding habitat for waterbirds. The threatened NZ dabchick, banded dotterel, scaup, shags, pied stilts and Caspian terns are just some of the area's residents. Small silica inlets within Sulphur Bay provide a nationally significant site as one of few North Island colonies of black-billed gulls. About 60 pairs of Southern black-billed gull also breed within the sanctuary each year.
What is left?
Many of the spectacular geothermal features within the Rotorua geothermal field have disappeared. Whakarewarewa's Geyser Flat is NZ's only remaining major field, yet a number of its geysers are no longer active. Waikite geyser last played in 1968 and its present dormancy is the longest on record. The Wairoa geyser used to play to heights of up to 60 metres. Its last natural eruption was in 1940, although it played through the 1950s with the aid of soap. The geyser terraces featured a series of pools as recently as the 1970s - these pools have now been replaced by areas of grass. Geyser Flat is not alone in its predicament.
Five major geyser fields existed in NZ 110 years ago - Rotomahana, Orakei Korako, Whakarewarewa, Wairakei and Spa. Only Whakarewarewa remains with any significant number of active geysers. The Orakei Korako field was largely drowned when the Waikato River was raised for hydro-electricity. Development of the Wairakei field for geothermal energy resulted in a dramatic decline in ground water levels at both the Wairakei and Spa (7 km away) fields and the loss of surface features such as all 70 of its geysers and at least another 170 alkaline springs. The Rotomahana field was destroyed by natural causes - the 1886 Tarawera eruption. Of more than 200 geysers active in the central North Island in the 1950s, just over 40 remain in the 1990s.
Colourful sinter terraces were once a feature of the Rachel Spring and have gradually been destroyed over the last 100 years with development of the Government Gardens. There were several thermal bathing areas around Sulphur Bay, but rubbish dumping and building in the vicinity have long since destroyed them. The re-alignment of SH5 has also destroyed geothermal areas near Whakarewarewa. Urban and industrial development adjoining the geothermal field has already destroyed much of the associated shrublands, their unique prostrate kanuka communities and rare plants. Extraction of fluid and heat energy has also affected and reduced the extent of thermal vegetation.
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