• Energy Research

Les coléoptères Carabidae sont un bon marqueur de l'impact des activités humaines et du changement climatique sur les environnements de haute altitude. Un inventaire de ces insectes du sol a été réalisé en 2017 dans la partie haute du cirque de Troumouse (Gèdre, Hautes-Pyrénées), entre 2100 et 2400 m d'altitude, dans la perspective d'un suivi des populations de Carabidae périglaciaires sur le long terme après la disparition imminente des glaciers de La Munia et de Pène Blanque. Carabid beetles are often used as an indicator of changes caused by human pressure and global warming in high altitude environments. A survey of this insect family was carried out in 2017 in the upper part of the Cirque de Troumouse (Gèdre, Hautes-Pyrénées, France), between 2,100 and 2,400 m above sea level, as a baseline for a long term monitoring program, in view of the imminent disappearance of the glaciers of La Munia and Pène Blanque.

Most of the world’s mountain glaciers have been retreating for more than a century in response to climate change. Glacier retreat is evident on all continents, and the rate of retreat has accelerated during recent decades. Accurate, spatially explicit information on the position of glacier margins over time is useful for analyzing patterns of glacier retreat and measuring reductions in glacier surface area. This information is also essential for evaluating how mountain ecosystems are evolving due to climate warming and the attendant glacier retreat. Here, we present a non-comprehensive spatially explicit dataset showing multiple positions of glacier fronts since the Little Ice Age (LIA) maxima, including many data from the pre-satellite era. The dataset is based on multiple historical archival records including topographical maps; repeated photographs, paintings, and aerial or satellite images with a supplement of geochronology; and own field data. We provide ESRI shapefiles showing 728 past positions of 94 glacier fronts from all continents, except Antarctica, covering the period between the Little Ice Age maxima and the present. On average, the time series span the past 190 years. From 2 to 46 past positions per glacier are depicted (on average: 7.8).

Glaciers are retreating globally, and the resulting ice-free areas provide an experimental system for understanding species colonization patterns, community formation, and dynamics. The last several years have seen crucial advances in our understanding of biotic colonization after glacier retreats, resulting from the integration of methodological innovations and ecological theories. Recent empirical studies have demonstrated how multiple factors can speed up or slow down the velocity of colonization and have helped scientists develop theoretical models that describe spatiotemporalchanges in community structure. There is a growing awareness of how different processes (e.g., time since glacier retreat, onset or interruption of surface processes, abiotic factors, dispersal, biotic interactions) interact to shape community formation and, ultimately, their functional structure through succession. Here, we examine how these studies address key theoretical questions about community dynamics and show how classical approaches are increasingly being combined with environmental DNA metabarcoding and functional trait analysis to document the formation of multitrophic communities, revolutionizing our understanding of the biotic processes that occur following glacier retreat.

AbstractThe worldwide retreat of glaciers is causing a faster than ever increase in ice‐free areas that are leading to the emergence of new ecosystems. Understanding the dynamics of these environments is critical to predicting the consequences of climate change on mountains and at high latitudes. Climatic differences between regions of the world could modulate the emergence of biodiversity and functionality after glacier retreat, yet global tests of this hypothesis are lacking. Nematodes are the most abundant soil animals, with keystone roles in ecosystem functioning, but the lack of global‐scale studies limits our understanding of how the taxonomic and functional diversity of nematodes changes during the colonization of proglacial landscapes. We used environmental DNA metabarcoding to characterize nematode communities of 48 glacier forelands from five continents. We assessed how different facets of biodiversity change with the age of deglaciated terrains and tested the hypothesis that colonization patterns are different across forelands with different climatic conditions. Nematodes colonized ice‐free areas almost immediately. Both taxonomic and functional richness quickly increased over time, but the increase in nematode diversity was modulated by climate, so that colonization started earlier in forelands with mild summer temperatures. Colder forelands initially hosted poor communities, but the colonization rate then accelerated, eventually leveling biodiversity differences between climatic regimes in the long term. Immediately after glacier retreat, communities were dominated by colonizer taxa with short generation time and r‐ecological strategy but community composition shifted through time, with increased frequency of more persister taxa with K‐ecological strategy. These changes mostly occurred through the addition of new traits instead of their replacement during succession. The effects of local climate on nematode colonization led to heterogeneous but predictable patterns around the world that likely affect soil communities and overall ecosystem development.

Models that relate species distributions and climate to predict the future geographical range of species in response to forecast climate change have shown that species living at high altitudes are expected to be particularly affected. Presently, the global trend towards a rapid climate warming represents a major concern for high-altitude carabid beetles, specifically for the populations living in glacialised mountain areas. Most of the high altitude carabid species are endemic and cold-adapted, have low dispersal abilities and present small and/or isolated populations. These threats are triggering an increase of their extinction risk. Some researchers have demonstrated both local-scale extinctions and upward shift to higher altitudes. A key point is whether the losses determined by climate change could be mitigated by species’ survival in micro-refugium areas. Traditionally, the current species distribution in climate-limited ecosystems, like those at high altitude, have been described underlining the role of cold-stage refugia during the Last Glacial Maximum (c. 22000 years BP). On the other hand, no studies addressed the question if the present-day distribution of cold-adapted mountain species is driven by climate conditions occurring during the past and/or current warm periods. More recently, the potential role of some ice-related mountain landforms as warm-stage refugia was documented. It suggests that these landforms could be able to promote the long-term survival of cold-adapted species when the surrounding habitats become climatically unfavorable, thus more effort should be done to investigate the ecology these kind of harsh habitats.