Scientists' warning of threats to mountains

Biodiversity in mountain soils above the treeline

Biological diversity in mountain ecosystems has been increasingly studied over the last decade. This is also the case for mountain soils, but no study to date has provided an overall synthesis of the current state of knowledge. Here we fill this gap with a first global analysis of published research on cryptogams, microorganisms, and fauna in mountain soils above the treeline, and a structured synthesis of current knowledge. Based on a corpus of almost 1400 publications and the expertise of 37 mountain soil scientists worldwide, we summarise what is known about the diversity and distribution patterns of each of these organismal groups, specifically along elevation, and provide an overview of available knowledge on the drivers explaining these patterns and their changes. In particular, we document an elevation-dependent decrease in faunal diversity above the treeline, while for cryptogams there is an initial increase above the treeline, followed by a decrease towards the nival belt. Thus, our data confirm the key role that elevation plays in shaping the biodiversity and distribution of these organisms in mountain soils. The response of prokaryote diversity to elevation, in turn, was more diverse, whereas fungal diversity appeared to be substantially influenced by plants. As far as available, we describe key characteristics, adaptations, and functions of mountain soil species, and despite a lack of ecological information about the uncultivated majority of prokaryotes, fungi, and protists, we illustrate the remarkable and unique diversity of life forms and life histories encountered in alpine mountain soils. By applying rule- as well as pattern-based literature-mining approaches and semi-quantitative analyses, we identified hotspots of mountain soil research in the European Alps and Central Asia and revealed significant gaps in taxonomic coverage, particularly among biocrusts, soil protists, and soil fauna. We further report thematic priorities for research on mountain soil biodiversity above the treeline and identify unanswered research questions. Building upon the outcomes of this synthesis, we conclude with a set of research opportunities for mountain soil biodiversity research worldwide. Soils in mountain ecosystems above the treeline fulfil critical functions and make essential contributions to life on land. Accordingly, seizing these opportunities and closing knowledge gaps appears crucial to enable science-based decision making in mountain regions and formulating laws and guidelines in support of mountain soil biodiversity conservation targets.

Potential ecotoxicological effects of global change on organisms inhabiting high-mountain lakes in the Alps

High-mountain lakes in the Alps are highly sensitive freshwater ecosystems, increasingly impacted by climate change, pollution, and anthropogenic disturbances. This discussion assesses the ecotoxicological effects of global change such as rising temperatures, earlier snowmelt, glacier retreat, permafrost thaw, increased ultraviolet radiation, and pollutant deposition on aquatic organisms. A systematic literature search identified only nine studies explicitly addressing these ecotoxicological aspects. Given the limited availability of studies on Alpine high-mountain lakes, this analysis draws mainly on research from other high-altitude aquatic ecosystems. Rising temperatures alter metabolic rates, species distributions, pathogen susceptibility, and trophic interactions, disrupting ecological balance. Glacier retreat and permafrost thaw modify nutrient cycling, favoring cyanobacteria over diatoms, with cascading effects on food webs. These temperature shifts also increase oxygen demand and metabolic stress in aquatic organisms. Biofilm and zooplankton community shifts further destabilize food web dynamics, while macroinvertebrate assemblages become dominated by thermophilic taxa, affecting organic matter decomposition and nutrient availability. Amphibians are particularly vulnerable, as warming facilitates disease outbreaks like chytridiomycosis. Additionally, glacial melt and permafrost thaw release toxic substances, which bioaccumulate across trophic levels, inducing oxidative stress and reproductive impairments in fish, amphibians, and invertebrates. Contaminant biomagnification threatens entire food webs, compromising ecosystem as well as human health. Increased ultraviolet radiation exacerbates oxidative stress and interacts with pollutants, intensifying physiological damage. Future research should prioritize long-term monitoring, controlled exposure experiments, and predictive models. Conservation strategies must mitigate contaminants and enhance ecosystem resilience to protect biodiversity in these fragile environments.

Awaiting discovery: How biases in faunistic surveys hinder conservation in mountain protected areas-A case study from Romania's oldest national park

It is virtually impossible to compile a complete list of species and map their distributions in any protected area; nevertheless, a near complete inventory is vital for an adequate management plan. We use Retezat National Park (Romania) as a case study to assess the bias in faunistic inventories over the past 70 years. Retezat National Park is one of the most studied in Eastern Europe since it shelters some of the last patches of virgin old-growth forest in Europe. We reviewed the scientific literature published since the early 1900s dealing with faunistic surveys and retrieved the occurrence records available on GBIF for the study area. We identified a total of 4374 animal species belonging to 2113 genera, 494 families, 99 orders, 23 classes, and nine phyla. The number of publications started to accumulate after 1979, when the park became a Biosphere Reserve, reached a peak in the early 2000 and severely decreased during the last decade, highlighting a decline in the researchers' interest in faunistic surveys and, possibly, a delay between data collection and their publication. GBIF-mediated data made a small contribution, most records (60%) being collected in 2019. The bias analyses included only the distribution records available in the scientific literature, since they were already validated through peer-review. The number of publications and background of experts involved influenced the taxonomic coverage and inventory completeness. We found a strong spatial bias in terms of inventory coverage, with diversity hotspots located near roads and research facilities. Our study provides a roadmap for cost-effective future faunistic studies by prioritizing conservation efforts towards the most understudied areas and taxa within the park.

Winter and summer conditions affect the mountain population of Carabus variolosus, a ground beetle of European conservation concern

The changing climate has a significant impact on insect populations. Numerous species are challenged by increasing temperatures, changes in precipitation regimes, and reduction of snow cover, which alters soil moisture patterns in their habitats. Among them is Carabus variolosus Fabricius, 1787, a strongly hygrophilous, stenotopic species. The aim of our research was to analyze intra-seasonal changes in the first capture and activity of C. variolosus and to assess the potential impact of climatic factors on its abundance by analyzing climatic conditions during the summer of species activity, the preceding summer, and the winter before its emergence. Additionally, we aimed to determine whether different climatic conditions affect its spring and autumn activity. Our 4-year study revealed significant inter-seasonal variations in the first capture and activity patterns. We confirmed that C. variolosus is a spring breeder with adult summer diapause, and low activity of young beetles in autumn. Over 90 % of beetles were captured for the first time during the breeding season. The highest activity occurred in May, which seems to be male-driven, as the capture rate for females gradually decreased over time. Different climatic conditions influenced captures during the spring and autumn activity. Spring activity is correlated with conditions from the previous summer and winter, while autumn activity is related only to the summer conditions of the same year.

Diversity and Distribution Patterns of Amphibians in the Huangshan Mountain Region: The Roles of Climate and Human Activities

Global climate change and human activities are significant threats to biodiversity, contributing to the endangerment of approximately 41% of amphibian species worldwide. In this study, we applied field survey methods, the MaxEnt model, and integrated climate and human activity data to predict potential changes in the diversity and distribution of amphibian species in Huangshan Mountain, China. In this study, we have found 23 amphibian species, belonging to two orders, eight families, and 18 genera. The MaxEnt models showed that the distance from farmland (contributing 26.2%), shrubs (15.6%), and waterbodies (10.6%), as well as the NDVI (Normalized Difference Vegetation Index) (10.1%), significantly influence species distribution and diversity, suggesting that amphibian species prefer habitats with lower levels of human disturbance. Our models also showed that Bio3 (isothermal) (8.9%) and Bio8 (mean temperature of wettest quarter) (8.6%) have a significant impact on the species distribution and diversity, suggesting that amphibians are influenced by temperature and humidity. Our field survey showed that seasonal variation in amphibian diversity revealed significant correlations between climatic factors. Specifically, amphibian species diversity was positively correlated with wind speed, soil moisture, and rainfall (p < 0.05), while amphibian abundance was significantly linked to soil temperature, soil moisture, and rainfall (p < 0.05). These findings underscore the critical role of both climatic conditions and habitat structure in shaping amphibian populations and their distribution in Huangshan Mountain. Therefore, local management authorities should continue to monitor the marginal areas of the region, taking into account key human disturbances and climatic factors that favor the formation of amphibian diversity hotspots. Protective buffer zones should be established to provide effective refuges for amphibians.

Revealing the contribution of mountain ecosystem services research to sustainable development goals: A systematic and grounded theory driven review

Ecosystem services are the bridge between people and nature, especially for mountains, which cover more than two thirds of the world's territory, and are able to provide a diversity of ecosystem services and are significant for the enhancement of human well-being. Understanding how mountain ecosystem services (MES) support The United Nations (UN) Sustainable Development Goals (SDGs) is critical to realizing effective benefits from mountain resources, yet the extent to which MES support the SDGs is currently unclear and needs to be further explored. This study systematically reviewed the current research works by using grounded theory. We searched the Web of Science platform for papers closely related to mountain ecosystem services (2008-2022) and obtained 2010 papers, and further streamlined the most representative 114 papers based on the direct correlation between typical mountains, ecosystem service, and SDGs in the literature. We then explored the relationship between MES and specific SDGs and focused on the most strongly linked goals. The study indicated: (1) 66 targets (39%) and 12 SDGs (71%) were found, and we categorized the linkages into three categories, benefit, synergize, benefit & synergize. SDG3, 11, 13, 15 are goals that most strongly link to the MES, Subclasses storage and soil conservation services of ES are the most studied; (2) There is a gap between research and specific SDGs, and we need to focus on specific goals with relevant MES that are poorly researched but emphasized in SDGs; (3) The extent and emphasis of attention to mountain ecosystem services varied globally across continental regions. Therefore, we summarized a sustainable management model for mountain features. Policy makers are advocated to use our recommendations as a reference based on the specific features of the local mountains in combination with the development aims.

Insight into diversity change, variability and co-occurrence patterns of phytoplankton assemblage in headwater streams: a study of the Xijiang River basin, South China

Phytoplankton has been used as a paradigm for studies of coexistence of species since the publication of the "paradox of the plankton." Although there are a wealth of studies about phytoplankton assemblages of lakes, reservoirs and rivers, our knowledge about phytoplankton biodiversity and its underlying mechanisms in mountain headwater stream ecosystems is limited, especially across regional scales with broad environmental gradients. In this study, we collected 144 phytoplankton samples from the Xijiang headwater streams of the Pearl River across low altitude (< 1,000 m) located in Guangxi province, intermediate altitude (1,000 m < altitude <2,000 m) in Guizhou province and high altitude (> 2,000 m) in Yunnan province of China. Our study revealed high phytoplankton diversity in these streams. Freshwater phytoplankton, including cyanobacteria, Bacillariophyta, Chlorophyta, Rhodophyta, Chrysophyta, Euglenophyta, Glaucophyta, Phaeophyta and Cryptophyta, were all detected. However, phytoplankton alpha diversity exhibited a monotonic decreasing relationship with increasing altitude. High altitudes amplified the "isolated island" effect of headwater streams on phytoplankton assemblages, which were characterized by lower homogeneous selection and higher dispersal limitation. Variability and network vulnerability of phytoplankton assemblages increased with increasing altitudes. Our findings demonstrated diversity, variability and co-occurrence patterns of phytoplankton assemblages linked to environmental factors co-varying with altitude across regional scales.

Ecological features facilitating spread of alien plants along Mediterranean mountain roads

Invasive alien species represent a major threat to global biodiversity and the sustenance of ecosystems. Globally, mountain ecosystems have shown a degree of resistance to invasive species due to their distinctive ecological features. However, in recent times, the construction of linear infrastructure, such as roads, might weaken this resistance, especially in the Mediterranean basin region. Roads, by acting as efficient corridors, facilitate the dispersal of alien species along elevation gradients in mountains. Here, we investigated how the ecological features and road-associated disturbance in native plant communities affected both the occurrence and cover of alien plant species in Central Apennines (Italy). We implemented the MIREN road survey in three mountain transects conducting vegetation sampling in plots located both adjacent to and distant from the roads at intervals of ~ 100 m in elevation. We then used community-weighted means of Ecological Indicator Values for Europe together with Disturbance Indicator Values applied to plant species of native communities as predictors of alien species occurrence and cover in a machine-learning classification and regression framework. Our analyses showed that alien species' occurrence was greater in proximity to the road where high soil disturbance occurred and in warm- and light-adapted native communities. On the other hand, alien species cover was more strongly related to moderate grazing pressure and the occurrence of nitrophilic plant communities. These findings provide a baseline for the current status of alien plant species in this Mediterranean mountain region, offering an ecological perspective to address the challenges associated with their management under global change.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10530-024-03418-y.

Influences of ski-runs, meadow management and climate on the occupancy of reptiles and amphibians in a high-altitude environment of Italy

Alpine ecosystems harbour a rich and highly specialised biodiversity, which is particularly susceptible to anthropogenic disturbances such as habitat loss and fragmentation as well as to climate change. Combined with other forms of land-use conversion, construction and maintenance of ski resorts can have severe consequences on alpine biodiversity. In this study, we show how one amphibian and two reptile species, namely Rana temporaria, Zootoca vivipara and Vipera berus, respond to such impacts by means of a multi-season occupancy analysis. We found all three species both in and outside ski-runs, showing that these habitats do not necessarily preclude their occurrence. Contrarily, this is influenced more by microhabitat availability, such as ground vegetation, humid areas and rock cover, rather than by macro-characteristics like elevation or habitat type. Moreover, we found a climatic influence on the year-to-year occupancy change of the species, with activity-month conditions being more relevant than overwintering ones. Our results demonstrate how, in the specific case of reptiles and amphibians, ski resorts do not necessarily limit species' occurrence and that a mild series of management actions might secure the species' persistence in the area.

Biofilm community composition is changing in remote mountain lakes with a relative increase in potentially toxigenic algae

Mountain lakes provide clear drinking water to humankind but are strongly impacted by global change. Benthic biofilms are crucial for maintaining water quality in these oligotrophic lakes, yet little is known about the effects of global change on mountain biofilm communities. By combining analyses of metabarcoding data on 16S and 18S rRNA genes with climatic and environmental data, we investigated global change effects on the composition of biofilm prokaryotic and micro-eukaryotic assemblages in a five-year monitoring program of 26 Pyrenean lakes (2016-2020). Using time-decay relationships and within-lake dissimilarity modelling, we show that the composition of both prokaryotic and micro-eukaryotic biofilm communities significantly shifted and their biodiversity declined from 2016 to 2020. In particular, analyses of temporal trends with linear mixed models indicated an increase in the richness and relative abundance of cyanobacteria, including potentially toxigenic cyanobacteria, and a concomitant decrease in diatom richness and relative abundance. While these compositional shifts may be due to several drivers of global change acting simultaneously on mountain lake biota, water pH and hardness were, from our data, the main environmental variables associated with changes for both prokaryotic and micro-eukaryotic assemblages. Water pH and hardness increased in our lakes over the study period, and are known to increase in Pyrenean lakes due to the intensification of rock weathering as a result of climate change. Given predicted climate trends and if water pH and hardness do cause some changes in benthic biofilms, those changes might be further exacerbated in the future. Such biofilm compositional shifts may induce cascading effects in mountain food webs, threatening the resilience of the entire lake ecosystem. The rise in potentially toxigenic cyanobacteria also increases intoxication risks for humans, pets, wild animals, and livestock that use mountain lakes. Therefore, our study has implications for water quality, ecosystem health, public health, as well as local economies (pastoralism, tourism), and highlights the possible impacts of global change on mountain lakes.

Changing with the times: Seasonal environmental gradients unveil dynamic bat assemblages and vulnerability

Uncovering the temporal and spatial dynamics of biological communities in response to biotic and abiotic drivers is essential to predict the effects of environmental change on biodiversity. Similarly, estimating species vulnerability in the face of such dynamics is crucial for implementing effective conservation actions. We explored how bat diversity changes over the year across an altitudinal gradient and identified the environmental drivers that shape bat communities. By analysing species' marginality within the biophysical niche space, we evaluated bats' vulnerability to foreseeable environmental changes. Our results suggest that altitude, the proportion of forest cover and shrub cover are the main drivers shaping bat communities year-round. Additionally, while some bat species are restricted to a single ecological assemblage (or ecological preferences group), others show greater plasticity throughout the year. Importantly, we found that although bats associated with highland habitats and forests could be particularly vulnerable to environmental changes (in particular Myotis mystacinus), this vulnerability correlates poorly with their national conservation status. We suggest that species' ecological plasticity is critical for the resilience of biological communities exposed to environmental changes and should be considered when planning tailored conservation strategies.

Plant invasion risk inside and outside protected areas: Propagule pressure, abiotic and biotic factors definitively matter

Invasive alien species are among the main global drivers of biodiversity loss posing major challenges to nature conservation and to managers of protected areas. The present study applied a methodological framework that combined invasive Species Distribution Models, based on propagule pressure, abiotic and biotic factors for 14 invasive alien plants of Union concern in Italy, with the local interpretable model-agnostic explanation analysis aiming to map, evaluate and analyse the risk of plant invasions across the country, inside and outside the network of protected areas. Using a hierarchical invasive Species Distribution Model, we explored the combined effect of propagule pressure, abiotic and biotic factors on shaping invasive alien plant occurrence across three biogeographic regions (Alpine, Continental, and Mediterranean) and realms (terrestrial and aquatic) in Italy. We disentangled the role of propagule pressure, abiotic and biotic factors on invasive alien plant distribution and projected invasion risk maps. We compared the risk posed by invasive alien plants inside and outside protected areas. Invasive alien plant distribution varied across biogeographic regions and realms and unevenly threatens protected areas. As an alien's occurrence and risk on a national scale are linked with abiotic factors followed by propagule pressure, their local distribution in protected areas is shaped by propagule pressure and biotic filters. The proposed modelling framework for the assessment of the risk posed by invasive alien plants across spatial scales and under different protection regimes represents an attempt to fill the gap between theory and practice in conservation planning helping to identify scale, site, and species-specific priorities of management, monitoring and control actions. Based on solid theory and on free geographic information, it has great potential for application to wider networks of protected areas in the world and to any invasive alien plant, aiding improved management strategies claimed by the environmental legislation and national and global strategies.

Ambient ozone - New threat to birds in mountain ecosystems?

Mountain ecosystems are inhabited by species with specific characteristics enabling survival at high altitudes, which make them at risk from various pressures. In order to study these pressures, birds represent excellent model organisms due to their high diversity and position at the top of food chains. The pressures upon mountain bird populations include climate change, human disturbance, land abandonment, and air pollution, whose impacts are little understood. Ambient ozone (O₃) is one of the most important air pollutants occurring in elevated concentrations in mountain conditions. Although laboratory experiments and indirect course-scale evidence suggest its negative effects on birds, population-level impacts remain unknown. To fill this knowledge gap, we analysed a unique 25-years long time series of annual monitoring of bird populations conducted at fixed sites under constant effort in a Central European mountain range, the Giant Mountains, Czechia. We related annual population growth rates of 51 bird species to O₃ concentrations measured during the breeding season and hypothesized (i) an overall negative relationship across all species, and (ii) more negative O₃ effects at higher altitudes due to increasing O₃ concentration along altitudinal gradient. After controlling for the influence of weather conditions on bird population growth rates, we found an indication of the overall negative effect of O₃ concentration, but it was insignificant. However, the effect became stronger and significant when we performed a separate analysis of upland species occupying the alpine zone above treeline. In these species, populations growth rates were lower after the years experiencing higher O₃ concentration indicating an adverse impact of O₃ on bird breeding. This impact corresponds well to O₃ behaviour and mountain bird ecology. Our study thus represents the first step towards mechanistic understanding of O₃ impacts on animal populations in nature linking the experimental results with indirect indications at the country-level.

Intense touristic activities exceed climate change to shape aquatic communities in a mountain lake

Mountain lakes are especially vulnerable to climate change, but are also increasingly exposed to local anthropogenic development through winter and summer tourism. In this study, we aimed to tease apart the influence of tourism from that of climate in a mountain lake located within one of the largest French ski resorts, by combining paleolimnological and present ecological data. The reconstructed long-term ecological dynamics highlighted an increase in lake biological production from the end of the Little Ice Age up to the 1950s, suggesting a historical dominance of climate control. Afterward, a major drop in pelagic production occurred at the same time as the watershed erosion increased and peaked in the 1990s, concomitant with massive digging for the ski resort expansion. The benthic invertebrates collapsed in the 1980s, concomitantly with the onset of massive salmonid stocking and recent warming. Stable isotope analyses identified benthic invertebrates as the major salmonid diet resource and suggested a possible direct impact of salmonid stocking on benthic invertebrates. However, habitat use may differ among salmonid species as suggested by the way fish DNA was preserved in surficial sediment. The high abundances of macrozooplankton further confirmed the limited reliance of salmonids on pelagic resources. The variable thermal tolerance of benthic invertebrates suggested that the recent warming may mostly affect littoral habitats. Our results indicate that winter and summer tourism may differently affect the biodiversity of mountain lakes and could collectively interfere with the ecological impacts of recent warming, making local management of primary importance to preserve their ecological integrity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00027-023-00968-6.

Standardised inventories of lepidopterans and odonates from Serra da Estrela Natural Park (Portugal) - setting the scene for mountain biodiversity monitoring

Background

Mountain insect biodiversity is unique, but is menaced by different drivers, particularly climate and land-use changes. In mainland Portugal, the highest mountain - Serra da Estrela - is one of the most important biodiversity hotspots, being classified as Natural Park since 1976. Many lepidopteran and odonate species, including rare and protected species, are known to occur in Serra da Estrela, but basic knowledge on their abundance, distribution and ecology is still lacking. Standardised sampling of these communities is crucial to provide valuable biological information to support short-term decision-making for conservation management, setting simultaneously the standards for mountain biodiversity monitoring aiming to tackle the effects of environmental change in the long-term.

New information

This study reports novel information on lepidopteran and odonate species diversity, distribution and abundance from Serra da Estrela Natural Park (Portugal). Seventy-two lepidopteran and 26 odonate species were sampled in this protected area, including the first findings of Apaturailia (Denis & Schiffermüller, 1775), Macromiasplendens (Pictet, 1843) and Vanessavirginiensis (Drury, 1773). New populations of Euphydriasaurinia (Rottemburg, 1775) and Oxygastracurtisii (Dale, 1834), protected species under the Habitats Directive, were found in this Natural Park and novel distribution and ecological data were collected for most species, including several rare species and subspecies [e.g. Aeshnajuncea (Linnaeus, 1758), Coenonymphaglycerioniphioides Staudinger, 1870, Cyanirissemiargus (Rottemburg, 1775) and Sympetrumflaveolum (Linnaeus, 1758)]. All data were collected using standardised sampling allowing its use as a baseline for biodiversity monitoring in Serra da Estrela.

The importance of a holistic approach to the factors determining population abundances

Research Highlight: Ogilvie, J. E., & CaraDonna, P. J. (2022). The shifting importance of abiotic and biotic factors across the life cycles of wild pollinators. Journal of Animal Ecology, 91, 2412-2423. https://doi.org/10.1111/1365-2656.13825. As global change and its multiple impacts continue to unfold across most of the planet, understanding how populations of wild species respond to changing conditions has become a major focus of ecological studies. Ogilvie and CaraDonna (Ogilvie & CaraDonna, 2022) focus on understanding how biotic and abiotic conditions affect bumblebee abundances. A major advance in their work is that, rather than focusing on a single measure of abundance at a particular life stage for each of the seven bumblebee species they survey (e.g. adult abundance), they focus on understanding the drivers of population abundance across the different stages of the species' life cycles. The authors specifically assess how three factors in particular, climate conditions, floral resource availability and previous life-stage abundances impact these abundances. A main finding in their study is that each of these three factors directly impacted a different life stage, showing that just focusing on a single life-stage would have resulted on a biased and incomplete picture of how abiotic and biotic factors affect bumblebee population dynamics. Studies like this one emphasize the need to focus on understanding the demographic mechanisms that determine population abundances.