The distribution and drivers of tree cover in savannas and forests across India

The distribution of forest and savanna biomes and the role of resources (climate and soil) and disturbances (fire and herbivory) in determining tree-grass dynamics remains elusive and variable across geographies. This is especially problematic in Indian savannas which have been historically misclassified as degraded forests and are targeted for tree-planting. Here, we examine biome distribution and determinants through the lens of tree cover across India. Our analyses reveal four distinct zones of differing tree cover, with intermediate zones containing savanna vegetation. Rainfall seasonality determines maximum possible tree cover non-linearly. Once rainfall seasonality is factored out, soil sand fraction and topography partially explain residual variation of tree cover. High domestic livestock herbivory and other anthropogenic pressures reduce tree cover. Lastly, lack of detectable fires precludes robust conclusions about the relationship between fire and tree cover. By considering these environmental drivers in restoration planning, we can improve upon simplistic tree planting initiatives that may be detrimental to Indian savannas

Proximity and size of protected areas in Asian borderlands enable transboundary conservation

Asia has over 80% of the Earth’s border hotspots for threatened transboundary wildlife, yet only limited research has been done on the distribution of protected areas across international borders in the continent. To address this gap, we conducted a spatial analysis of protected areas across 42 Asian countries. Our study aimed to understand the distribution, proximity, and land-use changes within border protected areas. Two cases were examined, evaluating the spatial relationships at different buffer distances from international borders. Our findings revealed that Asian countries have larger protected areas in borderlands, particularly up to 50 km from borders, as compared to regions further away from the border. Importantly, the median distance between protected areas across international borders is nearly three times shorter than those within the same country. However, the rate of change in natural habitats within protected areas between 2001 and 2019 showed no correlation with their distance from the border. The proximity of protected areas across Asian borders offers opportunities for enhancing connectivity. A larger extent of multi-use protected areas (IUCN1-6+) near borders compared to strict protected areas (IUCN1-4) can facilitate the engagement of communities, which are crucial in transboundary conservation initiatives. Our results can help Asian countries as they work toward their commitments as part of the Kunming–Montreal Global Biodiversity Framework to protect at least 30% of the Earth’s surface area by 2030

Human land occupation regulates the effect of the climate on the burned area of the Brazilian Cerrado

Human activities and climate change are transforming fire regimes globally. The interaction between these two drivers is poorly understood, yet critical if we aim at predicting how biomes will respond to novel fire regimes. In the Brazilian Cerrado, altered fire regimes are threatening its unique biodiversity and ecosystem functioning. Here, using geospatial data for the period 1985-2020 and a causal inference framework to design Bayesian statistical models, we demonstrate that a larger human presence in the landscape (≥40% land-use area) reduces the Cerrado’s burned area and hinders its responsiveness to climate; while climatic effects only become apparent in landscapes with little human presence, where hotter and drier conditions increase burned area. Finally, we find spatially heterogeneous burned area trends over time, with increases associated to climate change in landscapes that have remained mostly intact, and decreases caused by anthropic expansion. Both diverging trends have important implications for the conservation of the Cerrado as land-use expansion and climate change continue to unfold

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests

ests face increasing climate risk, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, Ψ50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk, little is known about how these vary across Earth’s largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters Ψ50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both Ψ50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth–mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon, with strong implications for the Amazon carbon sink

Plant trait and vegetation data along a 1314 m elevation gradient with fire history in Puna grasslands, Perú

Alpine grassland vegetation supports globally important biodiversity and ecosystems that are increasingly threatened by climate warming and other environmental changes. Trait-based approaches can support understanding of vegetation responses to global change drivers and consequences for ecosystem functioning. In six sites along a 1314 m elevational gradient in Puna grasslands in the Peruvian Andes, we collected datasets on vascular plant composition, plant functional traits, biomass, ecosystem fluxes, and climate data over three years. The data were collected in the wet and dry season and from plots with different fire histories. We selected traits associated with plant resource use, growth, and life history strategies (leaf area, leaf dry/wet mass, leaf thickness, specific leaf area, leaf dry matter content, leaf C, N, P content, C and N isotopes). The trait dataset contains 3,665 plant records from 145 taxa, 54,036 trait measurements (increasing the trait data coverage of the regional flora by 420%) covering 14 traits and 121 plant taxa (ca. 40% of which have no previous publicly available trait data) across 33 families

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests

Funding: Data collection was largely funded by the UK Natural Environment Research Council (NERC) project TREMOR (NE/N004655/1) to D.G., E.G. and O.P., with further funds from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES, finance code 001) to J.V.T. and a University of Leeds Climate Research Bursary Fund to J.V.T. D.G., E.G. and O.P. acknowledge further support from a NERC-funded consortium award (ARBOLES, NE/S011811/1). This paper is an outcome of J.V.T.’s doctoral thesis, which was sponsored by CAPES (GDE 99999.001293/2015-00). J.V.T. was previously supported by the NERC-funded ARBOLES project (NE/S011811/1) and is supported at present by the Swedish Research Council Vetenskapsrådet (grant no. 2019-03758 to R.M.). E.G., O.P. and D.G. acknowledge support from NERC-funded BIORED grant (NE/N012542/1). O.P. acknowledges support from an ERC Advanced Grant and a Royal Society Wolfson Research Merit Award. R.S.O. was supported by a CNPq productivity scholarship, the São Paulo Research Foundation (FAPESP-Microsoft 11/52072-0) and the US Department of Energy, project GoAmazon (FAPESP 2013/50531-2). M.M. acknowledges support from MINECO FUN2FUN (CGL2013-46808-R) and DRESS (CGL2017-89149-C2-1-R). C.S.-M., F.B.V. and P.R.L.B. were financed by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES, finance code 001). C.S.-M. received a scholarship from the Brazilian National Council for Scientific and Technological Development (CNPq 140353/2017-8) and CAPES (science without borders 88881.135316/2016-01). Y.M. acknowledges the Gordon and Betty Moore Foundation and ERC Advanced Investigator Grant (GEM-TRAITS, 321131) for supporting the Global Ecosystems Monitoring (GEM) network (gem.tropicalforests.ox.ac.uk), within which some of the field sites (KEN, TAM and ALP) are nested. The authors thank Brazil–USA Collaborative Research GoAmazon DOE-FAPESP-FAPEAM (FAPESP 2013/50533-5 to L.A.) and National Science Foundation (award DEB-1753973 to L. Alves). They thank Serrapilheira Serra-1709-18983 (to M.H.) and CNPq-PELD/POPA-441443/2016-8 (to L.G.) (P.I. Albertina Lima). They thank all the colleagues and grants mentioned elsewhere [8,36] that established, identified and measured the Amazon forest plots in the RAINFOR network analysed here. The authors particularly thank J. Lyod, S. Almeida, F. Brown, B. Vicenti, N. Silva and L. Alves. This work is an outcome approved Research Project no. 19 from ForestPlots.net, a collaborative initiative developed at the University of Leeds that unites researchers and the monitoring of their permanent plots from the world’s tropical forests [61]. The authros thank A. Levesley, K. Melgaço Ladvocat and G. Pickavance for ForestPlots.net management. They thank Y. Wang and J. Baker, respectively, for their help with the map and with the climatic data. The authors acknowledge the invaluable help of M. Brum for kindly providing the comparison of vulnerability curves based on PAD and on PLC shown in this manuscript. They thank J. Martinez-Vilalta for his comments on an early version of this manuscript. The authors also thank V. Hilares and the Asociación para la Investigación y Desarrollo Integral (AIDER, Puerto Maldonado, Peru); V. Saldaña and Instituto de Investigaciones de la Amazonía Peruana (IIAP) for local field campaign support in Peru; E. Chavez and Noel Kempff Natural History Museum for local field campaign support in Bolivia; ICMBio, INPA/NAPPA/LBA COOMFLONA (Cooperativa mista da Flona Tapajós) and T. I. Bragança-Marituba for the research support.Tropical forests face increasing climate risk1,2, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, Ψ50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk3-5, little is known about how these vary across Earth's largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters Ψ50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both Ψ50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth-mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon6,7, with strong implications for the Amazon carbon sink.Publisher PDFPeer reviewe

Frugivory and seed dispersal in the Cerrado: Network structure and defaunation effects

International audienceSeed dispersal is a fundamental process that is highly threatened by the rapid decline of large-bodied frugivores worldwide. The Brazilian Cerrado, the largest savanna in the world, represents an ideal site for investigating seed dispersal because of its biodiversity, environmental challenges, and knowledge shortfalls. We performed a systematic literature review to analyze the seed dispersal network in the Cerrado and the potential impacts of the defaunation of large-bodied frugivores on it. We considered network metrics, calculated the defaunation index of the frugivore assemblage, and compared traits among different fruit-sized plants and their respective dispersers in the network. We retrieved 1565 interactions involving 193 plant species and 270 animal species. Results show that the Cerrado seed dispersal network is slightly nested and considerably modular, dominated by small- to medium-sized generalist species, such as passerines, marsupials, and mesocarnivores. Nonetheless, large-bodied frugivores like the lowland tapir have a key role in the network due to their great foraging and network integration capacity. The Cerrado frugivore assemblage is moderately defaunated, with possible effects in its interactions with large-fruited plants. The Cerrado's defaunation and functional loss of large vertebrates deserve urgent attention to further understand the impacts on seed dispersal mechanisms and ecosystem functioning

Extensive woody encroachment altering Angolan miombo woodlands despite cropland expansion and frequent fires

International audienceWoody encroachment (WE) and agricultural expansion are widespread in tropical savannas, where they threaten biodiversity and ecosystem function. In Africa's largest savanna, the miombo woodlands, cropland expansion is expected to cause extensive habitat loss over the next 30 years. Meanwhile, widespread WE is altering the remaining untransformed vegetation. Quantifying the extent of both processes in the Angolan miombo woodlands (~570,000 km2) has been challenging due to limited infrastructure, a history of conflict, and widespread landmines. Here, we analyze spectral satellite imagery to investigate the extent of WE and cropland expansion in the Angolan miombo woodlands since 1990. We asses WE using two complementary metrics: multi-decade canopy greenness trends and conversion from grassland to woodland. We also examine whether WE trends are driven by landscape fragmentation and decreasing fire frequency. We found that from 1990 to 2020, 34.1% of the Angolan miombo woodlands experienced significant WE or was converted to cropland, while open grassy vegetation declined by 62%. WE advanced rapidly even in areas experiencing extraordinarily high burn frequencies and was not adequately explained by changing temperature or precipitation. WE was concentrated far from the agricultural frontier, in remote areas with low population densities. These results challenge the hypothesis that human-altered fire regimes are the primary driver of WE in mesic savannas. The results will help decision-makers conserve the miombo woodlands' biodiversity and ecosystem services, by highlighting that strategies to slow habitat loss must address WE and cropland expansion togethe

Understanding ecological transitions under recurrent wildfire : A case study in the seasonally dry tropical forests of the Chiquitania, Bolivia

Wildfires in tropical forests are likely to become a more dominant disturbance due to future increasing feedbacks between rapid frontier expansion and more frequent droughts. This study evaluates the effects of fire recurrence on seasonally dry tropical forests of the Chiquitania region, located in the southern rim of Amazonia, eastern lowlands of Bolivia. Effects were assessed in terms of changes in biomass, forest structure, species diversity and composition. Forest plots were established in well-conserved study sites to compare unburnt forests with forests burned once, twice and three times in the period 2000-2012. Inventories were collected for trees, palms and lianas, including identification of species and measurement of morphological traits related to fire tolerance. Biomass was estimated using different allometric equations, and species composition, richness, abundance and dominance were compared. We found a significant loss in biomass, and putative effects on small and large trees after recurrent burns. The observed patterns in this study suggest that Chiquitano forests respond to recurrent fires through a shift in tree species composition with already-present fire-tolerant species becoming more dominant. This transition presented losses in biomass but increases in species richness. Insights into a possible transition to a more fire-adapted state is of great relevance for forest and fire management strategies in the region, as this transition may become irreversible in a future regime of more frequent wildfires, expected due to drier climatic conditions with increasing patterns of forest fragmentation and spreading use of fire into new forest frontiers.</p

Proximity and size of protected areas in Asian borderlands enable transboundary conservation

International audienceAsia has over 80% of the Earth’s border hotspots for threatened transboundary wildlife, yet only limited research has been done on the distribution of protected areas across international borders in the continent. To address this gap, we conducted a spatial analysis of protected areas across 42 Asian countries. Our study aimed to understand the distribution, proximity, and land-use changes within border protected areas. Two cases were examined, evaluating the spatial relationships at different buffer distances from international borders. Our findings revealed that Asian countries have larger protected areas in borderlands, particularly up to 50 km from borders, as compared to regions further away from the border. Importantly, the median distance between protected areas across international borders is nearly three times shorter than those within the same country. However, the rate of change in natural habitats within protected areas between 2001 and 2019 showed no correlation with their distance from the border. The proximity of protected areas across Asian borders offers opportunities for enhancing connectivity. A larger extent of multi-use protected areas (IUCN1-6+) near borders compared to strict protected areas (IUCN1-4) can facilitate the engagement of communities, which are crucial in transboundary conservation initiatives. Our results can help Asian countries as they work toward their commitments as part of the Kunming–Montreal Global Biodiversity Framework to protect at least 30% of the Earth’s surface area by 2030