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October 2017 Issue
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The battle above the treeline

Lupins, though beautiful, are one species that has made the leap into the high country. Photo: Philip Hulme
Invasive weeds are muscling their way into alpine areas as the climate warms, establishing in the high country at twice the speed of natives, according to a recent study.

Above the treeline, there is an invasion taking place. As the climate warms, alpine plants are creeping higher up the mountains to find the cool conditions where they can survive. But new research has found alien plants are twice as likely to take their place.

The study, published in Nature Climate Change, looked at how plants were spreading into alpine areas in Italy, but a Kiwi scientist involved in the research says New Zealand could be even more vulnerable than Europe.

Lincoln University biology professor Philip Hulme is an expert on how weeds spread. He says, although New Zealand’s climate is warming at about half the rate of Europe, we have far more weeds ready to leap up the slopes as the snowline retreats.

“We are probably the weediest area in the world,” Hulme says. “There are now as many alien plants as native species here, and many of these could establish in alpine environments.”

The research also found that weeds were concentrated around development, like roads and ski fields. As alpine areas are coming under increasing pressure from development and tourism, Hulme says we should be concerned.

“Alien plants are really good at making use of any human disturbance. Things like roads, ski fields, 4WD tracks – they love that.”

Trampers are also unwitting vehicles for weeds to hitch a ride up the slopes. With the Great Walks and other alpine tramps attracting more people from overseas, the risk of more foreign invaders being introduced is increasing.

“The iconic mountain passes and tracks, like the Routeburn, Milford, or even the Travers-Sabine, have increasing numbers of tourists who can potentially bring in material from other hikes around the world and which could establish,” says Hulme.

Research has already found weed plants concentrate around backcountry huts.

“You go to any hut and most of the small herbaceous plants are not natives.”

So what can be done? Hulme says the first step is to research how weeds are establishing in the high country.

“Getting good data is essential if we want to keep our mountain landscapes free of weeds such as gorse, broom and wilding pines.

“Historically, we were doing great things surveying flora, but that has largely stopped. It’s not seen as sexy science, so these surveys don’t cut the mustard for funding.”

But trampers could help fill that knowledge vacuum. Hulme is advocating for a system where trampers can report and monitor weeds on trails and around huts. The information could be uploaded to an online database which could show which plants are establishing and where. Rangers could also be trained to keep an eye out for invasive plants.

“There is scope to engage with the tramping community as citizen scientists,” he says.

In the meantime, Hulme recommends trampers clean their boots after each tramp as a precaution against spreading weed seeds.