Centauria iberica, an invasive species (in the foreground here) seen in the higher elevations of Kashmir Himalaya. Credit: Irfan Rashid

A study has revealed a marked increase in the incidence of non-native species in mountainous regions, including in the Alps and the Himalayas.

Starting in 2007 the Rapid upwards spread of non-native plants in mountains across continents study mapped non-native species in 11 regions on five continents. Over a 10-year period the authors found an average increase of 16% in the number of non-native species1.

“Evidence reveals that non-native plant species are expanding their upper elevation limits in 10 out of the 11 surveyed regions,” the authors said. These upper range limit changes observed after just five years in five of the regions indicate how rapidly non-native species were spreading up in mountains around the world, especially along road corridors, they added.

The study found roads provide ideal dispersal routes for many non-native plant species, so range expansions along roads are faster than in other habitats.

“Roadside surveys like ours might therefore be valuable for early detection of possible emerging threats to native species and ecosystems,” the authors wrote. Future work should look at the species traits that promote fastest rates of spread, and the species with potential for greatest impacts. The features of high-elevation ecosystems associated with greater levels of invasion also need to be studied, they added.

Evelin Iseli, the study’s lead author, told Nature India that the advance of non-native species into high elevation ecosystems is “so fast that we can observe it over less than a decade, highlighting the speed at which our vegetation is changing”. Iseli said their findings highlight the urgent need to expand monitoring schemes and enact management plans for high elevation ecosystems, which harbour high levels of biodiversity, and are also experiencing particularly rapid environmental changes.

“The newly published study is based on the database collected and managed by the MIREN (Mountain Invasion Research Network). When the MIREN network was set up in 2005, very little was known about the status of plant invasions in mountains,” Iseli said.

A standardised survey for mountain regions worldwide and continuous re-surveys every five years, can directly compare trends between regions, helping understand general patterns and regional differences, she said.

Irfan Rashid, of Kashmir University’s Department of Botany, and a steering committee member for MIREN in south Asia, told Nature India that the study gives new insights on species movement. “While upward movement of native species in mountains is well recognised and relatively well documented, long-term studies on non-native species in mountainous regions are rare,” Rashid said.