Rare and vulnerable: Sphagnum-dominated mire changes under climate threats in the Western Alps
Assigned Session: FS 3.183: Data and methods for assessing knowledge and trends in mountain biodiversity and ecosystem worldwide
Abstract ID: 3.13336 | Not reviewed | Requested as: Talk | TBA | TBA
Alessandra Pollo (1)
Ludovica, Oddi (2); Simone, Eusebio Bergò (2); Consolata, Siniscalco (2)
(1) University of Torino, Via Accademia Albertina, 13, 10123 Torino, IT
(2) Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina, 13, 10123, Torino, Italia, IT
Abstract
Sphagnum-dominated mires are rare and highly vulnerable ecosystems, particularly at the southern edge of their distribution, where climatic conditions are less favorable. Mires have traditionally been considered relatively stable, exhibiting little to no change in floristic composition over several decades. This research aimed to contribute to challenging this perspective by analysing the changes in Sphagnum-dominated mires in the Western Alps over just a decade. We resurveyed 139 plots across 14 sites, comparing historical data from 1998 and 2011 with new surveys conducted in 2023. Our results revealed significant shifts in plant composition, structure, and ecological conditions over just 12 years, largely driven by climate change. Analysis of climate data confirmed increasing temperatures, declining precipitation, and increasing evaporation across the study sites. Under these climatic trends, an increase in species richness and diversity was observed, particularly in vascular plants. Woody and generalist species expanded at the expense of mire specialists, including Sphagnum species, suggesting both a generalisation of the vegetation and an ongoing drying process. The local extinction of species with the phytosociological optimum in mires was also detected. The impact of climate change was confirmed by the higher increase in species richness in mires that experienced higher decline in precipitation over the past three decades. Beyond these changes observed over just 12 years, long-term resurvey spanning 25 years revealed emerging signs of acidification and eutrophication. Mires at the southern edge of their distribution exhibited climate-driven changes occurring at a much faster rate than natural succession and than the higher-latitude mires previously monitored through resurveys. The rapid decline of mires poses a severe threat to the ecological integrity of these ecosystems, which play a crucial role in carbon sequestration, water regulation, and biodiversity conservation. In particular, the Wester Alps risk losing glacial relict species hosted in the mires. Urgent conservation measures are necessary to mitigate further degradation and preserve the ecosystem services these ecosystems provided.
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