Sustainable management of geothermal vegetation in the Waikato Region, New Zealand, including application of ecological indicators and new monitoring technology trials

Abstract Geothermal vegetation – influenced by surface expressions of heat from the Earth’s interior – is naturally rare both in New Zealand and internationally. The varied nature of geothermal manifestations, due to varying combinations of temperature, chemistry, hydrology, and localised protection from frosts, results in rare and unusual habitats for plants. These naturally uncommon ecosystems are classed as threatened and critically endangered, and include habitats for species occurring outside ‘normal’ latitudinal and altitudinal ranges. The varied nature of geothermal vegetation, one of the most threatened ecosystems in New Zealand, has important implications for management, including retention of existing areas and the maintenance and enhancement of ecological values. Most geothermal vegetation in New Zealand occurs in the central North Island in the Taupo Volcanic Zone, with c.74% of the total extent of New Zealand’s geothermal vegetation located within the Waikato Region, and the remaining 26% located within the Bay of Plenty Region. Inventories of geothermal vegetation and identifications of management priorities have been undertaken regularly in the Waikato Region since 2000, with the latest having been undertaken in 2014, covering over 863 ha of geothermal habitat within 15 geothermal systems. Energy production (thermal and hydro-electricity, heating, and industrial uses) and land use changes such as mining, farming, forestry, urban development, tourism, fire, and herbicide and/or fertilizer drift have resulted in the loss of significant geothermal areas in the past, and such activities continue to threaten geothermal vegetation. Invasion of pest plants, particularly introduced conifers and other woody plant species, continues to be a major threat at many sites. Threats at each site, vulnerability to those threats, actions required to address threats, and the benefits and priorities of ecological management have been identified. Active restoration management is being undertaken by the Department of Conservation, tangata whenua, regional and local government, private landowners, and forestry companies. There are considerable opportunities for further restoration initiatives, at sites where work has already been undertaken and at all other sites. New threats have also been recognised, showing the importance of regular monitoring and inventory assessments. Continued monitoring and appropriate planning is a key requirement to improve management of this nationally rare ecosystem. Monitoring, protection, and restoration, where possible, are essential requirements to halt the decline of these fragile and unique ecosystems. To assist with management, a set of ecological indicators for geothermal systems was developed and applied across geothermal habitat within the Waikato Region. These indicators provide a measurable benchmark against which loss can be measured. Scores can be used to assess site condition and overall change within and across sites. In addition, new technology for undertaking monitoring was explored at one geothermal site as a case study. A drone was used to capture a range of imagery, as drones may be an ideal solution for geothermal site monitoring given the hazards to field surveys in geothermal areas.