- Through multiple field expeditions, we collected samples representative of glaciers all over the world (Fig. 1-3)
- We used the power of eDNA metabarcoding to obtain high-resolution measures of biodiversity in these areas
Environmental DNA (eDNA) is the DNA that can be extracted from environmental samples without isolating the remains of organisms. Environmental samples contain the eDNA of multiple organisms, that can be amplified, compared with reference databases and identified in a procedure named eDNA metabarcoding. We extracted eDNA from >1200 soil samples, and amplified it using primes targeting multiple components of biodiversity: bacteria, fungi, protists, plants and animals.
- We performed bioinformatic analyses: from sequences to biodiversity information.
Several methodological analyses enhanced the rigour of our study. We compared approaches for soil preservation to identify the most robust protocol (Guerrieri et al. 2020) and contributed to methodological essays describing the best practices for biodiversity analyses using metabarcoding (Chen & Ficetola 2019; Zinger et al. 2019; Ficetola & Taberlet 2023). We generated a huge amount of genomic data that required extensive bioinformatics analyses.
- We produced high-resolution data on the environmental features of glacier forelands, particularly climate, soil and vegetation.
We produced the first reconstruction at very high resolution of temperature in proglacial environments at the global scale. These data showed that glacier forelands are warming much faster than other mountain areas (Marta et al. 2023).
We performed multiple analyses of soil features, to identify properties that affect the development of communities, and confirmed the importance of these parameters for soil fauna. We also showed that soil organic matter increases with time in glacier forelands, but the patterns of soil development are different across areas of the world (Fig. 4; Khedim et al 2021).
- We measured the biodiversity of communities.
eDNA data allowed measuring the development of biodiversity. We detected >10000 taxonomic units of bacteria, fungi, protists, plants and animals. The diversity of all groups of organisms increased through time after glacier retreat, but differences between taxa and areas of the world are strong.
- We show that communities evolve through two distinct mechanisms: species addition and replacement, and the importance of these mechanisms varied over time.
Taxa addition dominated immediately after glacier retreat, while replacement became more important for late-successional communities (Fig. 5).
- We show that biotic interactions, particularly mutualisms, are extremely important to favour colonization.
We found strong relationships between plants and fungi (e.g. mycorrhizal fungi), even at the early stage of colonization. This indicates that interactions have a major role for biotic colonization (Carteron et al 2024; Fig. 6). These associations depends from the balance between multiple biotic and abiotic factors.
- We show that climatic differences between areas of the world have strong impacts on the development of biodiversity.
Colonization is faster in forelands with mild summer temperatures, particularly at the early stages after glacier retreat. The effects of climate on biotic colonization led to heterogeneous but predictable patterns around the world that can affect likely determine the overall ecosystem development (Guerrieri et al 2024; Fig. 7)
Overall, the project greatly contributed to improve our understanding of the impact of climate change on biodiversity.
From the scientific point of view, it resulted in a large number of papers by project members (29 accepted papers, including papers in Nature Ecology & Evolution, Nature Plants, Nature Communications…)
The project results have been disseminated with a large number of strategies, including scientific conferences, TV and radio broadcasting, the social media, popularized publications and exhibitions.
We expect that the project results will provide practitioners, managers and policy makers with the much-needed knowledge for better managing and preserving the unique biodiversity of mountain ecosystems.
