Olivier Dangles’s research while affiliated with Université Paul-Valéry Montpellier and other places

Ignorance of the rational use of insecticides leads farmers in developing countries such as Ecuador to exceed the limit of permitted applications. In addition, little is known about the effect of insecticides on entomofauna of Lupinus mutabilis (lupine). This study aims to analyze the effect of insecticides on pests and beneficial insects, with special emphasis on pollinators, without neglecting the effect on crop yield. The entomofauna associated with Andean Lupin was used as a reference. Seventy-nine agricultural fields were evaluated in Cotopaxi-Ecuador, with the treatments with chemicals, without chemicals, and without any control. Once the experiment was presented to the participating group, the farmers chose the management treatment for their fields with recommendations from the researchers. For insect monitoring, yellow sticky and plate traps were used to obtain variables of insect abundance and diversity. The use and application of pesticides was recorded using surveys developed with Survey 123. The results showed that the application of insecticides was not always effective in controlling the pests studied. In addition, the treatments evaluated had different effects according to the type of insect pollinator analyzed. On the other hand, the study also showed that certain pests, especially borers, could induce a positive response (70 % more flowers) that can actually benefit the final yield. These results suggest that pest controls for this crop should be more targeted and carried out before flowering to avoid causing damage to pollinators and borers, as well as natural enemies of pests.

Climate change impacts on humans and ecosystems depend on the intensity, timing, and spatial variability of these changes. While considerable attention has been paid to current and future changes in temperature patterns, comparatively less attention has been devoted to water availability for humans and ecosystems. The aridity index (AI), the ratio of precipitation to potential evapotranspiration, is a common metric used to assess water availability within ecosystems. However, the role of snow in AI calculations within snowy eco-regions is often neglected, resulting in an incomplete understanding of water balance dynamics in these environments. In this study, we estimate aridification under ongoing climate change in Andean eco-regions (AEs), focusing on two horizons: 2050–2060 and 2090–2100. Using monthly TerraClimate data from 2013–2018, we calculated a mean AI for each AE, taking into account the absence of snow (pixels with a snow water equivalent (SWE) < 10 mm/month) and its presence (AI-snow; pixels with a SWE > 10 mm/month). We show that AI allows to differentiate the eco-regions, but that the incorporation of snow in the AI calculation highlights the heterogeneity of aridity conditions within some eco-regions with energy-limited regimes (AI > 1) in the snowy zones and water-limited regimes (AI < 1) elsewhere. Analysis of the CORDEX-SAM regional projections for the periods 2050–2060 and 2090–2100 indicates a general shift towards drier conditions prevailing over wetter conditions in most eco-regions, notably: the Southern Andean Steppe, the Central Andean Wet Puna, the Santa Marta Páramo, and the Peruvian Yungas. The projected reduction in snowfall in CORDEX-SAM, coupled with glacier volume loss, appears to be contributing to the prevalence of aridification across many AEs. These findings highlight potential transitions towards aridification in diverse eco-regions, with repercussions on water availability for humans and ecosystems.

The global retreat of glaciers is dramatically altering mountain and high-latitude landscapes, with new ecosystems developing from apparently barren substrates1–4. The study of these emerging ecosystems is critical to understanding how climate change interacts with microhabitat and biotic communities and determines the future of ice-free terrains1,5. Here, using a comprehensive characterization of ecosystems (soil properties, microclimate, productivity and biodiversity by environmental DNA metabarcoding⁶) across 46 proglacial landscapes worldwide, we found that all the environmental properties change with time since glaciers retreated, and that temperature modulates the accumulation of soil nutrients. The richness of bacteria, fungi, plants and animals increases with time since deglaciation, but their temporal patterns differ. Microorganisms colonized most rapidly in the first decades after glacier retreat, whereas most macroorganisms took longer. Increased habitat suitability, growing complexity of biotic interactions and temporal colonization all contribute to the increase in biodiversity over time. These processes also modify community composition for all the groups of organisms. Plant communities show positive links with all other biodiversity components and have a key role in ecosystem development. These unifying patterns provide new insights into the early dynamics of deglaciated terrains and highlight the need for integrated surveillance of their multiple environmental properties⁵.

Rivers and streams contribute to global carbon cycling by decomposing immense quantities of terrestrial plant matter. However, decomposition rates are highly variable, and large-scale patterns and drivers of this process remain poorly understood. Using a cellulose-based assay to reflect the primary constituent of plant detritus, we generated a predictive model (81% variance explained) for cellulose-decomposition rates across 514 globally distributed streams. A large number of variables were important for predicting decomposition, highlighting the complexity of this process at the global scale. Predicted cellulose-decomposition rates, when combined with genus-level litter-quality attributes, explain published leaf-litter-decomposition rates with impressive accuracy (70% variance explained). Our global map provides estimates of rates across vast understudied areas of Earth, and reveals rapid decomposition across continental-scale areas dominated by human activities.

The development of terrestrial ecosystems depends greatly on plant mutualists such as mycorrhizal fungi. The global retreat of glaciers exposes nutrient‐poor substrates in extreme environments and provides a unique opportunity to study early successions of mycorrhizal fungi by assessing their dynamics and drivers. We combined environmental DNA metabarcoding and measurements of local conditions to assess the succession of mycorrhizal communities during soil development in 46 glacier forelands around the globe, testing whether dynamics and drivers differ between mycorrhizal types. Mycorrhizal fungi colonized deglaciated areas very quickly (< 10 yr), with arbuscular mycorrhizal fungi tending to become more diverse through time compared to ectomycorrhizal fungi. Both alpha‐ and beta‐diversity of arbuscular mycorrhizal fungi were significantly related to time since glacier retreat and plant communities, while microclimate and primary productivity were more important for ectomycorrhizal fungi. The richness and composition of mycorrhizal communities were also significantly explained by soil chemistry, highlighting the importance of microhabitat for community dynamics. The acceleration of ice melt and the modifications of microclimate forecasted by climate change scenarios are expected to impact the diversity of mycorrhizal partners. These changes could alter the interactions underlying biotic colonization and belowground–aboveground linkages, with multifaceted impacts on soil development and associated ecological processes.

Time delays complicates the analysis of trophic dependence, which requires large time series data to study local associations. Here we propose using species distribution modeling. This approach removes confounding time lag effects and allows using data obtained separately in the different species. Since the approach is correlative, it cannot be interpreted in terms of causality. We apply the method to the interaction between the invasive potato moth Tecia solanivora and its granulovirus PhoGV in the Northern Andes. Host density was analyzed based on 1206 pheromone trap data from 106 sampled sites in Ecuador, Colombia and Venezuela. Virus prevalence was evaluated in 15 localities from 3 regions in Ecuador and Colombia. glm models were optimized for both variables on bioclimatic variables. Predicted virus prevalence was not significantly correlated to host density in the sampled virus sites. Across the climatic range covered by the study, correlation was R=−0.053. Of the total population of insect in this range, 26% were expected to be infected. Infection status was also analyzed for spatial structure at different scales: storage bag, storage room, field, locality, country. Locality and storage bag explained respectively 8% and 26% of the total deviance in infection status in glm analysis. Field and storage structure differed within locality but not always in the same direction. This basic method may help studying statistical relationships between species density across a number of trophic models making use of existing non sympatric data, with none or limited additional sampling effort.

The mechanisms underlying plant succession remain highly debated. Due to the local scope of most studies, we lack a global quantification of the relative importance of species addition ‘versus’ replacement. We assessed the role of these processes in the variation (β-diversity) of plant communities colonizing the forelands of 46 retreating glaciers worldwide, using both environmental DNA and traditional surveys. Our findings indicate that addition and replacement concur in determining community changes in deglaciated sites, but their relative importance varied over time. Taxa addition dominated immediately after glacier retreat, as expected in harsh environments, while replacement became more important for late-successional communities. These changes were aligned with total β-diversity changes, which were more pronounced between early-successional communities than between late-successional communities (>50 yr since glacier retreat). Despite the complexity of community assembly during plant succession, the observed global pattern suggests a generalized shift from the dominance of facilitation and/or stochastic processes in early-successional communities to a predominance of competition later on.

The 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.

This chapter, Underwater flies, zooms in further on the book’s central theme with a focus on my specific research for more than a decade: the ecology of high-altitude waters. It discusses the amazing adaptations of aquatic invertebrates, fish, frogs and other mountain organisms and describes observational and experimental studies that have tried to decipher the respective role of physical factors such as water temperature, oxygen and turbidity on their survival. The author describes the high-tech and low-tech approaches and methodologies adopted or invented to deal with this, from thermal cameras and the mathematical technique of the Fourier transform, to a rock-piling intervention. These studies allowed a new understanding of how aquatic systems respond to melting ice: glaciers not only provide the water that makes aquatic life possible on mountain peaks, they also give rise to a mosaic of unique environmental conditions, detectable kilometers downstream from the glacier.