High exposure of global tree diversity to human pressure.

Safeguarding Earth's tree diversity is a conservation priority due to the importance of trees for biodiversity and ecosystem functions and services such as carbon sequestration. Here, we improve the foundation for effective conservation of global tree diversity by analyzing a recently developed database of tree species covering 46,752 species. We quantify range protection and anthropogenic pressures for each species and develop conservation priorities across taxonomic, phylogenetic, and functional diversity dimensions. We also assess the effectiveness of several influential proposed conservation prioritization frameworks to protect the top 17% and top 50% of tree priority areas. We find that an average of 50.2% of a tree species' range occurs in 110-km grid cells without any protected areas (PAs), with 6,377 small-range tree species fully unprotected, and that 83% of tree species experience nonnegligible human pressure across their range on average. Protecting high-priority areas for the top 17% and 50% priority thresholds would increase the average protected proportion of each tree species' range to 65.5% and 82.6%, respectively, leaving many fewer species (2,151 and 2,010) completely unprotected. The priority areas identified for trees match well to the Global 200 Ecoregions framework, revealing that priority areas for trees would in large part also optimize protection for terrestrial biodiversity overall. Based on range estimates for >46,000 tree species, our findings show that a large proportion of tree species receive limited protection by current PAs and are under substantial human pressure. Improved protection of biodiversity overall would also strongly benefit global tree diversity.

When Is Something an Alternative? A General Account Applied to Animal-Free Alternatives to Animal Research.

The first "R" from animal research ethics prescribes the replacement of animal experiments with animal-free alternatives. However, the question of when an animal-free method qualifies as an alternative to animal experiments remains unresolved.Drawing lessons from another debate in which the word "alternative" is central, the ethical debate on alternatives to germline genome editing, this paper develops a general account of when something qualifies as an alternative to something. It proposes three ethically significant conditions that technique, method, or approach X must meet to qualify as an alternative to Y: (1) X must address the same problem as Y, under an appropriate description of that problem; (2) X must have a reasonable chance of success, compared to Y, in solving the problem; and (3) X must not be ethically unacceptable as a solution. If X meets all these conditions, its relative advantages and disadvantages determine whether it is preferable, indifferent, or dispreferable as an alternative to Y.This account is then applied to the question of whether animal-free research methods qualify as alternatives to animal research. Doing so breaks down the debate around this question into more focused (ethical and other) issues and illustrates the potential of the account.

Safety profile of plasma for fractionation donated in the United Kingdom, with respect to variant Creutzfeldt-Jakob disease.

Plasma-derived medicinal products (PDMPs) are life-saving and life-improving therapies, but the raw material is in short supply: Europe depends on importation from countries including the United States. Plasma from donors resident in the United Kingdom has not been fractionated since 1999 when a precautionary measure was introduced in response to the outbreak of variant Creutzfeldt-Jakob disease (vCJD). Cases of vCJD have been far fewer than originally predicted in the 1990s. Since the introduction of leucodepletion in 1999, and accounting for the incubation period, more than 40 million UK-derived blood components have been issued with no reports of TT vCJD. In February 2021, the UK Government authorized manufacture of immunoglobulin from UK plasma. Following separate reviews concluding no significant difference in the risk posed, the United States, Australia, Ireland and Hong Kong also lifted their deferrals of blood donors with a history of living in the United Kingdom. Other countries are actively reviewing their position. Demand is rising for PDMPs, and Europe faces a threat of supply shortages. Industry and patient groups are clear that using UK plasma would bring significant immediate benefits to patients and to the resilience of the European supply chain. From this scientific review, we conclude that UK plasma is safe for fractionation and urge blood regulators and operators to take account of this safety profile when considering fractionation of UK plasma, and to revise their guidelines on the deferral of donors who have lived in, or received a transfusion in, the United Kingdom.

The acquisitive-conservative axis of leaf trait variation emerges even in homogeneous environments.

BACKGROUND AND AIMS: The acquisitive-conservative axis of plant ecological strategies results in a pattern of leaf trait covariation that captures the balance between leaf construction costs and plant growth potential. Studies evaluating trait covariation within species are scarcer, and have mostly dealt with variation in response to environmental gradients. Little work has been published on intraspecific patterns of leaf trait covariation in the absence of strong environmental variation. METHODS: We analysed covariation of four leaf functional traits [specific leaf area (SLA) leaf dry matter content (LDMC), force to tear (Ft) and leaf nitrogen content (Nm)] in six Poaceae and four Fabaceae species common in the dry Chaco forest of Central Argentina, growing in the field and in a common garden. We compared intraspecific covariation patterns (slopes, correlation and effect size) of leaf functional traits with global interspecific covariation patterns. Additionally, we checked for possible climatic and edaphic factors that could affect the intraspecific covariation pattern. KEY RESULTS: We found negative correlations for the LDMC-SLA, Ft-SLA, LDMC-Nm and Ft-Nm trait pairs. This intraspecific covariation pattern found both in the field and in the common garden and not explained by climatic or edaphic variation in the field follows the expected acquisitive-conservative axis. At the same time, we found quantitative differences in slopes among different species, and between these intraspecific patterns and the interspecific ones. Many of these differences seem to be idiosyncratic, but some appear consistent among species (e.g. all the intraspecific LDMC-SLA and LDMC-Nm slopes tend to be shallower than the global pattern). CONCLUSIONS: Our study indicates that the acquisitive-conservative leaf functional trait covariation pattern occurs at the intraspecific level even in the absence of relevant environmental variation in the field. This suggests a high degree of variation-covariation in leaf functional traits not driven by environmental variables.

Similar factors underlie tree abundance in forests in native and alien ranges.

AIM: Alien plant species can cause severe ecological and economic problems, and therefore attract a lot of research interest in biogeography and related fields. To identify potential future invasive species, we need to better understand the mechanisms underlying the abundances of invasive tree species in their new ranges, and whether these mechanisms differ between their native and alien ranges. Here, we test two hypotheses: that greater relative abundance is promoted by (a) functional difference from locally co-occurring trees, and (b) higher values than locally co-occurring trees for traits linked to competitive ability. LOCATION: Global. TIME PERIOD: Recent. MAJOR TAXA STUDIED: Trees. METHODS: We combined three global plant databases: sPlot vegetation-plot database, TRY plant trait database and Global Naturalized Alien Flora (GloNAF) database. We used a hierarchical Bayesian linear regression model to assess the factors associated with variation in local abundance, and how these relationships vary between native and alien ranges and depend on species' traits. RESULTS: In both ranges, species reach highest abundance if they are functionally similar to co-occurring species, yet are taller and have higher seed mass and wood density than co-occurring species. MAIN CONCLUSIONS: Our results suggest that light limitation leads to strong environmental and biotic filtering, and that it is advantageous to be taller and have denser wood. The striking similarities in abundance between native and alien ranges imply that information from tree species' native ranges can be used to predict in which habitats introduced species may become dominant.

Does the leaf economic spectrum hold within plant functional types? A Bayesian multivariate trait meta-analysis.

The leaf economic spectrum is a widely studied axis of plant trait variability that defines a trade-off between leaf longevity and productivity. While this has been investigated at the global scale, where it is robust, and at local scales, where deviations from it are common, it has received less attention at the intermediate scale of plant functional types (PFTs). We investigated whether global leaf economic relationships are also present within the scale of plant functional types (PFTs) commonly used by Earth System models, and the extent to which this global-PFT hierarchy can be used to constrain trait estimates. We developed a hierarchical multivariate Bayesian model that assumes separate means and covariance structures within and across PFTs and fit this model to seven leaf traits from the TRY database related to leaf longevity, morphology, biochemistry, and photosynthetic metabolism. Although patterns of trait covariation were generally consistent with the leaf economic spectrum, we found three approximate tiers to this consistency. Relationships among morphological and biochemical traits (specific leaf area [SLA], N, P) were the most robust within and across PFTs, suggesting that covariation in these traits is driven by universal leaf construction trade-offs and stoichiometry. Relationships among metabolic traits (dark respiration [Rd ], maximum RuBisCo carboxylation rate [Vc,max ], maximum electron transport rate [Jmax ]) were slightly less consistent, reflecting in part their much sparser sampling (especially for high-latitude PFTs), but also pointing to more flexible plasticity in plant metabolistm. Finally, relationships involving leaf lifespan were the least consistent, indicating that leaf economic relationships related to leaf lifespan are dominated by across-PFT differences and that within-PFT variation in leaf lifespan is more complex and idiosyncratic. Across all traits, this covariance was an important source of information, as evidenced by the improved imputation accuracy and reduced predictive uncertainty in multivariate models compared to univariate models. Ultimately, our study reaffirms the value of studying not just individual traits but the multivariate trait space and the utility of hierarchical modeling for studying the scale dependence of trait relationships.

Mapping local and global variability in plant trait distributions.

Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global scale is challenging. Typically, in Earth system models, characterization of plant diversity has been limited to grouping related species into plant functional types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally. Using the largest global plant trait database and state of the art Bayesian modeling, we created fine-grained global maps of plant trait distributions that can be applied to Earth system models. Focusing on a set of plant traits closely coupled to photosynthesis and foliar respiration-specific leaf area (SLA) and dry mass-based concentrations of leaf nitrogen ([Formula: see text]) and phosphorus ([Formula: see text]), we characterize how traits vary within and among over 50,000 [Formula: see text]-km cells across the entire vegetated land surface. We do this in several ways-without defining the PFT of each grid cell and using 4 or 14 PFTs; each model's predictions are evaluated against out-of-sample data. This endeavor advances prior trait mapping by generating global maps that preserve variability across scales by using modern Bayesian spatial statistical modeling in combination with a database over three times larger than that in previous analyses. Our maps reveal that the most diverse grid cells possess trait variability close to the range of global PFT means.

Leaf economics and plant hydraulics drive leaf : wood area ratios.

Biomass and area ratios between leaves, stems and roots regulate many physiological and ecological processes. The Huber value Hv (sapwood area/leaf area ratio) is central to plant water balance and drought responses. However, its coordination with key plant functional traits is poorly understood, and prevents developing trait-based prediction models. Based on theoretical arguments, we hypothesise that global patterns in Hv of terminal woody branches can be predicted from variables related to plant trait spectra, that is plant hydraulics and size and leaf economics. Using a global compilation of 1135 species-averaged Hv , we show that Hv varies over three orders of magnitude. Higher Hv are seen in short small-leaved low-specific leaf area (SLA) shrubs with low Ks in arid relative to tall large-leaved high-SLA trees with high Ks in moist environments. All traits depend on climate but climatic correlations are stronger for explanatory traits than Hv . Negative isometry is found between Hv and Ks , suggesting a compensation to maintain hydraulic supply to leaves across species. This work identifies the major global drivers of branch sapwood/leaf area ratios. Our approach based on widely available traits facilitates the development of accurate models of above-ground biomass allocation and helps predict vegetation responses to drought.

When are infection risks of blood transfusion tolerable? Towards understanding the ethical views of stakeholders in the blood supply.

BACKGROUND AND OBJECTIVES: The perception of transfusion-transmitted infections (TTIs) is sensitive to various concerns besides the probability and impact of infection, and some of these concerns may be ethically relevant. This paper aims to advance thinking about blood safety policies by exploring and explaining stakeholders' reasons to consider TTI risks tolerable or intolerable. MATERIALS AND METHODS: Inspired by critical empirical ethics and phenomenological hermeneutics, we held interviews and focus group discussions to explore the moral experience of policymakers, hematologists, blood donors and recipients. Respondents were invited to discuss general concerns about the blood supply, to address the tolerability of TTI risks compared with other hazards and to comment on the costs of blood safety. Arguments for tolerance or intolerance towards TTI risks were analysed qualitatively. RESULTS: Stakeholders' views could be clustered into seven categories: (1) clinical impact; (2) probability of infection; (3) avoidability of infection; (4) cost and health benefits; (5) other consequences of safety measures; (6) non-consequentialist ethical arguments; and (7) stakeholders' interests. Various arguments were offered that resonate with current ethical thinking about blood safety. Assuming that resources spent on inefficient blood safety measures could be applied more beneficially elsewhere, for example, responders typically expressed tolerance towards TTI risks. Some other arguments seem novel, for instance arguments for risk intolerance based on the low probability of infection and arguments for risk tolerance if patients have a poor prognosis. CONCLUSION: Understanding the moral experience of stakeholders enriches ethical debate about blood safety and prepares developing more widely acceptable policies.

Donor blood screening and moral responsibility: how safe should blood be?

Some screening tests for donor blood that are used by blood services to prevent transfusion-transmission of infectious diseases offer relatively few health benefits for the resources spent on them. Can good ethical arguments be provided for employing these tests nonetheless? This paper discusses-and ultimately rejects-three such arguments. According to the 'rule of rescue' argument, general standards for cost-effectiveness in healthcare may be ignored when rescuing identifiable individuals. The argument fails in this context, however, because we cannot identify beforehand who will benefit from additional blood screening tests. On the 'imposed risk' argument, general cost-effectiveness standards do not apply when healthcare interventions impose risks on patients. This argument ignores the fact that imposing risks on patients is inevitable in healthcare and that these risks can be countered only within reasonable limits. Finally, the 'manufacturing standard' argument premises that general cost-effectiveness standards do not apply to procedures preventing the contamination of manufactured medical products. We contend that while this argument seems reasonable insofar as commercially manufactured medical products are concerned, publicly funded blood screening tests should respect the standards for general healthcare. We conclude that these particular arguments are unpersuasive, and we offer directions to advance the debate.

A synthesis of radial growth patterns preceding tree mortality.

Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-continental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1-100 years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks.

The Precautionary Principle and the Tolerability of Blood Transfusion Risks.

Tolerance for blood transfusion risks is very low, as evidenced by the implementation of expensive blood tests and the rejection of gay men as blood donors. Is this low risk tolerance supported by the precautionary principle, as defenders of such policies claim? We discuss three constraints on applying (any version of) the precautionary principle and show that respecting these implies tolerating certain risks. Consistency means that the precautionary principle cannot prescribe precautions that it must simultaneously forbid taking, considering the harms they might cause. Avoiding counterproductivity requires rejecting precautions that cause more harm than they prevent. Proportionality forbids taking precautions that are more harmful than adequate alternatives. When applying these constraints, we argue, attention should not be restricted to harms that are human caused or that affect human health or the environment. Tolerating transfusion risks can be justified if available precautions have serious side effects, such as high social or economic costs.

An inventory of concerns behind blood safety policies in five Western countries.

BACKGROUND: The availability of costly safety measures against transfusion-transmissible infections forces Western countries to confront difficult ethical questions. How to decide about implementing such measures? When are such decisions justified? As a preliminary to addressing these questions, we assessed which concerns shape actual donor blood safety policymaking in five Western countries. STUDY DESIGN AND METHODS: Our qualitative study involved determining which issues had been discussed in advisory committee meetings and capturing these issues in general categories. Appropriate documents were identified in collaboration with local decision-making experts in Canada, Germany, the Netherlands, the United States, and the United Kingdom. The introduction of hepatitis B virus nucleic acid testing and selected measures against variant Creutzfeldt-Jakob disease, West Nile virus, and Q-fever were chosen as cases representing decision-making on safety measures with high costs and low or uncertain added safety. RESULTS: A broad inventory of concerns was established, including: 1) nine categories of advantages and disadvantages of candidate safety policies; 2) six kinds of difficulties in assessing risks and forecasting the effects of safety policies; 3) 13 decision-making principles; and 4) six kinds of practical barriers hampering the translation of candidate policies into decisions. CONCLUSION: Blood safety policymaking involves a wide variety of competing concerns, and approaches to reconcile these considerations are themselves contested. Developing a systematic decision-making approach requires ethical reflection on, among others, reasonable costs of safety and the value of transparency in public policy.

Global beta-diversity of angiosperm trees is shaped by Quaternary climate change.

As Earth's climate has varied strongly through geological time, studying the impacts of past climate change on biodiversity helps to understand the risks from future climate change. However, it remains unclear how paleoclimate shapes spatial variation in biodiversity. Here, we assessed the influence of Quaternary climate change on spatial dissimilarity in taxonomic, phylogenetic, and functional composition among neighboring 200-kilometer cells (beta-diversity) for angiosperm trees worldwide. We found that larger glacial-interglacial temperature change was strongly associated with lower spatial turnover (species replacements) and higher nestedness (richness changes) components of beta-diversity across all three biodiversity facets. Moreover, phylogenetic and functional turnover was lower and nestedness higher than random expectations based on taxonomic beta-diversity in regions that experienced large temperature change, reflecting phylogenetically and functionally selective processes in species replacement, extinction, and colonization during glacial-interglacial oscillations. Our results suggest that future human-driven climate change could cause local homogenization and reduction in taxonomic, phylogenetic, and functional diversity of angiosperm trees worldwide.

Climatic and soil factors explain the two-dimensional spectrum of global plant trait variation.

Plant functional traits can predict community assembly and ecosystem functioning and are thus widely used in global models of vegetation dynamics and land-climate feedbacks. Still, we lack a global understanding of how land and climate affect plant traits. A previous global analysis of six traits observed two main axes of variation: (1) size variation at the organ and plant level and (2) leaf economics balancing leaf persistence against plant growth potential. The orthogonality of these two axes suggests they are differently influenced by environmental drivers. We find that these axes persist in a global dataset of 17 traits across more than 20,000 species. We find a dominant joint effect of climate and soil on trait variation. Additional independent climate effects are also observed across most traits, whereas independent soil effects are almost exclusively observed for economics traits. Variation in size traits correlates well with a latitudinal gradient related to water or energy limitation. In contrast, variation in economics traits is better explained by interactions of climate with soil fertility. These findings have the potential to improve our understanding of biodiversity patterns and our predictions of climate change impacts on biogeochemical cycles.

Towards a New Generation of Trait-Flexible Vegetation Models.

Plant trait variability, emerging from eco-evolutionary dynamics that range from alleles to macroecological scales, is one of the most elusive, but possibly most consequential, aspects of biodiversity. Plasticity, epigenetics, and genetic diversity are major determinants of how plants will respond to climate change, yet these processes are rarely represented in current vegetation models. Here, we provide an overview of the challenges associated with understanding the causes and consequences of plant trait variability, and review current developments to include plasticity and evolutionary mechanisms in vegetation models. We also present a roadmap of research priorities to develop a next generation of vegetation models with flexible traits. Including trait variability in vegetation models is necessary to better represent biosphere responses to global change.

Low growth resilience to drought is related to future mortality risk in trees.

Severe droughts have the potential to reduce forest productivity and trigger tree mortality. Most trees face several drought events during their life and therefore resilience to dry conditions may be crucial to long-term survival. We assessed how growth resilience to severe droughts, including its components resistance and recovery, is related to the ability to survive future droughts by using a tree-ring database of surviving and now-dead trees from 118 sites (22 species, >3,500 trees). We found that, across the variety of regions and species sampled, trees that died during water shortages were less resilient to previous non-lethal droughts, relative to coexisting surviving trees of the same species. In angiosperms, drought-related mortality risk is associated with lower resistance (low capacity to reduce impact of the initial drought), while it is related to reduced recovery (low capacity to attain pre-drought growth rates) in gymnosperms. The different resilience strategies in these two taxonomic groups open new avenues to improve our understanding and prediction of drought-induced mortality.

Experiments Are Necessary in Process-Based Tree Phenology Modelling.

In boreal and temperate trees, air temperature is a major environmental factor regulating the timing of spring phenological events, such as vegetative bud burst, through underlying physiological processes. This has been established by experimental research, and mathematical process-based tree phenology models have been developed based on the results. The models have often been applied when assessing the effects of climate change. Currently, there is an increasing trend to develop process-based tree phenology models using only observational phenological records from natural conditions. We point out that this method runs a high risk of producing models that do not simulate the real physiological processes in the trees and discuss experimental designs facilitating the development of biologically realistic process-based models for tree spring phenology.

Phylogenetic patterns and phenotypic profiles of the species of plants and mammals farmed for food.

The origins of agriculture were key events in human history, during which people came to depend for their food on small numbers of animal and plant species. However, the biological traits determining which species were domesticated for food provision, and which were not, are unclear. Here, we investigate the phylogenetic distribution of livestock and crops, and compare their phenotypic traits with those of wild species. Our results indicate that phylogenetic clustering is modest for crop species but more intense for livestock. Domesticated species explore a reduced portion of the phenotypic space occupied by their wild counterparts and have particular traits in common. For example, herbaceous crops are globally characterized by traits including high leaf nitrogen concentration and tall canopies, which make them fast-growing species and proficient competitors. Livestock species are relatively large mammals with low basal metabolic rates, which indicate moderate to slow life histories. Our study therefore reveals ecological differences in domestication potential between plants and mammals. Domesticated plants belong to clades with traits that are advantageous in intensively managed high-resource habitats, whereas domesticated mammals are from clades adapted to moderately productive environments. Combining comparative phylogenetic methods with ecologically relevant traits has proven useful to unravel the causes and consequences of domestication.