Tropical forest canopies are the biosphere's most concentrated atmospheric interface for carbon, water and energy1,2. However, in most Earth System Models, the diverse and heterogeneous tropical forest biome is represented as a largely uniform ecosystem with either a singular or a small number of fixed canopy ecophysiological properties3. This situation arises, in part, from a lack of understanding about how and why the functional properties of tropical forest canopies vary geographically4. Here, by combining field-collected data from more than 1,800 vegetation plots and tree traits with satellite remote-sensing, terrain, climate and soil data, we predict variation across 13 morphological, structural and chemical functional traits of trees, and use this to compute and map the functional diversity of tropical forests. Our findings reveal that the tropical Americas, Africa and Asia tend to occupy different portions of the total functional trait space available across tropical forests. Tropical American forests are predicted to have 40% greater functional richness than tropical African and Asian forests. Meanwhile, African forests have the highest functional divergence-32% and 7% higher than that of tropical American and Asian forests, respectively. An uncertainty analysis highlights priority regions for further data collection, which would refine and improve these maps. Our predictions represent a ground-based and remotely enabled global analysis of how and why the functional traits of tropical forest canopies vary across space.

Leaf venation architecture varies greatly among living and fossil plants. However, we still have a limited understanding of when, why and in which clades new architectures arose and how they impacted leaf functioning. Using data from 1,000 extant and extinct (fossil) plants, we reconstructed approximately 400 million years of venation evolution across clades and vein sizes. Overall, venation networks evolved from having fewer veins and less smooth loops to having more veins and smoother loops, but these changes only occurred in small and medium vein sizes. The diversity of architectural designs increased biphasically, first peaking in the Paleozoic, then decreasing during the Cretaceous, then increasing again in the Cenozoic, when recent angiosperm lineages initiated a second and ongoing phase of diversification. Vein evolution was not associated with temperature and CO2 fluctuations but was associated with insect diversification. Our results highlight the complexity of the evolutionary trajectory and potential drivers of venation network architecture. This study reconstructs the evolution of leaf venation networks, describing the transition from fewer, corrugated veins to high vein density and smoother loops. It also suggests herbivory as a potential driver of venation architectural changes.

The Amazon basin hosts the most biodiverse and intact ecosystems on Earth, yet human activities are an increasing threat. Metal contamination due to mining constitutes one of these major threats, but its impacts remain poorly quantified. We provide the first quantitative assessment of biodiversity exposure to mining-associated metals—mercury [Hg], arsenic [As], copper [Cu], Zinc [Zn], and lead [Pb]—across the Amazon. Around 66% of the Amazon’s 38,890 species of birds, plants, mammals, reptiles, amphibians, and fishes are exposed to metal contamination, including biodiversity hotspots and Indigenous territories. Safeguarding the Amazon’s role as a global reservoir of biodiversity, ecosystem function, and cultural heritage requires addressing metal contamination not only as a localized issue, but as a pervasive threat to global biodiversity. ### Competing Interest Statement The authors have declared no competing interest. National Youth Science Foundation, 2243809

Increasing drought pressure under anthropogenic climate change may jeopardize the potential of tropical forests to capture carbon in woody biomass and act as a long-term carbon dioxide sink. To evaluate this risk, we assessed drought impacts in 483 tree-ring chronologies from across the tropics and found an overall modest stem growth decline (2.5% with a 95% confidence interval of 2.2 to 2.7%) during the 10% driest years since 1930. Stem growth declines exceeded 10% in 25% of cases and were larger at hotter and drier sites and for gymnosperms compared with angiosperms. Growth declines generally did not outlast drought years and were partially mitigated by growth stimulation in wet years. Thus, pantropical forest carbon sequestration through stem growth has hitherto shown drought resilience that may, however, diminish under future climate change.

Questions Alpine grasslands are affected by a range of global change drivers, including land-use change, climate warming and pollution. How these drivers interact and affect plant functional communities is poorly understood. We used plant functional traits to test the single and interactive effects of warming, nitrogen addition and grazing on alpine grassland communities and assessed the importance of intraspecific trait variation.Location Alpine and sub-alpine grasslands in western Norway.Methods For three years, we applied global change treatments to test the effects of warming with nitrogen addition, and warming with grazing at an alpine and sub-alpine plant community. We measured six plant functional traits related to plant size and leaf economics, including intraspecific trait variation.Results Our results show that warming and nitrogen addition shifted size-related traits in plant communities towards taller plants with larger leaves, and more strongly in the alpine than in the sub-alpine plant community. Warming also affected leaf economic traits, promoting faster traits in the alpine and slower traits in the sub-alpine plant community. Grazing shifted communities to faster leaves (grazing tolerant) in the sub-alpine community and slower leaves (grazing avoidance) in the alpine community. There were no interactive effects between the global change drivers. The relative contributions of species turnover and intraspecific trait variation to overall trait variation differed between origins of the two plant communities.Conclusions We show that these global change drivers shift alpine and sub-alpine plant communities in different directions, likely due to differences in resource availability. Our results support the need for site-specific management strategies in these systems.

Using county-level data from the United States, we assessed allometric scaling relationships of coronavirus disease (COVID-19) cases, deaths and age structure within and across the first four major waves of the pandemic (wild-type, alpha, delta, omicron). Results generally indicate that the burden of cases disproportionately impacted larger-sized counties, while the burden of deaths disproportionately impacted smaller counties. This may be partially due to multiple interacting social mechanisms, including a higher proportion of older adults who live in smaller counties. Moreover, these likely social mechanisms interacting with vaccinations and virus waves created a dynamic pattern whereby the rate and magnitude of infections and deaths were population- and time-dependent. Our results offer a novel perspective on the scaling dynamics of infectious diseases, highlighting how both the rate and magnitude of COVID-19 cases and deaths scale differently across counties. Population size and age structure are key factors in predicting disease burden. Our findings have practical implications, suggesting that scaling-informed public health policies could more effectively allocate resources and interventions to mitigate the impact of future epidemics across heterogeneous populations.

Low temperatures and nutrient limitation have shaped Arctic plant communities, which are now affected by biome‐wise changes in both climate and nutrient cycling. Rising temperatures are favouring taller plant species with more resource‐acquisitive traits across the Arctic tundra. Simultaneously, declines in seabird populations may reduce subsidies of marine‐derived nutrients to terrestrial ecosystems, potentially favouring more resource‐conservative plant traits. It is crucial to understand the consequences of these concurrent changes in climate and marine‐derived nutrient inputs from seabirds for the functional composition and roles of Arctic plant communities. We use a 'space‐for‐time approach' to compare the functional composition of vascular plant communities across two elevational gradients in High Arctic Svalbard, one where climate is the major environmental driver and one influenced by nutrient input from a seabird colony. We assess changes in 13 traits related to plant size, leaf economics and nutrient cycling along the two gradients, and we also explore the relative contributions of species turnover and intraspecific variation to total trait variation across and between the gradients. Elevation per se had little impact on the plant functional composition. Instead, plants at the top of the seabird nutrient gradient, closest to the nesting sites, were taller and had resource‐acquisitive trait values, such as larger and thicker leaves and higher leaf nutrient contents. Enriched soil δ 15 N‰ signatures at these sites correlated with resource‐acquisitive values of leaf area, specific leaf area, leaf dry matter content, leaf phosphorous content and with enriched leaf δ 15 N‰ signatures. This variation in leaf economic traits and isotopes was largely driven by intraspecific variation at the nutrient gradient, whereas species turnover dominated at the reference gradient. Our results are consistent with marine‐derived nutrient subsidies from seabirds being a major driver of functional trait variation in Arctic vegetation. Ongoing declines in seabird populations may therefore affect terrestrial primary producer communities in the Arctic and beyond, with potentially important but unknown implications for biodiversity, consumer and decomposer communities, and ecosystem processes. Read the free Plain Language Summary for this article on the Journal blog.

PREMISE:Within plant communities, few species are abundant, and most are locally rare. Worldwide, 36% of plant species are exceedingly rare and often face high extinction risk. However, the community phylogenetic impact of the loss of rare plants is largely unknown in many systems. We address this gap by investigating how rare species contribute to phylogenetic diversity, considering multiple metrics of rarity and multiple elevations in a subalpine plant community. METHODS:We collected abundance data at three sites near the Rocky Mountain Biological Laboratory (Colorado, USA). We calculated each species' range size from public occurrence data. We calculated phylogenetic signal for abundance and range size, compared community phylogenetic metrics weighted by range size and abundance to unweighted metrics, and quantified the change in phylogenetic diversity when removing single species and groups of species ranked by rarity. RESULTS:We found phylogenetic signal for abundance, but not range size. There was no difference between rarity-weighted and -unweighted phylogenetic diversity metrics. Finally, phylogenetic diversity did not decline more when we removed single rare species or groups of rare species than when we removed single common species and groups of common species. CONCLUSIONS:We found that rare species, whether at low abundance or with a small range, do not disproportionately contribute to phylogenetic diversity in our subalpine plant community. These results were consistent across elevations. Instead, rare species might provide phylogenetic redundancy with common species. Deeper understanding of functional differentiation is needed to understand contributions of rare species to this system.

PREMISE:Leaf mass per area (LMA) links leaf economic strategies, community assembly, and climate and can be reconstructed from woody non-monocot angiosperm (WNMA) fossils using the petiole metric (PM; petiole width2/leaf area). Reliable interpretation of LMA reconstructed from the fossil record is limited by an incomplete understanding of how PM and LMA are correlated at the community scale and what climatic parameters drive variation of both measured and reconstructed LMA of WNMAs globally. METHODS:A modern, global, community-scale data set of in situ WNMA LMA and PM was compiled to test leading hypotheses for environmental drivers of LMA and quantify LMA-PM relationships. Correlations among PM, LMA, climate (Köppen types and continuous data), and leaf habit were assessed and quantified using several uni- and multivariate methods. RESULTS:Community mean LMA increased under warmer and less seasonal temperatures. Drought-prone communities had the highest LMA variance, likely due to disparity between riparian and non-riparian microhabitats. PM and LMA were correlated for community mean and variance, and their correlations with climate were similar. These patterns indicate that climatic correlatives of modern LMA can inform relative trends in reconstructed fossil LMA. In contrast, matching "absolute" LMA distributions between fossil and modern sites does not allow reliable inference of analogous climate types. CONCLUSIONS:This study furthers our understanding of processes influencing the assembly of WNMA leaf economic strategies in plant communities, highlighting the importance of temperature seasonality and habitat heterogeneity. We also provide a method to reconstruct, and refine the framework to interpret, community-scale LMA in the fossil record.

Species occurrence data is the fundamental unit of any species distribution analysis, biodiversity patterns, species extinction vulnerability, and temporal trends. This data is also a critical component of monitoring progress towards global biodiversity targets, such as those included in the Kunming-Montreal Global Biodiversity Framework (GBF) of the Convention on Biological Diversity (CBD). Recent years have seen massive growth and digitisation of global species occurrence datasets, yet the headline indicators of the GBF’s monitoring framework relies on the IUCN RedList index as the species conservation indicator. This paper explores the largest global species distribution databases, and outlines some of the remaining challenges to bringing these data together for enhanced decision making. Countries such as Japan and South Korea have seen dramatic expansions of data coverage, whilst North Africa, Central Asia, and the High Seas have not witnessed comparable growth. In the oceans, expanding geographic coverage partially comes from tracking data from a small number of species. In terms of environmental space, other types of sampling effort are disproportionately concentrated on the temperate continental shelf and slope areas of the north Atlantic. Most of the world's most biodiverse areas, especially in the Tropics, both on land and in the ocean still lack data, and concerted efforts will be needed to improve the coverage of these regions. Furthermore, few long-term monitoring programs exist, and accurately inferring change from small numbers of unstandardised collecting events resulting in a large quantity of uncurated data is challenging. Among other measures, journals should request standardised data be added to the key repositories to address biodiversity data gaps and barriers to usability. Governments should also support the sharing of species occurrence data through standardised data infrastructure, such as GBIF and OBIS, and also ensure support for data curation and quality control to minimize impacts of species misidentification records.

Developing a predictive science of the biosphere depends heavily on the rapidly expanding biodiversity data that are commonly stored in biodiversity databases. Despite the proliferation of biodiversity databases, their independent operation has limited data discovery, comparison, and synthesis. Therefore, the biodiversity informatics community has called for improved alignment among these efforts to better catalog Earth's biodiversity. The primary challenges are incomplete knowledge of existing databases and incongruent taxonomic systems and data schemas. Addressing these issues will require development of a database registry, means to compare database contents, taxonomic harmonization, and tools that enable users to merge disparate databases based on their needs, all within a community of practice that enables people of various skill levels and roles to participate. We believe that synthesis and integration, driven by a growing and thriving community, will be the next stage of biodiversity informatics and will help unlock the full potential of biodiversity information.

Understanding the capacity of forests to adapt to climate change is of pivotal importance for conservation science, yet this is still widely unknown. This knowledge gap is particularly acute in high-biodiversity tropical forests. Here, we examined how tropical forests of the Americas have shifted community trait composition in recent decades as a response to changes in climate. Based on historical trait-climate relationships, we found that, overall, the studied functional traits show shifts of less than 8% of what would be expected given the observed changes in climate. However, the recruit assemblage shows shifts of 21% relative to climate change expectation. The most diverse forests on Earth are changing in functional trait composition but at a rate that is fundamentally insufficient to track climate change.

Aim Nearly 8% of species could go extinct from climate change; many organisms are already experiencing declines in abundance, local extinction, and range shifts. How such changes impact community diversity is an open question in most systems. Whether changes in phylogenetic diversity parallel those in traditional diversity metrics is also often unknown. We used experimentally transplanted plant communities to ask how different aspects of community diversity change with environmental factors across elevation, and whether phylogenetic relationships predict individual species’ responses to change. Location We experimentally transplanted subalpine plant communities down and upslope across 400 m of elevation at the Rocky Mountain Biological Laboratory, Gothic, CO, USA, to simulate climate warming and cooling. Methods We identified how experimental warming and cooling impacted community diversity by testing for differences in species richness, Shannon diversity, and phylogenetic diversity among transplant treatments. We tested for phylogenetic signal in each species’ change in percent cover among treatments. Finally, we assessed if aspects of species’ rarity (and thus their putative extinction risk) predicted post-transplant change independently or in addition to their phylogenetic relationship within the community. Results We found that species richness and Shannon diversity decreased in cooled treatments and increased in some warmed treatments. In contrast, phylogenetic diversity increased in the cooled treatment and did not change in the warmed treatments. Individual species’ changes in response to warming and cooling were not correlated with phylogeny or aspects of rarity. Main conclusions Our results suggest that species losses in cooled treatments are phylogenetically dispersed, increasing phylogenetic diversity, even as richness and Shannon diversity decline. Increasing richness and Shannon diversity in warmed treatments suggests that new species from across the phylogeny can colonize after transplantation, leading to stability in phylogenetic diversity under warming at this time scale, with further change likely as extinction debts are paid. ### Competing Interest Statement The authors have declared no competing interest. National Science Foundation, https://ror.org/021nxhr62, 1750280, 2225078, 2225076, 2020300359 United States Department of Agriculture, https://ror.org/01na82s61, 2023-67013-40169

Droughts are a natural hazard of growing concern as they are projected to increase in frequency and severity for many regions of the world. The identification of droughts and their future characteristics is essential to building an understanding of the geography and magnitude of potential drought change trajectories, which in turn is critical information to manage drought resilience across multiple sectors and disciplines. Adding to this effort, we developed a dataset of global historical and projected future drought indices over the 1980-2100 period based on downscaled CMIP6 models across multiple shared socioeconomic pathways (SSP). The dataset is composed of two indices: the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) for 23 downscaled global climate models (GCMs) (0.25-degree resolution), including historical (1980-2014) and future projections (2015-2100) under four climate scenarios: SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. The drought indices were calculated for 3-, 6- and 12-month accumulation timescales and are available as gridded spatial datasets in a regular latitude-longitude format at monthly time resolution.

Plant functional trait-based approaches are powerful tools to assess the consequences of global environmental changes for plant ecophysiology, population and community ecology, ecosystem functioning, and landscape ecology. Here, we present data capturing these ecological dimensions from grazing, nitrogen addition, and warming experiments conducted along a 821 m a.s.l. elevation gradient and from a climate warming experiment conducted across a 3,200 mm precipitation gradient in boreal and alpine grasslands in Vestland County, western Norway. From these systems we collected 28,762 plant and leaf functional trait measurements from 76 vascular plant species, 88 leaf assimilation-temperature responses, 577 leaf handheld hyperspectral readings, 2.26 billion leaf temperature measurements, 3,696 ecosystem CO2 flux measurements, and 10.69 ha of multispectral (10-band) and RGB cm-resolution imagery from 4,648 individual images obtained from airborne sensors. These data augment existing longer-term data on local climate, soils, plant populations, plant community composition, and ecosystem functioning from within the same experiments and study systems and from similar systems in other mountain regions globally.

AimEcological and anthropogenic factors shift the abundances of dominant and rare tree species within local forest communities, thus affecting species composition and ecosystem functioning. To inform forest and conservation management it is important to understand the drivers of dominance and rarity in local tree communities. We answer the following research questions: (1) What are the patterns of dominance and rarity in tree communities? (2) Which ecological and anthropogenic factors predict these patterns? And (3) what is the extinction risk of locally dominant and rare tree species?LocationGlobal.Time period1990-2017.Major taxa studiedTrees.MethodsWe used 1.2 million forest plots and quantified local tree dominance as the relative plot basal area of the single most dominant species and local rarity as the percentage of species that contribute together to the least 10% of plot basal area. We mapped global community dominance and rarity using machine learning models and evaluated the ecological and anthropogenic predictors with linear models. Extinction risk, for example threatened status, of geographically widespread dominant and rare species was evaluated.ResultsCommunity dominance and rarity show contrasting latitudinal trends, with boreal forests having high levels of dominance and tropical forests having high levels of rarity. Increasing annual precipitation reduces community dominance, probably because precipitation is related to an increase in tree density and richness. Additionally, stand age is positively related to community dominance, due to stem diameter increase of the most dominant species. Surprisingly, we find that locally dominant and rare species, which are geographically widespread in our data, have an equally high rate of elevated extinction due to declining populations through large-scale land degradation.Main conclusionsBy linking patterns and predictors of community dominance and rarity to extinction risk, our results suggest that also widespread species should be considered in large-scale management and conservation practices.

In the face of climate change, understanding the dynamic responses of vegetation is crucial for predicting shifts in biosphere functioning. Plant functional traits, particularly leaf mass per area (LMA), are critical links between plant metabolism, vegetation responses to climate change, and the broader exchanges of energy and matter within the biosphere. Despite their importance, a comprehensive, predictive understanding of traits and biosphere changes is hampered by spatial and temporal gaps in trait observations. Here, we introduce a novel remote sensing method for the global, continuous mapping of LMA and its historical shifts. Consistent with ecological theory predicting a widespread decrease in LMA with global warming, our findings reveal a global LMA reduction of 6.5-7.6 % between 1985 and 2019, primarily due to increasing temperatures. This decrease varies among biomes, with evergreen conifer and tropical forests showing the most significant declines. Due to LMA connections with carbon metabolism in ecosystems, a global decrease in LMA points to a quickening of the carbon cycle, including largely unexplored contributions to increased global photosynthesis in recent decades. Collectively, these results signal an ongoing widespread and profound transformation in the functioning of the biosphere resulting from climate-related changes in vegetation and its traits.