Climate Warming Research Articles

Assessing the response of marine fish communities to climate change and fishing.

Globally, marine fish communities are being altered by climate change and human disturbances. We examined data on global marine fish communities to assess changes in community-weighted mean temperature affinity (i.e., mean temperatures within geographic ranges), maximum length, and trophic levels, which, respectively, represent the physiological, morphological, and trophic characteristics of marine fish communities. Then, we explored the influence of climate change and fishing on these characteristics because of their long-term role in shaping fish communities, especially their interactive effects. We employed spatial linear mixed models to investigate their impacts on community-weighted mean trait values and on abundance of different fish lengths and trophic groups. Globally, we observed an initial increasing trend in the temperature affinity of marine fish communities, whereas the weighted mean length and trophic levels of fish communities showed a declining trend. However, these shift trends were not significant, likely due to the large variation in midlatitude communities. Fishing pressure increased fish communities' temperature affinity in regions experiencing climate warming. Furthermore, climate warming was associated with an increase in weighted mean length and trophic levels of fish communities. Low climate baseline temperature appeared to mitigate the effect of climate warming on temperature affinity and trophic levels. The effect of climate warming on the relative abundance of different trophic classes and size classes both exhibited a nonlinear pattern. The small and relatively large fish species may benefit from climate warming, whereas the medium and largest size groups may be disadvantaged. Our results highlight the urgency of establishing stepping-stone marine protected areas to facilitate the migration of fishes to habitats in a warming ocean. Moreover, reducing human disturbance is crucial to mitigate rapid tropicalization, particularly in vulnerable temperate regions.

Assessing CESM2 Clouds and Their Response to Climate Change Using Cloud Regimes

Abstract The Community Earth System Model, version 2 (CESM2), has a very high climate sensitivity driven by strong positive cloud feedbacks. To evaluate the simulated clouds in the present climate and characterize their response with climate warming, a clustering approach is applied to three independent satellite cloud products and a set of coupled climate simulations. Using k-means clustering with a Wasserstein distance cost function, a set of typical cloud configurations is derived for the satellite cloud products. Using satellite simulator output, the model clouds are classified into the observed cloud regimes in both current and future climates. The model qualitatively reproduces the observed cloud configurations in the historical simulation using the same time period as the satellite observations, but it struggles to capture the observed heterogeneity of clouds which leads to an overestimation of the frequency of a few preferred cloud regimes. This problem is especially apparent for boundary layer clouds. Those low-level cloud regimes also account for much of the climate response in the late twenty-first century in four shared socioeconomic pathway simulations. The model reduces the frequency of occurrence of these low-cloud regimes, especially in tropical regions under large-scale subsidence, in favor of regimes that have weaker cloud radiative effects.

Spawning fish maintains trophic synchrony across time and space beyond thermal drivers.

Increasing ocean temperature will speed up physiological rates of ectotherms. In fish, this is suggested to cause earlier spawning due to faster oocyte growth rates. Over time, this could cause spawning time to become decoupled from the timing of offspring food resources, a phenomenon referred to as trophic asynchrony. We used biological data, including body length, age, and gonad developmental stages collected from >125,000 individual Northeast Arctic cod (Gadus morhua) sampled between 59 and 73° N in 1980-2019. Combined with experimental data on oocyte growth rates, our analyses show that cod spawned progressively earlier by about a week per decade, partly due to ocean warming. It also appears that spawning time varied by more than 40 days, depending on year and spawning location. The significant plasticity in spawning time seems to be fine-tuned to the local phytoplankton spring bloom phenology. This ability to partly overcome thermal drivers and thus modulate spawning time could allow individuals to maximize fitness by closely tracking local environmental conditions important for offspring survival. Our finding highlights a new dimension for trophic match-mismatch and should be an important consideration in models used to predict phenology dynamics in a warmer climate.

Shifts in mycorrhizal types of fungi and plants in response to fertilisation, warming and herbivory in a tundra grassland.

Climate warming is severely affecting high-latitude regions. In the Arctic tundra, it may lead to enhanced soil nutrient availability and interact with simultaneous changes in grazing pressure. It is presently unknown how these concurrently occurring global change drivers affect the root-associated fungal communities, particularly mycorrhizal fungi, and whether changes coincide with shifts in plant mycorrhizal types. We investigated changes in root-associated fungal communities and mycorrhizal types of the plant community in a 10-yr factorial experiment with warming, fertilisation and grazing exclusion in a Finnish tundra grassland. The strongest determinant of the root-associated fungal community was fertilisation, which consistently increased potential plant pathogen abundance and had contrasting effects on the different mycorrhizal fungal types, contingent on other treatments. Plant mycorrhizal types went through pronounced shifts, with warming favouring ecto- and ericoid mycorrhiza but not under fertilisation and grazing exclusion. Combination of all treatments resulted in dominance by arbuscular mycorrhizal plants. However, shifts in plant mycorrhizal types vs fungi were mostly but not always aligned in their magnitude and direction. Our results show that our ability to predict shifts in symbiotic and antagonistic fungal communities depend on simultaneous consideration of multiple global change factors that jointly alter plant and fungal communities.

Vaccinium dwarf shrubs responses to experimental warming and herbivory resistance treatment are species- and context dependent

Climate change impacts on species and ecosystem functioning may depend on climatic context and study systems. Climate warming and intensified herbivory are two stressors to plants that often appear in combination and are predicted to increase in cold environments. Effects of multiple drivers on plant performance are difficult to predict and warrant studies that use experimental manipulations along climatic gradients to produce more realistic knowledge. Our three study sites by the Sognefjord in Norway, that differed mainly in climatic conditions (ca. 5°C growing season difference), ranged from hemi-boreal lowland (100 masl, Low), via boreal mid-montane (500 masl) to alpine timberline (900 masl, High) bioclimates. At each site, in a randomized block design, we simulated growing-season warming using open-top chambers (OTCs) and experimentally induced herbivory resistance using the plant hormone methyl jasmonate (MeJA). We recorded growth, mortality, flower and fruit numbers, and insect herbivory on tagged ramets in permanent plots across three years (2016-2018) in three open woodland populations of two functionally important plant species with contrasting traits, Vaccinium myrtillus (bilberry) and V. vitis-idaea (lingonberry). Growth of both dwarf shrubs decreased with warming in the warm lowland populations (Low) but increased in the alpine populations (High). Shoot mortality increased most with warming at Low but was reduced at High. Reproduction, both flowering and fruiting, decreased with induced resistance treatment, but the effect was larger when warmed for bilberry and increased with elevation for both species. Leaf herbivory in bilberry increased with warming at Low but decreased at High. The combined warming and resistance treatment had only synergistic negative interaction effects on fruit numbers in bilberry. The clear context- and species-dependent effects of climate warming and increased resistance in this study may predict a potential decline in performance, as well as abundance and distribution, of these functionally important Vaccinium species at our lowest site. Bilberry reproduction appeared to be particularly susceptible to both climate warming and induced resistance in the manipulated populations. Such combined negative effects on plant performance are likely to have considerable knock-on effects via altered species’ interactions and ecosystem functioning.

Impacts and State‐Dependence of AMOC Weakening in a Warming Climate

AbstractAll climate models project a weakening of the Atlantic Meridional Overturning Circulation (AMOC) strength in response to greenhouse gas forcing. However, the climate impacts of the AMOC decline alone cannot be isolated from other drivers of climate change using existing Coupled Model Intercomparison Project simulations. To address this issue, we conduct idealized experiments using the EC‐Earth3 climate model. We compare an abrupt 4×CO2 simulation with the same experiment, except we artificially fix the AMOC strength at preindustrial levels. With this design, we can formally attribute differences in climate change impacts between these two experiments to the AMOC decline. In addition, we quantify the state‐dependence of AMOC impacts by comparing the aforementioned experiments with a preindustrial simulation in which we artificially reduce the AMOC strength. Our findings demonstrate that AMOC decline impacts are state‐dependent, thus understanding AMOC impacts on future climate change requires targeted model experiments.

The Potential of Absorbing Aerosols to Enhance Extreme Precipitation

AbstractUnderstanding the impact of various climate forcing agents, such as aerosols, on extreme precipitation is socially and scientifically vital. While anthropogenic absorbing aerosols influence Earth's energy balance and atmospheric convection, their role in extreme events remains unclear. This paper uses convective‐resolving radiative‐convective‐equilibrium simulations, with fixed solar radiation, to investigate the influence of absorbing aerosols on extreme precipitation comprehensively. Our findings reveal an underappreciated mechanism through which absorbing aerosols can, under certain conditions, strongly intensify extreme precipitation. Notably, we demonstrate that a mechanism previously reported for much warmer (hothouse) climates, where intense rainfall alternates with multi‐day dry spells, can operate under current realistic conditions due to absorbing aerosol influence. This mechanism operates when an aerosol perturbation shifts the lower tropospheric radiative heating rate to positive values, generating a strong inhibition layer. Our work highlights an additional potential effect of absorbing aerosols, with implications for climate change mitigation and disaster risk management.

Spatiotemporal Variations in Snow Cover on the Tibetan Plateau from 2003 to 2020

The variations in snow cover on the Tibetan Plateau play a pivotal role in comprehending climate change patterns and governing hydrological processes within the region. This study leverages daily snow cover data and the NASA Digital Elevation Model (DEM) from 2003 to 2020 to analyze spatiotemporal snow cover days and assess their responsiveness to climatic shifts by integrating meteorological data. The results reveal significant spatial heterogeneity in snow cover across the Plateau, with a slight decreasing trend in annual average snow cover duration. Snow cover is predominantly observed during the spring and winter seasons, constituting approximately 32% of the total snow cover days annually. The onset and cessation of snow cover occur within a range of 120–220 days. Additionally, an increasing trend in snow cover duration below 5000 m altitude was observed, in addition to a decreasing trend above 5000 m altitude. Sub-basin analysis delineates the Tarim River Basin as exhibiting the lengthiest average annual snow cover duration of 83 days, while the Yellow River Basin records the shortest duration of 31 days. The decreasing trend in snow cover duration closely aligns with climate warming trends, characterized by a warming rate of 0.17 ± 0.54 °C per decade, coupled with a concurrent increase in precipitation at a rate of 3.09 ± 3.81 mm per year. Temperature exerts a more pronounced influence on annual snow cover duration variation compared to precipitation, as evidenced by a strong negative correlation (CC = −0.67). This study significantly augments the comprehension of hydrological cycle dynamics on the Tibetan Plateau, furnishing essential insights for informed decision-making in water resource management and ecological conservation efforts.

Ecogeographic rules in a common Neotropical treefrog: No clinal variation along a mountain range

AbstractBody and limb size are associated with many aspects of the biology of animals. Geographic variation in morphological traits has often been investigated through ecogeographical rules. Bergmann's rule posits an inverse relationship between body size and temperature in homeotherms, while Allen's rule posits that endothermic animals inhabiting colder climates have relatively shorter protruding parts (e.g., limbs) in comparison to populations from warmer climates. However, the applicability and validity of these rules in poikilotherms are currently contentious. In this study, we aimed to test predictions of Bergmann's and Allen's rules in populations of the Neotropical frog Boana platanera. We analysed 142 adult male museum specimens from 17 localities along a mountain range in western Venezuela. We obtained six external morphological measurements and assessed the correlation of body size and limb size with temperature data for each locality. Our results were contrary to the expectations but consistent with previous studies. All this together indicates that exceptions to the Bergmann's and Allen's rules are frequent and idiosyncratic in anurans. We discuss alternative hypotheses that could explain geographic variation of body and limb size in future studies.

Species richness responds to buffer effectiveness and competitive priorities in simulations of alpine microrefugia

AbstractAimMicrorefugia on alpine slopes may allow species to persist in a warming climate. How plant species richness could respond to of the effectiveness of climatic buffering, defined as the difference in climate change in a microrefugium in comparison to that of an open alpine slope as mediated by competitive priority effects, is explored.LocationAlpine habitat anywhere.TaxonVascular plants.MethodsA simple spatially explicit model of plant species with adaptations across a climatic gradient simulates reproduction, dispersal, and mortality through climatic change. The effectiveness of microrefugia in buffering climate change and levels of competitive priority effects are included as factors that alter demographic rates in an experimental framework. Spatial patterns of microrefugia and differences in dispersal are also simulated. Differences in mean species richness were analysed.ResultsThe number of species conserved, relative to an instantaneous equilibrium calculation with the same climatic change, decreases with inclusion of a period of change (transient vs. instantaneous, equilibrium change) and further with competitive priority effects. In these simulations, the number of species conserved does not simply increase with buffer effectiveness, as hypothesized, but instead is bimodal.Main ConclusionsThe dip in number of species conserved in the middle range of buffer effectiveness occurs because barriers develop. These are temporal ecological traps, wherein species adapted to the middle of a climatic gradient become extinct, because their colonization of microrefugia is blocked by an extinction debt of resident species. The inertia that allows these demographic consequences is increased by competitive priorities. The highest levels of buffering and resulting inertia will not be ubiquitous but the bimodal pattern indicates that assessments of the role of microrefugia need to recognize the temporal species‐environment and species‐species interactions that will change the number of species conserved versus extinctions.

Response Mechanism of cbbM Carbon Sequestration Microbial Community Characteristics in Different Wetland Types in Qinghai Lake

Carbon-sequestering microorganisms play an important role in the carbon cycle of wetland ecosystems. However, the response mechanism of carbon-sequestering microbial communities to wetland type changes and their relationship with soil carbon remain unclear. To explore these differences and identify the main influencing factors, this study selected marsh wetlands, river wetlands and lakeside wetlands around Qinghai Lake as research subjects. High-throughput sequencing was employed to analyze the functional gene cbbM of carbon-sequestering microorganisms. The results revealed that the alpha diversity of cbbM carbon-sequestering microorganisms mirrored the trend in total carbon content, with the highest diversity observed in marsh wetlands and the lowest in lakeside wetlands. The dominant bacterial phylum was Proteobacteria, with prevalent genera including Thiothrix, Acidithiobacillus, and Thiodictyon. Acidithiobacillus served as a biomarker in lakeside wetlands, while two other genera were indicative of marsh wetlands. The hierarchical partitioning analysis indicated that the diversity of cbbM carbon-fixing microorganisms was primarily influenced by the total nitrogen content, while the community structure was significantly affected by the soil total carbon content. Moreover, an increased soil temperature and humidity were found to favor the carbon fixation processes of Thiomicrospira, Thiomonas, Polaromonas, and Acidithiobacillus. In summary, changes in wetland types seriously affected the characteristics of cbbM carbon sequestration in microbial communities, and a warm and humid climate may be conducive to wetland carbon sequestration.

High photoreactivity of chromophoric dissolved organic matter derived from Ulva prolifera and Sargassum

The epipelagic macroalgae of Ulva prolifera and Sargassum are the primary contributors to widespread seaweed tides globally. Both ocean plants release large amounts of chromophoric dissolved organic matter (CDOM) into the surrounding seawater. The photochemical reactivity of this CDOM, however, has not been adequately addressed. In this study, we extracted CDOM from Ulva prolifera and Sargassum, examined their ultraviolet (UV)-visible absorption characteristics, and quantified their broadband apparent quantum yields (AQY) of absorbance photobleaching and photomineralization (in terms of CO2, CO, and CH4 photoproduction). On a per-unit-weight basis, Sargassum leached 3.5 times more CDOM than did Ulva prolifera in terms of the absorption coefficient averaged over 254–500 nm. Both Ulva prolifera and Sargassum CDOM were characterized by quasi-exponential decay absorption spectra, with Sargassum CDOM exhibiting a distinct shoulder over 310–350 nm suggestive of mycosporine amino acids. The Sargassum CDOM had a higher photobleaching AQY but lower photomineralization AQYs compared to Ulva prolifera CDOM. The photobleaching and photomineralization AQYs of both macroalgal CDOM are, however, orders of magnitude higher than those of CDOM in various natural waters. Potential photoproduction rates of CO2 and CO from the Ulva prolifera CDOM and Sargassum CDOM during the bloom periods are several times to orders of magnitude higher than the air-sea fluxes of these gases in the absence of the macroalgae. This study demonstrates that CDOM released by Ulva prolifera and Sargassum is extremely prone to photobleaching and photomineralization, rendering floating mats of these plants in oceans as potential “hotspots” of greenhouse gas emissions to the atmosphere. This photochemical feedback should be considered when assessing ocean afforestation as a CO2 removal approach to mitigate climate warming.

Surface topography modelling and ice flow velocity mapping of Dalk Glacier, East Antarctica: application of UAV remote sensing

Abstract. The Antarctic Ice Sheet is the largest potential contributor to global sea level rise due to global climate warming, making it important to monitor changes in the marginal outlet glacier dynamics and surface topography. The unmanned aerial vehicle (UAV), a new platform, has been proven to be a useful tool in glaciological applications because it can collect data in a variety of ways and has a high spatial and temporal resolution compared to traditional ground-based measurements and remote sensing from space. In this study, we used the combined UAV platform composed of the DJI Mavic 3 Enterprise (M3E) and M300 (L1) versions to perform high-accuracy on-site investigations of Dalk Glacier, a typical outlet glacier near the Zhongshan Station in East Antarctica. During the 39th Chinese Antarctic Expedition (CHINARE) in 2022–2023, UAV surveys with multiple sensors were performed. The M3E optical camera makes it possible to reconstruct high-resolution ortho-mosaic and digital elevation models (DEMs) of Dalk Glacier with high accuracy based on photogrammetric principles, helping us to extract the features of glacier surface topography, while dense point clouds derived from the L1 LiDAR camera are used to validate and improve the three-dimensional accuracy. To further monitor the dynamics and stability of Dalk Glacier, we generate ice flow velocity maps using ortho-mosaics for the years 2019, 2020, and 2023. The spatiotemporal changes in ice flow velocities were further compared with the products derived from satellite remote sensing data.

Spatio‐temporal shift in body size and plumage coloration is associated with the magnitude of climate change in a cosmopolitan owl

AbstractAimClimatic gradients shape geographic variation in phenotypic traits that are involved in animal thermoregulation. Therefore, increasing temperatures under global warming are expected to cause change over time in traits that show predictable spatial patterns according to environmental clines (body and appendage size, tegument coloration), as well exemplified by biogeographic rules and shown by increasing literature at a local scale. However, whether temporal shifts in phenotypic traits vary spatially according to the magnitude of the change in local climatic conditions is still unknown.LocationWorld.TaxonBarn owl species complex (Tyto alba group).MethodsBy using thousands of museum specimens collected across the globe from 1901 to 2018, we calculated within‐population change over time in wing length, bill length and melanin‐based plumage coloration and examined whether these trends differed across geographic regions, latitudes and gradients of climate changes.ResultsWe showed that populations exposed to an increasing warmer climate were subjected to a more marked decrease in body size, as gauged by wing length, and also absolute bill length that displayed a similar, although less steep, pattern of shrinking over time. In addition, phaeomelanin‐based ventral plumage colour has become paler in regions where the climate changed into warmer and drier, and darker where both temperature and precipitation increased.Main ConclusionsThese trends are generally coherent with the predictions based on Bergmann's and Gloger's rules, but not Allen's rule, and suggest that temporal shifts in body size and tegument colour depend on the magnitude of the alteration in climatic conditions, with populations living in regions where the climate has changed the most that are subjected to more marked phenotypic changes. Spatio‐temporal variation in climate has driven within‐species phenotypic clines, and it is expected to increase differences among populations according to the predicted further climate change.

A Genome-Wide Analysis of the BAM Gene Family and Identification of the Cold-Responsive Genes in Pomegranate (Punica granatum L.)

Beta-amylases (BAMs, EC 3.2.1.2), belonging to a multigene family, play a pivotal role in starch breakdown and are also involved in hormonal and stress responses, notably to cold stress. Pomegranate trees (Punica granatum L.) are adapted to warm climates and are sensitive to cold temperatures. In this study, we analyzed eight PgBAM genes from the pomegranate genome dataset. These members unevenly distributed across chromosomes and were categorized into four groups based on their orthologous members. The motif composition was highly consistent among most members. In contrast, exon numbers and arrangements were conserved within groups or subgroups, whereas significant diversity was observed between different groups. A syntenic analysis revealed that three PgBAM members (PgBAM1/4/5) showed a total of 11 syntenic relationships with the BAM members from Arabidopsis, kiwifruit, and Chinese white pear, respectively. Promoter binding motif prediction suggested potential roles for PgBAMs’ genes in light, stress, hormones, and development signaling. Gene expression indicated that PgBAM4 was predominantly expressed in leaves, PgBAM7 in flowers, and PgBAM8 in roots and leaves and during fruit ripening, particularly in pericarp development. A transcriptome analysis identified the starch and sucrose metabolism pathway (map00500) as a key factor in the cold stress response of cold-sensitive cultivar ‘Tunisia’ seedlings. PgBAM4 exhibited remarkable expression and was closely associated with the cold-responsive BAM genes, characterized by a closer phylogenetic relationship, conserved catalytic residues, and similar secondary and tertiary structures. Moreover, the differences in soluble sugar levels and PgBAM4 expression were closely associated with the varying cold stress resistance observed between ‘Tunisia’ and ‘Sanbai’ seedlings. Furthermore, yeast one-hybrid assays confirmed that PgCBF7, a critical transcription factor for enhancing freezing tolerance, binds to the promoter region of PgBAM4. Our findings provide a systematic overview of the PgBAM gene family and shed new light on the regulatory mechanisms underlying cold stress tolerance in pomegranate.

Amplification of the discrepancy between simplified and physics-based wet-bulb globe temperatures in a warmer climate

The Simplified Wet Bulb Globe Temperature (sWBGT) is widely used in heat stress assessments for climate-change studies, but its limitations have not been thoroughly explored. Building on recent critiques of sWBGT's use for current climate on global scale, this study examines sWBGT's biases using dynamically-downscaled sub-daily climate projections under multiple future emission scenarios. The analysis is aimed at understanding caveats in the application of sWBGT and the uncertainties in existing climate change analysis dependent on sWBGT. Results indicate sWBGT's biases are heavily influenced by local near-surface air temperature, with overestimation of heat stress in East Asia regions, particularly hot and humid areas, due to static assumptions of radiation and wind speed. This overestimation is amplified in warmer climates, leading to exaggerated projected heat stress increases in future. In contrast, underestimations are found for heat stress levels attributed to low wind speeds and strong radiations, such as over the Tibetan Plateau and certain extreme events. Additionally, sWBGT underestimates variability in extreme heatwave events compared to WBGT in both current and future climates, irrespective of overestimation in absolute heatwave intensities. This study emphasizes the limitations of sWBGT, especially in future warmer climates. Importance of sub-daily data for capturing daily maximum heat stress level and reflecting diurnal variations in different components is also discussed. In conclusion, we recommend using Liljegren's model (i.e., physics-based calculation) with high-resolution sub-daily climate data for more accurate outdoor heat stress assessments in climate change studies.

Resisting the heat wave: Revealing inequalities in matching between heat exposure risk and healthcare services in a megacity

Climate warming and the growing urban heat island effect are exacerbating the unequal public health crisis in megacities, and thus it is important to assess the equity of matching relationship between the healthcare services and the heat exposure risk. We selected 255 census units in Tianjin city for the study, and calculated a heat exposure index based on the universal thermal climate index (UTCI) and constructed a comprehensive urban healthcare services evaluation system to measure the degree of mismatch between the two. The results showed the following. (1) The heat exposure risk and healthcare services followed an increasing pattern from the Outer suburb area (OSA) to the Metropolitan development area (MDA) and then to the Main urban area (MUA). (2) The overall imbalance in matching was low in the OSA, whereas the healthcare services were relatively insufficient in the MDA, and the heat exposure risk and healthcare services were relatively balanced in the MUA. (3) The degree of matching between the core and peripheral parts of the MUA was severely polarized, with an overall pattern of excess healthcare in the core area and a high risk of heat exposure in the peripheral areas. The results can provide effective guidance for rationalizing the allocation of healthcare resources from a heat exposure perspective, and provide a policy basis for risk management and fund investment.

Global convergence in terrestrial gross primary production response to atmospheric vapor pressure deficit.

Atmospheric vapor pressure deficit (VPD) increases with climate warming and may limit plant growth. However, gross primary production (GPP) responses to VPD remain a mystery, offering a significant source of uncertainty in the estimation of global terrestrial ecosystems carbon dynamics. In this study, in-situ measurements, satellite-derived data, and Earth System Models (ESMs) simulations were analysed to show that the GPP of most ecosystems has a similar threshold in response to VPD: first increasing and then declining. When VPD exceeds these thresholds, atmospheric drought stress reduces soil moisture and stomatal conductance, thereby decreasing the productivity of terrestrial ecosystems. Current ESMs underscore CO2 fertilization effects but predict significant GPP decline in low-latitude ecosystems when VPD exceeds the thresholds. These results emphasize the impacts of climate warming on VPD and propose limitations to future ecosystems productivity caused by increased atmospheric water demand. Incorporating VPD, soil moisture, and canopy conductance interactions into ESMs enhances the prediction of terrestrial ecosystem responses to climate change.

A Warm Welcome to the Alps—The Northward Expansion of Trithemis annulata (Odonata, Libellulidae) in Italy

Climate warming has already influenced the distribution, community composition, and phenology of European Odonata. Trithemis annulata had been confined to the southern regions of Italy for over 150 years. In only four decades, it has expanded its range and has recently been observed inhabiting several alpine valleys. A dataset of 2557 geographical distribution data points spanning the years 1825–2023 was compiled using various resources, with the aim to analyse the chrono-story of the expansion of T. annulata. A further aim was to investigate the climatic conditions that best explain its current and future distribution. Over a period of 43 years, the species steadily extended its northern range margin at an approximate rate of 12 km/year. Once it reached the Po Plain, the expansion accelerated to an average speed of 34 km/year. However, its northward shift lagged behind the warming climate as we estimated an average speed of 28 km/year. In the future, the area suitable for T. annulata is expected to significantly increase in Italy. Surprisingly, we did not observe any consistent upward shift. Trithemis annulata has considerably expanded its distribution due to human-induced climate warming. The northernmost populations now inhabit Alpine valleys, potential gateways to central Europe.

ToTE: A global database on trees of the treeline ecotone.

Globally, treelines form a transition zone between tree-dominated forest downslope and treeless alpine vegetation upslope. Treelines represent the highest boundary of "tree" life form in high-elevation mountains and at high latitudes. Recently, treelines have been shifting upslope in response to climate warming, so it has become important to understand global tree diversity and treeline distributions. However, to the best of our knowledge, no global database on tree flora of treelines exists, which limits our capacity to undertake macroecological analyses. Here, for the first time, we present a global data set on the trees of the treeline ecotone, supported by an online ToTE database. We synthesized the database from 1202 studies published over the last 60 years (1962 to 2022) following the Preferred Reporting Items in Systematic Reviews and Meta-Analysis (PRISMA) protocol. We classified the tree species in the database into three categories: treeline tree (TL) species, near to treeline (NTL) tree species, and tree species with an upper montane range limit (TUMR). The ToTE Version-1 presents a total of 208 tree taxa, including 189 species, five subspecies, and 14 varieties, belonging to 54 genera and 26 families distributed across 34 mountain regions worldwide that either grow exactly at the treeline or have a range limit below the treeline. Of the total taxa, 155, 14, and 39 belong to TL, NTL, and TUMR, respectively. Genera such as Abies, Picea, Pinus, Larix, and Juniperus are more represented in the treeline tree category. On the other hand, Acer, Prunus, Populus, and Quercus have more representatives in the near to treeline category, whereas Erica, Nothofagus, and Polylepis contribute more tree species with an upper montane range limit. Furthermore, families such as Rosaceae and Pinaceae include trees that occur both at the treeline and with an upper montane range limit, whereas Sapindaceae includes trees that occur exclusively near to treeline. Our database also includes information on the global distribution patterns of treeline tree species richness across mountains and biomes. The mountains with the highest number of tree species are the Andes (39) followed by the Himalaya (37). Close to 67% of tree species show restricted distributions in different mountains, with the highest endemism in the Andes and the Himalaya. In terms of tree species distribution, Pinus sylvestris was widespread, with a distribution across nine mountain regions, followed by Picea glauca and Fagus sylvatica, both distributed across five mountain regions. In terms of species' distribution across biomes, the temperate biome harbors the highest treeline tree species richness (152 species), which may reflect the fact that the majority of studies are available from the temperate regions of the world. The remaining 56 species are distributed within five other biomes, with the least in dry tropical and subarctic (four species each). Furthermore, currently 40 treeline tree species fall under different International Union for Conservation of Nature threat categories. We anticipate that our database will help advance research on macroecological, biogeographic, evolutionary, climate-change, and conservation aspects of the treeline on a global scale. The data are released under a Creative Commons Attribution 4.0 international license. Please cite this data paper when the data are reused.