Humans, climate change risk killing New Zealand's unique alpine plants
Some of New Zealand's alpine plants risk extinction due to the increasing popularity of New Zealand's mountains with tourists, skiers and mountain bikers.
New research shows that weeds spread into mountainous areas twice as fast as native plants, largely on the back of roads and other human developments.
It could have repercussions in a warming world: When temperatures rise, plants naturally spread to higher areas where it is cooler.
The findings indicate that because weeds move faster than natives, they risk smothering native species out of existence in their own habitat.
The international research was published in the Nature Climate Change journal on Tuesday. It analysed 20 years of data from one part of the European Alps in Italy.
The situation could be "more dire" for New Zealand, which was infected with weeds in greater quantities than other countries, study co-author and Lincoln University plant biosecurity professor Philip Hulme said.
"I think there are particular consequences for New Zealand, because we have so many more weeds than there are in Italy, and some of those weeds are pretty vigorous," he said.
"I expect many of them to be able to move pretty quickly up mountains."
New Zealand has more than 600 alpine plant species, almost all of which are found only here.
Among them are buttercups, lilies, snow tussocks and daisies, all of which developed to survive in extreme conditions. They are already under pressure due to warmer temperatures altering their habitat.
The research found all plants could spread, but weeds were more likely to be close to a road, allowing them to spread more quickly through cars and people.
It warned that more roads in alpine areas would be "worrisome" and would likely come at the expense of native plants.
"Further increases in road density along alpine elevation gradients should be considered with caution, as the presence of this habitat can accelerate non-native plant invasion," it said.
Tourists are increasingly flocking to New Zealand's alpine land, creating pressure for more infrastructure in once remote areas.
Weeds such as lodgepole pine had already established above the native treeline, and others could soon join them, Hulme said.
Wilding conifers from North America were high elevation species and could also prosper in higher areas.
The need for developments that fuelled their spread should be considered closely.
"I think we've got to be very careful with the developments we've had," Hulme said.
"Clearly there's economic benefits to having ski stations up in alpine areas, but with different types of tourism . . . mountain bikers are increasingly moving to high alpine areas, four-wheel-drives, all of these things mean more likelihood of disturbing the landscape that's there but opening it up to invasion by weeds.
"We must take action soon otherwise our native alpine plant communities are likely to suffer dramatic changes with ongoing warming and increasing human activity in mountain regions."
About 11 per cent of New Zealand is alpine, according to Department of Conservation figures. Most alpine areas are in the South Island.