Tongariro Alpine Crossing’s unique Ngarotopounamu Emerald  Lakes are once more shimmering blue and green after being cleared of an invasive weed.

For years the lakes’ shores and shallows have been smothered by the invasive Juncus bulbosus, a native Eurasian and North African weed that was introduced to New Zealand over a century ago. 

DOC rangers have conducted weed control around the lakes since 2019, and weed density is now down to undetectable levels. This is a win, not just for biodiversity but for hapū and others who value the iconic Ngarotopounamu.

DOC supervisor Danial Van der Lubbe said monitoring will continue to ensure the weed does not grow in the lakes again. “The next step for us is eDNA testing of the larger Blue Lake for Juncus – we haven’t detected anything visually, but the eDNA check will tell us for sure.”

The testing is part of a Tongariro Alpine Crossing sustainability project that includes a range of changes to manage environmental and cultural outcomes.