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To investigate the relative contributions of current vs. historical factors in explaining broad-scale diversity gradients using a combination of contemporary factors and a quantitative estimate of the temporal accessibility of areas for recolonization created by glacial retreat following the most recent Ice Age. The part of the Nearctic region of North America that was covered by ice sheets during the glacial maximum 20 000 BP. We used range maps to estimate the species richness of mammals and terrestrial birds in 48 400 km2 cells. Current conditions in each cell were quantified using seven climatic and topographical variables. Historical conditions were estimated using the number of years before present when an area became exposed as the ice sheets retreated during the post-Pleistocene climate warming. We attempted to tease apart contemporary and historical effects using multiple regression, partial regression and spatial autocorrelation analysis. A measure of current energy inputs, potential evapotranspiration, explained 76–82% of the variance in species richness, but time since deglaciation explained an additional 8–13% of the variance, primarily due to effects operating at large spatial scales. Because of spatial covariation between the historical climates influencing the melting of the ice sheet and current climates, it was not possible to partition their effects fully, but of the independent effects that could be identified, current climate explained two to seven times more variance in richness patterns than age. Factors acting in the present appear to have the strongest influence on the diversity gradient, but an historical signal persisting at least 13 000 years is still detectable. This has implications for modelling changes in diversity patterns in response to future global warming. [ABSTRACT FROM AUTHOR]

Broad-scale spatial patterns of species richness are very strongly correlated with climatic variables. If there is a causal link, i.e. if climate directly or indirectly determines patterns of richness, then when the climatic variables change, richness should change in the manner that spatial correlations between richness and climate would predict. The present study tests this prediction using seasonal changes in climatic variables and bird richness. We used a grid of equal area quadrats (37 000 km2) covering North and Central America as far south as Nicaragua. Summer and winter bird distribution data were drawn from monographs and field guides. Climatic data came from published sources. We also used remotely sensed NDVI (normalized difference vegetation index — a measure of greenness). Bird species richness changes temporally (between summer and winter) in a manner that is close to, but statistically distinguishable from, the change one would predict from models relating the spatial variation in richness at a single time to climatic variables. If one further takes into account the seasonal changes in NDVI and within-season variability of temperature and precipitation, then winter and summer richness follow congruent, statistically indistinguishable patterns. Our results are consistent with the hypothesis that climatic variables (temperature and precipitation) and vegetation cover directly or indirectly influence patterns of bird species richness. [ABSTRACT FROM AUTHOR]

Aim: Each year, wild and managed fires burn roughly 4 million km2 [~400 million hectares (Mha)] of savanna, forest, grassland and agricultural ecosystems. Land use and climate change have altered fire regimes throughout the world, with a trend toward higher‐severity fires found from Australia, the Americas, Europe and Asia, to the Arctic. In 2020, there were notable catastrophic fires in Australia (in the 2019/20 Austral fire season), the Western United States, South America and Siberia. These fires defined much of the global fire year and were compounded by the socio‐economic disruption of the Coronavirus 2019 (COVID‐19) pandemic. Location: Global. Time period: 2020. Major taxa studied: Flora and fauna. Methods: The Global Ecology and Biogeography special issue, 'Increasing threat of wildfires: the year 2020 in perspective', includes 18 papers that catalogue these fire events, their drivers and their impacts on flora and fauna. Results: Collectively, these papers highlight the importance of fire response traits, exposure and sensitivity to interacting threats in determining fire impacts. Main conclusions: The scale of the 2020 megafires has helped identify new research areas required to more comprehensively assess fire impacts on biodiversity and biogeochemistry and to inform ecosystem management. [ABSTRACT FROM AUTHOR]

Aim: Range shifts are expected to occur when populations at one range margin perform better than those at the other margin, yet no global trend in population performances at range margins has been demonstrated empirically across a wide range of taxa and biomes. Here we test the prediction that, if impacts of ongoing climate change on performance in marginal populations are widespread, then populations from the high‐latitude margin (HLM) should perform as well as or better than central populations, whereas low‐latitude margin (LLM) populations should perform worse. Location: Global. Time period: 1995–2019. Major taxa studied: Plants and animals. Methods: To test our prediction, we used a meta‐analysis to quantify empirical support for asymmetry in the performance of high‐ and low‐latitude margin populations compared to central populations. Performance estimates (survival, reproduction, or lifetime fitness) for populations occurring in their natural environment were derived from 51 papers involving 113 margin‐centre comparisons from 54 species and 705 populations from the Americas, Europe, Africa and Australia. We then related these performance differences to climatic differences among populations. We also tested whether patterns are consistent across taxonomic kingdoms (plants vs animals) and across realms (marine vs terrestrial). Results: Populations at margins performed significantly worse than central populations, and this trend was primarily driven by the low‐latitude margin. Although the difference was of small magnitude, it was largely consistent across biological kingdoms and realms. Differences in performance were weakly (p =.08) related to the difference in average temperatures between central and marginal populations. Main conclusions: The observed asymmetry in performance in marginal populations is consistent with predictions about the effects of global climate change, though further research is needed to confirm the effect of climate. It indicates that changes in demographic rates in marginal populations can serve as early‐warning signals of impending range shifts. [ABSTRACT FROM AUTHOR]

Aim: Previous analyses of remotely sensed data detected the multimodality of the tree‐cover distribution of the boreal forest, and identified areas with potentially alternative tree‐cover states. This paper aims at investigating the causes of multimodality and multistability of the boreal forest, their influence on the asymmetric tree species distribution between Eurasia and North America, and whether multistability could be associated with recent greening trends in leaf area index (LAI) and normalized difference vegetation index (NDVI). Location: Eurasian and North American boreal forests. Time period: 2000–2010. Major taxa studied: Boreal forest plant functional types. Methods: We employ a conceptual model based on tree species competition to simulate the sensitivity of tree cover to stochastic disturbances and to changes in environmental factors. We include different plant functional types based on survival adaptations, and force the model with remotely sensed environmental data. We analyse the model as a dynamical system. We use metrics from statistics and information theory to compare the detection of alternative tree‐cover states and greening trends in LAI and NDVI. Results: We find that multimodality and multistability can emerge through competition between different plant functional types. Additionally, our model is able to reproduce the asymmetry in tree species distribution between Eurasia and North America. Moreover, changes in permafrost distribution can be associated with phenomenological bifurcation points of the model. Finally, we find that the detection of multistable areas is not affected by recent vegetation trends, whereas shifts between alternative states could have affected the greening trends. Main conclusions: Tree‐cover multistability in the boreal region can emerge through competition between species subject to periodic disturbances. Changes in permafrost thaw and distribution could be responsible for the asymmetry in tree species distribution between North America and Eurasia. Climate change and permafrost degradation could cause shifts in tree‐cover states and dominant species. Recent vegetation greening trends in multistable areas could have been affected by shifts between alternative states. [ABSTRACT FROM AUTHOR]

This paper attempts some preliminary evaluation of the potential of agroforestry techniques as a forestry strategy for controlling atmospheric CO[sub 2]—a critical greenhouse gas. The end-use scenario that attempts to meet the wood and related needs of the nation while mitigating climate change was adopted. The net emission estimate for the Forestry Sector in 1990—the base year for the study—was 9.5 million tonnes of carbon (MtC). Based on this figure, projections into the year 2030 gave cumulative net emissions of 427.4 and 580.5 MtC at 1.3% and 2.6% deforestation rates respectively. However, mitigating with agroforestry techniques, assuming that about 76% of the estimated 39.5 million ha of farmland in the country is committed to a variety of agroforestry systems, the results show that a total of 1530 MtC can be withdrawn from the atmosphere by the year 2030. The paper concludes that there is a reasonable case for the use of agroforestry techniques in the country, both as a means of sustaining soil productivity and as a strategy for mitigating climate change. [ABSTRACT FROM AUTHOR]

Aim This paper presents a new global burned area (BA) product developed within the framework of the European Space Agency's Climate Change Initiative (CCI) programme, along with a first assessment of its potentials for atmospheric and carbon cycle modelling. Innovation Methods are presented for generating a new global BA product, along with a comparison with existing BA products, in terms of BA extension, fire size and shapes and emissions derived from biomass burnings. Main conclusions Three years of the global BA product were produced, accounting for a total BA of between 360 and 380 Mha year−1. General omission and commission errors for BA were 0.76 and 0.64, but they decreased to 0.51 and 0.52, respectively, for sites with more than 10% BA. Intercomparison with other existing BA datasets found similar spatial and temporal trends, mainly with the BA included in the Global Fire Emissions Database (GFED4), although regional differences were found (particularly in the 2006 fires of eastern Europe). The simulated carbon emissions from biomass burning averaged 2.1 Pg C year−1. [ABSTRACT FROM AUTHOR]

Aim The 'centre-periphery hypothesis' ( CPH) predicts that species performance (genetics, physiology, morphology, demography) will decline gradually from the centre towards the periphery of the geographic range. This hypothesis has been subjected to continuous debate since the 1980s, essentially because empirical studies have shown contrasting patterns. Moreover, it has been proposed that species performance might not be higher at the geographic range centre but rather at the environmental optimum or at sites presenting greater environmental stability in time. In this paper we re-evaluate the CPH by disentangling the effects of geographic, climatic and historical centrality/marginality on the demography of three widely distributed plant species and the genetic diversity of one of them. Location Europe and North America. Methods Based on a species distribution modelling approach, we test whether demographic parameters (vital rates, stochastic population growth rates, density) of three plant species of contrasting life-forms, and the genetic diversity of one of them, are higher at their geographic range centres, climatic optima or projected glacial refugia. Results While geographic, climatic and historical centre-periphery gradients are often not concordant, overall, none of them explain well the distribution of species demographic performance, whereas genetic diversity responds positively only to a historical centrality, related to post-glacial range dynamics. Main conclusions To our knowledge, this is the first assessment of the response of species performance to three centrality gradients, considering all the components of different species life cycles and genetic diversity information across continental distributions. Our results are inconsistent with the idea that geographically, climatically or historically marginal populations generally perform worse than central ones. We particularly emphasize the importance of adopting an interdisciplinary approach in order to understand the relative effects of contemporary versus historical and geographic versus ecological factors on the distribution of species performance. [ABSTRACT FROM AUTHOR]

Aim Seed traits related to recruitment have direct relevance for plant fitness and persistence. Trait variation in time and among populations may increase species resilience and ultimately reduce the risk of extinction. However, patterns of among-population variation in critical recruitment traits remain poorly known and are often disregarded when considering extinction risk under future climates. Location Global. Methods In this paper we review and synthesize current knowledge about among-population variation in physiological and morphological traits related to plant recruitment. We outline the consequences of that variation for species persistence under climate change, and discuss the implications for conservation, management and restoration. Results The evaluated studies provide compelling evidence that among-population variation in traits underpinning seedling emergence, growth and establishment is widespread. Contrary to expectations, environmental gradients do not appear to be reliable predictors of variation among populations and responses are often individualistic. Likewise, well-established cross-species patterns are not consistently reflected among populations within a species. As the pattern of this variation is unpredictable, we cannot make simple generalizations about how this variation is allocated across geographic ranges or the extent of environmental versus fixed genetic differences. Nor do these patterns clearly elucidate the potential for this variation to mitigate negative effects of climate change. Main conclusions If we ignore among-population variation in seed traits, or assume it will follow simple environmental clines, we do so at our own peril. The consequences of such an approach are likely to include biased forecasts of future range dynamics, hindering identification of the genetic material most appropriate for conservation, restoration and management. Further research that integrates ecology and emerging evolutionary genetic techniques to identify the distribution of seed traits within foundation species and the mechanisms driving them is urgently required to guide the management and maintenance of systems in the face of rapidly changing climates. [ABSTRACT FROM AUTHOR]

Aim In this paper, we applied the concept of 'hierarchical filters' in community ecology to model marine species distribution at nested spatial scales. Location Global, Mediterranean Sea and the Gulf of Gabes ( Tunisia). Methods We combined the predictions of bioclimatic envelope models ( BEMs) and habitat models to assess the current distribution of 20 exploited marine species in the Gulf of Gabes. BEMs were first built at a global extent to account for the full range of climatic conditions encountered by a given species. Habitat models were then built using fine-grained habitat variables at the scale of the Gulf of Gabes. We also used this hierarchical filtering approach to project the future distribution of these species under both climate change (the A2 scenario implemented with the Mediterranean climatic model NEMOMED8) and habitat loss (the loss of Posidonia oceanica meadows) scenarios. Results The hierarchical filtering approach predicted current species geographical ranges to be on average 56% smaller than those predicted using the BEMs alone. This pattern was also observed under the climate change scenario. Combining the habitat loss and climate change scenarios indicated that the magnitude of range shifts due to climate change was larger than from the loss of P. oceanica meadows. Main conclusions Our findings emphasize that BEMs may overestimate current and future ranges of marine species if species-habitat relationships are not also considered. A hierarchical filtering approach that accounts for fine-grained habitat variables limits the uncertainty associated with model-based recommendations, thus ensuring their outputs remain applicable within the context of marine resource management. [ABSTRACT FROM AUTHOR]

Aim Little is known about how marine biodiversity responds to oceanographic and climatic changes over the decadal to centennial time-scales which are most relevant for predicted climate changes due to greenhouse gas forcing. This paper aims to reveal decadal-centennial scale deep-sea biodiversity dynamics for the last 20,000 years and then explore potential environmental drivers. Location The North Atlantic Ocean. Methods We investigated deep-sea benthic microfossil records to reveal biodiversity dynamics and subsequently applied comprehensive ecological modelling to test possible environmental factors (i.e. surface productivity, seasonality of productivity or deepwater circulation related to bottom-water temperature) that may have influenced deep-sea biodiversity over these time-scales. Results Deep-sea biodiversity changed synchronously with stadial-interstadial climate changes over the last 20,000 years across a large area of the North Atlantic in both ostracod crustaceans and foraminiferan protozoa (in spite of their different dispersal abilities). Species diversity rapidly increased during abrupt stadial events during the last deglacial and the Holocene interglacial periods. These include the well-known Heinrich 1, the Younger Dryas and the 8.2 ka events when the strength of Atlantic Meridional Overturning Circulation ( AMOC) decreased. There is also evidence for quasi-cyclic changes in biodiversity at a c. 1500-year periodicity, consistent with the well-known '1500-year climatic cycle'. Statistical analyses revealed that AMOC variability (probably specifically the variability in AMOC-driven bottom-water temperature) is correlated with deep-sea biodiversity. Main conclusions Our finding of a significant AMOC-diversity relationship may indicate pervasive control of the diversity of deep-sea benthic species by rapidly changing climate, specifically bottom-water temperature, over decadal to centennial time-scales. Our results, based on highly resolved fossil records, may portend pervasive, synchronous and sudden ecosystem responses to human-induced changes to climate and ocean circulation in this century. [ABSTRACT FROM AUTHOR]

Aim Predicting the migration of vegetation in response to climate change is often done using a climate-driven vegetation model; however, the assumption of full migration (where seeds are not limited by distance or barriers) is a common criticism. Previous efforts to incorporate limitations on seed dispersal have occurred exclusively in bioclimatic envelope models. This paper describes how limitations on seed dispersal were integrated into a physiologically based dynamic vegetation model, LPJ-GUESS. Location An idealized landscape, representative of temperate and boreal forests in North America. Methods LPJ-GUESS already simulates establishment, growth, reproduction and competition. I used a generic seed dispersal kernel to determine the probability of dispersal between grid cells, and a logistic function to determine the spread between patches within a grid cell. Plant functional types were parameterized to represent three temperate tree species, Acer, Pinus and Tsuga, by using published dispersal kernels and life-history measurements. Simulations were run with full and limited migration, and compared with past vegetation migration rates. Results Using the old assumption of full migration, the entire landscape was colonized at the same time (migration rates of 270-380 m year−1). With the new limited dispersal, species colonized the landscape one row at a time, at rates which corresponded well with independent migration estimates based on genetic or pollen reconstructions ( Acer, 141 m year−1; Pinus, 76 m year−1). Tsuga was the only species where simulated migration rates (85 m year−1) were quite a bit slower than historical migration estimates. Main conclusions The new model was able to simulate reasonable migration rates, which is a substantial improvement over previous assumptions of full migration. Migration estimates which include the effects of limitations on dispersal, demography, competition and plant physiology will also improve our understanding of how climate change and various other processes can influence plant range shifts. [ABSTRACT FROM AUTHOR]

Aim The increased incidence of large fires around much of the world in recent decades raises questions about human and non-human drivers of fire and the likelihood of increased fire activity in the future. The purpose of this paper is to outline a conceptual framework for examining where human-set fires and feedbacks are likely to be most pronounced in temperate forests world-wide and to establish and test a methodology for evaluating this framework using palaeoecological records. Location Tasmania, north-western USA, southern South America and New Zealand. Methods We outline a conceptual framework for predicting the sensitivity of ecosystems to human impacts on fire regimes and then use a circum- Pacific comparison of existing historical reconstructions of fire, climate, human settlement and vegetation to evaluate this approach. Results Previous research investigating important controls on fire activity shows that the sensitivity of temperate ecosystems to human-set fires is modulated by the frequency of natural fire occurrence, fuel moisture and fuel type and availability. Palaeoecological data from four temperate regions suggest that the effects of anthropogenic burning are greatest where fire is naturally rare, vegetation is poorly adapted to fire and fuel biomass is abundant and contiguous. Alternatively, where fire activity is naturally high and vegetation is well adapted to fire, evidence of human influence on fire and vegetation is less obvious. Main conclusions Palaeofire records suggest that the most dynamic and persistent ecosystem transitions occur where human activities increase landscape flammability through fire-vegetation feedbacks. Rapid forest transitions in biomass-rich ecosystems such as New Zealand and areas of Tasmania and southern South America illustrate how landscapes experiencing few fires can shift past tipping points to become fire-prone landscapes with new alternative stable state communities. Comparisons of palaeoecological data from different regions with similar biophysical gradients but different human settlement histories can provide new opportunities for understanding ecosystem vulnerability to fire-climate-human interactions. [ABSTRACT FROM AUTHOR]

Aim This paper aims to project areas of olive cultivation into future scenarios. Accordingly, we first asked the question whether global circulation models ( GCMs) are able to reproduce past climatic conditions and we used historical ranges of olive cultivation as a palaeoclimate proxy. Location The Mediterranean basin. Methods We used an ecological model, calibrated and validated for modern times, to test the reliability of a general circulation model ( NCAR-CSM GCM) in reproducing past ranges of olive tree cultivation inferred from the literature, archaeo-botanical investigations and fossil pollen analyses. Results The re-constructions of olive growing areas, obtained for the Medieval Climate Anomaly (MCA, 1200-1300 AD) and the Little Ice Age (LIA, 1600-1700 AD) by coupling the outputs of NCAR-CSM to the ecological model, were in agreement to those observed. Simulations of olive growing areas for future time-windows showed that a northwards expansion of the species is expected to occur by 2100. Main conclusions These results demonstrate that the NCAR-CSM can provide an accurate reconstruction of past climate with results sensitive to climate forcing factors and thus, it is more likely to give reliable projections for the future. Additionally, the warming and drying conditions expected in the coming decades may determine changes across the Mediterranean basin that is unprecedented. [ABSTRACT FROM AUTHOR]

Aim Climate change and loss of apex predators can affect ecosystem structure and function through modified limitation processes. We investigated, on a continental scale, whether mesopredator abundance is limited from the top down by large predators, as predicted by the mesopredator release hypothesis, or by bottom-up factors. The mesopredator in focus is the red fox Vulpes vulpes, a key predator in many ecosystems due to its strong effects on prey abundance. Location Europe and northern Asia. Methods Data on red fox density were compiled from published papers and reports. For each site, we collated presence-absence data on large carnivores ( Lynx lynx, Canis lupus, Canis aureus) and remote sensing data for factors potentially related to bottom-up limitation (winter severity, summer temperature, human density, primary productivity, tree cover). The data were analysed through structural equation modelling. Results The presence of lynx had a direct negative effect on red foxes, suppressing fox abundance. Also winter severity had a negative effect on red fox abundance, and in Eurasia as a whole this effect was partially mediated through lynx. Within the lynx distribution range, winter severity was the only bottom-up factor significantly affecting red fox abundance. Outside the lynx distribution range, primary productivity, summer temperature and human density had a positive effect on red fox abundance. Main conclusions Our results show that apex predators can limit mesopredator abundance on a continental scale, thus supporting the mesopredator release hypothesis. Winter severity also affected red fox abundance, partially due to an interaction between lynx and winter conditions. On the continental scale a complex network of processes operates with varying effects depending on mediation processes. Our results imply that apex predators can have an important effect on ecosystem structure by limiting mesopredator abundance, and we suggest that apex predators may dampen increases in mesopredator abundance driven by global warming. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim This paper describes a set of integrative scenarios developed in the ALARM (Assessing LArge-scale environmental Risks for biodiversity with tested Methods) project. The ultimate aim of ALARM was to develop and test methods and protocols for the assessment of large-scale environmental risks to biodiversity and to evaluate mitigation options. Scenarios provide a tool for exploring such risks and the policy options to mitigate them; therefore they play a central role within the ALARM project. Methods Three integrative scenarios (liberalization, business as might be usual, sustainability) were developed and illustrated using the econometric model described in a subsequent paper. They are contextualized with projections from climate models and provide the input for model-based assessments of biodiversity trends. Additionally, three shock scenarios were developed (Gulf Stream collapse, peak oil, pandemic) to demonstrate the limits of linear extrapolation. As these extend beyond model capabilities, they are discussed semi-quantitatively based on modelling insights. Results Although the policy impacts on biodiversity are different for different pressures, biomes and species groups, some general trends could be identified. An extension of current EU policies will act as a brake on current trends by slowing down the loss of biodiversity in many cases and in most biomes, but it will be capable of neither halting nor of reversing the loss. Liberalization has the effect of accelerating biodiversity loss across the board, with few exceptions. A coherent sustainability scenario is clearly the most effective at preserving biodiversity, but the variant tested here still does not halt losses in all cases. Main conclusions Current EU policies for protecting biodiversity appear to be insufficient to reverse ongoing losses. Coherent sustainability strategies are effective at conserving biodiversity, but in order to assess losses and then reverse them, measures would need to be introduced that extend beyond the steps tested in the ALARM sustainability scenario. [ABSTRACT FROM AUTHOR]

Aim Many species are currently expanding their ranges in response to climate change, but the mechanisms underlying these range expansions are in many cases poorly understood. In this paper we explore potential climatic factors governing the recent establishment of new palm populations far to the north of any other viable palm population in the world. Location Southern Switzerland, Europe, Asia and the world. Methods We identified ecological threshold values for the target species, Trachycarpus fortunei, based on gridded climate data, altitude and distributional records from the native range and applied them to the introduced range using local field monitoring and measured meteorological data as well as a bioclimatic model. Results We identified a strong relationship between minimum winter temperatures, influenced by growing season length and the distribution of the palm in its native range. Recent climate change strongly coincides with the palm's recent spread into southern Switzerland, which is in concert with the expansion of the global range of palms across various continents. Main conclusions Our results strongly suggest that the expansion of palms into (semi-)natural forests is driven by changes in winter temperature and growing season length and not by delayed population expansion. This implies that this rapid expansion is likely to continue in the future under a warming climate. Palms in general, and T. fortunei in particular, are significant bioindicators across continents for present-day climate change and reflect a global signal towards warmer conditions. [ABSTRACT FROM AUTHOR]

Aim Species richness depends on climate and land use. Maintaining locations with favourable climate and land-use patterns is critical for protecting biodiversity because the loss of either can reduce the species richness that an area supports. Currently, the Guiana Shield (GS) receives abundant precipitation and has relatively light land use. For species richness this constitutes a good–good combination of climate and land use, respectively. In contrast, much of eastern Brazil receives low levels of precipitation and has heavy land use, which is a bad–bad combination for species richness. Thus, the current distribution of precipitation and land use in northern South America is relatively favourable for biodiversity. Palaeoclimate and model studies suggest, however, that the precipitation patterns for the two regions have switched before and could switch in response to greenhouse gas emissions. This paper examines the potential consequences of reconfiguring climate with respect to existing land-use patterns using South America as an example. Location South America north of 20° S and east of the Andes. Methods Ecosystem structure and function are modelled under (1) historical climate and (2) altered precipitation following a shift in the location of the Inter-Tropical Convergence Zone (ITCZ). The distribution of precipitation, biomes, net primary productivity (NPP) and land use are then used to predict levels of species richness under the two climate scenarios. Results Climate changes could shift the distribution of vegetation and NPP such that conditions favourable for species richness in the GS region disappear. If land-use patterns were not prohibitive in eastern Brazil, the improved climate conditions there could compensate for the GS loss (assuming migratory barriers are overcome). Instead, existing land-use patterns cause the combined species richness projected for the two regions to plummet. Main conclusions Human activities will alter current configurations of land use and climate throughout the world. For species richness, new configurations are likely to include both positive and negative combinations of climate and land use. However, the irreversibility of past extinctions due to land-use patterns loads the dice against species richness. [ABSTRACT FROM AUTHOR]

Aim Climate change has the potential to have an impact on the distribution of ticks and tick-borne diseases. This paper identifies the changes in climate suitability for the tick Rhipicephalus (Boophilus) microplus in the Americas by analysing climate data for the period 1950–99. Location The model was applied to the American continent. Methods A model based on Environmental Niche Modelling was used on a gridded (0.5°) long-term (1950–99) climate data set. A map of the core range of the species was constructed, and areas where habitat suitability (HS) changes suddenly over short time periods were identified as regions of high sensitivity. Tendency of climate in the continent was evaluated and scenarios constructed for 2025 and 2050. Results Regions of high sensitivity included the southern USA, Mexico and western and central Argentina. Analysis of climate variables in these regions identified water vapour pressure deficit and evaporation as underlying the high sensitivity of habitat suitability in the USA and Mexico, and showed that episodes of high variability are linked to the El Niño Southern Oscillation. Projections of the tendency of HS as observed for the 1950–99 period point to an increase in this value in parts of the southern USA and in central Argentina, a finding that can be attributed to the progressive increase in minimum and yearly averaged temperatures. Conclusions Short-term changes in climate may drive the system into unstable situations with sudden changes in habitat suitability for the target tick in specific zones of the Americas. Results suggest an increased abiotic (climate) suitability for R. microplus in areas whose habitat is currently unsuitable for this species. [ABSTRACT FROM AUTHOR]

Interannual land cover change plays a significant role in food security, ecosystem processes, and regional and global climate modelling. Measuring the magnitude and location and understanding the driving factors of interannual land cover change are therefore of utmost importance to improve our understanding and prediction of these impacts and to better differentiate between natural and human causes of land cover change. Despite advances in quantifying the magnitude of land cover change, the interpretation of the observed land cover change in terms of climatic, ecological and anthropogenic processes still remains a complex issue. In this paper, we map land cover change across sub-Saharan Africa and examine the influences of rainfall fluctuations on interannual change.The analysis was applied to sub-Saharan Africa.Ten-day rainfall estimates (RFE) obtained from National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center (CPC) were used to extract information on inter and intra-annual rainfall fluctuations. The magnitude of land cover change was quantified based on the multitemporal change vector method measuring year-to-year differences in bidirectional reflectance distribution function (BRDF) corrected 16-day enhanced vegetation index (EVI) data from the Moderate Resolution Imaging Spectro-radiometer (MODIS). Statistical models were used to estimate the relationship between short-term rainfall variability and the magnitude of land cover change. The analysis was stratified first by physiognomic vegetation type and second by chorological data on species distribution to gain insights into spatial variations in response to short-term rainfall fluctuations.The magnitude of land cover change was significantly related to rainfall variability at the 5% level. Stratification considerably strengthened the relationship between the magnitude of change and rainfall variability. Explanatory power of the models ranged fromR2 = 0.22 for the unstratified model to 0.40–0.96 for the individual models stratified by patterns of species distribution. The total variability explained by the combined models including the influence of rainfall and differences in vegetation response ranged from 22% for the model not stratified by vegetation to 76% when stratified by chorological data.Using this methodology, we were able to measure the contribution of natural variation in precipitation to land cover change. Several ecosystems across sub-Saharan Africa are highly sensitive to short-term rainfall variability. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to propose a new tool, in the form of Quantitative Bioclimatic Models (QnBMs), for reconstructing past climates based on fossil mammal associations. As a case study, European climatic conditions during the basal early Pleistocene will be inferred using QnBMs.The study uses faunas throughout the world to develop a quantitative bioclimatic model, which is then applied to Quaternary faunas from Eurasia.The models were constructed by applying multivariate linear regression to modern mammal faunas and climates from all over the world. The models were validated with a second group of modern faunas, which includes several from transitional zones between different climates (ecotones). To test the reliability of the method when applied to fossil associations, the results obtained for the Pleistocene have been compared with those obtained from palynology.Validation of the models shows that as many as 11 climatic factors can be inferred with high reliability using the regression models developed in this work. Comparisons of results in the late Pleistocene–Holocene of Barová (Czech Republic) between a palynological study and the quantitative bioclimatic analysis show a high degree of similarity. The results for the early Pleistocene show colder and drier climatic conditions for Europe than today.The application of the quantitative bioclimatic models to present day as well as Quaternary mammal faunas proves to be a useful tool for palaeoclimatic reconstruction during the Quaternary and probably most of the Neogene. Transfer functions are presented for a complete set of climatic factors, allowing a precise estimation of the climate in a locality from its mammal fauna. [ABSTRACT FROM AUTHOR]

This paper presents a probabilistic method of pollen spectra analysis. The method relies on a pollen taxon characterization using biotic and abiotic plant attribute modes, and their occurrence in a given pollen spectrum at a specific site. This type of analysis can provide an interpretation, which can lead to the reconstruction of the biome and, to an extent, of the abiotic conditions at the site.The analysis has been carried out at the European scale using data provided by the European Pollen Database for about 1000 sites. This dataset contains about 50,000 pollen spectra from the last 21 ka. In these spectra, each pollen taxon has been characterized by a set of 10 chosen attributes. These have been selected with regard to their relevance in biome reconstruction, but also on the basis of available literature. By using the probability of occurrence of each taxon in a given pollen spectrum, it is possible to calculate an affinity index for the spectrum to the attribute considered. To overcome difficulties caused by pollen identification in low diversified pollen spectra, a co-occurrence concept has been used to give more information.The method has been validated on a set of 1327 modern surface samples by comparing the results to the major climatic and environmental variables that control the distribution of the vegetation. A reconstruction exercise on various characteristics of the plants was then carried out on a 6-ka dataset. This confirmed previous studies by showing a strong dominance of deciduous forest over most of Europe, related to a milder climate than at present in the north and a wetter and colder climate than at present in the south. By analysing the change in pollen/seed dispersion strategies and the light requirement, we show that the history of vegetation dynamics in relation to human influences can be assessed using this method.Our results show that the probabilistic method is an objective tool for pollen assemblage analysis. It allows reconstruction of various characteristics of the vegetation at the continental and global scale for periods and sites with significantly different climate conditions. This method can also be used to compare maps of vegetation attributes for the validation of the new generalized dynamic ecosystems models. [ABSTRACT FROM AUTHOR]

ABSTRACT Modelling strategies for predicting the potential impacts of climate change on the natural distribution of species have often focused on the characterization of a species’ bioclimate envelope. A number of recent critiques have questioned the validity of this approach by pointing to the many factors other than climate that play an important part in determining species distributions and the dynamics of distribution changes. Such factors include biotic interactions, evolutionary change and dispersal ability. This paper reviews and evaluates criticisms of bioclimate envelope models and discusses the implications of these criticisms for the different modelling strategies employed. It is proposed that, although the complexity of the natural system presents fundamental limits to predictive modelling, the bioclimate envelope approach can provide a useful first approximation as to the potentially dramatic impact of climate change on biodiversity. However, it is stressed that the spatial scale at which these models are applied is of fundamental importance, and that model results should not be interpreted without due consideration of the limitations involved. A hierarchical modelling framework is proposed through which some of these limitations can be addressed within a broader, scale-dependent context. [ABSTRACT FROM AUTHOR]

1. This paper aims to demonstrate the use of available vegetation data from the phytosociological literature in preliminary analyses to generate hypotheses regarding vegetation and climate change. 2. Data for over 3000 samples of calcareous grassland, mesotrophic grassland, heath and woodland vegetation were taken from the literature for a region in the west of Atlantic Europe and subjected to ordination by detrended correspondence analysis in order to identify the main gradients present. 3. Climate data were obtained at a resolution of 0.5° from an existing database. The relationship between vegetation composition and climate was investigated by the correlation of the mean scores for the first two ordination axes for each 0.5° cell with the climate and location variables. 4. The ordinations resulted in clear geographical gradients for calcareous grasslands, heaths and woodlands but not for mesotrophic grasslands. Significant correlations were shown between some of the vegetation gradients and the climate variables, with the strongest relationships occurring between the calcareous grassland gradients and July temperature, latitude and oceanicity. Some of the vegetation gradients were also inferred to reflect edaphic factors, management and vegetation history. 5. Those gradients that were related to temperature were hypothesized to reflect the influence of a progressively warmer climate on species composition, providing a baseline for further studies on the influence of climate change on species composition. 6. The validity of the literature data was assessed by the collection of an original set of field data for calcareous grasslands and the subsequent ordination of a dataset containing samples from both the literature and the field. The considerable overlap between the samples from the literature and the field suggest that literature data can be used, despite certain limitations. Such preliminary analyses, using readily available data, can thus achieve... [ABSTRACT FROM AUTHOR]

Increases in the atmospheric concentration of carbon dioxide and associated changes in climate may exert large impacts on plant physiology and the density of vegetation cover. These may in turn provide feedbacks on climate through a modification of surface-atmosphere fluxes of energy and moisture. This paper uses asynchronously coupled models of global vegetation and climate to examine the responses of potential vegetation to different aspects of a doubled-CO[sub 2] environmental change, and compares the feedbacks on near-surface temperature arising from physiological and structural components of the vegetation response. Stomatal conductance reduces in response to the higher CO[sub 2] concentration, but rising temperatures and a redistribution of precipitation also exert significant impacts on this property as well as leading to major changes in potential vegetation structure. Overall, physiological responses act to enhance the warming near the surface, but in many areas this is offset by increases in leaf area resulting from greater precipitation and higher temperatures. Interactions with seasonal snow cover result in a positive feedback on winter warming in the boreal forest regions. [ABSTRACT FROM AUTHOR]

Motivation: Host to intricate networks of marine species, coral reefs are among the most biologically diverse ecosystems on Earth. Over the past few decades, major degradations of coral reefs have been observed worldwide, which is largely attributed to the effects of climate change and local stressors related to human activities. Now more than ever, characterizing how the environment shapes the dynamics of the reef ecosystem (e.g., shifts in species abundance, community changes, emergence of locally adapted populations) is key to uncovering the environmental drivers of reef degradation, and developing efficient conservation strategies in response. To achieve these objectives, it is pivotal that environmental data describing the processes driving such ecosystem dynamics, which occur across specific spatial and temporal scales, are easily accessible to coral reef researchers and conservation stakeholders alike. Main types of variable contained: Multiple environmental variables characterizing various facets of the reef environment, including water chemistry and physics (e.g., temperature, pH, chlorophyll concentration), local anthropogenic pressures (e.g., boat traffic, distance from agricultural or urban areas) and sea currents patterns. Spatial location and grain: Worldwide reef cells of 5 by 5 km. Time period and grain: Last 3–4 decades, monthly and yearly resolution. Major taxa and level of measurement: Environmental data important for coral reefs and associated biodiversity. Software format: Interactive web application available at https://recifs.epfl.ch. [ABSTRACT FROM AUTHOR]

Aim: Climate change regulates autumn leaf senescence date (LSD), exhibiting a strong phenological control of plant carbon uptake. Unlike the delaying effect of daily mean temperature (Tmean) on LSD, the impact of warming asymmetry in daytime and nighttime, as evidenced by variations of the diurnal temperature range (DTR), remains elusive. The objectives of this study were to investigate physiological and ecological impacts of DTR on LSD using long‐term in situ observations and to predict the future trends of LSD under warming. Location: Europe. Time period: 1950–2015. Major taxa studied: Plant phenology. Methods: We used partial correlation analysis, multiple linear regression and ridge regression to explore the impacts of DTR on LSD. To quantify the importance of potential drivers of LSD, we trained random forest models and applied the SHapley Additive exPlanations method to isolate the marginal contributions of each predictor on LSD. For LSD modelling and projection, we first evaluated two temperature‐driven LSD models [i.e., cooling‐degree‐day (CDD, without DTR effect) and day–night‐temperature CDD (DNCDD, with DTR effect)], then applied them to predict future LSDs. Results: We found that observational increases in Tmean and DTR had contrasting effects on LSD. Increased Tmean delayed the LSD, whereas larger DTR overall had an advancing effect. Considering the DTR effect, the Tmean sensitivity of LSD was 14% lower than presently estimated (2.4 vs. 2.8 days °C−1). Warming asymmetry‐related drought stress and plant functional traits (i.e., plant isohydricity and water‐use efficiency) potentially explained the advancing effect of DTR on LSD. We found that current projections of future LSD are overestimated because the DTR effect is discounted, suggesting the need for an adequate understanding of how plant phenology responds to warming asymmetry. Main conclusions: Our findings highlight the importance of DTR in controlling LSD variations with an advancing‐dominant effect and call for the improvement of phenology modelling incorporating the DTR effect. Given that DTR showed a globally narrowing trend over the last several decades, more efforts are needed to understand the potential ecological impacts of warming asymmetry and vegetation response to climate change. [ABSTRACT FROM AUTHOR]

Aim: Until recently, complete information on global reptile distributions has not been widely available. Here, we provide the first comprehensive climate impact assessment for reptiles on a global scale. Location: Global, excluding Antarctica. Time period: 1995, 2050 and 2080. Major taxa studied: Reptiles. Methods: We modelled the distribution of 6296 reptile species and assessed potential global and realm‐specific changes in species richness, the change in global species richness across climate space, and species‐specific changes in range extent, overlap and position under future climate change. To assess the future climatic impact on 3768 range‐restricted species, which could not be modelled, we compared the future change in climatic conditions between both modelled and non‐modelled species. Results: Reptile richness was projected to decline significantly over time, globally but also for most zoogeographical realms, with the greatest decreases in Brazil, Australia and South Africa. Species richness was highest in warm and moist regions, with these regions being projected to shift further towards climate extremes in the future. Range extents were projected to decline considerably in the future, with a low overlap between current and future ranges. Shifts in range centroids differed among realms and taxa, with a dominant global poleward shift. Non‐modelled species were significantly stronger affected by projected climatic changes than modelled species. Main conclusions: With ongoing future climate change, reptile richness is likely to decrease significantly across most parts of the world. This effect, in addition to considerable impacts on species range extent, overlap and position, was visible across lizards, snakes and turtles alike. Together with other anthropogenic impacts, such as habitat loss and harvesting of species, this is a cause for concern. Given the historical lack of global reptile distributions, this calls for a re‐assessment of global reptile conservation efforts, with a specific focus on anticipated future climate change. [ABSTRACT FROM AUTHOR]

Aim: Phenological models have become a vital tool for predicting future phenological responses to global climate change. Recently, machine learning (ML) has been used successfully to develop phenological models based on ground observations. However, fitting an observation series that has been observed for only a few years (or even a decade) can easily lead to overfitting, and it is still a great challenge to predict future phenology accurately based on a short observation series. Here, based on historical ground phenological observations, we construct an ML‐based binary classification phenological model that can be applied to temperate trees. Innovation: We thoroughly describe the construction process of a species‐specific ML‐based binary classification phenological model that is suitable for phenological predictions in both spring and autumn. Through experiments, we evaluate 18 commonly used ML classification algorithms and the effects of two parameters on the prediction performance of the model. Finally, we compare the performance between the binary classification model and six widely used ecophysiological models for accuracy of spring phenological prediction. Main conclusions: The median root mean square error (RMSE) of the binary classification model for the first flowering date (93 observation series) was only 2.99 days, which proves that it is a good method of phenological prediction for temperate trees. This model can effectively overcome the insufficient sample size of ground observations for specific species and provide new insights of phenological predictions for tropical and subtropical trees. The comparison of different ML algorithms showed that the median root mean square errors of the six algorithms were <3.5 days, and lower than those of six ecophysiological models (>3.7 days) in prediction of spring phenology. In addition, this model can help us to infer plant physiological mechanisms and drivers of phenological change and provide more accurate predictions of plant phenological responses to climate change. [ABSTRACT FROM AUTHOR]

Aim: While drought and shade are critical factors that determine seedling survival and growth, whether the responses of woody seedlings to drought are facilitated, aggravated or unaffected by shade remains uncertain. Location: Global. Time period: 1993 to 2021. Major taxa studied: Woody plants. Methods: We compiled 58 studies (including 75 woody species from 33 families) in which water and light availability were simultaneously manipulated, and conducted a meta‐analysis on the acclimation and adaptive responses of biomass production and allocation and leaf traits to drought and/or shade. Results: Shade alleviated the adverse impact of drought on photosynthesis (A) by decreasing stomatal limitation and photoinhibition, and increasing leaf relative water content, and thus facilitated biomass production, but shade aggravated the effect of drought on osmotic adjustment as evidenced by the lack of responses of osmotic potential at the full turgor and modulus elasticity at the maximum turgor to drought under shade. The effects of drought and shade on biomass allocation and specific leaf area were orthogonal. Biomass responses to drought and its interaction with shade were least responsive for drought‐tolerators, but the individual and interactive effects of shade and drought on most traits showed little dependence on shade tolerance. Drought–shade interaction increased root biomass and root mass fraction more for deciduous angiosperms than for evergreen angiosperms. Main conclusions Both shade and drought had negative impacts on biomass production and photosynthesis, but their interaction had positive effects that were less significant for drought‐tolerators and evergreen angiosperms. In contrast to shade, drought increased biomass allocation to roots, but shade and drought had orthogonal effects on biomass allocation and leaf morphology. These acclimation and adaptive responses of woody seedlings to drought and shade individually and interactively have important implications for predicting woody plant growth and distribution under global climate changes. [ABSTRACT FROM AUTHOR]

Aim: Fungi are major drivers of ecosystem functioning. Increases in aridity are known to negatively impact fungal community composition in dryland ecosystems globally; yet, much less is known on the potential influence of other environmental drivers, and whether these relationships are linear or nonlinear. Time period: 2017–2021. Location: Global. Major taxa studied: Fungi. Methods: We re‐analysed multiple datasets from different dryland biogeographical regions, for a total of 912 samples and 1,483 taxa. We examined geographical patterns in community diversity and composition, and spatial, edaphic and climatic factors driving them. Results: UV index, climate seasonality, and sand content were the most important environmental predictors of community shifts, showing the strongest association with the richness of putative plant pathogens and saprobes. Important nonlinear relationships existed with each of these fungal guilds, with increases in UV and temperature seasonality above 7.5 and 900 SD (standard deviation x 100 of the mean monthly temperature), respectively, being associated with an increased probability of plant pathogen and unspecified saprotroph occurrence. Conversely, these environmental parameters had a negative relationship with litter and soil saprotroph richness. Consequently, these ecological groups might be particularly sensitive to shifts in UV radiation and climate seasonality, which is likely to disturb current plant–soil dynamics in drylands. Main conclusions: Our synthesis integrates fungal community data from drylands across the globe, allowing the investigation of fungal distribution and providing the first evidence of shifts in fungal diversity and composition of key fungal ecological groups along diverse spatial, climatic and edaphic gradients in these widely distributed ecosystems. Our findings imply that shifts in soil structure and seasonal climatic patterns induced by global change will have disproportionate consequences for the distribution of fungal groups linked to vegetation and biogeochemical cycling in drylands, with implications for plant–soil interactions in drylands. [ABSTRACT FROM AUTHOR]

Aim: Soil organic carbon (SOC) stabilization has become an important topic in recent years in the context of global climate change. Microbial residues represent a significant component of stabilized SOC pools. However, spatial variations in the contributions of bacterial and fungal residues to SOC and their determinants at a continental scale remain poorly understood. We aimed to evaluate the spatial variations and controls of the contributions of microbial residues to SOC in forest topsoil. Location: North–south transect in eastern China. Time period: 2014. Major taxa studied: Forest ecosystems. Methods: A total of 195 surface (0–10 cm) soils were sampled from 28 forest sites across tropical and boreal forests in eastern China from July to August to assess how biotic and abiotic factors govern the geographic patterns of the contributions of soil microbial residues (indicated by amino sugars) to SOC. Results: Fungal residues (30.0%) had a greater average contribution to SOC than bacterial residues (15.5%). The contributions of bacterial (CBR) and total microbial residues (CMR) to SOC showed negative latitudinal patterns and were positively correlated with mean annual temperature (MAT). In contrast, the contribution of fungal residues to SOC (CFR) showed no clear geographic or climatic patterns. On average, the CBR (9.7%), CFR (21.1%) and CMR (30.8%) were lower in boreal forests than in other biome forests. SOC concentration negatively mediated CBR, CFR and CMR. The piecewise structural equation model results showed that MAT was the primary driver of the geographic pattern of CBR, whereas SOC and soil carbon : nitrogen ratio were more directly associated with the CFR. Additionally, plant factors and microbial properties (i.e., microbial biomass and composition) played relatively little roles in regulating CBR, CFR and CMR. Main conclusions These findings advance the current knowledge of the different geographic patterns of CBR and CFR regulated by different potential mechanisms in forest ecosystems. This highlights that the dynamics of microbial residues could potentially have unexpected consequences for topsoil SOC stocks under climate change. [ABSTRACT FROM AUTHOR]

Aim: To determine the ecological processes and drivers of range collapse, population decline and eventual extinction of the steppe bison in Eurasia. Location: Siberia. Time period: Pleistocene and Holocene. Major taxa studied: Steppe bison (Bison priscus). Methods: We configured 110,000 spatially explicit population models (SEPMs) of climate–human–steppe bison interactions in Siberia, which we ran at generational time steps from 50,000 years before present. We used pattern‐oriented modelling (POM) and fossil‐based inferences of distribution and demographic change of steppe bison to identify which SEPMs adequately simulated important interactions between ecological processes and biological threats. These "best models" were then used to disentangle the mechanisms that were integral in the population decline and later extinction of the steppe bison in its last stronghold in Eurasia. Results: Our continuous reconstructions of the range and extinction dynamics of steppe bison were able to reconcile inferences of spatio‐temporal occurrence and the timing and location of extinction in Siberia based on hundreds of radiocarbon‐dated steppe bison fossils. We showed that simulating the ecological pathway to extinction for steppe bison in Siberia in the early Holocene required very specific ecological niche constraints, demographic processes and a constrained synergy of climate and human hunting dynamics during the Pleistocene–Holocene transition. Main conclusions: Ecological processes and drivers that caused ancient population declines of species can be reconstructed at high spatio‐temporal resolutions using SEPMs and POM. Using this approach, we found that climatic change and hunting by humans are likely to have interacted with key ecological processes to cause the extinction of the steppe bison in its last refuge in Eurasia. [ABSTRACT FROM AUTHOR]

Aim: Given the influence of seasonality on most ecological systems, an emerging research area attempts to understand how community network structure is shaped by seasonal climatic variations. To do so, most researchers conduct their analyses using open networks due to the high cost associated with constructing their own community networks. However, unwanted structural differences from the unique sampling and construction methods used to create each open network likely make comparing these networks a difficult task. Here, with the largest set of open bipartite networks collected to date, we test whether seasonal climatic variations explain network structure while additionally accounting for construction/sampling differences between networks. Location: Trying to approach global. Time period: Contemporary. Major taxa studied: Plants and animals. Methods: Using 723 open bipartite networks, we test whether temperature and/or precipitation seasonality explains (un)weighted metrics of nestedness, modularity or specialization across plant–pollinator, seed‐dispersal, plant–ant, host–parasite or plant–herbivore systems. Results: Generally, seasonality only weakly explained network structure: at most 16% of the variation in weighted metrics and 5% of the variation in unweighted metrics. Instead, a control for sampling bias in networks, sampling intensity, often better explained many of the network structural metrics. When limiting our analyses to only intensely sampled networks, however, about 33% of the variation in weighted modularity and specialization was explained by seasonality, but only in plant–pollinator networks. Main conclusions: Altogether, we do not find strong evidence that seasonality explains network structure. Our study also highlights the large amount of structural differences in open networks, likely from the many different sampling and network construction techniques adopted by researchers when constructing networks. Hence, a definitive test for the relationship between network structure and seasonality across large spatial extents will require a dataset free from sampling and other biases, where networks are derived from a consistent sampling protocol that appropriately characterizes communities. [ABSTRACT FROM AUTHOR]

Aim: Anticipating when and where changes in species' demographic rates will lead to range shifts in response to changing climate remains a major challenge. Despite evidence of increasing mortality in dry forests across the globe in response to drought and warming temperatures, the overall impacts on the distribution of dry forests are largely unknown because we lack comparable large‐scale data on tree recruitment rates. Here, our aim was to develop range‐wide population models for dry forest tree species (pinyon pine and juniper), quantifying both mortality and recruitment, to better understand where and under what conditions species range contractions are occurring. Location: Western United States. Major taxa studied: Two pinyon pine (Pinus spp.) and three juniper (Juniperus spp.) species. Methods: We developed range‐wide demographic models for five species using forest inventory data from across the western United States and estimated population trends and climate vulnerability. Results: We find that four of the five species are declining in parts of their range, with Pinus edulis having the largest proportion of populations declining (24%). Population vulnerability increases with aridity and temperature, with up to ~50% of populations declining in the warmest and driest conditions. Mortality and recruitment were both essential to explaining where populations are declining. Main conclusions Our results suggest that dry forest species are undergoing an active range shift driven by both changing recruitment and mortality, and that increasing temperatures and drought threaten the long‐term viability of many of these species in their current range. While four of the five species examined were experiencing some declines, P. edulis is currently most vulnerable. Management actions such as reducing tree density may be able to mitigate some of these impacts. The framework we present to estimate range‐wide demographic rates can be applied to other species to determine where range contractions are most likely. [ABSTRACT FROM AUTHOR]

Aim: The aim was to determine reef connectivity and future coral cover levels under global scenarios of coral bleaching loss and potential recovery. Location: Global coral reefs. Time period: Present‐day to 2100. Major taxa studied: Scleractinian coral. Methods: We used a global coral larval dispersal model that describes population connectivity among reefs at a resolution of ⅙° × ⅙° (c. 18 km × 18 km) cells. To simulate different patterns of bleaching events, we ran three scenarios at different levels of coral reef habitat loss followed by a reseeding of coral larvae from surviving reefs to simulate recovery. Results: We found a total of 604 distinct reef networks, but more than half of the world's reef cells are contained in six large coral reef networks (294–5,494 cells), whereas the rest form smaller networks. In the bleaching scenario where previously identified predicted climate refugia were maintained, initial connectivity was largely preserved even when 71% of global coral reef habitat was lost, but the relict reef cells were unable to reseed even 50% of former coral reef habitat because many of the relict reefs are in the same networks as each other. In scenarios where refugia were lost first or with random loss, less of the initial connectivity was maintained, but more widespread reseeding was possible because more reef cells within smaller networks were maintained. Main conclusions: Our findings highlight the importance of maintaining functional coral reef habitat outside of predicted climate refugia to sustain connectivity globally, and suggest an important role for "stepping stone" reefs between the climate refugia. Without attention to these issues of habitat loss and connectivity, much of global coral reef habitat might not be reseeded without human intervention. [ABSTRACT FROM AUTHOR]

Aim: The environmental preferences of species are an important facet of their response to changing conditions, and these have long been thought to exhibit phylogenetic conservatism. However, these bioclimatic envelopes have not previously been imputed from climate records at the date and location of occurrence, and the strength of their phylogenetic signal has not been studied at a broad scale. Here, we combine records from global climate reconstructions with contemporaneous plant occurrences for all available terrestrial plant species and test for phylogenetic niche conservatism in plant climatic traits. Location: Global. Time period: 1901–2018. Major taxa studied: Terrestrial plants. Methods: We used >100 million plant records from the Global Biodiversity Information Facility (GBIF) to produce distributions of bioclimatic envelopes for >200,000 species, using a range of climate variables. We matched species observations to historical climate reconstructions from the European Centre for Medium‐Range Weather Forecasting (ECMWF) and compared this with WorldClim climate averages. We tested for phylogenetic signal in a supertree of plants using Pagel's λ. Finally, to investigate how well bioclimatic envelopes could be inferred for poorly known and rare species, we performed cross‐validation by removing occurrence records for some common species to test how accurately their bioclimatic envelopes were estimated. Results: We found extremely strong phylogenetic signals (λ > 0.9 in some cases) for climate variables from both climate datasets, including temperature, soil temperature, solar radiation and precipitation. We were also able to impute missing bioclimatic envelopes for artificially removed species, having a correlation with observed data of.7. Main conclusions: We reconstructed plant climatic tolerances for >200,000 plant species historically recorded on GBIF using a technique that could be applied to any comparable biodiversity dataset. Although global information on most species is sparse, we explored methods for bias correction and data imputation, with positive results for both. [ABSTRACT FROM AUTHOR]

Background: 'Megafire' is an emerging concept commonly used to describe fires that are extreme in terms of size, behaviour, and/or impacts, but the term's meaning remains ambiguous. Approach: We sought to resolve ambiguity surrounding the meaning of 'megafire' by conducting a structured review of the use and definition of the term in several languages in the peer‐reviewed scientific literature. We collated definitions and descriptions of megafire and identified criteria frequently invoked to define megafire. We recorded the size and location of megafires and mapped them to reveal global variation in the size of fires described as megafires. Results: We identified 109 studies that define the term 'megafire' or identify a megafire, with the term first appearing in the peer‐reviewed literature in 2005. Seventy‐one (~65%) of these studies attempted to describe or define the term. There was considerable variability in the criteria used to define megafire, although definitions of megafire based on fire size were most common. Megafire size thresholds varied geographically from > 100–100,000 ha, with fires > 10,000 ha the most common size threshold (41%, 18/44 studies). Definitions of megafire were most common from studies led by authors from North America (52%, 37/71). We recorded 137 instances from 84 studies where fires were reported as megafires, the vast majority (94%, 129/137) of which exceed 10,000 ha in size. Megafires occurred in a range of biomes, but were most frequently described in forested biomes (112/137, 82%), and usually described single ignition fires (59% 81/137). Conclusion: As Earth's climate and ecosystems change, it is important that scientists can communicate trends in the occurrence of larger and more extreme fires with clarity. To overcome ambiguity, we suggest a definition of megafire as fires > 10,000 ha arising from single or multiple related ignition events. We introduce two additional terms – gigafire (> 100,000 ha) and terafire (> 1,000,000 ha) – for fires of an even larger scale than megafires. [ABSTRACT FROM AUTHOR]

Aim: The aims were: (1) to identify the environmental drivers of interannual variation in wildfire extent and severity; (2) to examine temporal trends in climatic potential for large and severe wildfires; and (3) to assess whether environmental conditions experienced during the 2019–2020 mega‐fire season were anomalous. Location: South‐eastern Australia. Time period: 1953–2020. Major taxa studied: Temperate forests. Methods: We used satellite‐derived fire severity mapping from 1988 to 2020 to model the effects of drought, weather and fuels on the annual area burned and the proportion of the area burned that was impacted by high‐severity fire across four bioregions. Trends in wildfire extent and severity were then estimated from 1953 to 2020 using these derived models and gridded climate data to assess changes in climatic potential for large and severe wildfires. Estimates of wildfire extent and severity for the 2019–2020 fire season were then assessed against prior seasons (1953–2019). Results: Annual area burned was positively related to the severity of seasonal drought and frequency of fire weather conditions that promote substantial daily fire growth. Wildfire severity was elevated in years with severe fire weather and increased with increasing antecedent drought in years without severe fire weather. Fuels had a lesser effect on wildfire extent and severity than climate. Potential fire extent and severity have increased over time in response to an increased severity of drought and worsening fire weather conditions. Estimates of wildfire extent and severity during the 2019–2020 fire season approached the upper extreme within each bioregion, owing to widespread extreme climatic conditions. Main conclusions: The climatic potential for large and severe forest fires has increased across south‐eastern Australia since the 1950s, probably because of anthropogenic climate change. The magnitude and severity of the 2019–2020 fires reflected climatic conditions that are driving an increase in the size and severity of wildfires. [ABSTRACT FROM AUTHOR]

Aim: Mangrove forests are important coastal wetlands for the blue carbon budget and play a significant role in mitigating global climate change. However, spatial patterns of carbon stocks in mangrove forests on an island scale have not been quantified owing to methodological limitations and lack of understanding of controlling factors. We took the entire Hainan Island as a case study and aimed to carry out a comprehensive investigation of the spatial patterns and driving factors of carbon stocks in mangrove forests. Location: Southern China. Time period: 2017–2020. Major taxa studied: Mangrove forest. Methods: The upscaling method combined with field surveys and Sentinel‐2 imagery analysis were used to compare different models for optimization of mangrove ecosystem carbon stock estimations. We also used structural equation modelling (SEM) to evaluate the factors driving the distributional patterns of mangrove carbon stocks on an island scale. Results: The current total mangrove carbon stock of the entire Hainan Island was estimated to be 703,181 Mg C (with a mean density of 192 Mg C/ha), with the above‐ and below‐ground carbon stocks averaging at 44.7 and 147.3 Mg C/ha, respectively. The mangrove carbon storage in the north‐eastern region of the island was the highest and in the west region the lowest. Sediment nitrogen content and plant species diversity had the most positive driving effects on the distribution of total carbon stock for Hainan Island mangroves. Main conclusions: The combination of field surveys and Sentinel‐2 imagery analysis can be applied to regional‐scale estimations of carbon stocks for mangrove forests. Spatial pattens of mangrove carbon stocks vary among locations on Hainan Island, and soil nutrient (especially nitrogen) availability is the dominant factor regulating carbon stock variations along the land‐to‐sea gradient. Our findings have significant implications for better understanding the distribution of mangrove carbon stocks and quantification of the global blue carbon budget. [ABSTRACT FROM AUTHOR]

Aim: Marine biodiversity is increasingly threatened by overfishing and climate change, but it is still unclear how these drivers have shaped the functional diversity (FD) of marine fish. Here, we explore how the FD of commercial marine fish communities responds to climate change and fishing pressure. Major taxa studied: Marine fish. Location: China Seas. Time period: 1989–2018. Methods: We used a catch database of four individual species and 12 species groups that were reported continuously in China from 1989 to 2018. Seven traits were selected to calculate FD. We adopted generalized linear mixed models to analyse the complex relationship among climate change, fishing pressure and several metrics of marine fish FD. We identified the percentage change in diversity for communities to assess the relative contribution of each species or species group by removing individual species or a species group from the dataset. Results: Climate change and fishing pressure exerted statistically significant opposing effects on the functional evenness (FEve) and functional divergence (FDiv) of commercial fish communities. Increasing sea surface temperature had a significant positive effect on FEve but a negative effect on FDiv. In contrast, increasing fishing pressure had the opposite effects on FEve and FDiv. These results were driven by the significantly varying relative contributions of fish species or species groups to the functional space, whereby low‐trophic‐level pelagic fish species or species groups are closer to the boundaries of the functional trait space than high‐trophic‐level demersal fish species or species groups. Main conclusions: The FD of commercial marine fish communities responds significantly to climate warming and increasing fishing pressure, with opposite effects driven by different response patterns of fish species or species groups. Our results suggest that management actions should address the two issues simultaneously, because considering only one will unleash greater functional changes in the other. [ABSTRACT FROM AUTHOR]

Aim: Fresh carbon (C) inputs to the soil can have important consequences for the decomposition rates of soil organic matter (priming effect), thereby impacting the delicate global C balance at the soil–atmosphere interface. Yet, the environmental factors that control soil priming effect intensity remain poorly understood at a global scale. Location: Global. Time period: 1980–2020. Major taxa studied: Soil priming effect intensity. Methods: We conducted a global dataset of CO2 effluxes in 711 pairwise soils with 13C or 14C simple C sources inputs and without C inputs from incubation experiments in which isotope‐labelled C was used to quantify fresh C‐induced rather than exudate‐induced priming. Results: Soil priming effect intensity is predominantly positive. Soil texture and C content were identified as the most important factors associated with priming effects, with sandy soils from tropical and mid‐latitudes supporting the highest soil priming effect intensity, and soils with greater C content and fine textures from high latitudes maintaining the lowest soil priming effects. The negative association between C content and soil priming effect intensity was also indirectly driven by changing mean annual temperature, net primary productivity, and fungi : bacteria ratio. Using this information, we generated a global map of soil priming effect intensity, and found that the priming was lower at high latitudes and higher at lower latitudes. Main conclusions: Global patterns of soil priming effect intensity can be predicted using environmental data, with soil texture and C content playing a predominant role in explaining in priming effects. These effects were also indirectly driven by climate, vegetation and soil microbial properties. We present the first global atlas of soil priming effect intensity and advance our knowledge on the potential mechanisms underlying soil priming effect intensity, which are integral to improving the climate change and soil C dynamics components of Earth System models. [ABSTRACT FROM AUTHOR]

Aims: Terrestrial biodiversity is threatened by land use change. Modelling suggests that the remaining, potentially arable areas of natural intact vegetation (rNIV) of 9 of 35 global biodiversity hotspots may be converted to agriculture by 2050, committing their endemic species to extinction. Studies have shown that if the global population adopted a healthy, mostly plant based diet, agricultural area expansion can be reduced. We want to examine to what degree this applies to the regions covered by biodiversity hotspots. Location: Global. Time period: 2020–2050. Major taxa studied: No particular taxa. Methods: For every biodiversity hotspot, we simulate climate change impacts on agricultural productivity, and estimate food demand shifts from 2010 to 2050 by processing population and income growth projections. We quantify the net change in rNIV by 2050 in all hotspots by calculating the agricultural area necessary to meet the food demand under a business as usual, a healthy diet, a healthy diet plus agricultural intensification, and a healthy diet plus agricultural intensification plus crop change scenario. Results: In the healthy diet scenario, the rNIV of 16–21 hotspots can be preserved entirely, but 5–6 hotspots in less developed regions may lose all rNIV to agricultural area expansion. In these regions, a healthy diet implies an increase in consumed calories and no change in the already high share of plant‐based calories. When combined with agricultural intensification, these hotspots will still lose 7%–92% of rNIV. Only an additional change in crop mix patterns may preserve all. Main conclusions: While a change in dietary habits may be sufficient for preservation of rNIV in many hotspot regions, a healthy diet actually puts more pressure on rNIV in other hotspot regions. Intensifying agriculture and optimizing crop selection should be priorities in those regions to mitigate the expected loss of rNIV to agricultural expansion. [ABSTRACT FROM AUTHOR]

Aim: Our ability to understand how species may respond to changing climate conditions is hampered by a lack of high‐quality data on the adaptive capacity of species. Plant functional traits are linked to many aspects of species life history and adaptation to environment, with different combinations of trait values reflecting alternate strategies for adapting to varied conditions. If the realized climate limits of species can be partially explained by plant functional trait combinations, then a new approach of using trait combinations to predict the expected climate limits of species trait combinations may offer considerable benefits. Location: Australia. Time period: Current and future. Methods: Using trait data for leaf size, seed mass and plant height for 6,747 Australian native species from 27 plant families, we model the expected climate limits of trait combinations and use future climate scenarios to estimate climate change impacts based on plant functional trait strategies. Results: Functional trait combinations were a significant predictor of species climate niche metrics with potentially meaningful relationships with two rainfall variables (R2 =.36 &.45) and three temperature variables (R2 =.21,.28,.30). Using this method, the proportion of species exposed to conditions across their range that are beyond the expected climate limits of their trait strategies will increase under climate change. Main conclusions: Our new approach, called trait strategy vulnerability, includes three new metrics. For example, the climate change vulnerability (CCV) metric identified a small but important proportion of species (4.3%) that will on average be exposed to conditions beyond their expected limits for summer temperature in the future. These potentially vulnerable species could be high priority targets for deeper assessment of adaptive capacity at the genomic or physiological level. Our methods can be applied to any suite of co‐occurring plants globally. [ABSTRACT FROM AUTHOR]

Aim: Factors that make species resilient to climate change can be difficult to study with empirical data because conditions cannot be experimentally controlled. We used trait‐based evolutionary ecological agent‐based modelling to understand how dispersal, selection, extirpation, and other factors contribute to resilience under three climate change scenarios to test the extent to which high dispersal rate contributes to persistence of species and the extent to which they occupy large geographic ranges on an evolutionary time‐scale involving speciation, dispersal, gene flow, and extinction. Location: Hesperia (an imaginary continent with controlled environmental heterogeneity). Major taxa studied: Modelled mammalian herbivore clade with 16 terminal species, each of which is a metapopulation with a variable number of local populations. Methods: We used NetLogo to model trait‐based biotic responses to climate change in an environmentally heterogeneous continent in an evolving clade, the species of which are each represented by local populations that disperse and interbreed; they also are subject to selection, genetic drift, and local extirpation. We simulated mammalian herbivores, whose success depends on tooth crown height, vegetation type, precipitation and grit. Results: We found that high dispersal probability usually allowed species to successfully track their ancestral habitat as the continent's geography was altered by climate change. However, tracking was insufficient to allow species' traits to adapt to novel habitats that arose through the climate change process. High dispersal rates combined with moderate plasticity (lower extirpation risk) facilitated occupation of novel habitats, as did weak selective regimes. Main conclusions: The interaction between dispersal, probability of local extirpation, and selection intensity were jointly required to understand the likelihood of species survival and how widespread they would be. Diversity and geographic occupancy were maximized when parameters facilitated evolutionary adaptation to novel habitats. High rates of dispersal were sufficient for habitat tracking but insufficient by themselves to allow occupation of newly emerged environments. [ABSTRACT FROM AUTHOR]

Aim: The abundances and distributions of some species are more closely matched to variations in climate than others. Species traits that might influence how well the distribution and abundance of a species are matched to climatic variation include life history (e.g., body size and dispersal ability), ecology (e.g., habitat specialization and territoriality) and demography (e.g., population size). Here, we used a survey of bird abundances across the USA to assess the extent to which species abundances and distributions are predicted by climate (i.e., climate matching) and how species traits relate to interspecific variation in climate matching. Location: USA. Time period: 1983–2018. Major taxa studied: Birds. Methods: Species abundances were obtained from the North American Breeding Bird Survey. Climate matching was estimated as the predictive performance of species–climate models fitted using boosted regression trees and generalized additive models and modelled as a function of species traits. Results: Species traits explained 56% of the variation in climate matching among species. Intermediate‐sized species were more well matched to climate than smaller or larger species, as were species that lived primarily in forested compared with open habitats, species that were locally more abundant and species that were more territorial. Alternatively, species that were more specialized or had high variability in abundance among sites were less well matched to climate. We also found that species classified as "near threatened" were more well matched to climate, suggesting that these species might be more vulnerable to climate change. However, species classified as "vulnerable" were more decoupled from climate than those of "least concern", possibly owing to ecological drift associated with progressive population declines. Main conclusions: Our findings provide an ecological basis for understanding the extent to which species abundances and distributions match broad climatic gradients, which can provide the groundwork to improve our ability to predict distributions under global change. [ABSTRACT FROM AUTHOR]

Aim: Global declines in structurally complex habitats are reshaping both land‐ and seascapes in directions that affect the responses of biological communities to warming. Here, we test whether widespread loss of kelp habitats through sea urchin overgrazing systematically changes the sensitivity of fish communities to warming. Location: Global temperate latitudes. Time period: Modern. Major taxa studied: Fishes. Methods: Community shifts in thermal affinity related to habitat were assessed by simulating and comparing fish communities from 2271 surveys across 15 ecoregions. Results: We found that fishes in kelp and urchin barrens differed in realized thermal affinities and range sizes, but only in regions where species pools had high variability in the thermal affinities of species. Barrens on warm temperate reefs host relatively more warm‐affinity fish species than neighbouring kelp beds, highlighting the acceleration of tropicalization processes facilitated by urchin grazing. In contrast, proportionally more cool‐affinity fishes colonize barrens at high temperate latitudes, contributing to community lags with ocean warming in these regions. Main conclusions: Our findings implicate urchins as drivers of ecological change, in part by affecting ecological resilience to warming. [ABSTRACT FROM AUTHOR]

Aim: The aim was to identify the primary drivers of compositional change in breeding bird assemblages over a 40‐year period. Location: Britain. Time period: From 1970 to 2010. Major taxa studied: Birds. Methods: Using morphological trait measurements and a dataset of presence–absence data for British breeding birds surveyed in 10 km × 10 km hectads during two time periods, we calculated temporal taxonomic and functional beta diversity for each hectad alongside the change in species richness, mean nearest taxon distance (MNTD) and mean pairwise distance (MPD). We also estimated potential drivers of beta diversity, including climatic and land‐use and land‐cover (LULC) change variables, elevation and assemblage species richness in 1970 (1970rich). We used random forest regressions to test which variables best explained compositional change in the assemblages. We also assessed spatial taxonomic and functional change by analysing multiple‐site beta diversity and pairwise dissimilarities between time periods. Results: Initial (1970) species richness was the most important predictor (highest importance score) across all models, with areas characterized by higher initial richness experiencing less assemblage change overall. The coordinates included to capture spatial autocorrelation in the data were also important predictors of change. Most climate and LULC variables had relatively low explanatory power; elevation and average temperature were the most influential. All metrics increased slightly with increasing elevation, except for species richness change and MPD, which decreased. Main conclusions: The composition of British breeding bird assemblages changed substantially between 1970 and 2010. Spatial heterogeneity increased, both taxonomically and functionally. We show evidence that hectads with larger assemblages have been buffered from temporal diversity change and that those at higher elevations changed more in composition than those at lower elevations. Overall, coarse‐resolution climate and LULC explained only small to moderate amounts of variation, suggesting that stochastic assembly change or finer‐scale drivers might be drivers of temporal changes in assemblage composition. [ABSTRACT FROM AUTHOR]

Aim: The aims of this study were to evaluate the changes in the length of the time period between leaf‐out and flowering across temperate tree species, and associate these changes with potential physiological and environmental drivers to enhance mechanistic insight into these phenomena. Location: Central Europe. Time period: 1980–2016. Major taxa studied: Six temperate woody species. Methods: Statistical analyses were carried out based on long‐term ground observations of both spring leaf‐out and flowering across temperate tree species during 1980–2016, a period characterized by rapid warming. Results: The temperature sensitivity of flowering (−5.4 ± 0.04 days/℃, mean ± SE) was higher than that of leaf‐out (−4.6 ± 0.04 days/℃) across all species, regardless of whether leaf‐out occurred before or after flowering. This study postulates a hypothesis attributing the different temperature sensitivities to different thermal sensitivities, thermal requirements, and photoperiodic controls. Main conclusions: The larger temperature sensitivity of flowering than leaf‐out resulted in an extended time period between flowering and leaf‐out in species that bloom before leafing out, but a shorter time period between these phenophases in species with the opposite strategy. We would like to emphasize the importance of changes in time period between different phenophases, and we recommend conducting experimental research to reveal the underlying mechanisms of plant phenology response to climate change, and to explore its potential ecological implications. [ABSTRACT FROM AUTHOR]

Aim: Soil respiration (RS) is one of the largest fluxes in the global carbon cycle. It is composed of respiration by roots and heterotrophic organisms, with each component having distinctive drivers and sensitivities and, consequently, varying feedback potential to climate change. Global drivers of the total flux of RS are widely studied and generally accepted, but our understanding of the factors governing its component fluxes lags far behind. Location: Global. Time period: 1962–2015. Major taxa studied: Plant roots and soil microbes. Methods: Combining a newly updated global database of RS partitioning measurements with biotic and abiotic variables, we examined the world‐wide distribution of the proportion of the annual root respiration (Rroot) contribution to RS (Rroot:RS). We investigated how Rroot:RS varies by ecosystem type, measurement method and climate. We used a random forest model to predict the relationship between field measurements of Rroot:RS (n = 880) and 14 biotic and abiotic factors, including climate, nitrogen deposition, soil, mycorrhiza, biomass and satellite‐derived greenness. Finally, we present a global map of predicted Rroot:RS at 0.5° resolution. Results: Consistent with previous studies, we found no clear trends of mean Rroot:RS across ecosystem types and measurement methods. The area‐weighted overall mean of predicted Rroot:RS was.42 (SD ±.18; i.e., 42% of total global RS was generated by plant roots). Predicted Rroot:RS and related environmental factors did exhibit clear spatial patterns between climatic regions, with higher Rroot:RS in dry and cold regions and lower Rroot:RS in temperate and tropical regions. Main conclusions: Given that Rroot:RS is linked to plant carbon use efficiency (CUE, the ratio of net primary production to gross primary production), but generated from measurements completely independent of plant CUE, it might provide crucial insights into ecosystem‐ to global‐scale carbon cycling. This study thus provides a framework to explore global carbon allocation under global climate change. [ABSTRACT FROM AUTHOR]