Tongariro Crossing's distinctive Emerald Lakes have been declared weed free for the first time after years of work by Department of Conservation staff.
Known for their deep green hue caused partly by dissolved minerals, the Emerald Lakes fill explosion craters near the summit of Mt Tongariro.
Juncus bulbosus or bulbous rush, a weed commonly found in swampy places, has smothered the shores and shallows of these lakes for several years.
Department of Conservation (DOC) supervisor Danial Van der Lubbe said the lakes are an iconic part of the landscape.
"We know they are important to so many people — hapū, local communities, and those who complete the Tongariro Alpine Crossing — so it's for more than just biodiversity that we've tackled these weeds."
Rangers have conducted weed control around the edges of the lakes and in the lakes themselves biannually since 2019, and this year levels are down to undetectable levels for the first time.
"We still have some work to go around the edges, and will keep checking to make sure it doesn't pop up again in the lakes themselves," said Van der Lubbe.
"The next big step for us is eDNA testing of the larger Blue Lakes for Juncus — we haven't detected anything visually, but the eDNA check will tell us for sure."
eDNA refers to environmental DNA, collected from a variety of environmental samples rather than the traditional sample from an individual organism.
This testing is being conducted as part of the larger Tongariro Alpine Crossing sustainability project, which includes a range of changes to better manage environmental and cultural outcomes.
Tongariro water-bodies are considered tapu, or sacred, and walkers are asked to avoid swimming in them.
By staying clear of the water people can be assured they are upholding cultural values and preventing further weed incursions into the lakes.
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