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The Amazon Basin contains the largest and most diverse tropical rainforest in the world.Besides the Andes and the Atlantic Ocean, the rainforest is bounded to the north by the Guiana crystalline shield and to the south by the Brazilian crystalline shield, marked at their edges by cataracts in the rivers and often dominated by grasslands.

1. Knowledge of fish migration is a prerequisite to sustainable fisheries management and preservation, especially in large international river basins. In particular, understanding whether a migratory lifestyle is compulsory or facultative, and whether adults home to their natal geographic area is paramount to fully appraise disruptions of longitudinal connectivity resulting from damming. 2. In the Amazon, the large migratory catfishes of the Brachyplatystoma genus are apex predators of considerable interest for fisheries. They are believed to use the entire length of the basin to perform their life cycle, with hypothesized homing behaviours. Here, we tested these hypotheses, using the emblematic B. rousseauxii as a model species. 3. We sampled adults close to major breeding areas in the Amazon basin (upper Madeira and upper Amazonas) and assessed their lifetime movements by measuring variations in ⁸⁷Sr/⁸⁶Sr along transverse sections of their otoliths (ear stones) using laser ablation multicollector mass spectrometry (LA-MC-ICPMS). 4. We demonstrate that larvae migrate downstream from the Andean piedmont to the lower Amazon, where they grow over a protracted period before migrating upstream as adults. Contrary to prevailing inferences, not all fish spend their nursery stages in the Amazon estuary. By contrast, the passage in the lower or central Amazon seems an obligate part of the life cycle. We further evidence that most adults home to their natal geographic area within the Madeira sub-basin. Such long-distance natal homing is exceptional in purely freshwater fishes. 5. Synthesis and applications. By using otolith microchemistry, we were able to demonstrate a seemingly compulsory basin-wide migratory life cycle of large Amazonian catfishes. This makes them the organisms performing the longest migrations (>8000 km) in fresh waters. This exceptional life history is already jeopardized by two dams recently built in the Madeira River, which block a major migration route and access to a substantial part of their spawning grounds. Major impacts can be anticipated from the current and forthcoming hydroelectric development in the Amazon basin, not only on the populations and fisheries of this apex predator, but also on Amazonian food webs through trophic cascades.

Biodiversity contributes to the ecological and climatic stability of the Amazon Basin 1 , 2 , but is increasingly threatened by deforestation and fire 3 , 4 . Here we quantify these impacts over the past two decades using remote-sensing estimates of fire and deforestation and comprehensive range estimates of 11,514 plant species and 3,079 vertebrate species in the Amazon. Deforestation has led to large amounts of habitat loss, and fires further exacerbate this already substantial impact on Amazonian biodiversity. Since 2001, 103,079–189,755 km 2 of Amazon rainforest has been impacted by fires, potentially impacting the ranges of 77.3–85.2% of species that are listed as threatened in this region 5 . The impacts of fire on the ranges of species in Amazonia could be as high as 64%, and greater impacts are typically associated with species that have restricted ranges. We find close associations between forest policy, fire-impacted forest area and their potential impacts on biodiversity. In Brazil, forest policies that were initiated in the mid-2000s corresponded to reduced rates of burning. However, relaxed enforcement of these policies in 2019 has seemingly begun to reverse this trend: approximately 4,253–10,343 km 2 of forest has been impacted by fire, leading to some of the most severe potential impacts on biodiversity since 2009. These results highlight the critical role of policy enforcement in the preservation of biodiversity in the Amazon. Remote-sensing estimates of fires and the estimated geographic ranges of thousands of plant and vertebrate species in the Amazon Basin reveal that fires have impacted the ranges of 77–85% of threatened species over the past two decades.

The biosphere is undergoing critical transformations due to deforestation, agricultural expansion, and logging, which have led to biodiversity loss, degradation of ecosystem services, and climate change. In tropical forests such as the Ecuadorian Amazon, these pressures are especially severe because reductions in forest cover compromise key ecological processes. The purpose of this article is to analyze the relationship between shifting agriculture, food security, and conservation in the Ecuadorian Amazon, with emphasis on the agroforestry system known as the chakra practiced by Kichwa communities. This model integrates crops such as cacao, maize, and cassava with native trees, without chemical inputs, and constitutes a practice that is both culturally significant and environmentally sustainable. Whereas conventional shifting agriculture tends to reduce soil fertility and the forest’s regenerative capacity, chakras maintain important levels of floristic diversity, favor the conservation of endemic species, and provide ecosystem services such as carbon sequestration and nutrient regulation. In this sense, chakras represent a resilient yet context-dependent agroforestry alternative that connects food security and sovereignty, biological conservation, income, Indigenous identity, and climate-change mitigation, although their long-term sustainability remains influenced by market forces, land-use pressure, and policy support in tropical contexts.

The Amazon biome is home to the largest tropical forest on the planet and has the greatest global biodiversity on Earth. Despite this, several less charismatic taxonomic groups, such as amphibians, lack comprehensive studies on their species richness and spatial distribution in the Amazon Region. In this study, we investigated: i) patterns of richness and endemism of Amazonian amphibians across geopolitical and biogeographic divisions, ii) similarities between different Amazonian bioregions, iii) temporal trends in amphibian sampling, iv) conservation status of amphibians according to assessments of the IUCN and v) the importance of diverse data sources in building a robust database of amphibian occurrences. We aggregated data from four different sources: publicly accessible platforms, peer-reviewed articles, grey literature and fieldwork inventories spanning 15 years (2007–2021), ultimately compiling 160,643 records of 947 species across 7,418 sampled sites. The greatest diversity of species was found in Peru, Brazil and Ecuador, with notable amphibian diversity and endemism in regions such as the western basins and the Tapajós River Basin in the central-southern Amazon. Geographical analysis of species diversity revealed four distinct groups defined by latitudinal (the Amazon River) and longitudinal (the Juruá, Madeira and Tapajós Rivers) gradients, with low species similarity (< 40%), particularly in the basins of north-western Amazonia. Amphibian sampling in the Amazon has intensified since the 1950s with the establishment of important research centres such as INPA and the GOELD Museum in the Brazilian Amazon. Approximately 18% of Amazonian amphibian species face extinction risk, according to IUCN assessments, highlighting the need for comprehensive data sources to understand and conserve species in this megadiverse region. Our findings suggest that river systems likely influence Amazonian amphibian species composition due to biogeographic history, emphasising the need for robust taxonomic and spatial databases. This study, therefore, contributes a valuable large-scale dataset for Amazonian amphibians, guiding future research and strategies for amphibian conservation.

In the Colombian Amazon region, agricultural and livestock activities lead to changes in land use, transforming complex and heterogeneous natural landscapes into landscapes characterized by a matrix of pastures and forest fragments with low connectivity. These agroforestry landscapes play a crucial role in biodiversity conservation and the carbon cycle. The objective of this research was to determine the influence of landscape structure and spatial configuration in cacao-based agroforestry systems (SAFc) and silvopastoral systems (SSP) on carbon storage in the Colombian Amazon. The study was conducted across eight mosaics of rural production landscapes in the Amazon region, each consisting of a 1 km² grid where vegetation covers were classified, and landscape metrics were quantified. A total of 78 plots of 0.1 ha were established in 44 cover patches within the SAFc and SSP mosaics, and dasometric variables were measured to inventory carbon deposits in aboveground biomass, root biomass, litter, and herbaceous vegetation. It was estimated that, in the Colombian Amazon, the studied SAFc and SSP systems store an average of 15.20 Mg C ha ‐ 1 in their biomass. Carbon storage was positively correlated with landscape aggregation metrics and spatial configuration within the system mosaics. Mosaics with patches of symmetrical shapes and lower irregularity, exhibiting greater contiguity, showed higher biomass and carbon storage. Therefore, productive landscapes with complex and connected mosaics enhance the provision of regulatory ecosystem services through carbon storage. Restoration efforts in fragmented areas should be managed at the landscape level by expanding the area of planting patches, establishing patches with regular geometric configurations, and improving connectivity among patches of the same type.

Inter-relationships among mosquito vectors, Plasmodium parasites, human ecology, and biotic and abiotic factors, drive malaria risk. Specifically, rural landscapes shaped by human activities have a great potential to increase the abundance of malaria vectors, putting many vulnerable people at risk. Understanding at which point the abundance of vectors increases in the landscape can help to design policies and interventions for effective and sustainable control. Using a dataset of adult female mosquitoes collected at 79 sites in malaria endemic areas in the Brazilian Amazon, this study aimed to (1) verify the association among forest cover percentage (PLAND), forest edge density (ED), and variation in mosquito diversity; and to (2) test the hypothesis of an association between landscape structure (i.e., PLAND and ED) and Nyssorhynchus darlingi (Root) dominance. Mosquito collections were performed employing human landing catch (HLC) (peridomestic habitat) and Shannon trap combined with HLC (forest fringe habitat). Nyssorhynchus darlingi abundance was used as the response variable in a generalized linear mixed model, and the Shannon diversity index (H’) of the Culicidae community, PLAND, and the distance house-water drainage were used as predictors. Three ED categories were also used as random effects. A path analysis was used to understand comparative strengths of direct and indirect relationships among Amazon vegetation classes, Culicidae community, and Ny . darlingi abundance. Our results demonstrate that Ny . darlingi is negatively affected by H´ and PLAND of peridomestic habitat, and that increasing these variables (one-unit value at β 0 = 768) leads to a decrease of 226 ( P < 0.001) and 533 ( P = 0.003) individuals, respectively. At the forest fringe, a similar result was found for H’ (β 1 = -218; P < 0.001) and PLAND (β 1 = -337; P = 0.04). Anthropogenic changes in the Amazon vegetation classes decreased mosquito biodiversity, leading to increased Ny . darlingi abundance. Changes in landscape structure, specifically decreases in PLAND and increases in ED, led to Ny . darlingi becoming the dominant species, increasing malaria risk. Ecological mechanisms involving changes in landscape and mosquito species composition can help to understand changes in the epidemiology of malaria.

The transition from the Andes to the Amazon lowland hosts a high biodiversity and currently is facing several anthropogenic activities, including hydropower infrastructure projects. Little is known about the geomorphology of the Andean gorges, rivers and the interaction with the fish diversity upstream and downstream of gorges. The Marañón River is a major river that connects the Andes to the Amazon lowland and it carries 40% of the sediment load arriving to Brazil. The Santiago River is the last tributary into the Marañón River before the last gorge (Manseriche). Current plans for hydropower reservoirs include the construction of several dams along the Marañón River, being the largest with a 4,500 MW capacity at the Manseriche Gorge (MG). This study seeks to characterize the baseline processes of the hydrogeomorphology and fish diversity. Results show that the Santiago River is under transitional morphodynamic regime while the Marañón River is a fully developed anabranching river. This study reveals a clear difference in fish species richness and abundance between the upstream and downstream regions of the MG, with some species only found in specific regions. The MG acts as a natural boundary condition for the hydrogeomorphology and fish diversity. If the hydropower dam at MG was built, the reservoir in the upstream reach will produce the Santiago River to disappear and sedimentation to occur, consequently modifying sediment transport boundary conditions for the lower Marañón River. Downstream of the potential dam incision will occur, reducing lateral connectivity, particularly at sites where unique species were found. Plain Language Summary The Manseriche Gorge located at the transition from the Andes to the Amazon lowland imposes natural boundary conditions for hydrogeomorphology and fish diversity. If a hydropower dam is built at the Manseriche Gorge, several impacts will be observed such as the disappearance of tributary Santiago River, geomorphic and fish diversity alterations between upstream and downstream regions. Key Points Meandering and anabranching rivers are found along the transition from the Andes to the Amazon lowland The Manseriche Gorge acts as a natural boundary condition for hydrogeomorphology and fish diversity If the Manseriche hydropower dam was built, the Santiago River will disappear, and river connectivity and sediment supply to the Amazon lowland will be impacted

Wetlands perform many essential ecosystem services—carbon storage, flood control, maintenance of biodiversity, fish production, and aquifer recharge, among others—services that have increasingly important global consequences. Like biodiversity hotspots and frontier forests, the world's largest wetlands are now mapped and described by an international team of scientists, highlighting their conservation importance at the global scale. We explore current understanding of some ecosystem services wetlands provide. We selected four of these wetlands (the largest peatland, West Siberian Lowland; the largest floodplain, Amazon River Basin; the least-known wetland, Congo River Basin; and the most heavily developed wetland, Mississippi River Basin), and we illustrate their diversity, emphasizing values and lessons for thinking big in terms of conservation goals. Recognizing the global significance of these wetlands is an important first step toward forging global conservation solutions. Each of the world's largest wetlands requires a basinwide sustainable management strategy built on new institutional frameworks—at international, national, and regional levels—to ensure provision of their vital services.

Climate change is affecting biodiversity and ecosystem function worldwide, and the lowland tropics are of special concern because organisms living in this region experience temperatures that are close to their upper thermal limits. However, it remains unclear how and whether tropical lowland species will be able to cope with the predicted pace of climate warming. Additionally, there is growing interest in examining how quickly thermal physiological traits have evolved across taxa, and whether thermal physiological traits are evolutionarily conserved or labile. We measured critical thermal maximum (CTmax) and minimum (CTmin) in 56 species of lowland Amazonian frogs to determine the extent of phylogenetic conservatism in tolerance to heat and cold, and to predict species' vulnerability to climate change. The species we studied live in sympatry and represent ~65% of the known alpha diversity at our study site. Given that critical thermal limits may have evolved differently in response to different temperature constraints, we tested whether CTmax and CTmin exhibit different rates of evolutionary change. Measuring both critical thermal traits allowed us to estimate species' thermal breadth and infer their potential to respond to abrupt changes in temperature (warming and cooling). Additionally, we assessed the contribution of life history traits and found that both critical thermal traits were correlated with species' body size and microhabitat use. Specifically, small direct-developing frogs in the Strabomantidae family appear to be at highest risk of thermal stress while tree frogs (Hylidae) and narrow mouthed frogs (Microhylidae) tolerate higher temperatures. While CTmax and CTmin had considerable variation within and among families, both critical thermal traits exhibited similar rates of evolutionary change. Our results suggest that 4% of lowland rainforest frogs assessed will experience temperatures exceeding their CTmax, 25% might be moderately affected and 70% are unlikely to experience pronounced heat stress under a hypothetical 3°C temperature increase.