Global Change Biology

Sequential hurricane-heatwave events threaten forest resilience via understudied legacy effects. Using Bayesian Structural Time Series, piecewise Structural Equation Modeling, and a 21-event global synthesis, we quantify how structural degradation non-linearly amplifies productivity loss during subsequent heatwaves. Our Hurricane Michael (2018) case study reveals significant negative GPP legacy effects during the 2019 heatwave. Intact, tall and diverse canopies buffer microclimates and moderate thermal sensitivity. Hurricane-induced structural simplification removes this protection, exposing temperature-sensitive shaded leaves to extreme stress. We identified a context-dependent hydraulic trade-off: structural complexity provides shading but exacerbates forest sensitivity to water deficits during peak heat, the vulnerability of which reverses during the recovery phase. Globally, these legacy effects are triggered by heatwave intensity and modulated by soil type, with loamy-soil forests most vulnerable. These findings highlight the critical role of forest structure in forest responses to compound disturbances. Neglecting structural legacies in Earth System Models likely underestimates risks to global carbon sinks.

{middle dot} Globally, forest ecosystems face widespread mortality events. However, the independent impacts of distinct stressors, such as heat stress vs edaphic drought, remain poorly understood and physiological early warning indicators for tree mortality are urgently required. {middle dot} We exposed well-watered saplings of Fagus sylvatica, Pseudotsuga menziesii and Picea abies to summer heat waves and subsequent natural winter-desiccation. Physiological parameters (e.g. gas exchange, water uptake velocity via 2H labelling, and volatile organic compound emissions) were monitored throughout the growing season and survival was assessed regularly until subsequent spring to capture immediate and delayed mortality as a consequence of legacy effects. {middle dot} Heat exposure without soil water deficit, followed by winter desiccation, triggered species-specific mortality rates (51.8% F. sylvatica, 48.2% P. abies, 16.9% P. menziesii), with P. abies exhibiting significantly faster mortality response than the other species. Reduced water uptake, lower stomatal conductance, impaired photosynthetic efficiency, and altered VOC emissions distinguished non-surviving from surviving saplings months before visible damage in all three species. {middle dot} Heat stress drives mortality independent of edaphic drought, with sub-lethal physiological indicators detectable up to 10 months before visual signs. These early warning indicators could enable damage detection before lethal thresholds are crossed, offering new strategies for mitigating climate change-driven forest decline.

Biological invasions are a major driver of global change, reshaping ecosystems and threatening biodiversity worldwide. Anticipating where invaders will establish and where they will exert the strongest ecological impacts are key challenges for early detection and targeted management. Although Species Distribution Models (SDMs) are widely used to forecast biological invasions, they often provide uncertain estimates of establishment ranges and limited insight into invader performance, making it difficult to anticipate ecological impacts. Here, we address these limitations by integrating physiological information on invader performance with SDMs to identify regions of high invasion risk. Using the brown alga Rugulopteryx okamurae, one of the most prominent marine invaders in Europe, we first test alternative hypotheses of northern establishment limits: (i) a cold-survival constraint driven by winter temperatures and (ii) a growth constraint derived from the species' thermal performance. To identify the more likely scenario, we combine cold-tolerance experiments with seasonal growth comparisons between the invader and a native macroalga Dictyota dichotoma, whose established distribution allows physiological performance to be directly related to realised presence. Finally, we project seasonal growth of the invader across the predicted establishment range as a proxy for biomass accumulation and potential ecological impacts. Our results indicate that northern limit in Europe will be more likely constrained by winter survival rather than growth, extending the potential establishment range of Rugulopteryx to mid-Norway. In contrast, the highest impacts are likely to remain concentrated in southern Europe, where thermal conditions sustain high year-round growth. Overall, our approach illustrates how understanding the physiological response of invaders to their environment can improve the interpretation of SDM outputs and help identify areas at greatest risk of impact within their potential establishment range.

A direct empirical relationship between gross primary productivity (GPP) estimated by the eddy covariance method and satellite vegetation indices (VIs) has been widely observed across diverse ecosystems globally. Building on this observed covariation, VIs are frequently utilized as critical parameters - such as the fraction of absorbed photosynthetically active radiation (fPAR) - within light use efficiency (LUE) and greenness-based models for carbon cycle monitoring. However, actual canopy carbon assimilation is jointly governed by slowly evolving structural parameters and highly dynamic functional traits, such as physiological efficiency. The extent to which the macro-scale VI-GPP covariance is driven by structural scaffolding, and how this structural signal decouples from physiological function under environmental stress, remains to be systematically quantified. Here, we synthesized half-hourly eddy covariance measurements from 328 globally distributed sites and paired them with a rigorously angle-normalized Enhanced Vegetation Index (nadir view and fixed solar zenith angle at 30 degrees, EVI_SZA30). By applying a nonlinear light-response curve model across 54,720 high-frequency temporal windows, we mechanistically disentangled observed actual GPP (GPP_EC) into baseline photosynthetic capacity (P_c) and intrinsic quantum yield (alpha). Our results demonstrate that the macroscopic covariance between EVI_SZA30 and GPP_EC (R^2=0.554) is primarily driven by the index's robust ability to track structural capacity (P_c, R^2=0.538). In contrast, EVI_SZA30 exhibits limited sensitivity to high-frequency variations in functional traits like physiological efficiency (alpha, R^2=0.038). Particularly in water-limited biomes (e.g., open shrublands and woody savannas), intense environmental stress triggers rapid stomatal regulation while the physical canopy structure remains relatively stable. Consequently, the correlation between EVI and P_c becomes notably stronger than its correlation with actual GPP_EC, highlighting a pronounced structural-physiological decoupling. Because discrete overpasses by sun-synchronous polar-orbiting satellites face intrinsic temporal constraints in capturing sub-daily physiological down-regulation (e.g., midday photosynthetic depression), future monitoring paradigms could greatly benefit from the continuous, high-frequency observations provided by next-generation geostationary (GEO) satellites to bridge the gap between structural parameters and transient ecosystem function.

Intensifying fire regimes threaten forests globally, but the risk of persistent post-fire forest loss and its potential mitigation remains poorly quantified. We analyzed millions of wildfires worldwide from 2001 to 2024 and tracked recovery in satellite-observed forest structure and ecosystem function. Post-fire persistent forest loss, indicated by modeled non-recovery to pre-fire conditions over decadal timescales, affected 57.1% of burned forest area globally since 2001, with hotspots in Pacific temperate and southern boreal forests. We then identified 'crucial fires' as events exceeding a stringent modeled-risk probability threshold for persistent structural or functional non-recovery, with fire severity strongly predicting this loss. This severity dependence revealed a management pathway, as locations with prior low-severity fire experienced lower severity in subsequent wildfires and had lower modeled probability of becoming crucial. Under a model-based counterfactual scenario, applying the estimated severity attenuation was associated with a 7.6% reduction; the top 1% of road-accessible areas accounted for 35% of this reduction. These results provide a global framework for identifying where wildfire threatens forest resistance and where targeted low-severity fire management like prescribed fire might be used to combat global forest loss.

AimHere we aim to disentangle species-specific bioclimatic drivers of forest site productivity and project their future dynamics, providing a spatially explicit basis for anticipating climate-driven shifts in productivity and their implications for forest carbon sequestration. LocationIberian Peninsula. Time period1985-2014 (calibration); 2071-2100 (projected under CMIP6 scenarios). Major taxa studied21 Iberian tree species. MethodsWe used Site Form (SF) maps derived from the Third Spanish National Forest Inventory, spatially interpolating plot-level SF estimates as a continuous productivity index and relating them to 25 bioclimatic variables. Multiple linear regression models were selected via complementary stepwise and subset regression and validated on independent hold-out data (80%/20% split). ResultsValidated [Formula] ranged from 0.46 (Quercus faginea) to 0.97 (Pinus pinaster); 17 of 21 species reached [Formula]. BI013 precipitation of the wettest month), not BI014, was the most frequently retained predictor (15/17); BI014 was retained in only (11/17 models with a near-even sign split. Combining projected changes in mean productivity and habitat extent under SSP5-8.5, fifteen of sixteen applicable species lose total productivity by 2071-2100, six -- including Fagus sylvatica and Betula alba -- collapsing to below 1% of their reference-period value; only Pinus pinaster gains, and only under the lowest-emission pathway (up to 175%) -- under SSP5-8.5 it too loses productivity, albeit less than any other species (35% of its reference-period value retained). Limiting warming to SSP1-2.6 spares Mediterranean pine and oak species but not Euro-Siberian and montane ones. Main conclusionsThese validated, extrapolation-aware models reveal a near-universal, climate-driven collapse in Iberian forest site productivity, with direct implications for the carbon-sink potential currently attributed to these forest types, and provide a route to dynamic, climate-aware carbon-uptake estimates for the region.

Biodiversity losses continue to outpace traditional management, underscoring the need to understand adaptive capacity and the potential for interventions to increase fitness under climate change. We undertook a genome-wide association study on 156 Acropora palmata genets to investigate the genomic basis of areal growth, endosymbiont association, and thermal tolerance. Seven peaks on chromosomes 1, 3 and 14 were associated with endosymbiont shuffling and two peaks on chromosome 4 were associated with areal growth. As variants were located in non-coding regions we incorporated additional data from an independent field-transplant experiment to investigate their relationship with patterns of gene expression. Intersection of these datasets implicated melanocortin-like receptor activity and Ran GTPase activating protein 1 in endosymbiont composition and surface area growth, respectively. Results indicate that growth and endosymbiont associations may represent more viable intervention targets than temperature tolerance and highlight the need to better understand the role of non-coding variation in basic biology and development of restoration interventions.

Global change is driving rapid ocean warming, exposing organisms to both chronic temperature increases and acute marine heatwaves. Understanding how species cope with thermal stress is critical for predicting ecosystem resilience. Echinoderms are globally distributed and often function as foundational species, yet comparative assessments of upper thermal tolerance among species occupying contrasting thermal environments remain limited. Here, we address this gap by comparing upper thermal tolerance across three sea urchins with distinct biogeographic distributions: the latitudinally broad purple sea urchin (Strongylocentrotus purpuratus), the circumpolar green sea urchin (S. droebachiensis), and the tropical variegated sea urchin (Lytechinus variegatus). We quantified thermal limits after two acclimation treatments: ambient temperatures approximating native habitat conditions for each species and an elevated temperature (+6 C). We developed a novel assay to measure critical thermal maximum (CTmax), comparing variability and inconsistencies associated among multiple assays. Upper thermal tolerance increased with acclimation to elevated temperatures in all three species, but acclimatory capacity differed markedly, with S. droebachiensis showing the strongest response and S. purpuratus the weakest. Conversely, S. purpuratus had the highest thermal safety margin and thus the lowest proximity to its thermal ceiling. Our adhesion based CTmax method was more reproducible and the most precise compared to other metrics tested, providing an improved framework for quantifying physiological thermal limits of sea urchins. Together, these findings reveal substantial but unevenly distributed thermal resilience in ecologically diverse sea urchins, advancing our understanding of how foundational marine species may respond to future global change.

Anthropogenic warming exposes coral reefs to recurrent marine heatwaves (MHWs), yet responses to comparable thermal stress remain highly variable. A central challenge is determining whether reduced bleaching reflects acclimatization-like persistence of existing colonies or mortality-driven filtering that produces demographically depleted assemblages. Using colony-level surveys across the Florida Reef Tract (2014-2023), we show bleaching sensitivity declined from 2014 through 2022, consistent with ecological memory. A spatial matched-event framework integrating bleaching severity and adult colony density resolved these reduced-bleaching outcomes into two distinct pathways: demographic persistence (stable/increasing density) and mortality-filtered tolerance (declining density). Persistence pathways were maintained under predictable exposure regimes characterized by lower interannual thermal variability. This persistence was driven by weedy life-history taxa (e.g., Porites spp.) replacing historical framework builders, indicating stability reflects ecological reassembly rather than uniform increases in thermal tolerance. Under the unprecedented extremes of the 2023 MHW, this acclimatization-like buffering broke down, causing widespread sensitization and collapse of previously persistent networks. These results support a bounded ecological memory framework; prior exposure reduces bleaching sensitivity under predictable thermal regimes but fails under extreme heat stress. Consequently, modern refugia are best defined by adult standing stock retention representing systems undergoing selective ecological reassembly rather than full functional recovery.

Most evidence of the consequences of climate change in natural systems has focussed on shifts in mean temperature (1,2), but the effects of extreme climatic events (ECEs) remain far less understood. This is particularly true for very severe ECEs that may occur only once every few decades. Understanding the consequences of these severe events for natural populations is nonetheless critical, since their frequency is predicted to rise under current climate change (3). Here we combine a unique long-term dataset spanning almost five decades of breeding (>20,000 events) and morphological data (>120,000 observations) in adult and nestling great tits (Parus major) and blue tits (Cyanistes caeruleus) with fine-scale temperature records to examine the effects of an unprecedented heatwave in May 2026 on breeding success and morphology. Average temperature during the heatwave (22-29 May 2026) was 7.85 C above the historical record, reaching +10.5 C (+4.32 SD) at its peak (25-26 May). These record-breaking temperatures significantly reduced adult breeding success and nestling bmass relative to expectation in the absence of a heat-wave. Given the heatwave was widespread (Fig. 1A), our findings from a single, exceptionally well-studied population are likely to generalise to other species exposed to the same event, providing key evidence that severe ECEs can substantially harm wild populations.

Evidence is accumulating that global change is altering species distributions. Yet, detailed knowledge is missing about the relative and joint contribution of different drivers to observed species responses. Here, we implemented an impact attribution framework based on counterfactual simulations to assess the impact of climate and land use change on occupancy dynamics of North American breeding birds. We used a Bayesian framework to fit process-explicit dynamic occupancy models to long-term survey data for 159 species from 1995 to 2019, and quantified predictive performance using spatial and temporal cross-validation. We then assessed the relative importance and effect direction of climate and land use change while accounting for model predictive accuracy. Results indicate that climate change negatively affected 90 % of the species and land use change negatively impacted 96 %. Climate change emerged as more important than land use change for driving changes in occupancy across species. Remarkably, the effects of both drivers were mostly antagonistic rather than acting additively or synergistically. Climate was the most important driver for bird communities in the western USA, while land use change dominated in the southeast, and combined climate and land use change in the northeast. Our analysis demonstrates that recent changes in North American bird distributions are shaped by multiple global change drivers acting in concert. The effect of recent climate and land use change were mostly antagonistic, and thus trends in bird occupancy dynamics could not be understood by studying the impact of those drivers in isolation. By disentangling the effects of climate and land use change on biodiversity trends, impact attribution approaches can improve our understanding of global change impacts and can support conservation planning and more accurate and realistic projections of biodiversity response to global change.

Experimentally evolved, heat-tolerant algal symbionts (heat-evolved; HE) offer a promising means of enhancing coral holobiont thermotolerance under rapidly warming oceans. However, translating their benefits into restoration practices requires scalable delivery methods. Coral tissue fusion may provide one such pathway by facilitating HE symbiont transfer to wild corals; however, its feasibility remains largely untested. As an initial test, we paired adult isografts of Galaxea fascicularis and Psammocora columna hosting HE Cladocopium proliferum (SS8) with chemically bleached, SS8-naive recipients. Fusion was first observed after three days in G. fascicularis and nine days in P. columna. In both species, fusion was followed by increased pigmentation and photochemical efficiency at the recipients fusion interface relative to distal tissue and unfused controls. After [~]50 days, SS8 was detected at low levels (<3.5%) in 15/19 fused G. fascicularis recipients, although detection was also common among unfused horizontal-transmission controls maintained in the same water column (13/18). These findings provide the first empirical evidence that conspecific coral tissue fusion is associated with localised physiological recovery and can coincide with HE symbiont acquisition, while highlighting the need to distinguish tissue-mediated transfer from background horizontal transmission. Fusion may therefore represent a complementary pathway for beneficial symbiont delivery in assisted-evolution frameworks.

Temperate forests increasingly face extreme air temperature, but plant physiological responses, particularly alterations in carbon allocation or protection via volatile organic compound (VOC) emissions, remain poorly understood. We pulse-labelled well-watered saplings of Fagus sylvatica and Pseudotsuga menziesii in a controlled heat stress experiment with 13CO2 to quantify heat-induced shifts in CO2, VOC and C pool exchange, specifically analyzing compound-specific {delta}13C of terpenoids, water-soluble organic matter (WSOM) and dark respiration. Under heat stress, up to 50% of fresh assimilates were directed to maintenance respiration and 1-2% to VOC emissions, while net assimilation and water use efficiency decreased by 50-75% in both species. Heat directly affected metabolic processes and reduced turnover rates of fresh assimilates in F. sylvatica, but accelerated them in P. menziesii. Strong 13C labelling of some compounds, particularly acyclic ones, suggested increased de novo synthesis of specific terpenoids for heat stress protection. By tracing the fate of recently assimilated 13CO2 we demonstrate that heat stress reduces net carbon uptake and water use efficiency, disrupts turnover of C pools and increases carbon loss via respiration and de novo synthesis of specific VOCs, potentially diminishing net carbon uptake of forests under future heat extremes.

Snow algae are major biological drivers of snow darkening in polar and high-alpine environments. However, the direct contribution of algal pigmentation to snow reflectance has remained difficult to quantify because field observations cannot disentangle the effects of pigmentation from variation in biomass, species composition, and snow physical properties. Here, we characterized the optical effects of pigmentation using hyperspectral spectroradiometry to compare green, orange, and red cyst-like cells of a snow-derived Haematococcus isolate while controlling for developmental stage and cell abundance. Cysts became more red with increasing astaxanthin concentrations while chlorophyll-a concentrations remained relatively constant. Relative to green cysts, mean reflectance decreased by approximately 30% in orange cysts and 40% in red cysts. Integrated reflectance across the visible spectrum (350-800 nm) was negatively correlated with astaxanthin concentration. These results provide direct experimental evidence that algal pigmentation alone substantially reduces reflectance after controlling for cell abundance and developmental stage, and indicate that differences in snow physical properties may partly obscure this effect under natural field conditions. Our findings identify astaxanthin accumulation as an intrinsic driver of biological snow darkening and suggest that algal pigmentation, which may vary with species identity and physiological state, should be considered alongside biomass when predicting the radiative effects of snow algal blooms.

Many Sockeye salmon (Oncorhynchus nerka) populations have declined over recent decades, and climate change is likely to exacerbate these declines through direct and indirect ecological effects. The response to the associated environmental changes is likely to vary among life stages, populations, and regions. Quantitative estimates of climate change driven impacts that account for this variability could fill a critical gap and provide forward-looking insights into how sockeye are expected to respond to future climate-driven change across their lifecycle. To address this need we developed a hierarchical population dynamics model parameterized with juvenile, adult return and spawner abundance data from 13 sockeye salmon populations from Washington State to northern British Columbia. We used a formal causal inference framework that paired salmon abundance data with a suite of environmental covariates hypothesized to represent ecological conditions across the lifecycle. We used the model to estimate population-specific responses to each environmental driver, then combined parameter estimates with projections from down-scaled climate change models to estimate productivity responses to anticipated environmental change. We found that historical sockeye productivity was strongly associated with environmental covariates, which explained more interannual variability in return abundance than spawner abundance in most populations. However, the life stages and specific environmental covariates with the largest impacts differed among populations and regions, often displaying a latitudinal gradient. Increases in coastal ocean temperatures and mixed layer depth generally had negative effects though they varied among regions. Increased freshwater summer rearing and return migration temperatures had weaker but consistently negative effects. Under future climate conditions, projected changes in these environmental covariates are expected to result in substantial declines in productivity across most populations. Sockeye salmon display varying degrees of sensitivity to climate change across life stages, populations, and regions. Effective future management will require explicitly accounting for these life stage and population-specific responses.

The increasingly severe droughts in the Amazon Basin make it urgent to understand the resilience of tropical tree species and their microbiota. Plant-associated fungi and bacteria (i.e. extended phenotype) modulate drought stress for their hosts, but their role in recovery dynamics remains poorly understood. To test the impact of different drought durations on the recovery of both physiology and microbiota of tropical trees, we followed the responses of nearly 1,000 seedlings belonging to seven tropical tree species of seasonally flooded (SF) forests in a greenhouse experiment. Seedlings were subjected to different droughts, reflecting a current, a projected and an extreme drought scenario of the French Guiana climate. Plant responses were monitored after the drought and after rewetting. Plant performance was estimated through leaf gas exchange, photochemical functioning, leaf water potentials and water-related traits as well as morphological traits. Bacterial and fungal leaf communities were characterized with respectively 16S and ITS2 markers using high-throughput sequencing. Increasing the duration of the drought reduced the ability of plants to recover physiological functions, with differences among species which were only partially predicted by their drought tolerance strategies. Bacterial diversity increased in most plant host species after mild drought but not under the most severe stress. Bacterial dispersion and turnover responses were strongly host species-specific, without a general directional pattern across species. Fungal communities showed greater compositional stability, but exhibited consistently higher turnover compared to bacterial communities during both drought and recovery, with no convergence toward control composition. Finally, none of the recovery networks mirrored the architecture of the control network, regardless of prior drought duration, demonstrating that the integrated extended phenotype does not recover even when individual traits show signs of recovery. Our results reveal that both physiological recovery and microbial community recovery are strongly shaped by the plant host species identity and drought duration This study widens knowledge of SF tropical forests, vulnerable habitats in the context of climate change, through the lens of the associated microbial communities and functional traits. Beyond the effects of an increasingly uncertain climate combined with a rise in the frequency of extreme events, our study places emphasis on including tree species extended phenotypes in considering their recovery dynamics.

Corals are increasingly threatened by climate change, yet the interplay between ocean warming and fungal infection remains experimentally underexplored. Here, we demonstrate that thermal stress exacerbates the pathogenicity of the fungus Aspergillus sydowii, driving physiological collapse and functional reorganization in the octocoral Sclerophytum sp. We deployed a 34-day mesocosm heat-stress experiment and quantified performance, mortality, and taxonomic and functional microbiome shifts. Combined heat and fungal exposure proved highly lethal, causing 45% mortality compared to 7% under heat exposure alone. Re-isolation from diseased nubbins implicates A. sydowii as the causal agent. Metagenomic profiling indicated that physiological collapse was underpinned by a functional transition from mutualism to antagonism in the microbiome. Specifically, combined heat and fungal stress triggered a depletion of ankyrin- and WD40-repeat proteins - hallmarks of symbiotic stability - concurrent with a surge in genes involved in fungal cell wall degradation and secondary metabolite biosynthesis. While surviving holobionts recovered full photosynthetic efficiency after combined stress, their microbiomes did not revert to baseline. Instead, they assembled into a taxonomically distinct configuration characterized by enrichments of sulfate-reducers (Thermodesulfobacteriota) and thermotolerant phototrophs (Thermosynechococcales). This suggests that despite the rapid photosystem recovery, the holobiont retained a complex legacy of thermal and biotic stress across both its internal chemical microenvironment and its microbiome. These findings highlight the decoupled recovery processes of different holobiont components, demonstrating that even though some corals may survive severe climate-driven disease, they emerge as ecologically reorganized entities.

The number of species introduced outside of their historical ranges by human activity continues to rise. A subset of these species establishes, form self-sustaining populations, and some (invasive alien species) go on to cause substantial harm to biodiversity and ecosystems. Preventing new invasive alien species from establishing is the key focus of interventions, because post-establishment management is costly and often fails. However, it remains unclear how effective multilateral efforts have been in curbing the rise. Here we show that the emergence of new invasive alien species across countries is slowing, and trends are similarly negative across geographically diverse countries. Using data and modelling advances, we find a 35% reduction in the establishment of new invasive alien species over a policy-relevant 50-year time frame. The findings directly inform the assessment of progress for the invasive alien species target of the Kunming-Montreal Global Biodiversity Framework, and provide a global baseline for monitoring rates of invasive alien species establishment. Furthermore, the slowdown suggests that policy and investment over recent decades to prevent invasive alien species from entering and establishing in countries have had a positive effect.

Anthropogenic climate change is threatening global biodiversity, with sea turtles particularly vulnerable as offspring sex and developmental success are strongly influenced by incubation temperature. Behavioral plasticity, including the seasonal distribution of reproductive output, may provide short-term mechanisms for mitigating these impacts. Here, we investigated season-wide hatchling sex ratios and emergence success in a small population of green turtles (Chelonia mydas), tracking individual females across their nesting seasons. Sex ratios varied markedly through the nesting season, with later nests producing a greater proportion of male hatchlings. Moreover, sex ratios were relatively consistent among nests laid by individual females. Overall, females producing more nests over a season also produced more male offspring, suggesting that both nesting phenology and reproductive output influence individual contributions to future population demographics. Mechanistic models indicate that hatchling sex ratios have trended towards female-biased ratios (>80% female) over the past 50 years, and are projected to approach complete feminization by 2100 under continued warming. Although emergence success currently remains high (>85%), it is predicted to decline sharply after mid-century, with viable hatchling production falling to [~]30% by the end of the century. Models further show that maintaining contemporary sex ratios and emergence success will require unrealistically large delays in nesting phenology, and that even extreme shifts in phenology become ineffective by 2100. Together, these findings demonstrate that individual females can increase male hatchling production by nesting later and producing more nests, but behavioral plasticity alone is unlikely to offset the accelerating impacts of climate change on this population.

Tree populations can respond to climate change through migration, phenotypic plasticity, or genetic evolution. Despite long generation times of forest tree species, recent studies suggest that their evolutionary responses may occur rapidly. Using oaks as a model system, we synthesize evidence from 88 common garden studies and from historical, retrospective and longitudinal approaches to explore how populations have adapted to climatic variability across different biomes, and assess the consistency and pace of evolutionary responses across spatial and temporal climatic gradients. We found that approximately 61% of the studies exhibited significant differences among populations but climatic drivers and adaptive strategies differed among biomes. Temperature-related clines predominated in temperate regions, with populations from warmer origins showing longer growing seasons and higher growth potential. In seasonally dry biomes, aridity favored increased drought tolerance in Mediterranean populations but drought avoidance in tropical populations. Allochronic studies revealed genetic changes over decades to millenia in response to climate changes, with warming associated with increased growth and reduced specific leaf area in temperate oaks. Thus, spatial differentiation and temporal evolution were generally congruent in direction for most traits except for leaf unfolding, while short-term evolutionary rates exceeded long-term estimates by two to three orders of magnitude. In summary, provenance trials can provide useful information on the direction of climate-driven evolution for some traits, but may underestimate its contemporary pace. More studies are needed to evaluate whether standing genetic variation of forest tree species is sufficient to track current climate change.