Common drivers shaping niche distribution and climate change responses of one hundred tree species.

Climate change is increasingly contributing to climatic mismatches, in which habitat suitability changes outpace the dispersal abilities of species. Climate niche models (CNM) have been widely used to assess such impacts on tree species. However, most studies have focused on either a single or a limited number of species, or have employed a fixed set of climate variables for multiple species. These limitations are largely due to the constraints of data availability, the complexity of the modeling algorithms, and integration approaches for the projections of diverse species. Therefore, whether specific climatic drivers determine the climatic niches of multiple tree species remains unclear. In this study, CNMs were developed for 100 economically and ecologically important tree species in China and were used to project their future distribution individually and collectively. Continentality was the predominant climate variable, affecting 71 species, followed by seasonal precipitation, which also significantly influenced over 50 species. Of the 100 tree species, the climate niche extent was projected to expand for 29 ("winners"), contract for 36 ("losers"), be stable for 27, and fluctuate for the remaining eight species. Principal component analysis showed that winners and losers were differentiated by geographic variables and the top five climatic variables, however, not by species type (deciduous vs. evergreen or conifer vs. broadleaf). The regions with the highest species richness were mainly distributed in the Hengduan Mountains, a global biodiversity hotspot, and were predicted to increase from 5.2% to 7.5% of the total area. Areas with low species richness were projected to increase from 33.0% to 42.4%. Significant shifts in species composition were anticipated in these biodiversity-rich areas, suggesting potential disruption owing to species reshuffling. This study highlights the urgent need for proactive forest management and conservation strategies to address the impacts of climate change on tree species and preserve ecological functions by mitigating climatic mismatches. In addition, this study establishes a framework to identify the common environmental drivers affecting niche distribution and evaluates the collective patterns of multiple tree species, thereby providing a scientific reference for enhanced forestry management and climate change mitigation.

How Social Considerations Improve the Equity and Effectiveness of Ecosystem Restoration.

Ecosystem restoration is an important means to address global sustainability challenges. However, scientific and policy discourse often overlooks the social processes that influence the equity and effectiveness of restoration interventions. In the present article, we outline how social processes that are critical to restoration equity and effectiveness can be better incorporated in restoration science and policy. Drawing from existing case studies, we show how projects that align with local people's preferences and are implemented through inclusive governance are more likely to lead to improved social, ecological, and environmental outcomes. To underscore the importance of social considerations in restoration, we overlay existing global restoration priority maps, population, and the Human Development Index (HDI) to show that approximately 1.4 billion people, disproportionately belonging to groups with low HDI, live in areas identified by previous studies as being of high restoration priority. We conclude with five action points for science and policy to promote equity-centered restoration.

Conceptual Links between Landscape Diversity and Diet Diversity: A Roadmap for Transdisciplinary Research.

Malnutrition linked to poor quality diets affects at least 2 billion people. Forests, as well as agricultural systems linked to trees, are key sources of dietary diversity in rural settings. In the present article, we develop conceptual links between diet diversity and forested landscape mosaics within the rural tropics. First, we summarize the state of knowledge regarding diets obtained from forests, trees, and agroforests. We then hypothesize how disturbed secondary forests, edge habitats, forest access, and landscape diversity can function in bolstering dietary diversity. Taken together, these ideas help us build a framework illuminating four pathways (direct, agroecological, energy, and market pathways) connecting forested landscapes to diet diversity. Finally, we offer recommendations to fill remaining knowledge gaps related to diet and forest cover monitoring. We argue that better evaluation of the role of land cover complexity will help avoid overly simplistic views of food security and, instead, uncover nutritional synergies with forest conservation and restoration.

Historical dynamics in ecosystem service bundles.

Managing multiple ecosystem services (ES), including addressing trade-offs between services and preventing ecological surprises, is among the most pressing areas for sustainability research. These challenges require ES research to go beyond the currently common approach of snapshot studies limited to one or two services at a single point in time. We used a spatiotemporal approach to examine changes in nine ES and their relationships from 1971 to 2006 across 131 municipalities in a mixed-use landscape in Quebec, Canada. We show how an approach that incorporates time and space can improve our understanding of ES dynamics. We found an increase in the provision of most services through time; however, provision of ES was not uniformly enhanced at all locations. Instead, each municipality specialized in providing a bundle (set of positively correlated ES) dominated by just a few services. The trajectory of bundle formation was related to changes in agricultural policy and global trends; local biophysical and socioeconomic characteristics explained the bundles' increasing spatial clustering. Relationships between services varied through time, with some provisioning and cultural services shifting from a trade-off or no relationship in 1971 to an apparent synergistic relationship by 2006. By implementing a spatiotemporal perspective on multiple services, we provide clear evidence of the dynamic nature of ES interactions and contribute to identifying processes and drivers behind these changing relationships. Our study raises questions about using snapshots of ES provision at a single point in time to build our understanding of ES relationships in complex and dynamic social-ecological systems.

Cropping history trumps fallow duration in long-term soil and vegetation dynamics of shifting cultivation systems.

In the study of shifting cultivation systems, fallow duration is seen as the key determinant of vegetation and soil dynamics: long fallows renew soil fertility, biomass, and biodiversity. However, long fallow systems are increasingly replaced around the world with short-medium fallow systems, and awareness is growing of the need to look across multiple (not just single) crop-fallow cycles to accurately understand observed soil and vegetation patterns. In a study from Peru that builds on 50+ years of field-level land-use histories, we found that, over multiple crop-fallow cycles, farmers' cropping practices mattered more than fallow duration for biodiversity and soil fertility. After initial clearing of primary forest, a precipitous decline occurred in tree species richness of fallows (>50%) with gradual but continued loss thereafter (~0.5 species/yr), which resulted in shifts in species composition over time. For soils, the decline in fertility was more gradual with each additional cycle of cropping resulting in lowered soil organic matter, available phosphorus, and exchangeable sodium levels, even in fields with long fallow durations. In the most intensively used sites, soils experienced a 16% decline of soil organic matter over 4+ cycles. In contrast to previous studies, biomass accumulation and carbon stocks were not related to cropping history or to the number and duration of cycles observed. This suggests that biodiversity-soils-biomass dynamics may not necessarily "move together" in these systems. These results point to the importance of the number of crop-fallow cycles over fallow duration in driving soil fertility and vegetation dynamics under shifting cultivation in the Peruvian Amazon. Overtime shifting cultivation may erode soil fertility and biodiversity levels even if long fallows persist. As the decline in soils appears slow, it may be possible to address this effect with the use of amendments, however biodiversity declines and species compositional changes may be much harder to reverse.

Acceleration and novelty: community restoration speeds recovery and transforms species composition in Andean cloud forest.

Community-based tropical forest restoration projects, often promoted as a win-win solution for local communities and the environment, have increased dramatically in number in the past decade. Many such projects are underway in Andean cloud forests, which, given their extremely high biodiversity and history of extensive clearing, are understudied. This study investigates the efficacy of community-based tree-planting projects to accelerate cloud forest recovery, as compared to unassisted natural regeneration. This study takes place in northwest Andean Ecuador, where the majority of the original, highly diverse cloud forests have been cleared, in five communities that initiated tree-planting projects to restore forests in 2003. In 2011, we identified tree species along transects in planted forests (n = 5), naturally regenerating forests (n = 5), and primary forests (n = 5). We also surveyed 120 households about their restoration methods, tree preferences, and forest uses. We found that tree diversity was higher in planted than in unplanted secondary forest, but both were less diverse than primary forests. Ordination analysis showed that all three forests had distinct species compositions, although planted forests shared more species with primary forests than did unplanted forests. Planted forests also contained more animal-dispersed species in both the planted canopy and in the unplanted, regenerating understory than unplanted forests, and contained the highest proportion of species with use value for local people. While restoring forest increased biodiversity and accelerated forest recovery, restored forests may also represent novel ecosystems that are distinct from the region's previous ecosystems and, given their usefulness to people, are likely to be more common in the future.

Land-use poverty traps identified in shifting cultivation systems shape long-term tropical forest cover.

In this article we illustrate how fine-grained longitudinal analyses of land holding and land use among forest peasant households in an Amazonian village can enrich our understanding of the poverty/land cover nexus. We examine the dynamic links in shifting cultivation systems among asset poverty, land use, and land cover in a community where poverty is persistent and primary forests have been replaced over time--with community enclosure--by secondary forests (i.e., fallows), orchards, and crop land. Land cover change is assessed using aerial photographs/satellite imagery from 1965 to 2007. Household and plot level data are used to track land holding, portfolios, and use as well as land cover over the past 30 y, with particular attention to forest status (type and age). Our analyses find evidence for two important types of "land-use" poverty traps--a "subsistence crop" trap and a "short fallow" trap--and indicate that the initial conditions of land holding by forest peasants have long-term effects on future forest cover and household welfare. These findings suggest a new mechanism driving poverty traps: insufficient initial land holdings induce land use patterns that trap households in low agricultural productivity. Path dependency in the evolution of household land portfolios and land use strategies strongly influences not only the wellbeing of forest people but also the dynamics of tropical deforestation and secondary forest regrowth.

Historical forest baselines reveal potential for continued carbon sequestration.

One-third of net CO(2) emissions to the atmosphere since 1850 are the result of land-use change, primarily from the clearing of forests for timber and agriculture, but quantifying these changes is complicated by the lack of historical data on both former ecosystem conditions and the extent and spatial configuration of subsequent land use. Using fine-resolution historical survey records, we reconstruct pre-EuroAmerican settlement (1850s) forest carbon in the state of Wisconsin, examine changes in carbon after logging and agricultural conversion, and assess the potential for future sequestration through forest recovery. Results suggest that total above-ground live forest carbon (AGC) fell from 434 TgC before settlement to 120 TgC at the peak of agricultural clearing in the 1930s and has since recovered to approximately 276 TgC. The spatial distribution of AGC, however, has shifted significantly. Former savanna ecosystems in the south now store more AGC because of fire suppression and forest ingrowth, despite the fact that most of the region remains in agriculture, whereas northern forests still store much less carbon than before settlement. Across the state, continued sequestration in existing forests has the potential to contribute an additional 69 TgC. Reforestation of agricultural lands, in particular, the formerly high C-density forests in the north-central region that are now agricultural lands less optimal than those in the south, could contribute 150 TgC. Restoring historical carbon stocks across the landscape will therefore require reassessing overall land-use choices, but a range of options can be ranked and considered under changing needs for ecosystem services.

Forest-linked livelihoods in a globalized world.

Forests have re-taken centre stage in global conversations about sustainability, climate and biodiversity. Here, we use a horizon scanning approach to identify five large-scale trends that are likely to have substantial medium- and long-term effects on forests and forest livelihoods: forest megadisturbances; changing rural demographics; the rise of the middle-class in low- and middle-income countries; increased availability, access and use of digital technologies; and large-scale infrastructure development. These trends represent human and environmental processes that are exceptionally large in geographical extent and magnitude, and difficult to reverse. They are creating new agricultural and urban frontiers, changing existing rural landscapes and practices, opening spaces for novel conservation priorities and facilitating an unprecedented development of monitoring and evaluation platforms that can be used by local communities, civil society organizations, governments and international donors. Understanding these larger-scale dynamics is key to support not only the critical role of forests in meeting livelihood aspirations locally, but also a range of other sustainability challenges more globally. We argue that a better understanding of these trends and the identification of levers for change requires that the research community not only continue to build on case studies that have dominated research efforts so far, but place a greater emphasis on causality and causal mechanisms, and generate a deeper understanding of how local, national and international geographical scales interact.

Legacies of historical land use on regional forest composition and structure in Wisconsin, USA (mid-1800s-1930s-2000s).

Historical land use can influence forest species composition and structure for centuries after direct use has ceased. In Wisconsin, USA, Euro-American settlement in the mid- to late 1800s was accompanied by widespread logging, agricultural conversion, and fire suppression. To determine the maximum magnitude of change in forest ecosystems at the height of the agricultural period and the degree of recovery since that time, we assessed changes in forest species composition and structure among the (1) mid-1800s, at the onset of Euro-American settlement; (2) 1930s, at the height of the agricultural period; and (3) 2000s, following forest regrowth. Data sources included the original U.S. Public Land Survey records (mid-1800s), the Wisconsin Land Economic Inventory (1930s), and U.S. Forest Service Forest Inventory and Analysis data (2000s). We derived maps of relative species dominance and tree diameters for the three dates and assessed change using spatial error models, nonmetric multidimensional scaling ordination, and Sørenson distance measures. Our results suggest that since the mid-1800s, hemlock and white pine have declined in absolute area from 22% to 1%, and the proportion of medium (25-<50 cm) and large-diameter (> or = 50 cm) trees of all species has decreased from 71% to 27% across the entire state. Early-successional aspen-birch is three times more common than in the mid-1800s (9% vs. 3%), and maple and other shade-tolerant species are increasing in southern areas formerly dominated by oak forests and savannas. Since the peak agricultural extent in the 1930s, species composition and tree size in northern forests have shown some recovery, while southern forests appear to be on a novel trajectory of change. There is evidence of regional homogenization, but the broad north-south environmental gradient in Wisconsin constrains overall species composition. Although the nature of the future forests will be determined in part by climate change and other exogenous variables, land use is likely to remain the driving factor.