Concern about the rapid advance of exotic invasive plants in the high mountains

Due largely to the harshness of its climate and the difficulties of access, until recently the high mountain was an environment that remained oblivious to the impact of human activity and the advance of invasive species so frequent in the lower lands. But hand in hand with climate change and greater construction of roads and infrastructure, the situation began to change for the worse: the richness of exotic invasive plant species (not native to the place) in different mountainous regions of all continents grew on average by 16% in 10 years, according to a new study published in the journal Nature Ecology & Evolution.” Mountains are ecosystems of high conservation value, characterized by great biodiversity and the presence of unique species, both plant and animal. But there is a growing degree of invasion of exotic plants, which constitutes a threat to biodiversity and the ecosystem and cultural services they provide, such as water supply, flow regulation, among others,” Agustina Barros, CONICET researcher at the Argentine Institute of Nivology, Glaciology and Environmental Sciences (IANIGLA) in Mendoza, told the CyTA-Leloir Agency. and one of the co-authors of the work.” Although we do not know the ecological impact of many of the exotic species recorded in the mountains, we know that some can compete for pollinators and, therefore, affect the reproduction of native plants; alter soil characteristics (pH, nutrients, among others); or dispute resources, among other impacts,” added the graduate in Environmental Management and Master in Wildlife Management.Led by Iseli Evelin and Jake Alexander, from the Institute of Integrative Biology of the Federal Institute of Technology (ETH) Zurich, in Switzerland, the research had the participation of 34 scientists who analyzed the situation in high areas of the continental United States, Hawaii, central and southern Chile, Norway, Switzerland, Tenerife (Spain), India, and Australia.” Climate change, added to the pressure of human activity with the construction of new roads and unplanned infrastructure, the increase in the frequency of fires and intensive domestic livestock, are the factors that promote the advance of non-native plants towards the mountains, “described the Argentine scientist. And he warned: “This is very worrying in high Andean environments, where plants tend to be slow growing and have very limited distributions in space.” The work was promoted by the World Mountain Invasion Research Network (MIREN), which seeks to understand the effects of global change on the distribution of species and biodiversity in these elevated environments. For this, the MIREN Network develops observational and experimental studies that every five years measure and monitor the presence of exotic and native species along mountain vehicular roads. In the last publication, changes in mountain ecosystems in 11 regions of the world were assessed. With Valeria Aschero, Alisa Álvarez and Lorena Bonjour, also CONICET scientists in Mendoza, Agustina Barros is part of a group that was baptized PIBAS (for the acronym in English of “Plant Invasions and Biodiversity in the Andes”). “With them, and the voluntary support of members of our institutions and students, we established a MIREN site in 2017 in three Mendoza protected mountain areas,” said Barros, who noted that the country has another MIREN site in Bariloche.As at the time of the preparation of the new study they had barely a year of measurements, Argentina was not part of the recently published analysis. But they have already completed the second monitoring of 2022. “Although we have not finished the comparative analyses, the observed patterns do not escape global trends in terms of an increase in the richness of exotic species and in the advance in the limit of their distribution,” said Barros.One of the exotic invasive species that has triggered alarm signals is rosehip (Rosa rubiginosa), native to Europe and introduced for ornamental purposes about a century ago. According to Barros, specimens were detected at heights of up to 3,700 meters above sea level, when in 2017 that same species, on the roads surveyed, did not “climb” beyond 3,000 meters. “The rapid speed of expansion of this species is a growing concern for the arid Andes because of its possible impacts on native vegetation and ecosystems, since it requires more water than resident plants and that can affect local hydrology and soil conditions,” said Barros, who added that the invasion affects other regions.mountain areas of Argentina, including Patagonia.” We have found that the average number of alien species in our region is similar to that observed at the MIREN sites of Chile, the United States and Australia. Most come from Europe and Asia, although there are also natives of the United States,” Barros said. And he mentioned the cases of the “dandelion” (Taraxacum officinale) and the pines Pinus ponderosa and Pinus contorta. Better preventionBeyond the increase in temperature due to climate change, human activity is another of the great promoters of the expansion of exotic species towards heights. “The roads and trails act as vectors of dispersion from the valleys to higher elevations, since the seeds are transferred in the wheels and the equipment of the vehicles, in the same way that happens with the footwear and clothing of the people and the movement of cows, horses and goats,” exemplified Barros. Limiting the rapid advance of invasive plants to heights represents a great challenge, since it implies the commitment of multiple sectors – scientific, governmental, civil society, companies – in a coordinated manner. “At the global, regional and local levels, biosecurity controls need to be strengthened to prevent the dispersal of seeds of exotic species adhered to equipment, vehicles, bicycles or clothing,” he emphasized. And he graphed: “In several countries of the world there are cleaning stations before entering a protected area; a super simple and economical measure.”Agustina Barros and Alisa Álvarez studying in Aconcagua paths.Finally, Barros mentioned that another good control strategy is the planning of public use in mountain protected areas. “In places where tourism is popular and there are no formal paths, multiple informal trails are generated. This has a greater impact on vegetation and promotes the dispersal of exotic plants. In addition, intensive grazing of domestic livestock in areas of high conservation value should be avoided, with guidelines and agreements agreed between producers and government authorities on environmental matters,” he proposed. Long-term monitoring networks allow us to know the speed of expansion of exotic species and detect those with the greatest potential for invasion in order to make decisions before trends become problems. “Our studies warn about the urgency of establishing mitigation and prevention measures to stop the proliferation of invasive vegetation and thus avoid potential impacts on ecosystems,” concluded Barros.

Original source in Spanish