The international study published in Nature Ecology & Evolution found approximately 16 per cent increase in non-native plant species across 11 sites surveyed in Australia, Chile, Hawaii, India, USA, Norway, Switzerland and the Spanish island of Tenerife.
Associate Professor John Morgan said upward movements of native species in mountains is well known and relatively well documented but long-term studies that focus on non-native species in mountainous regions are rare.
“Within just a decade, we see non-native plants reaching new upper-range limits. This is both surprising and alarming,” Associate Professor Morgan said.
“By surveying native and non-native species on the side of roads leading up to the mountains, we could see the change over several years.
“Mountainous areas have historically been less prone to non-native plants, though climate and increasing human activity at these elevations is changing that,” Associate Professor Morgan said.
Field data was gathered from plots observed at five-year intervals, each time during peak growing season.
This study suggests that in an era of local and global anthropogenic changes, non-native plant species in mountains will continue to expand upwards regardless of their introduction point.
Non-native species are often introduced first in the lowlands areas (as garden plants and agricultural pasture species) and they then spread upward to the mountain tops – a predictable movement even without climate warming.
Threats posed to native ecosystems by non-native plant species at a higher elevation will likely increase. This makes it increasingly necessary to monitor the spread of non-native species into mountains, to ensure their early detection and eradication.
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