Conference Agenda

Glaciers are shrinking at an alarming rate. As techniques and knowledge improved, it was discovered they host a variety of cold-adapted taxa. Intrinsically fragmented and isolated, mountain glaciers are thought to host high biodiversity, especially in cryoconite holes, still poorly known as isolation prevents investigations. Small mountain glaciers have shorter response times to climatic oscillations and a higher probability of disappearance. This suggests studying high-altitude biodiversity before glaciers are lost due to climate change.

We collected 502 cryoconite samples from cryoconite holes on 19 glaciers in the Alps, Andes, Karakoram, Mount Kenya, Patagonia, Sierra Nevada, and Svalbard. The bacterial community composition was studied by sequencing the hypervariable regions V5-V6 of the 16S rRNA gene. Diversity within communities was analysed through ecological indexes, while biogeography was analysed using cluster and redundancy analysis.

All bacterial communities presented a low evenness (Gini Index > 0.95) and samples from the same glacier clustered together with few exceptions. Glaciers close to one another also tended to cluster together.

Our results are the first assessment of the global diversity of bacterial communities in cryoconite holes on mountain glaciers and the first evidence of a biogeographical pattern at the global level.

The acceleration of global warming is leading to ever-larger areas of land becoming exposed as glaciers retreat. In the tropical Andes, these novel ecosystems are being closely scrutinised by scientists and stakeholders as they modify the availability of ecosystem services such as water resources, natural hazards, carbon sequestration and cultural services. The trajectory of these novel ecosystems will depend largely on their capacity to be colonised by vegetation. Based on the study of seven post-glacial chronosequences in South America, we present here some elements of these trajectories. Over a period of 150 years after glacial retreat in Bolivia and Peru, plant succession is strongly constrained by the access of propagules to proglacial margins, wind-dispersed seeds being the most likely to colonise the area. Nurse plants are absent or insufficiently mature to accelerate succession, even though they have a vital role to play in this type of ecosystem. In Colombia, alpine plants are both from tropical and temperate origins but plants of tropical origin and shape have great difficulty in establishing themselves and plants of temperate origin, smaller, are the winners in the novel ecosystems. We discuss how these new plant assemblages could affect tropical alpine ecosystem services.

Global warming leads to a worldwide glacier shrinking, which results in new proglacial plant communities’ establishment. The general patterns of primary succession following glacier retreat are relatively well understood. However, the effect of snow cover variation and the reduction in its protective effects against frost damage to plants have not yet been studied. We characterized proglacial snow cover duration along an equatorial to temperate latitudinal gradient to infer how snow cover duration influences proglacial plants functional diversity. We used 150 data loggers buried in 13 post-glacial chronosequences (tropical Andes, European Alps and Pyrenees) to monitor soil temperatures (1 ~ 3 years) and detect snow presence. We profiled at each site plant taxonomy and community-weighted functional traits (LDMC, SLA, Growth form, etc.). The results confirm that annual snow cover was almost absent at equatorial latitudes and remained very short in tropical regions, whereas it lasted up to 10 months in temperate regions. We found a higher proportion of facilitating life form diversity in tropical plant communities, and we hypothesized that facilitation processes are more pronounced where snow cover duration is shorter. Accordingly, in an accelerated warming context, interactions between plants in tropical alpine ecosystems could be of a more facilitating type.

Succession, a cornerstone in ecology, remains incompletely understood. Succession is a complex phenomenon influenced by interacting and continuously changing factors operating at different temporal and spatial scales, each one having successional consequences. The lack of consideration for specific contexts and the properties of targeted taxa hampers a comprehensive understanding of successional trajectories and their prediction.

To assesses various successional trajectories on a wide geographical scale and integrating several taxonomic groups, we used environmental DNA to efficiently obtain standardized inventories of soil communities colonizing forelands after glacier retreat. Soil samples were collected along chronosequences (representing 1-419 years of succession) in 46 forelands around the world.

Taxonomic richness increased over succession, showing a consistent pattern among taxa and across regions, but rates varied among groups. Moreover, the local climate modulated successional rates, with colonization starting earlier in forelands with milder summer temperatures. The changes in the community composition of microbes contrasted with other taxa. For plants, springtails, insects and earthworms, dissimilarity and the importance of taxa addition decreased with time while replacement became more important on late communities.

In general, we observed heterogeneous but predictable patterns. Our study highlights the importance of multi-taxa and global studies in defining generalized features of succession.

Understanding biodiversity and ecosystem processes in the Arctic is of key importance for mitigating against rapid environmental and climate change. Greenland is currently experiencing increases in temperature and precipitation, along with greater climatic and environmental variability. This causes changes within plant communities including, vegetation shifts, shrub expansion, and earlier and shorter flowering seasons that lead to complex responses within Arctic terrestrial ecosystems. Our research focuses on plant diversity and plant-pollinator interactions. We aim to:

1. Quantify Greenlandic floral diversity patterns using museomics and metadata from herbarium specimens, along with corresponding key environmental drivers.

2. Investigate the effect of habitat and latitude on plant-pollinator networks using pollen DNA metabarcoding.

3. Model how both floral diversity and pollinator ecosystem processes may alter with future environmental changes.

Greenland's strong climatic gradients and vegetation zones, combined with the excellent coverage of climate data and extensive herbarium collections, make the island an important study system for understanding current and future changes in the Arctic environment. The outcomes of this research will help to predict the consequences of future environmental change to Arctic terrestrial ecosystems, and support public awareness, conservation efforts and policy development to protect Arctic biodiversity.

Melting glaciers are emblematic symbols of the accelerated warming of alpine ecosystems. Climate change scenarios forecast their disappearance from central Europe by 2100. This dramatic melt will however open new spaces for species, ultimately leading to the formation of new alpine habitats. Among them, of special interest and conservation value are high-alpine alluvial zones as they host unique – but little known and studied – biodiversity values. However, these alluvial zones and their biodiversity are also at risk for new infrastructure development like damming for hydropower production or sediment exploitation. With the aim to provide spatially explicit recommendations to the authorities, policy-makers, and organizations as a scientific basis for decision-making, we are starting a project that will (1) identify where these high-alpine alluvial habitats are and will appear across Switzerland, (2) evaluate their actual and future biodiversity value using bioindicator species, (3) identify where conflicts with infrastructure development are likely to arise and how to evaluate potential trade-offs with biodiversity conservation. Combining geomorphology and biodiversity through spatially explicit modeling, this project aims for a ranking of the Swiss proglacial alluvial areas based on their conservation value and potential vulnerability to infrastructure development over two global warming horizons: 2050 and 2100.