High sensitivity of tropical forest birds to deforestation at lower altitudes

Habitat conversion is a major driver of tropical biodiversity loss, but its effects are poorly understood in montane environments. While community-level responses to habitat loss display strong elevational dependencies, it is unclear whether these arise via elevational turnover in community composition and interspecific differences in sensitivity or elevational variation in environmental conditions and proximity to thermal thresholds. Here we assess the relative importance of inter- and intraspecific variation across the elevational gradient by quantifying how 243 forest-dependent bird species vary in sensitivity to landscape-scale forest loss across a 3000-m elevational gradient in the Colombian Andes. We find that species that live at lower elevations are strongly affected by loss of forest in the nearby landscape, while those at higher elevations appear relatively unperturbed, an effect that is independent of phylogeny. Conversely, we find limited evidence of intraspecific elevational gradients in sensitivity, with populations displaying similar sensitivities to forest loss, regardless of where they exist in a species' elevational range. Gradients in biodiversity response to habitat loss thus appear to arise via interspecific gradients in sensitivity rather than proximity to climatically limiting conditions

Understanding different dominance patterns in western Amazonian forests

Dominance of neotropical tree communities by a few species is widely documented, but dominant trees show a variety of distributional patterns still poorly understood. Here, we used 503 forest inventory plots (93,719 individuals ≥2.5 cm diameter, 2609 species) to explore the relationships between local abundance, regional frequency and spatial aggregation of dominant species in four main habitat types in western Amazonia. Although the abundance-occupancy relationship is positive for the full dataset, we found that among dominant Amazonian tree species, there is a strong negative relationship between local abundance and regional frequency and/or spatial aggregation across habitat types. Our findings suggest an ecological trade-off whereby dominant species can be locally abundant (local dominants) or regionally widespread (widespread dominants), but rarely both (oligarchs). Given the importance of dominant species as drivers of diversity and ecosystem functioning, unravelling different dominance patterns is a research priority to direct conservation efforts in Amazonian forests

Reduced body sizes in climate-impacted tropical insect assemblages are primarily explained by range shifts

Both community composition changes due to species redistribution and within-species size shifts may alter body size structures under climate warming. Here we assess the relative contribution of these processes in community-level body size changes in tropical moth assemblages that moved uphill during a period of warming. Based on resurvey data for seven assemblages (>8000 individuals) on Mt. Kinabalu, Borneo in 1965 and 2007, we show significant wing-length reduction (mean shrinkage of 1.3% per species). Range shifts explain most size re-structuring, due to uphill shifts of relatively small species, especially at high elevations. Overall, mean forewing length shrank by ca. 5%, much of which accounted for by species range boundary shifts (3.9%), followed by within-boundary distribution changes (0.5%), and within-species size shrinkage (0.6%). We conclude that the effects of range shifting predominate, but considering species physiological responses is also important for understanding community size reorganization under climate warming

Trade-offs between multifunctionality and profit in tropical smallholder landscapes

Land-use transitions can enhance the livelihoods of smallholder farmers but potential economic-ecological trade-offs remain poorly understood. Here, we present an interdisciplinary study of the environmental, social and economic consequences of land-use transitions in a tropical smallholder landscape on Sumatra, Indonesia. We find widespread biodiversity-profit trade-offs resulting from land-use transitions from forest and agroforestry systems to rubber and oil palm monocultures, for 26,894 aboveground and belowground species and whole-ecosystem multidiversity. Despite variation between ecosystem functions, profit gains come at the expense of ecosystem multifunctionality, indicating far-reaching ecosystem deterioration. We identify landscape compositions that can mitigate trade-offs under optimal land-use allocation but also show that intensive monocultures always lead to higher profits. These findings suggest that, to reduce losses in biodiversity and ecosystem functioning, changes in economic incentive structures through well-designed policies are urgently needed

Life history, climate and biogeography interactively affect worldwide genetic diversity of plant and animal populations.

Understanding how biological and environmental factors interactively shape the global distribution of plant and animal genetic diversity is fundamental to biodiversity conservation. Genetic diversity measured in local populations (GDP) is correspondingly assumed representative for population fitness and eco-evolutionary dynamics. For 8356 populations across the globe, we report that plants systematically display much lower GDP than animals, and that life history traits shape GDP patterns both directly (animal longevity and size), and indirectly by mediating core-periphery patterns (animal fecundity and plant dispersal). Particularly in some plant groups, peripheral populations can sustain similar GDP as core populations, emphasizing their potential conservation value. We further find surprisingly weak support for general latitudinal GDP trends. Finally, contemporary rather than past climate contributes to the spatial distribution of GDP, suggesting that contemporary environmental changes affect global patterns of GDP. Our findings generate new perspectives for the conservation of genetic resources at worldwide and taxonomic-wide scales

Amazon tree dominance across forest strata

The forests of Amazonia are among the most biodiverse plant communities on Earth. Given the immediate threats posed by climate and land-use change, an improved understanding of how this extraordinary biodiversity is spatially organized is urgently required to develop effective conservation strategies. Most Amazonian tree species are extremely rare but a few are common across the region. Indeed, just 227 ‘hyperdominant’ species account for >50% of all individuals >10 cm diameter at 1.3 m in height. Yet, the degree to which the phenomenon of hyperdominance is sensitive to tree size, the extent to which the composition of dominant species changes with size class and how evolutionary history constrains tree hyperdominance, all remain unknown. Here, we use a large floristic dataset to show that, while hyperdominance is a universal phenomenon across forest strata, different species dominate the forest understory, midstory and canopy. We further find that, although species belonging to a range of phylogenetically dispersed lineages have become hyperdominant in small size classes, hyperdominants in large size classes are restricted to a few lineages. Our results demonstrate that it is essential to consider all forest strata to understand regional patterns of dominance and composition in Amazonia. More generally, through the lens of 654 hyperdominant species, we outline a tractable pathway for understanding the functioning of half of Amazonian forests across vertical strata and geographical locations

Land sparing outperforms land sharing for Amazonian bird communities regardless of surrounding landscape context

Publication status: PublishedAbstract Two strategies are central to the debate regarding agricultural development: one integrates farming and conservation (land sharing), and the other separates farming and conservation, intensifying production to allow the offset of natural habitat (land sparing). The role of wildlife‐friendly habitat in the wider surrounding landscape (landscape wildlife friendliness (WF)) in promoting farmland diversity is potentially an unexplored benefit of land sharing. We sampled birds across primary forests and cattle pastures in the western Amazon, where terrestrial biodiversity peaks. We tested the hypothesis that increased landscape WF will lead to increased species richness (SR) on farmland, even at low levels of ‘on‐farm’ wildlife‐friendly habitat (farm WF). We show that while there is a minor increase in SR linked to increased levels of landscape WF, a large component of the avian community is functionally absent. Most forest‐dependent species are missing from pasture, even at high levels of farm WF. For these species, the preservation of blocks of contiguous forest under land sparing is vastly superior. We modelled both strategies under different levels of production. Land sparing always retained significantly higher SR than land sharing, regardless of the level of landscape WF. Synthesis and applications. Landscape wildlife friendliness (WF) provided through land sharing is of limited benefit to many tropical forest‐dependent species that are unable to move across or utilise pasture, even at high levels of farm and landscape WF. To ensure the persistence of these species, policymakers should urgently implement sustainable intensification mechanisms to increase farmland productivity while enabling the protection of large blocks of spared natural habitat. </jats:p

Avian phylogenetic and functional diversity are better conserved by land-sparing than land-sharing farming in lowland tropical forests

Abstract The transformation of natural habitats for farming is a major driver of tropical biodiversity loss. To mitigate impacts, two alternatives are promoted: intensifying agriculture to offset protected areas (land sparing) or integrating wildlife‐friendly habitats within farmland (land sharing). In the montane and dry tropics, phylogenetic and functional diversity, which underpin evolutionary values and the provision of ecosystem functioning and services, are best protected by land sparing. A key question is how these components of biodiversity are best conserved in the more stable environments of lowland moist tropical forests. Focusing on cattle farming within the Colombian Amazon, we investigated how the occupancy of 280 bird species varies between forest and pasture spanning gradients of wildlife‐friendly features. We then simulated scenarios of land‐sparing and land‐sharing farming to predict impacts on phylogenetic and functional diversity metrics. Predicted metrics differed marginally between forest and pasture. However, community assembly varied significantly. Wildlife‐friendly pastures were inadequate for most forest‐dependent species, while phylogenetic and functional diversity indices showed minimal variation across gradients of wildlife‐friendly features. Land sparing consistently retained higher levels of Faith's phylogenetic diversity (~30%), functional richness (~20%) and evolutionarily distinct lineages (~40%) than land sharing, and did so across a range of landscape sizes. Securing forest protection through land‐sparing practices remains superior for conserving overall community phylogenetic and functional diversity than land sharing. Synthesis and applications: To minimise the loss of avian phylogenetic diversity and functional traits from farming in the Amazon, it is imperative to protect large blocks of undisturbed and regenerating forests. The intensification required within existing farmlands to make space for spared lands while meeting agricultural demand needs to be sustainable, avoiding long‐term negative impacts on soil quality and other ecosystem services. Policies need to secure the delivery of both actions simultaneously. </jats:p