The Rotorua Department of Conservation team are undertaking an annual census - monitoring rare geothermal wetland ferns.
Twenty kilometres south of Rotorua, the Department of Conservation is undertaking an annual census, monitoring rare geothermal wetland ferns.
Known for its hot pools, Waikite Valley is home to several species of unique and endangered ferns which bask in the warmth of the spring-fed Otamakokore Stream.
Paul Cashmore, technical advisor (Flora) at Rotorua Department of Conservation said the wetland was rare.
“You’ve got this additional heat dynamic going on which is resulting in not only a range of geothermal fern species but also some unique geothermal features.
“Good examples of geothermal wetlands are extremely rare. Obviously geothermal is restricted to the Rotorua Taupō volcanic zone, so they don’t occur throughout the country.”
The ferns’ success is largely due to the improving condition of the wetland and helping hands from local volunteers and DoC rangers.
Threatened species along the stream include the Cyclosorus; soft fern - or Christella; thermal ladder fern or Nephrolepis; and another species called Hyperlepis.
The annual stock-take of the ferns is a time-consuming process, with rangers having to manually count each live frond when doing the annual census in January.
“We count the entire length of stream and count every individual live frond of these four key geothermal threatened species.
“It takes us two days ... It involves very carefully walking up and down the stream on both sides with two counters and a recorder.”
The 13-hectare wetland, on the Waikite Valley Thermal Reserve, was once farmland but for more than a decade DoC has been on a restoration mission, including pest and weed control too.
Cashmore said there are opportunities for other parties to continue the restoration work downstream but the bulk of work within the reserve had been done. Pest and weed control is an ongoing job.
Thanks to the programme there’s been an increase in most species but there remains some uncertainty as to what the future holds with climate change and extreme weather events.
“We get really hard frost in Waikite and if it’s warmer in winter that’s going to mean less frost, which potentially means our fern species won’t be getting nipped off by the frost quite so bad,” Cashmore said.
But it’s a two-edged sword that could see many of the weed species survive winter.
“It’s a bit unknown, but I think some of the big issues we’re going to have are more weed species and longer growing seasons.”
Cashmore said the possibility of more heavy rainfall events in the future could lead to higher stream levels and possible erosion in some places.
