Vegetation in the Wairakei-Tauhara Geothermal system: History and future options

Abstract

The Wairakei-Tauhara Geothermal System (WTGS), contains c.164 hectares of discontinous geothermal vegetation and habitat that has a complex history of natural and anthropogenic change. A key feature is the extensive areas of geothermal kanuka-dominant vegetation on geothermally-heated ground. The WTGS supports populations of nine plant species classified as being either Threatened or At Risk. Changes to the patterns and dynamics of geothermal vegetation in the WTGS are linked to the
effects of energy extraction. Energy extraction commenced in 1958 on the WTGS at Wairakei Power Station and since then has been subject to multiple modifications and expansions. The extraction has resulted in changes and losses to some steamy habitats (mostly alongside geothermal streams, springs, and geysers), reducing habitat for species that require steamy habitats. Between the 1950s and 1980s, there was a marked increase in geothermally-heated ground habitats, substantially increasing the extent of geothermal kanuka. Since the late 1980s geothermally-heated ground habitats have been slowly declining in size, although the extent of geothermal kanuka-dominant vegetation remainsconsiderably larger than before energy extraction began. Monitoring and assessment of WTGS geothermal habitats has been undertaken regularly since the early 2000s. Here we present findings of these assessments, including our identification of some recent changes at specific sites. We
also present options for the future management of geothermal vegetation in the WTGS under two scenarios: continued use (though modified energy extraction), compared to the likely effects of no further energy extraction. We determined that continued extraction, at least in the short term can provide opportunities to invest in the protection of geothermal habitats and species. For steamy habitats this can sometimes be achieved through artificial creation of lost habitats. Careful restoration management of the highest quality remaining geothermal habitats in the WTGS is also recommended.