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Abstract We describe the geographical variation in tree species composition across Amazonian forests and show how environmental conditions are associated with species turnover. Our analyses are based on 2023 forest inventory plots (1 ha) that provide abundance data for a total of 5188 tree species. Within-plot species composition reflected both local environmental conditions (especially soil nutrients and hydrology) and geographical regions. A broader-scale view of species turnover was obtained by interpolating the relative tree species abundances over Amazonia into 47,441 0.1-degree grid cells. Two main dimensions of spatial change in tree species composition were identified. The first was a gradient between western Amazonia at the Andean forelands (with young geology and relatively nutrient-rich soils) and central–eastern Amazonia associated with the Guiana and Brazilian Shields (with more ancient geology and poor soils). The second gradient was between the wet forests of the northwest and the drier forests in southern Amazonia. Isolines linking cells of similar composition crossed major Amazonian rivers, suggesting that tree species distributions are not limited by rivers. Even though some areas of relatively sharp species turnover were identified, mostly the tree species composition changed gradually over large extents, which does not support delimiting clear discrete biogeographic regions within Amazonia.

Abstract The fire crises in the Amazon continues to increase the risk of large-scale forest dieback, threatening regional biodiversity and global climate. This issue gained international attention in 2019 when fires in the Brazilian Amazon led to a fire ban imposition. Despite the uncertainty of its impact, the fire ban was reenacted in subsequent years. Here we assess the effectiveness of each fire ban by comparing observed fire counts with climate-driven predictions of fire for 2019–2021. While the 2019 ban likely reduced the number of fires to expected levels, it was largely ineffective in the years that followed. Four years later in 2023 under a different political dynamic, the Brazilian Amazon faced another fire crisis. Resolving this recurrent issue requires interventions that target the underlying causes of fire and extend beyond emergency measures, including long-term strategies focused on landscape management, public awareness and education, and engagement with local communities and stakeholders.

The Brazilian Amazon is one of Earth’s most biodiverse and ecologically important regions. However, research investments for biodiversity in the biome are disproportionately low compared with other regions of Brazil. In 2022, the Amazon received 13% of master's, doctoral and postdoctoral scholarships and hosted 11% of all researchers working in biodiversity postgraduate programs. Amazonian institutions received approximately 10% of all federal budget spent on grants and scholarships and about 23% of all resources destined to support long-term ecological sites. The cities of Manaus and Belém concentrate about 90% of all grants and scholarships available for the entire region. Despite per capita research investment in the Amazon being equal to or better than that available for the more economically developed regions of Brazil, the distribution of resources by area is highly unequal. Increasing research funding for the Amazon region requires differential input by federal agencies and more transnational collaborations and integration between Amazonian programs and international funds.

Acoustic monitoring has proven to be an effective tool for monitoring biotic soundscapes in the marine, terrestrial, and aquatic realms. Recently it has been suggested that it could also be an effective method for monitoring soil soundscapes, but has been used in very few studies, primarily in temperate and polar regions.We present the first study of soil soundscapes using passive acoustic monitoring in tropical forests, using a novel analytical pipeline allowing for the use of in-situ recording of soundscapes with minimal soil disturbance. We found significant differences in acoustic index values between burnt and unburnt forests and the first indications of a diel cycle in soil soundscapes.These promising results and methodological advances highlight the potential of passive acoustic monitoring for large-scale and long-term monitoring of soil biodiversity. We use the results to discuss research priorities, including relating soil biophony to community structure and ecosystem function, and the use of appropriate hardware and analytical techniques.

Wildfires associated with land-use and climate change have considered a key driver to the Amazon forest collapse. However, achieving a detailed understanding of how human-related disturbances impact forest successional trajectories needs comprehensive information spanning forest strata. Here, we investigate the impact of recurrent wildfires on forest structure, species diversity, and composition, making a comprehensive assessment of the regenerating, understory, and canopy tree communities in a sustainable use reserve in the eastern Amazon. Plant communities were described across 16 forest stands (old-growth, burned once and twice) sampling a total of 3620 individuals and 326 tree and palm species. Wildfires affected all attributes of forest structure. Aboveground biomass decreased by 44% in forest burned once, and 71% in twice-burned forest stands. Forest canopy was the most affected strata after the second fire, with a 44%-decrease compared to unburned forest. The same pattern emerged for basal area, which decreased by an average of 27.5% after the first fire and 53.8% following the second fire event. Overall, plant communities experienced a 50%-loss of species richness after two fires, including both dominant and rare species. Plant communities also became more dissimilar as fire events accumulated, with 58%–61% increase in species dissimilarity following two fires events. As wildfires reoccured, the old-growth forests of our focal landscape were converted into a mosaic of regenerating forest stands dominated by local short-lived pioneers (i.e. low-biomass early-regenerating forest stands) and a few tree species less sensitive to fire. Our findings highlight the urgent need to secure a resilient future for Amazonian forests with actions needed to support local livelihoods whilst reducing the prevalence of ignitions sources and allowing forest recovery.