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The density of wood is a key indicator of the carbon investment strategies of trees, impacting productivity and carbon storage. Despite its importance, the global variation in wood density and its environmental controls remain poorly understood, preventing accurate predictions of global forest carbon stocks. Here we analyse information from 1.1 million forest inventory plots alongside wood density data from 10,703 tree species to create a spatially explicit understanding of the global wood density distribution and its drivers. Our findings reveal a pronounced latitudinal gradient, with wood in tropical forests being up to 30% denser than that in boreal forests. In both angiosperms and gymnosperms, hydrothermal conditions represented by annual mean temperature and soil moisture emerged as the primary factors influencing the variation in wood density globally. This indicates similar environmental filters and evolutionary adaptations among distinct plant groups, underscoring the essential role of abiotic factors in determining wood density in forest ecosystems. Additionally, our study highlights the prominent role of disturbance, such as human modification and fire risk, in influencing wood density at more local scales. Factoring in the spatial variation of wood density notably changes the estimates of forest carbon stocks, leading to differences of up to 21% within biomes. Therefore, our research contributes to a deeper understanding of terrestrial biomass distribution and how environmental changes and disturbances impact forest ecosystems.

Transformative change is needed to align common small‐scale ecological restoration approaches with expectations to restore millions of hectares of degraded lands globally. Currently, most restoration projects target small areas using costly manual methods that cannot be scaled up to meet global commitments. We propose that a judicious integration of agricultural practices into ecological restoration offers an opportunity to address this issue. This transformative process relies on three sequential and interconnected steps: (1) ensure that sufficient land is truly available for restoration; (2) compensate for the loss of agricultural production, income, or land value to encourage landholders to opt for restoration; and (3) develop scalable, affordable, and effective methods for restoring native ecosystems across the pledged hundreds of millions of hectares to deliver benefits to both nature and people. Large‐scale terrestrial restoration will require incorporating agronomic practices into the restoration toolbox to go beyond vague, ambitious promises and wishful thinking.

Applied nucleation and other spatially patterned restoration methods are promising approaches for scaling up projects to meet ambitious international restoration commitments in an ecologically and economically sound manner. Much of the corresponding literature to date, however, has centered around theoretical discussions and small‐scale studies that are largely divorced from constraints faced by restoration practitioners. We briefly review recent academic literature about applied nucleation and other spatially patterned restoration methods and discuss practical challenges to their implementation. We offer several recommendations to move spatially patterned restoration from an academic conversation to scalable application, including: (1) comparing different planting designs and natural regeneration within the same system at an appropriate scale; (2) monitoring ecological outcomes throughout the restored area over sufficient time to evaluate recovery; (3) quantifying costs and documenting other logistical constraints to implementation; and (4) exploring methods for using unplanted areas to provide benefits to landholders until planted vegetation establishes.

Aim: Ecological 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?. Location: Global. Time period: 1990–2017. Major taxa studied: Trees. Methods: We 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. Results: Community 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 conclusions: By 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.

Understanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, evergreen and deciduous trees. To address these gaps, we conducted a global, ground-sourced assessment of forest leaf-type variation by integrating forest inventory data with comprehensive leaf form (broadleaf vs needle-leaf) and habit (evergreen vs deciduous) records. We found that global variation in leaf habit is primarily driven by isothermality and soil characteristics, while leaf form is predominantly driven by temperature. Given these relationships, we estimate that 38% of global tree individuals are needle-leaved evergreen, 29% are broadleaved evergreen, 27% are broadleaved deciduous and 5% are needle-leaved deciduous. The aboveground biomass distribution among these tree types is approximately 21% (126.4 Gt), 54% (335.7 Gt), 22% (136.2 Gt) and 3% (18.7 Gt), respectively. We further project that, depending on future emissions pathways, 17-34% of forested areas will experience climate conditions by the end of the century that currently support a different forest type, highlighting the intensification of climatic stress on existing forests. By quantifying the distribution of tree leaf types and their corresponding biomass, and identifying regions where climate change will exert greatest pressure on current leaf types, our results can help improve predictions of future terrestrial ecosystem functioning and carbon cycling.

1. Biodiversity is an important component of natural ecosystems, with higher species richness often correlating with an increase in ecosystem productivity. Yet, this relationship varies substantially across environments, typically becoming less pronounced at high levels of species richness. However, species richness alone cannot reflect all important properties of a community, including community evenness, which may mediate the relationship between biodiversity and productivity. If the evenness of a community correlates negatively with richness across forests globally, then a greater number of species may not always increase overall diversity and productivity of the system. Theoretical work and local empirical studies have shown that the effect of evenness on ecosystem functioning may be especially strong at high richness levels, yet the consistency of this remains untested at a global scale. 2. Here, we used a dataset of forests from across the globe, which includes composition, biomass accumulation and net primary productivity, to explore whether productivity correlates with community evenness and richness in a way that evenness appears to buffer the effect of richness. Specifically, we evaluated whether low levels of evenness in speciose communities correlate with the attenuation of the richness–productivity relationship. 3. We found that tree species richness and evenness are negatively correlated across forests globally, with highly speciose forests typically comprising a few dominant and many rare species. Furthermore, we found that the correlation between diversity and productivity changes with evenness: at low richness, uneven communities are more productive, while at high richness, even communities are more productive. 4. Synthesis. Collectively, these results demonstrate that evenness is an integral component of the relationship between biodiversity and productivity, and that the attenuating effect of richness on forest productivity might be partly explained by low evenness in speciose communities. Productivity generally increases with species richness, until reduced evenness limits the overall increases in community diversity. Our research suggests that evenness is a fundamental component of biodiversity–ecosystem function relationships, and is of critical importance for guiding conservation and sustainable ecosystem management decisions.

The Atlantic Forest is a global biodiversity hotspot and a significant provider of ecosystem services to 65% of the Brazilian population. Due to being highly threatened, it is protected by federal law 11,428/2006, which establishes forest use restrictions based on native vegetation successional stages in the Atlantic Forest, with more advanced stages receiving more protection. The classification parameters are established at the state level. However, the parameters employed to classify forest fragments in different successional stages are subjective and imprecise, negatively impacting environmental permitting and related offset policies. Here, we critically assessed the major limitations in applying the 11,428/2006 law and presented alternatives for establishing a more transparent, applicable, legally safe, and effective protocol for identifying the conservation value of forest fragments. We also highlight problems related to sampling, indicators, and methodologies and present guidelines for revising the parameters for applying the Atlantic Forest law and associated state-level resolutions. We suggest an inclusive two-step analysis based on vegetation structure, forest cover history, biodiversity, ecosystem services (social), and landscape indicators. By employing a more technological approach and transferring part of the assessment responsibility to the state-level environmental agencies instead of allowing self-declared reports by landowners, our proposal focuses on the potential for evaluating ecological integrity among different successional classes by forest types. As nearly 90% of the remaining Brazilian Atlantic Forest is located within private lands, improving this legal instrument is essential for protecting the vulnerable biodiversity of this unique and threatened biome.

Abstract: Aim: To determine the relationships between the functional trait composition of forest communities and environmental gradients across scales and biomes and the role of species relative abundances in these relationships. Location: Global. Time period: Recent. Major taxa studied: Trees. Methods: We integrated species abundance records from worldwide forest inventories and associated functional traits (wood density, specific leaf area and seed mass) to obtain a data set of 99,953 to 149,285 plots (depending on the trait) spanning all forested continents. We computed community‐weighted and unweighted means of trait values for each plot and related them to three broad environmental gradients and their interactions (energy availability, precipitation and soil properties) at two scales (global and biomes). Results: Our models explained up to 60% of the variance in trait distribution. At global scale, the energy gradient had the strongest influence on traits. However, within‐biome models revealed different relationships among biomes. Notably, the functional composition of tropical forests was more influenced by precipitation and soil properties than energy availability, whereas temperate forests showed the opposite pattern. Depending on the trait studied, response to gradients was more variable and proportionally weaker in boreal forests. Community unweighted means were better predicted than weighted means for almost all models. Main conclusions: Worldwide, trees require a large amount of energy (following latitude) to produce dense wood and seeds, while leaves with large surface to weight ratios are concentrated in temperate forests. However, patterns of functional composition within‐biome differ from global patterns due to biome specificities such as the presence of conifers or unique combinations of climatic and soil properties. We recommend assessing the sensitivity of tree functional traits to environmental changes in their geographic context. Furthermore, at a given site, the distribution of tree functional traits appears to be driven more by species presence than species abundance.

Extensive evidence shows that regional (gamma) diversity is often lower across restored landscapes than in reference landscapes, in part due to common restoration practices that favor widespread species through selection of easily-grown species with high survival and propagation practices that reduce genetic diversity. We discuss approaches to counteract biotic homogenization, such as reintroducing species that are adapted to localized habitat conditions and are unlikely to colonize naturally; periodically reintroducing propagules from remnant populations to increase genetic diversity; and reintroducing higher trophic level fauna to restore interaction networks and processes that promote habitat heterogeneity. Several policy changes would also increase regional diversity; these include regional coordination amongst restoration groups, financial incentives to organizations producing conservation-valued species, and experimental designations for rare species introductions.

Restoring tropical forests still relies on expensive tree planting. Timber production from native trees offers a promising opportunity to make restoration financially viable, but species growth data are lacking. We assessed the potential of tropical forest restoration plantations for producing native timber in the Atlantic Forest. For that we inventoried a chronosequence of unmanaged restoration plantation sites with ten commercial native tree species. Then we developed growth models and used the Growth-Oriented Logging (GOL) method to inform targeted management decisions, including an optimized timber-focused scenario, based on growth and bole quality assessment. Usually, growth-rate classes for saw wood production would be defined according to the time necessary for achieving 35 cm in DBH. Harvesting age was markedly reduced using GOL for species of fast-growth (from 70 to 50–75 years). Following GOL, basal area was 42 ± 30% larger at harvest (taking 35 ± 23% more time) or 60 ± 16.5% smaller (taking 66 ± 16% less time). The optimized scenario speeded tree-size achievement and anticipated harvesting in an average of 58 years. Species selection, individualization, and silvicultural management are critical for producing timber in forest restoration programs.

A growing number of initiatives at global, regional and national scales propose to plant millions, billions or even trillions of trees as a simple solution to resolve complex environmental problems. However, tree planting is much more complicated than it seems. We summarize the multifaceted decision‐making process needed and offer guidelines to increase the success of the proposed ambitious efforts to increase tree cover world‐wide. Given the varied definitions of and motivations for tree planting, it is critical that stakeholders work together to clearly define the biophysical and socioeconomic goals of each project. Then a series of questions must be addressed about where and how (e.g. planting trees vs. allowing for natural forest regrowth) to most effectively achieve these goals and minimize unintended negative consequences, as well as how, when and by whom success of efforts will be evaluated. Key guidelines to successfully increase tree cover include: (a) first addressing the underlying drivers of deforestation; (b) integrating decision‐making across scales from local to global; (c) tailoring tree planting strategies to clearly stated project goals and planning, adaptively managing and evaluating success over a sufficiently long timeframe; (d) focusing on the forest ecosystem as a whole, and not just the trees; (e) coordinating different land uses and (f) involving stakeholders at all stages of the planning process. Synthesis and applications. Tree planting, along with other strategies to increase tree cover in appropriate locations and contexts, can make a valuable contribution to ensuring the ecological and social well‐being of our planet in coming decades, but only if these efforts are considered as one component of multifaceted solutions to complex environmental problems and are carefully planned, implemented and monitored over a sufficiently long time‐scale with stakeholder engagement and broader consideration of socio‐ecological complexities.

International forest landscape restoration commitments have promoted the restoration of millions of hectares of degraded and deforested lands globally, but few forest restoration approaches provide both ecologically‐sound and financially‐viable solutions for achieving the spatial scale proposed. One potential revenue source for restoration is selective harvesting of timber, a product for which there is a clear global market and increasing demand. The use of commercially valuable exotic trees may attract farmers to restoration, but can be a major concern for ecologists. Here, we present results collected over 7 years from experimental studies at three sites across the Brazilian Atlantic Forest to assess the impacts of incorporating exotic eucalypts as a transitional stage in tropical forest restoration on above‐ground biomass accumulation, native woody species regeneration and financial viability. Biomass accumulation was nine times greater in mixed eucalypt‐native species plantations than native only plantings due to fast eucalypt growth. Nonetheless, the growth of native non‐pioneer trees was not affected or only slightly reduced by eucalypts prior to logging. Eucalypts did not negatively affect the natural regeneration of native woody species before or after eucalypt logging. Canopy cover regrew quickly but was slightly lower a year following logging in mixed eucalypt‐native species plantations. Natural regeneration richness and planted non‐pioneer growth were similar across treatments in the post‐logging period. We found higher variation of biomass accumulation and native species regeneration among sites than between plantation types within sites. The income from eucalypt wood production offset 44%–75% of restoration implementation costs. Synthesis and applications. Many of the negative effects attributed to eucalypts on the growth and natural regeneration of native trees depend on features of the production system, landscape structure, soil, and climate in which they are grown, rather than the effects of eucalypts per se. In Brazil's Atlantic Forest region, exotic eucalypts can become important allies of tropical forest restoration, and their use and investment opportunities should be considered within the portfolio of options supported by public and private funding and policies.

Abstract The central motivation to restore ecosystems at a planetary scale has been to reverse degradation and provide multiple environmental benefits, but key global players like governments may be more interested in social outcomes from undertaking restoration, such as job creation. Assessing the job opportunities stemming from ongoing restoration programmes can leverage additional investments for their implementation and support their long‐term maintenance. Here, we aimed to understand and quantify current and potential ecosystem restoration jobs in Brazil, based on a widely distributed online survey performed in 2020 and led by the main restoration networks in the country. We explored the structure, job distribution and outputs of the national restoration supply chain. At the beginning of 2020, 4713 temporary and 3510 permanent jobs were created, nearly 60% of which were generated by organizations specialized in restoration, mainly from the non‐profit (48%) and private (37%) sectors. Restoration jobs were concentrated in organizations working in one (58%) or two (28%) biomes, and the vast majority were in the Atlantic Forest (85%). Similarly, most restoration jobs were concentrated in the southeast region (61%), with one‐third in the state of São Paulo. This geographical distribution was more strongly associated with the states' GDP than with the legal deficit of native vegetation area. Nearly 20% of the restoration jobs were terminated during the COVID‐19 pandemic in 2020. We estimate that restoration activities can generate 0.42 jobs per hectare undergoing restoration, which could potentially create 1.0–2.5 million direct jobs through the implementation of Brazil's target of restoring 12 million hectares. We conclude by reinforcing the value of ecosystem restoration in promoting economic development and job creation, which can be crucial to promote countries' effective engagement in the UN Decade on Ecosystem Restoration. We also highlight the critical role of grassroots organizations to maximize restoration opportunities for socioeconomic development during the post‐pandemic economic recovery. Read the free Plain Language Summary for this article on the Journal blog.

Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes.

The nutrient demands of regrowing tropical forests are partly satisfied by nitrogen-fixing legume trees, but our understanding of the abundance of those species is biased towards wet tropical regions. Here we show how the abundance of Leguminosae is affected by both recovery from disturbance and large-scale rainfall gradients through a synthesis of forest inventory plots from a network of 42 Neotropical forest chronosequences. During the first three decades of natural forest regeneration, legume basal area is twice as high in dry compared with wet secondary forests. The tremendous ecological success of legumes in recently disturbed, water-limited forests is likely to be related to both their reduced leaflet size and ability to fix N2, which together enhance legume drought tolerance and water-use efficiency. Earth system models should incorporate these large-scale successional and climatic patterns of legume dominance to provide more accurate estimates of the maximum potential for natural nitrogen fixation across tropical forests.

The selection of ecological indicators is an important step toward more effective restoration monitoring. The debate between Reid (2015) and Durigan and Suganuma (2015) regarding the usefulness of species composition for monitoring restoration trajectory is timely and salient, but it lacks a middle way proposal to balance ecological relevance and practical viability. We propose a way forward to resolving this debate, namely using easily measurable functional traits, a type of compositional measure, as an indicator. Assessing functional composition trajectory may help overcome some limitations with taxonomic identification and provide more meaningful outcomes to evaluate restoration success.

Tropical deforestation drivers are complex and can change rapidly in periods of profound societal transformation, such as those during a pandemic. Evidence suggests that the COVID-19 pandemic has spurred illegal, opportunistic forest clearing in tropical countries, threatening forest ecosystems and their resident human communities. A total of 9583 km2 of deforestation alerts from Global Land Analysis & Discovery (GLAD) were detected across the global tropics during the first month following the implementation of confinement measures of local governments to reduce COVID-19 spread, which is nearly double that of 2019 (4732 km2). We present a conceptual framework linking tropical deforestation and the current pandemic. Zoonotic diseases, public health, economy, agriculture, and forests may all be reciprocally linked in complex positive and negative feedback loops with overarching consequences. We highlight the emerging threats to nature and society resulting from this complex reciprocal interplay and possible policy interventions that could minimize these threats.

The complexity of ecological systems is a major challenge for practitioners and decision-makers who work to avoid, mitigate and manage environmental change. Here, we illustrate how metaecology – the study of spatial interdependencies among ecological systems through fluxes of organisms, energy, and matter – can enhance understanding and improve managing environmental change at multiple spatial scales. We present several case studies illustrating how the framework has leveraged decision-making in conservation, restoration and risk management. Nevertheless, an explicit incorporation of metaecology is still uncommon in the applied ecology literature, and in action guidelines addressing environmental change. This is unfortunate because the many facets of environmental change can be framed as modifying spatial context, connectedness and dominant regulating processes - the defining features of metaecological systems. Narrowing the gap between theory and practice will require incorporating system-specific realism in otherwise predominantly conceptual studies, as well as deliberately studying scenarios of environmental change.

Forest and landscape restoration (FLR) could benefit from the land sharing/sparing approaches to support decisions. We discuss four questions potentially shaping FLR outcomes in agricultural landscapes in the context of land sharing/sparing decisions: (1) Which are the main focuses of restorative interventions?; (2) Which kind of restored forests should these interventions target?; (3) Which restorative interventions should be implemented and where?; and (4) What are the major factors influencing restoration outcomes? Some restorative interventions embraced by FLR may compete with specific land uses and thus require careful planning to minimize trade-offs and maximize synergies. Decision making on the restorative intervention combination needs considering the spatial distribution and configuration of the final land uses in the landscape together with its social context and a multi-stakeholder process. Ultimately, finding the right balance between land sharing/sparing approaches will also require navigating governance issues that regulate FLR implementation.

Achieving ambitious global restoration commitments is a huge challenge. The Atlantic Forest Restoration Pact, created in 2009 as a movement to restore 15 Mha of degraded/deforested lands by 2050, pledged 1 Mha towards the 2020 Bonn Challenge. We documented the restoration of an estimated 673,510–740,555 ha of native forests from 2011 to 2015 in the Atlantic Forest, and expect that a total of 1.35–1.48 Mha will be under recovery by 2020. The Pact is one of the first Brazilian restoration initiatives to monitor an international restoration commitment and to demonstrate that ambitious targets can be reached. Part of this success in large-scale restoration is related to three main Pact activities: (i) development of restoration governance, communication and articulation; (ii) promotion of strategies to influence public policies; and (iii) establishment of restoration monitoring systems. The experience and lessons learned by the Pact could inspire and inform other restoration initiatives worldwide.

First-order streams in Brazil are protected by the Native Vegetation Protection Law of Brazil (NVPL), which regulates the land-use in rural properties and is linked with aquatic conservation. We investigated the importance of the data-set resolution to identify first-order streams (State of São Paulo, Brazil) and estimated its length compared to other water bodies. We found that first-order streams represent around 58% of the total length of the drainage system. In addition, we compared this database with that of the Environmental Rural Registry (CAR in Portuguese). Compared with the lower resolution data-set, the length of first-order streams self-declared in CAR was 80% lower. We also found a concerning number of small dams in first-order streams, which severely changes their dynamics. Therefore, we recommend the use of finer resolution data-sets in order to create tools to support legal compliance that goes beyond the limited information provided by CAR.

While research demonstrates the utmost importance of tropical secondary forests for biodiversity conservation and the provision of ecosystem services, these forests are being continuously converted for agriculture, as well as being degraded by a variety of human-induced disturbances. Therefore, in addition to understanding the formation, functioning, and development of tropical secondary forests, it is also vital that the protection and maturation of secondary forests become a focus of public policies aimed at maximizing the conservation of iodiversity and provision of ecosystem services in human-modified landscapes. Here we review the drivers of the conversion and degradation of tropical secondary forests in human-dominated Brazilian landscapes. Based on this review, and examples of successful reforestation initiatives, we propose policy options based on ecological, socioeconomic, and legal aspects of forest management and conservation for two contrasting scenarios – high- and low-modified tropical landscapes, exemplified by the Brazilian biomes of the Atlantic Forest and Amazon respectively. This framework provides a new and more holistic approach for sustaining and promoting a favorable outlook for the conservation of secondary forests in Brazil and across the tropics in general.