The study tested whether DNA deposited or regurgitated by carrion flies could support surveys of terrestrial vertebrate diversity without directly observing or capturing animals. It also examined two ways to pool fly samples for sequencing and a field collection method designed to reduce the time required to survey large numbers of locations.

Sampling took place at Los Amigos Biological Station in the Madre de Dios region of the western Amazon, where the landscape includes old-growth terra firme forest, floodplain forest, dense stands of Guadua bamboo and Mauritia flexosa palm swamps. The researchers collected flies at 24 locations along six trail segments, three in floodplain habitat and three in terra firme habitat, over three days.

At each site, the team netted 10 flies directly from a white plastic grocery bag loosely tied around an open bag of rotting pork. Each fly was placed in a sterile 1.5- or 2-milliliter tube. After 3–5 hours at ambient temperature to allow flies to regurgitate or deposit vertebrate DNA, the flies were removed and preserved in 90% ethanol for morphological identification. The remaining tubes were dried with silica gel, stored at minus 20 degrees Celsius and later transferred to Utah State University, where they were held at minus 70 degrees Celsius. Because carrion flies were often difficult to identify beyond family level, the most common families were Calliphoridae, Sarcophagidae, Mesembrinellidae and Tachinidae.

In the laboratory, direct PCR lysis buffer and proteinase K were added to the tubes, followed by vortexing, incubation and heat treatment. The resulting solution was used directly as the PCR template, without macerating whole flies, dissecting their digestive tracts, or formally extracting and purifying DNA. The PCR targeted an approximately 138-base-pair fragment of the mitochondrial 16S rRNA gene and included blocking primers for human and domestic pig DNA. The authors noted that environmental DNA extraction kits typically cost US$3–8 per sample and that extracting 24 samples commonly takes 2–4 hours, although the study did not directly compare extraction-free PCR with conventional extraction.

Following quality filtering, denoising and chimera removal, the individual-fly and template-pool libraries retained 2,547,579 reads, while the PCR-product-pool library retained 3,086,005 reads. The researchers used BLAST and a naïve Bayes classifier to assign operational taxonomic units, supplementing uncertain assignments with local expertise and a published species checklist. After human and domestic-species sequences, the bobcat positive control and sequences that could not be assigned to family level were removed, 40 operational taxonomic units representing 31 wild vertebrate taxa remained. These included 27 mammalian taxa and four anurans, although 26 mammalian taxa were assigned to species known from the study area, three only to genus and two only to family. Two family-level assignments were designated presumed species based on local fauna knowledge and reference-sequence limitations.

Vertebrate DNA was recovered from 44.2% of individual flies, and some flies carried DNA from several vertebrates: 63 contained one taxon, 31 contained two, 10 contained three, one contained four and one contained five. Black spider monkey was detected in 40 of 240 flies, Bolivian squirrel monkey in 31 and lowland tapir in 14. The researchers described the eastern pygmy marmoset detection as uncertain because the species had not been observed at the study site, the top BLAST match was 93.4% to a related species and the naïve Bayes classifier supported only a genus-level assignment. They proposed DNA from a dead marmoset drifting downriver as one possible explanation for its detection in 10 flies, not a confirmed cause. A white-lipped peccary assignment was also inferred from local context after both classifiers produced a problematic match to Chacoan peccary, while a tayra assignment was inferred from a mustelid-level classification and local fauna knowledge.

The pooling comparison showed substantial differences between approaches. Template pooling, which combined lysis-buffer templates before the initial PCR, detected a mean of 2.25 vertebrate species per site, compared with 4.96 from individually sequenced flies, and reproduced the individual-fly species list at only one of 24 sites. PCR-product pooling, in which individual flies were first amplified and their products combined before indexing, detected a mean of 5.04 species per site and 29 species overall, the same total as the individual-fly analysis. Rarefying the PCR-product pools to the template-pool read depth changed only two site-level detections, indicating that sequencing depth alone did not explain the difference between the pooling methods.

The findings show that extraction-free carrion-fly iDNA can recover a broad range of rainforest vertebrates, including arboreal primates, at one Peruvian research site while reducing laboratory processing relative to maceration or digestive-tract extraction. Post-PCR pooling also closely reproduced individual-fly detections in this setting and may reduce sequencing costs. The study was limited to 240 flies from one site over three days, and capture rates may vary with location, weather, season and day. Taxonomic precision was constrained by the short 16S marker and incomplete reference sequences, while the absence of a direct comparison with formal DNA extraction prevents claims that the workflows are equivalent in every setting.

Subject of Research: Evaluation of extraction-free carrion-fly iDNA metabarcoding for surveying rainforest mammals

Article Title: An efficient iDNA method for surveying rainforest mammals with carrion flies

Article References: Rodgers, T. W., Basto, A., Castro, R., Groves, E. M. R., Xu, C. C. Y., Hernández, E., Mock, K. E., & Forsyth, A. (2026). An efficient iDNA method for surveying rainforest mammals with carrion flies. Metabarcoding and Metagenomics, 10, Article e174834. https://doi.org/10.3897/mbmg.10.174834

Image Credits: AI Generated

DOI: 10.3897/mbmg.10.174834

Keywords: carrion flies, invertebrate-derived DNA, environmental DNA, mammal surveys, Amazon rainforest, direct PCR, DNA metabarcoding, sample pooling, biodiversity monitoring, 16S rRNA, efficient, iDNA

The study examined nocturnal observations from the Amazon Tall Tower Observatory, or ATTO, in the central Amazon. Measurements were collected from 8 to 19 August 2022, while the nights of 20 and 21 August were excluded because several required variables, including longwave radiation and carbon dioxide flux observations, were unavailable. The network combined the 325 m ATTO tall tower with an 81 m Instant tower positioned 670 m away. Sensors at 14 height levels measured atmospheric variables, trace gases and turbulent fluxes, which were calculated at 30-minute intervals and corrected for outliers, temporal trends, wind-field rotation, time lags, spectral losses, crosswind effects and density fluctuations. The within-canopy measurements represented dense forest, whereas the tall tower stood in a more disturbed, open-forest environment. The researchers defined the aerodynamic canopy top as 32 m and treated the period from 18:00 to 06:00 local time as nocturnal.

To estimate the height of the nocturnal boundary layer, the authors applied five criteria based on vertical profiles of potential temperature, carbon dioxide, horizontal wind speed, gradient Richardson number and turbulent kinetic energy. Because observations were available at discrete heights, second-order logarithmic functions were fitted to the temperature, carbon dioxide and wind profiles, while Richardson number and turbulent kinetic energy were linearly interpolated. Across all methods, estimated heights ranged from 74 to 298 m, and the mean across the five criteria generally remained between 142 and 164 m during the night. The temperature-based estimate averaged 150 ± 27.1 m, the carbon-dioxide estimate 145 ± 42.2 m, and the wind-based estimate 156 ± 46.5 m. The Richardson-number method averaged 134 ± 29.5 m, whereas the turbulent-kinetic-energy method averaged 193 ± 50.9 m; the latter could be applied in only about 20% of the analyzed hours.

Wind conditions contributed to the variation among the height estimates. Weak nocturnal low-level jets occurred during the nights of 12–13 and 17–18 August, with maximum wind speeds of 5.5 m s−1. These nights had low-level jet nose heights between 80 and 100 m, wind speeds no greater than 3.0 m s−1 at the top of the tower and shallow boundary layers no higher than 135 m. On nights with nearly linear vertical wind profiles, including 13–17 August, wind-based boundary-layer estimates were at least 167 m. The overall results were consistent with previous ATTO studies, which reported nocturnal boundary-layer heights from 81 to 247 m. Differences were expected because each criterion responds to a different physical process. The study suggests that gradient-based approaches may provide useful estimates where detailed vertical turbulence measurements are unavailable, while noting that elevated turbulent layers can complicate the Richardson-number and turbulent-kinetic-energy methods.

The vertical structure evolved in opposing directions within and above the canopy. At the canopy-atmosphere interface, between 25 and 81 m, the potential-temperature gradient increased from 0.040 to 0.046 K m−1 through the night, while the carbon-dioxide gradient strengthened from −0.09 to −0.51 ppm m−1. Below the canopy, between 5 and 25 m, the temperature gradient decreased from 0.067 to 0.015 K m−1 and the carbon-dioxide gradient increased from −1.77 to −0.69 ppm m−1. Air above the forest therefore became more strongly stratified as the night progressed, while air within the canopy became better mixed. The authors associated the canopy mixing with a locally cold layer in the dense crown, roughly between 15 and 30 m, which can promote sinking motions. Turbulence observations in selected periods were consistent with downward movement of cold air within the canopy.

To distinguish the idealized stability regimes, the researchers applied six criteria involving potential temperature, carbon dioxide, wind speed, Richardson number, turbulent kinetic energy and friction velocity. Only eight hours, distributed across four nights with two consecutive hours per night, satisfied all six criteria for either regime. The mean boundary-layer height in the selected strongly stable profiles was 133 m, compared with 165 m in the weakly stable profiles. Between 25 and 50 m, the strongly stable regime contained a 2.08 K temperature increase, compared with 1.29 K in the weakly stable regime. The carbon-dioxide gradient between 38 and 79 m was −21.8 ppm in strongly stable profiles and −5.5 ppm in weakly stable profiles. Above roughly 200 m, differences in turbulent kinetic energy, Richardson number and friction velocity largely disappeared, suggesting that the regimes’ turbulent differences did not substantially affect the residual layer.

Budget calculations showed how mechanical mixing and buoyancy produced the contrasting regimes. In the weakly stable case, shear production at the canopy top was 6.20 × 10−3 ± 2.05 × 10−3 m2 s−3, far larger than the strongly stable value of 0.16 × 10−3 ± 0.52 × 10−3 m2 s−3. Buoyant consumption was −1.70 × 10−3 ± 0.94 × 10−3 m2 s−3 in the weakly stable regime and −0.30 × 10−3 ± 0.31 × 10−3 m2 s−3 in the strongly stable regime. Dissipation was also greater in the weakly stable case, at −4.69 × 10−3 ± 0.25 × 10−3 m2 s−3, compared with −0.43 × 10−3 ± 0.44 × 10−3 m2 s−3 in the strongly stable case. The turbulent-kinetic-energy tendency itself was 10 to 100 times smaller than the individual budget terms. These observations support a decoupled canopy beneath the stable layer during strongly stable conditions and a coupled, shear-mixed canopy during weakly stable conditions.

The heat budget quantified differences in exchange across the interface. Turbulent heat-flux divergence at the canopy top was −3.62 ± 1.54 K h−1 in weakly stable periods and −1.23 ± 0.79 K h−1 in strongly stable periods, consistent with stronger mechanical mixing in the former. The atmospheric longwave cooling rate at the canopy top was −0.24 ± 0.35 K h−1 in weakly stable conditions and −0.35 ± 0.02 K h−1 in strongly stable conditions. Cloud cover may have reduced cooling during two weakly stable periods. Because longwave radiation was measured at only one height, the cooling rate was estimated with the RTE + RRTMGP radiative-transfer model driven by downscaled ERA5 temperature and moisture profiles. Comparisons at 75 m showed an absolute mean difference of 6.92 W m−2 and a standard error of 3.90 W m−2. The model-based estimate nevertheless introduced additional uncertainty, and the heat-budget residual remained substantial.

Carbon dioxide transport was similarly sensitive to canopy-atmosphere coupling. At the canopy top, turbulent carbon-dioxide transport averaged 33.94 ± 37.45 ppm h−1 in weakly stable periods and 23.39 ± 9.54 ppm h−1 in strongly stable periods, although the weakly stable estimate was much more variable. At 50 m, the mean nocturnal carbon-dioxide flux was 3.82 µmol m−2 s−1 during weakly stable conditions, with a maximum of 6.38 µmol m−2 s−1. In the decoupled strongly stable regime, the average was only 0.16 µmol m−2 s−1. Weakly stable mixing transported carbon-dioxide-rich air upward from the canopy, while strong stability inhibited that exchange and favored accumulation beneath the forest crown. The simplified carbon-dioxide budget omitted horizontal advection and other terms, and an estimated horizontal gradient could account for much of the remaining negative residual.

The findings are limited to one two-week measurement period in the 2022 dry season at a single central-Amazon site, where topography and heterogeneous forest structure limit direct extrapolation to the wider basin. Wet-season clouds, precipitation and turbulent activity differ from those observed here, while one year of measurements cannot characterize interannual variability. The budgets also assumed horizontal homogeneity and negligible subsidence, and their residuals included observational uncertainty, advection, pressure effects and other unmeasured processes. Nevertheless, the results provide an observational benchmark for testing nocturnal parameterizations. The authors call for schemes that explicitly represent tall, multilayer canopies, intermittent turbulent bursts and stability-dependent coupling, supported by measurements at intervals of five minutes or less and by high-resolution observations of the cooling layer between 20 and 30 m.

Subject of Research: Observation-driven analysis of Amazonian dry-season nocturnal boundary-layer dynamics and carbon dioxide transport

Article Title: From prototypical regimes to observed complex dynamics and CO2 transport in the Amazonian nocturnal boundary layer

Article References: Huitema, A. C., de Feiter, V. S., González-Armas, R., Hartogensis, O. K., van Asperen, H., Dias-Júnior, C. Q., & Vilà-Guerau de Arellano, J. (2026). From prototypical regimes to observed complex dynamics and CO 2 transport in the Amazonian nocturnal boundary layer. Atmospheric Chemistry and Physics, 26(20), 14725-14747. https://doi.org/10.5194/acp-26-14725-2026

Image Credits: AI Generated

DOI: 10.5194/acp-26-14725-2026

Keywords: Amazon rainforest, nocturnal boundary layer, carbon dioxide transport, canopy-atmosphere exchange, turbulent kinetic energy, atmospheric stability, Amazon Tall Tower Observatory, climate models, dry-season observations, intermittent turbulence, prototypical, regimes

The study, led by mycologist João Araújo of the New York Botanical Garden and colleagues, focused on the Adolpho Ducke Reserve, a 100-square-kilometer patch of primary rainforest embedded within the city of Manaus. The team surveyed the reserve’s understory, documenting ants that had been killed by Ophiocordyceps and noting exactly where the fungal spore-bearing structures, called ascomata, emerged from the victims’ bodies. They then collected samples of the mosses and liverworts, collectively known as bryophytes, growing at these sites, along with additional bryophyte samples from elsewhere in the reserve.

Back in the laboratory, the researchers used DNA metabarcoding to identify the fungi living within the bryophyte tissues. They amplified a genetic marker called TEF1-alpha and sequenced the resulting DNA using Oxford Nanopore technology, a portable sequencing platform capable of reading long DNA fragments. The analysis revealed a startling diversity of fungal life: across all the bryophyte samples, the team detected 2,677 distinct fungal taxa, spanning a wide range of ecological roles from decomposers to plant pathogens.

Crucially, the most abundant group of fungi detected within the mosses was Ophiocordyceps itself. The researchers found DNA of these zombie-ant fungi in nearly every bryophyte sample, including mosses growing far from any infected ants. The team identified several species known to infect ants in the region, including Ophiocordyceps camponoti-renggeri, Ophiocordyceps kniphofioides, and Ophiocordyceps monacidis, among others. The detection of these species within moss tissues, rather than merely on their surfaces, suggests the fungi were living as endophytes within the plants.

The findings build on years of fieldwork by Araújo and colleagues, who had previously noticed that certain ant-infecting Ophiocordyceps species in the Amazon seemed to preferentially manipulate their victims into biting specific plants before dying. Infected Camponotus ants, for example, were repeatedly found locked in a death grip on moss carpets, particularly those of the moss Octoblepharum, with the fungal ascomata emerging from their bodies. Other species showed similar affinities for bromeliads, palm trees, and other understory plants. These observations hinted that the fungi might have some physiological connection to the plants their victims died on, but the mechanism remained unknown.

The new study provides the first direct evidence that Ophiocordyceps can live within bryophyte tissues in the Amazon. The researchers propose that the fungi may use mosses as a refuge or reservoir, persisting in the environment between ant infections. This hidden endophytic stage could serve several functions: it might allow the fungi to survive unfavorable conditions, such as dry seasons when ant hosts are scarce; it could provide a substrate for the fungi to reproduce sexually, which some species require to complete their life cycle; or it might even play a role in the fungi’s dispersal, with spores or fragments carried away by rain, wind, or animals.

The idea that Ophiocordyceps has a plant-associated stage is not entirely new. Previous studies in Asia had found that the caterpillar fungus Ophiocordyceps sinensis, which infects ghost moth larvae on the Tibetan Plateau, also lives within the tissues of alpine plants. And researchers had detected DNA of Ophiocordyceps within mosses in temperate regions of North America and Europe. But the Amazon study is the first to systematically document this phenomenon in the tropics, where the diversity of both fungi and bryophytes is far greater.

The researchers also note that the endophytic stage may explain some puzzling aspects of the zombie-ant fungi’s ecology. For example, the fungi are known to be highly host-specific, with each species typically infecting only one or a few ant species. Yet the fungi must also find their hosts in a complex, three-dimensional forest environment. If the fungi persist within bryophytes, which form extensive carpets on the forest floor and on tree trunks, they may be able to wait in ambush for passing ants, increasing their chances of infection. The fungi’s preference for certain plants, such as Octoblepharum mosses, may reflect the microhabitat preferences of their ant hosts, which often forage on these substrates.

The study also raises questions about the evolutionary history of the zombie-ant fungi. The researchers suggest that the endophytic lifestyle may be an ancestral trait, retained from the fungi’s origins as plant-associated organisms. Molecular studies have shown that Ophiocordyceps is closely related to other fungi that live within plants, and the ability to colonize plant tissues may have provided the evolutionary stepping stone for the fungi’s later colonization of insects. If so, the zombie-ant fungi’s famous mind-control abilities may have evolved from a more mundane capacity to live within plants.

The findings have implications for conservation as well. The Adolpho Ducke Reserve is one of the few remaining patches of primary rainforest within Manaus, and it faces pressures from urbanization and climate change. If Ophiocordyceps depends on bryophytes for part of its life cycle, then the conservation of these fungi may require the protection of the mosses and liverworts they inhabit. Bryophytes are sensitive to environmental changes, including drying and pollution, and their decline could have cascading effects on the fungi that depend on them.

The researchers plan to continue their work in the Amazon, investigating the physiological interactions between Ophiocordyceps and its bryophyte hosts. They hope to determine whether the fungi receive nutrients from the plants, whether they reproduce within the bryophyte tissues, and whether the endophytic stage is essential for the fungi’s survival. They also plan to survey other regions of the Amazon to see how widespread the phenomenon is. For now, the study stands as a vivid reminder that even the most famous parasites in the natural world may have hidden lives waiting to be discovered, living quietly within the green carpets of the rainforest floor.

Subject of Research: Ecology and life cycle of Ophiocordyceps fungi in Amazonian bryophytes

Article Title: Metabarcoding reveals a hidden endophytic stage of the 'zombie-ant' fungus in Amazonian mosses

Article References: Alves-Júnior, T., Araújo, J. P. M. D., Góes-Neto, A., Mendes-Pereira, T., & Zartman, C. E. (2026). Metabarcoding reveals a hidden endophytic stage of the 'zombie-ant' fungus in Amazonian mosses. IMA Fungus, 17, Article e196998. https://doi.org/10.3897/imafungus.17.196998

Image Credits: AI Generated

DOI: 10.3897/imafungus.17.196998

Keywords: mycology, parasitology, entomology, bryophytes, Amazon rainforest, symbiosis, fungi, Metabarcoding, reveals, hidden, endophytic, stage

Ubristes belongs to the hoverfly family Syrphidae, but it is no ordinary flower visitor. The genus sits within the subfamily Microdontinae, an unusual lineage whose larvae are known to live inside ant nests. Adult microdontines are among the rarest and most poorly understood hoverflies in the tropics, with most species known from only one or two specimens. What makes Ubristes particularly striking is its strong resemblance to Neotropical stingless bees of the genus Trigona. The mimicry is built from a combination of long antennae, thickened hind legs armed with corbicula-like brushes on the tibiae, and a matching abdominal shape and colouration, a package that allows the fly to pass among the bees it imitates.

The new species was collected by hand-net along rainforest trails near Grand Selva Lodge and the Campo Cocha Community, at elevations of roughly 500 to 590 metres. The holotype and two paratype males were captured in September 2023 and September 2024, and an additional historical specimen from near Tena, collected in 1976 and held at the Natural History Museum in London, was also studied. The specimens are deposited in the Instituto Nacional de Biodiversidad in Quito, the Natural History Museum in London, and Museum Koenig in Bonn. Observers noted that the flies flew very low, close to the ground, with an erratic, zig-zag-like flight quite unlike the typical flight of most hoverflies, which may partly explain why the species had escaped detection for so long.

Morphologically, Ubristes mirabilissimus is a medium-sized to large hoverfly, measuring 12 to 14 millimetres in body length. Species of Ubristes are diagnosed by a scutellum without calcars and long, brush-like pilosity on the metatibia and metabasitarsomere, with hairs longer than the width of the tibia. Among the genera sharing this hind-leg pilosity, Ubristes alone bears a pair of lateral tubercles on the second abdominal segment at approximately half its length. The male genitalia are unique among all Microdontinae because of well-delimited, oval pits on both sides of the epandrium, structures named lateral fenestrae. These features, together with detailed differences in the cercus and surstylus, allowed the authors to separate the new species from its four known relatives.

What truly sets the new species apart, however, is its wing venation. In all previously described Ubristes species, the wing vein R4+5 carries a posterior appendix, a spur or additional vein extending into cell r4+5, a character also found in many other microdontine genera. In Ubristes mirabilissimus this appendix is entirely absent. As a consequence, the species would probably key out to the genus Hypselosyrphus in existing identification keys, since all Ubristes species differ from Hypselosyrphus and every other microdontine genus only by the presence of the lateral tubercles on tergite 2. The absence of the vein appendix, combined with the elongated abdomen, which is approximately 1.5 times as long as the head and thorax together, and the larger body size distinguishes the new species most notably from its closest relative, the black-bodied Ubristes flavitibia.

To document the species in full, the team applied a combination of classical and modern techniques. Male genitalia were dissected after softening the specimens in a wet chamber for 24 hours, then macerated in lactic acid at room temperature for another day before rinsing and storage in microvials with glycerine. Measurements were taken with an ocular micrometer in a stereo microscope, and high-quality images were produced through a Zeiss Stereo Discovery v12 microscope and processed by focus stacking with Axiovision software. A distribution map of all Ubristes species was drawn in Adobe Illustrator based on published locality information, with symbols placed by approximation because locality data for these rare flies is often imprecise.

The molecular component of the study marks a genuine milestone. One leg of each sequenced specimen was used for DNA extraction following established barcoding protocols, and the remnants were preserved and labelled as DNA voucher specimens. All new sequences were submitted to GenBank via the Barcode of Life Data System. The holotype and paratype males were successfully sequenced, and the resulting DNA barcodes are identical, constituting the first molecular data ever obtained for the genus Ubristes. A quick comparison against other sequences using BLAST showed that the new species’ barcodes share less than 85 percent similarity with other microdontine genera, underscoring how genetically distinct this lineage is and how much of the group’s diversity remains unsampled.

The known distribution of Ubristes mirabilissimus is confined to two localities in Napo Province, in the Amazonian part of Ecuador, approximately 35 kilometres apart. Both sites lie within lowland tropical rainforest, consistent with the ecology of the other Ubristes species, which appear to be rainforest inhabitants. The number of known localities per species across the entire genus is very low, two at maximum, so the true distribution patterns are undoubtedly very incomplete. Ecuador is now the second country from which two Ubristes species are recorded, as Ubristes ictericus was previously described from the same country.

Rarity or easy overcollection seems to be the norm for tropical Microdontinae. Besides the four specimens of the new species, only about ten Ubristes specimens are known to science in total: five of U. flavitibia, three of U. ictericus, one of U. jaguarinus, and one of U. rex. The authors suggest several possible explanations. Unlike most other hoverflies, for which visiting flowers is a characteristic habit, microdontines are rarely observed at flowers, so they escape the standard survey methods. Another possibility is an association with rare species of ants, or with ants that build their nests in forest canopies, keeping the adult flies out of reach. The larvae of Ubristes remain entirely unknown, although microdontine larvae are generally associated with ants.

The female of Ubristes mirabilissimus is unknown, and so is the male of Ubristes rex, raising the theoretical possibility that these two taxa could belong to the same species. The authors reject this on the basis of clear differences in wing venation, the absence versus presence of the spur on vein R4+5, and body colouration. For those Ubristes species where both sexes are known, namely U. flavitibia and U. ictericus, only minor differences in colour and morphology exist between males and females, so a similarly low degree of sexual dimorphism is expected in the two incompletely known species. With an identification key now provided for all five known Ubristes species, together with the first molecular data for the genus, the stage is set for future work to uncover more of the hidden diversity of these remarkable bee mimics in the Neotropical rainforest.

Subject of Research: Taxonomy and molecular characterization of a new stingless bee mimicking hoverfly species from the Ecuadorian Amazon

Article Title: Ubristes mirabilissimus sp. nov., a new stingless bee mimicking hoverfly from the Ecuadorian Amazon ( Diptera , Syrphidae , Microdontinae )

Article References: Reemer, M., & Mengual, X. (2026). Ubristes mirabilissimus sp. nov., a new stingless bee mimicking hoverfly from the Ecuadorian Amazon (Diptera, Syrphidae, Microdontinae). Evolutionary Systematics, 10(1), 47-54. https://doi.org/10.3897/evolsyst.10.185722

Image Credits: AI Generated

DOI: 10.3897/evolsyst.10.185722

Keywords: hoverflies, Syrphidae, Microdontinae, Ubristes, new species, Ecuador, Amazon rainforest, mimicry, DNA barcoding, taxonomy, mirabilissimus, stingless

The setting itself is remarkable. The reserve spans 737,088 hectares of federally protected forest bounded on the east by the Iriri River, a clear-water tributary of the Xingu. No roads or trails reach the study area; access requires roughly two days of navigation along the Xingu and Iriri rivers from Altamira. This remoteness has long kept botanists away, even though recent remote-sensing analyses based on airborne LiDAR data and deep learning had flagged the region as harboring extensive areas of high canopy palm cover. The new field survey confirms that prediction on the ground, and it does so with numbers that would impress any tropical ecologist.

Walking the transect on foot at roughly one kilometer per hour, at least two experienced observers censused a continuous twenty-meter-wide belt, partitioned into one hundred contiguous sampling units of twenty by fifty meters. In total they recorded 1,506 adult palm individuals belonging to eighteen taxa, seventeen identified to species level and one morphospecies to genus. Four species dominated overwhelmingly: Attalea speciosa with 527 individuals across 85 plots, Euterpe longibracteata with 267, Geonoma baculifera with 263, and Euterpe oleracea with 105. Together these four accounted for more than three-quarters of every palm counted. Species accumulation curves and multiple richness estimators, including Chao, Jackknife, and Bootstrap, converged on eighteen species, indicating that the sampling effort captured nearly the entire local palm flora.

Attalea speciosa, the babassu palm, reached an average density of 52.7 individuals per hectare and local peaks of 270 adult individuals per hectare within a single plot. Its hyperdominance is not merely a botanical curiosity. Palms can constitute up to a quarter of stems exceeding ten centimeters in diameter in some tropical forests, and biomass models developed specifically for palms suggest their carbon fixation capacity may be nearly a third higher than estimates based on dicotyledonous trees. In a region flagged by satellite for exceptional palm abundance, documenting which species dominate and where is directly relevant to understanding forest carbon dynamics in the eastern Amazon.

To understand why palms clustered where they did, the researchers extracted environmental data for the centroid of each sampling unit. From the TOPODATA digital elevation model, derived from Shuttle Radar Topography Mission data at thirty-meter resolution, they obtained altitude, slope, relief, exposure, and terrain shape. From HydroSHEDS they calculated the distance to the nearest perennial stream. And from CBERS-4A satellite imagery they derived the normalized difference vegetation index, or NDVI, a proxy for vegetation greenness and forest structure that ranged from 0.597 to 0.662 along the transect. Crucially, the team also recorded in the field the presence or absence of igarapés, the shallow, narrow, slow-moving streams typical of Amazonian environments that are generally invisible in satellite imagery.

The statistical architecture of the study was rigorous. A Redundancy Analysis linked community composition to the continuous environmental variables, with Variance Inflation Factors confirming no problematic multicollinearity. Species richness was modeled with a Gaussian General Linear Model for continuous predictors and analysis of variance for categorical ones, followed by Tukey’s Honestly Significant Difference tests for pairwise comparisons. For the six most abundant species, Bayesian regression models accommodated different response distributions, including zero-inflated count and presence-absence data, quantifying species-specific habitat associations with credible intervals rather than single point estimates.

The results revealed a striking division of labor among environmental factors. Community composition was significantly associated with NDVI, altitude, and distance to streams, which together explained 17.82 percent of the observed variation, with the first constrained axis accounting for 81.84 percent of the constrained variation. Species richness, by contrast, showed no significant association with any continuous variable but responded strongly to the presence of igarapés and to terrain shape. Plots containing igarapés had significantly higher richness than plots without them, with estimated marginal means of 2.07 versus 1.56 species per plot. Terrain shape mattered too: convex, water-divergent areas and concave, water-neutral areas supported higher richness than flat, water-convergent and flat, water-divergent terrains, and the categorical model explained fully half of the observed variation in richness.

The Bayesian models then exposed the ecological personalities of the dominant species. Attalea speciosa showed the strongest associations of all: its expected abundance decreased with increasing NDVI and was lower in plots containing igarapés, indicating a clear preference for relatively open forest patches away from streams. Geonoma baculifera and Euterpe oleracea displayed the opposite pattern, both positively associated with the presence of igarapés and substantially more abundant in riparian plots. Geonoma baculifera formed dense clusters reaching up to 630 individuals per hectare, comparable to densities reported for seasonally flooded sandy soils elsewhere in the eastern Amazon. Euterpe longibracteata responded more to terrain shape than to greenness, favoring flat water-neutral or convex water-convergent topographic positions. Models for the two Astrocaryum species showed lower explanatory power and broad credible intervals, warranting cautious interpretation.

The hyperdominance of Attalea speciosa carries a deeper historical resonance. In the neighboring Rio Iriri reserve on the opposite bank of the river, the same species was found hyperdominant and associated with historical forest disturbance, where archaeological evidence indicates that this disturbance dates to Indigenous occupation during the eighteenth century. The present-day dominance of babassu in the region may therefore reflect a long-term anthropogenic legacy rather than recent extractive activity, although in the newly surveyed area the relative contributions of natural disturbance regimes and historical human influence remain uncertain, and both may have contributed. This possibility ties the palm community to one of the most compelling narratives in Amazonian science: the recognition that many seemingly pristine forests bear the fingerprints of ancient human management.

The richness documented at RESEX Riozinho, seventeen identified species plus one morphospecies, exceeded that of the two other areas previously surveyed along the eastern margin of the Xingu Basin, where ten species were recorded in the Kayapó Indigenous Territory roughly 400 kilometers to the southwest and eleven near Altamira. This pattern fits the broader westward increase in palm diversity across Amazonia, associated with rising rainfall toward the center and west of the basin. Two widespread palms of the Xingu Basin, Socratea exorrhiza, the famous walking palm adapted to seasonally flooded soils through its stilt roots, and Oenocarpus bataua, long associated with Indigenous management and dispersal, both occurred at comparatively low local abundance, showing that regional hyperdominance is not necessarily mirrored at the plot scale. The occurrence of Iriartea deltoidea, among the most abundant Amazonian tree species despite having been recorded in relatively few floristic inventories, extends its documented distribution within the eastern Amazon.

What does this mean for conservation? Several palm species have been proposed as indicators or surrogates of biodiversity, and describing their local environmental associations may improve their application in conservation planning. The findings may also contribute to future ecological studies, restoration initiatives, and agroforestry projects involving native palms. Yet the researchers are careful about scope. Because these patterns were documented along a single continuous transect, they should be interpreted as spatial associations within the surveyed landscape rather than as general ecological relationships for the eastern Amazon. The relatively low proportion of variation in composition explained by the measured variables suggests that additional factors, such as edaphic properties and disturbance history, also shape the community.

Still, the broader lesson is unmistakable. In one of the least-studied corners of Pará, the architecture of the palm community is written in the language of streams, slopes, and forest greenness. Small watercourses that satellites cannot see turn out to matter more for palm diversity than the perennial rivers that they can, a finding that argues powerfully for the continued value of boots-on-the-ground botany in an age of remote sensing. As the Amazon faces intensifying pressures from deforestation corridors barely a hundred kilometers to the north and east, inventories like this one provide the floristic baselines against which all future change will be measured, and they remind us that the forest’s hidden kingdoms still await their cartographers.

Subject of Research: Palm community structure and its associations with topography, hydrography, and forest structure in the eastern Amazon

Article Title: Palm community structure in relation to topography, hydrography, and forest structure in the Iriri River Valley, eastern Amazon

Article References: Salm, R., von Schmalz, K. E., Ruz, E. H., de Souza, D. A., de Oliveira Jr, A. P., & Pereira, C. C. (2026). Palm community structure in relation to topography, hydrography, and forest structure in the Iriri River Valley, eastern Amazon. Neotropical Biology and Conservation, 21(4), 297-320. https://doi.org/10.3897/neotropical.21.e206551

Image Credits: AI Generated

DOI: 10.3897/neotropical.21.e206551

Keywords: Amazon, palm communities, topography, hydrography, NDVI, species distribution, Palm, community, structure, relation, forest, Iriri

Ozone is best known as a component of urban smog, but it is also a potent phytotoxin that costs global agriculture billions of dollars annually and suppresses the land carbon sink worldwide. Tropical forests are particularly exposed. The very traits that make them so productive, including dense canopies and high stomatal conductance, allow a large flux of ozone to enter leaves year-round. Recent experimental work has shown that tropical tree species are as susceptible to ozone damage as, or more susceptible than, many temperate species, meaning earlier studies that assumed lower sensitivity may have underestimated the problem. With the Amazon holding around 120 petagrams of carbon, even modest percentage losses in productivity carry global consequences for climate projections.

The research team employed the Joint UK Land Environment Simulator, JULES, a process-based land surface model that represents photosynthesis, stomatal behaviour, soil moisture dynamics and vegetation competition. Ozone concentrations were supplied by the UK Earth System Model, UKESM1, whose atmospheric chemistry scheme tracks the full oxidation cycles of ozone precursors including nitrogen oxides, carbon monoxide, methane and biogenic volatile organic compounds. The simulations spanned 1997 to 2024, a period punctuated by six major Amazon droughts, and were driven by observed meteorology from the CRU-JRA reanalysis, prescribed atmospheric carbon dioxide and annually varying crop and pasture fractions. By running paired simulations with and without ozone damage, the team isolated the carbon lost to the pollutant in every year of the record.

Validation of the model was a central concern. Simulated gross primary productivity reproduced the general interannual variability captured by two independent satellite products, Fluxsat and GOSIF, and the model’s tropospheric nitrogen dioxide columns matched observations from the OMI instrument on NASA’s Aura satellite, both in magnitude and spatial pattern during drought years. Because long-term surface ozone measurements in the Amazon remain scarce, the team also compared simulated variability against the TES satellite retrieval of lower-tropospheric ozone for 2005 to 2011, finding that the model reproduced interannual patterns with a coefficient of determination of 0.62, rising to 0.73 during August, the peak biomass burning season. The model had previously been evaluated against six Amazonian measurement sites and shown to capture spatial, seasonal and daily ozone variability.

The headline finding is a robust statistical relationship between fire activity and surface ozone. Across the 1997 to 2024 period, fire carbon emissions explained 72 percent of the year-to-year variance in simulated ozone concentrations, and the same linear relationship emerged independently in four additional Earth system models from the CMIP6 archive, despite their differing meteorology and chemistry schemes. Every major drought year except 2015 and 2023 showed above-average fire activity and elevated ozone, with 2024, the year of the most extreme drought and highest fire emissions in recent record, reaching unprecedented levels of both. This confirms that human-ignited fires, concentrated along the Arc of Deforestation where agricultural frontiers press into flammable degraded forest, are the dominant driver of ozone variability across the basin.

Quantifying the carbon consequences, the researchers found that the reduction in net annual carbon uptake caused by fire-related ozone damage equals 24 percent of direct fire carbon emissions, with an uncertainty range of 18 to 35 percent derived from observed variability in tropical tree ozone susceptibility. Put differently, for every tonne of carbon a fire sends directly into the atmosphere, an additional quarter of a tonne is effectively lost because ozone entering leaf stomata suppresses photosynthesis in surviving vegetation. The simulated interannual variability of this indirect loss was substantial, with a standard deviation of 38 teragrams of carbon per year and a total range of 129 teragrams across the study period. The authors caution that this should be read as an order-of-magnitude estimate, since uncertainties in stomatal representation and the ozone damage scheme itself remain unexplored.

A subtler and scientifically intriguing finding concerns the role of stomata, the microscopic pores through which plants both absorb carbon dioxide and take in ozone. Drought triggers stomatal closure, which can shield leaves from rising ozone concentrations, and rising atmospheric carbon dioxide plus warming-driven increases in vapour pressure deficit have produced a long-term declining trend in stomatal conductance across the Amazon. Sensitivity tests attributed this trend roughly equally to carbon dioxide effects and meteorological change. The result has been a gradual weakening of ozone damage over the past decade, with carbon dioxide increases alone avoiding approximately 2 teragrams of carbon loss per year. Yet this apparent protection is fragile. In 2024, record fire emissions overwhelmed the stomatal defence, producing significantly elevated ozone fluxes across the southern and south-western Amazon despite extensive stomatal limitation.

The regional anatomy of drought matters enormously. In the northern Amazon, drought produces only marginal ozone increases during the January to April dry season, and stomatal closure reduces ozone flux, yielding no statistically significant change in ozone damage. In the southern Amazon, by contrast, drought drives much stronger ozone increases during the July to October fire season, accompanied by a significant increase in ozone flux through stomata. During August, ozone damage in drought years reduced net primary productivity by an amount equal to half of the direct drought effect, and in individual years such as 2010 the ozone contribution exceeded the direct drought stress itself. The damage concentrates in the Arc of Deforestation, where almost all fires are human-initiated through clearing or agricultural escapes. The contrast between 2016, when low fire activity spared the region severe ozone damage, and 2024, when record burning erased any protection, illustrates how ignition, not drought alone, determines the outcome.

The study also raises an alarm for remote, previously untouched forest. Simulations of the 2005 and 2024 droughts show elevated ozone fluxes penetrating regions rarely exposed to pollution stress, and the authors hypothesise that vegetation lacking historical ozone exposure may prove especially sensitive. In 2024, forest disturbance from fire reached unprecedented scale even as deforestation rates declined, suggesting that degradation, not just clearance, now drives the fire-ozone-carbon cascade. Because the 2015/16 and 2023/24 droughts have both been partly attributed to anthropogenic climate forcing, and Earth system models project intensifying Amazonian drying through the twenty-first century, the authors argue that reducing deforestation must be paired with reducing forest degradation to cut drought-related fires and the ozone they generate.

The findings carry a clear message for carbon accounting and climate policy. Ozone damage is almost never included in national or global carbon budgets, yet it represents a substantial indirect emission pathway that amplifies the climate impact of every fire. The authors call for sustained ozone monitoring across the Amazon, particularly in remote regions, and for urgent development of more process-based representations of ozone effects on vegetation, including delayed damage, changes to respiration and carbon partitioning, and the sluggish stomatal responses observed in polluted air. As the climate continues to warm and droughts intensify, the invisible chemistry downwind of the flames may prove as consequential for the fate of the Amazon as the flames themselves.

Subject of Research: Fire-derived ground-level ozone damage to Amazon forest carbon uptake under extreme drought

Article Title: Fire-derived ozone intensifies carbon loss in Amazon forests under extreme droughts

Article References: Brown, F., Sitch, S., Folberth, G. A., Mercado, L. M., Cheesman, A. W., Barningham, S., Weber, J., Johnson, B., O’Sullivan, M., & Artaxo, P. (2026). Fire-derived ozone intensifies carbon loss in Amazon forests under extreme droughts. Communications Earth & Environment, 7(1), Article 790. https://doi.org/10.1038/s43247-026-04047-0

Image Credits: AI Generated

DOI: 10.1038/s43247-026-04047-0

Keywords: Amazon rainforest, ground-level ozone, wildfire emissions, drought, carbon cycle, stomatal conductance, land surface modelling, JULES, UKESM1, gross primary productivity, Arc of Deforestation, climate change

The drilling itself was an epic of endurance. Equipment was mobilized roughly 4,400 kilometers from Mariana in southeastern Brazil to the municipality of Rodrigues Alves, arriving in May 2023. Using a wireline diamond coring rig, the team began coring on 16 June 2023 with PQ tools producing cores 8.3 centimeters in diameter, progressively narrowing to HQ tools as depth increased. The original target was 2,000 meters, deep enough to reach the base of the Cenozoic fill, but the operation was halted at 923 meters after a cascade of setbacks. Alternating layers of unconsolidated sand and strongly cemented mudstone repeatedly defeated the engineers: casing had to be extended far deeper than planned at an added cost of about 150,000 US dollars, a casing string was dropped into the hole and had to be fished out, and at 750 meters the drill string became stuck by differential pressure and was ultimately cemented in place. When the borehole blocked at roughly 752 meters and two sidetrack attempts failed, the project’s executive committee chose to abandon the hole in December 2023 to preserve funds for a second site in the Marajó Basin. Even so, the team achieved 93 percent core recovery, an exceptional figure under such conditions.

What the core revealed surprised the sedimentologists. Apart from the uppermost 12 meters, the entire sequence belongs to a single lithostratigraphic unit, the Solimões Formation, dominated by feldspar-rich sands of Andean origin. The sediments record four facies associations: fining-upward channel and bar deposits up to 25 meters thick, cross-laminated fine sandstones, inclined heterolithic successions of sand and mud, and laminated claystones laid down on floodplains. Together they paint a picture of a vast, dynamic river system with migrating channels, exposed floodplains, and recurring soil formation, punctuated by paleosols bearing carbonate concretions and, in the deepest levels, gypsum crystals. Notably, the core contains no marine or brackish palynomorphs, weighing against long-standing hypotheses of marine transgressions or mega-lakes in the western Amazon during this interval and supporting instead a fluvial world akin to today’s great rivers and floodplain lakes.

The provenance story is unambiguous. Detrital zircon uranium-lead geochronology on sandstones, analyzed at rates of 300 grains per hour at the University of Arizona LaserChron Center, shows multi-modal age populations dominated by Permo-Triassic grains, with maximum depositional ages increasing steadily down-core: 5.8 plus or minus 0.21 million years at 178 meters, 7.8 at 300 meters, 8.6 at 497 meters, and 11.8 plus or minus 0.4 million years near the base at 863 meters. Heavy mineral assemblages rich in augite, hypersthene, and hornblende mirror those of the modern Amazon River channels, pointing to basic igneous rocks in the Andes as the dominant sediment source. Neodymium and strontium isotopes plot squarely within the field of eastern tropical Andean sediments, matching the suspended loads of the Solimões and Madeira rivers, the Amazon’s two great Andean tributaries. Feldspar-rich sands with low luminescence sensitivity quartz confirm immature, rapidly eroding Andean sources throughout most of the drilled section.

The pollen record may prove the core’s greatest gift to science. Of more than 1,800 palynomorph species identified so far, the assemblage differs markedly from Early to Middle Miocene floras recovered elsewhere in the western Amazon, such as at Contamana in Peru and in the Solimões Basin. Key biostratigraphic markers, including the first appearance datum of Cyatheacidites annulatus at 512 meters and the last appearance of Grimsdalea magnaclavata at 154 meters, indicate the upper 512 meters is no older than about 6 million years. Many of the dominant floral elements of the famous Pebas wetland system are rare or absent, suggesting the core samples a post-Pebas ecosystem that has rarely been studied because its sediments are seldom preserved. The flora is dominated by angiosperms and is highly diverse, with samples yielding up to 183 taxa in a single count of 745 grains, many represented by only one or two individuals, a pattern strikingly reminiscent of modern rainforest. Grasses, cycads, and conifers remain consistently low, offering no evidence of extensive savannas or climates significantly drier than today’s.

The uppermost 12 meters tell a different tale. Resting on a major erosional unconformity, these quartz-rich, mature sands contrast sharply with the feldspar-dominated sediments below. Luminescence dating, with quartz optically stimulated luminescence and feldspar post-infrared infrared stimulated luminescence protocols, indicates the sediments are older than roughly 200,000 years, likely older than 250,000 years, and the shift in composition suggests a fundamental reorganization of drainage: possibly the moment the Acre region was uplifted and disconnected from Andean sediment supply, giving rise to the modern watersheds of the Juruá and Purus rivers with headwaters in the elevated Fitzcarrald Arch.

The project also probed the deep biosphere and the carbon cycle. Real-time monitoring of drilling mud gas using the ICDP Online Gas Analysis system detected methane-rich zones at 250 to 380 and 420 to 588 meters, with stable carbon isotope values of methane ranging from minus 35 to minus 25 per mil, hinting at a mix of microbial and thermogenic sources. Pore-water isotopes, extruded from whole-round core samples with a hydraulic press, show a lower deuterium excess than local rainwater, consistent with water-rock interaction over long residence times. Laboratory incubations of sediment from 140 and 502 meters produced carbon dioxide but no methane after 22 days, leaving open whether the methane measured during drilling derives from an active microbial system, a dormant ancient one, or gases migrating from depth. DNA extractions from 66 depths, despite nine different protocols, consistently fell below detection limits, underscoring the extremely low biomass of this deep subsurface habitat.

Chemical weathering proxies add another layer. X-ray fluorescence of 213 samples reveals that the iron-to-potassium ratio, a tracer of Andean versus lowland sources and of weathering intensity, averages 0.56, close to modern suspended sediments of the Solimões River. X-ray diffraction shows sandstones averaging 55 percent quartz and 22 percent feldspar, confirming their arkosic, mineralogically immature character. Natural gamma spikes at seven depths, most dramatically a sharp peak at 346 meters coinciding with a magnetic susceptibility maximum, are suspected to be altered volcanic ashes, which could eventually provide precise tephrochronological anchors for the sequence.

Why does this matter beyond Amazonia? The Late Miocene and Pliocene were pivotal on multiple fronts: most living Amazonian species emerged then, Andean uplift accelerated and reorganized drainages, and atmospheric carbon dioxide levels were similar to those of 2025 and the coming decades. A high-resolution record from this interval, in the heart of the world’s largest rainforest, offers a natural experiment in how tropical biodiversity responds to tectonic landscape change and greenhouse climates. The companion core from the Marajó Basin in eastern Amazonia, drilled in 2024, likely covers the same interval, promising a basin-wide comparison from the Andean foreland to the Atlantic margin.

The team also invested in the region’s people. Twelve educational activities, from workshops to hands-on sessions with cores, rocks, and river sands, reached 240 residents of Rodrigues Alves and surrounding communities, while an inventory of 11 geosites along the Juruá River, including the thrust-faulted landscapes of Serra do Divisor National Park, laid groundwork for geoconservation. A virtual tour built from 21 panoramic 360-degree images now traces a geocultural itinerary from the Divisor Range to the Croa River. For the scientists, however, the real treasure remains locked in the 860 meters of core now archived at the University of Minnesota, where 34 researchers from seven countries logged and sampled roughly 5,000 specimens for more than 30 types of analyses. As those analyses mature, the Acre core is poised to fill the single most conspicuous gap in the fossil record of the Amazon’s making.

Subject of Research: Sedimentology, geochronology, and paleoecology of a Trans-Amazon Drilling Project core from the Acre Basin, western Brazil

Article Title: Initial results from a Trans-Amazon Drilling Project core from the Acre Basin of Brazil

Article References: Fritz, S. C., Sawakuchi, A. O., Noren, A., Baker, P. A., Silva, C., Jaramillo, C., de Almeida, R. P., Janikian, L., Bezerra, I. S., Barbosa, M., Bertassoli, D., Blankenship, R., Chiessi, C. M., Feakins, S. J., Garcia, M. D. G., Gautheron, C., Grivna, B., Hartmann, G., Kunkel, C., … Zamudio, B. (2026). Initial results from a Trans-Amazon Drilling Project core from the Acre Basin of Brazil. Scientific Drilling, 35(1), 127-157. https://doi.org/10.5194/sd-35-127-2026

Image Credits: AI Generated

DOI: 10.5194/sd-35-127-2026

Keywords: Amazon rainforest, Trans-Amazon Drilling Project, Acre Basin, Solimões Formation, drill core, Miocene, Pliocene, paleoclimate, biodiversity, detrital zircon, palynology, Andean uplift

The technical foundation of the study rests on radiocarbon dating, specifically accelerator mass spectrometry, or AMS, which allows researchers to determine the age of tiny fragments of charcoal recovered from lake sediments, soils, and archaeological deposits. Charcoal is effectively a fossil record of fire: when vegetation burns, some carbonized material is deposited in soils and water bodies, where it can survive for millennia. The team compiled 1,329 previously and newly dated charcoal fragments and burned archaeological materials, then applied summed probability analyses to the resulting distribution of radiocarbon ages. This statistical approach treats each dated sample as a probabilistic signal of fire activity at a given time and place, allowing researchers to detect broad regional patterns in fire frequency across the Holocene epoch, the roughly 11,700-year interval since the end of the last glacial period. The sites were grouped into six geographic regions: central, eastern, northwestern, southwestern, and southern Amazonia, together with the Guiana Shield.

The pre-human baseline that emerges from the data is remarkable for its emptiness. Glacial-aged paleoecological reconstructions from iconic research locations such as the Hill of Six Lakes in Brazil and the Serra Sul dos Carajás reveal that charcoal was either entirely absent or present only in minuscule quantities before human arrival. Even more striking is the Campo Libre sediment core, recovered from the Andean slopes of Ecuador, which recorded a total absence of fire for 30,000 consecutive years. That long silence ended only when humans appeared on the landscape around 4,500 years ago. In a region where wet forest conditions and dense, moisture-laden vegetation make natural ignition extraordinarily improbable, the absence of charcoal is not a gap in the record but a meaningful signal: these forests simply did not burn on their own.

The researchers describe the human arrival as the introduction of fire to a naïve landscape, a term with precise ecological meaning. Because Amazonian plants evolved for millions of years in the near-total absence of fire, they never developed the thick bark, serotinous cones, or resprouting strategies that characterize fire-adapted flora elsewhere in the world. Amazonian vegetation is evolutionarily fire-sensitive, meaning that even low-intensity burns can kill trees that would survive readily in savanna or boreal ecosystems. When a fire-using species began lighting fires regularly in a system that had been stable since the late Pleistocene, the ecological consequences were fundamental. Fire became a selective agent in a forest that had no evolutionary memory of it, filtering the flora not through adaptation to burning but through differential mortality.

The reconstructed ignition timeline unfolds in three distinct phases across the Holocene. Between 10,000 and 6,000 years ago, fires were highly restricted, occurring primarily in the basin’s peripheral areas and along the main channel of the Amazon River, where early human populations concentrated near waterways and riverine resources. This localized footprint shifted dramatically between 6,000 and 4,000 years ago, when the geographic spread of both fire and occupation sites accelerated sharply across most regions. Critically, this expansion coincided with the onset of early maize cultivation in northwestern and southwestern Amazonia, linking the spread of fire to the spread of agriculture. Slashing and burning to open garden plots and enrich soils with charcoal and ash would have introduced recurring ignition sources into forest interiors that had never before experienced them.

The third phase, between 3,000 and 2,000 years ago, saw fire penetrate the deep interior of the basin. Central Amazonia had functioned as a relatively fire-free refuge for thousands of years while the periphery burned, but it was ultimately transformed as expanding human influence and fire-use reached the very heart of the forest. This pattern suggests that pre-Columbian societies were not confined to easily accessible river margins but had established a substantial and widespread presence throughout the basin, managing and modifying the forest far from major waterways. The archaeological record of dated burned materials tracks this inland expansion in parallel with the soil charcoal record, providing two independent lines of evidence that converge on the same conclusion.

Perhaps the most dramatic chapter in this fire history is its ending, which unfolded in two phases over the last 700 years. The first decline in fire frequency occurred 600 to 700 years ago, several centuries before European arrival. Physical evidence from lake sediments shows a significant pollen surge during this window, a palynological signature of massive reforestation. The researchers interpret this as evidence for the early abandonment of lands and a major pre-Columbian shift in land use, indicating that Indigenous populations were relocating or reorganizing well before contact. The second and far larger decline followed the so-called Great Dying after A.D. 1541, when introduced disease, warfare, and enslavement killed an estimated 90 to 95 percent of Indigenous peoples in the Americas. As human ignitions vanished with the population, the forest entered a second, more extensive phase of recovery, regrowing over abandoned gardens, orchards, and settlements.

The ecological legacy of this ten-thousand-year fire history is written into the composition of the modern forest. The intensification of human-caused fire over the last two millennia accelerated changes in vegetation at rates and magnitudes that the researchers compare to major climatic shifts, including the deglaciation at the end of the Pleistocene and the extinction of Pleistocene megafauna. The impact was subtle rather than catastrophic: fire did not convert closed forest to grassland across the basin, but it selectively favored species that were already present and showed the greatest fire tolerance, such as certain palms, over fire-sensitive vegetation. Palms are among the most economically and culturally important plants in Amazonia today, and their current abundance may partly reflect millennia of human fire management. In this sense, the configuration of Amazonian plant communities is not a purely natural artifact of climate and soils but a composite of ecological and anthropogenic forces.

The study carries significant implications for conservation policy and for how scientists model the forest’s future. If the Amazon’s plant communities have been co-shaped by human activity for thousands of years, then the benchmark of a pristine, pre-human baseline is a myth, and restoration targets must account for the deep history of Indigenous land use embedded in the vegetation itself. The findings also sharpen concerns about the present: modern droughts and deforestation are reintroducing fire to a landscape whose flora remains as fire-sensitive as it was 10,000 years ago, but now at industrial scales and in a warming climate. Understanding that the Amazon’s forests have always burned only when people set them alight reframes contemporary fire as a solvable governance problem rather than an inevitable natural hazard, and it underscores the extent to which the forest’s past, and possibly its future, has been and will be written by human hands.

Subject of Research: Holocene pyrogeography of the Amazon basin and the role of human-ignited fire in shaping rainforest vegetation

Article Title: Human-driven fires have shaped the Amazonian forest for over 10,000 years

Article References: Human-driven fires have shaped the Amazonian forest for over 10,000 years. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Amazon rainforest, pyrogeography, radiocarbon dating, charcoal records, paleoecology, Indigenous land use, pre-Columbian fire, Holocene, fire-sensitive vegetation, maize cultivation, Great Dying, Frontiers of Biogeography

Ground-level ozone is not emitted directly by fires. Instead, it is a secondary pollutant, formed when reactive gases produced by combustion react chemically in the presence of sunlight. In the lower atmosphere, ozone is harmful to human health and, crucially, interferes with the physiology of plants. When ozone enters leaf tissue through the same microscopic pores that trees use to absorb carbon dioxide, it damages cells and impairs photosynthesis. For a forest already stressed by drought and fire, this additional burden means that the trees that survive a blaze are less able to resume their role as carbon absorbers in the months and years that follow. The result is a double blow to the climate: fires release carbon dioxide directly when biomass burns, and the ozone they generate suppresses the ability of the remaining forest to capture and store that gas.

The research team quantified this effect using nearly three decades of observations and a global vegetation model, tracking how ozone damage evolved between 1997 and 2024 alongside patterns of fire activity and drought. Their analysis shows that the impact of fire-driven ozone is strongest during major droughts, when hot, dry conditions simultaneously fuel more fires and leave vegetation more vulnerable to pollution damage. Alarmingly, three of the most extreme Amazon droughts of the past three decades — in 1997/98, 2015/16 and 2023/24 — all occurred during El Niño events, the warm phase of a natural, recurring global climate cycle. While El Niño is not caused by human activity, climate change means it now sits atop rising baseline temperatures, making it more likely to push global temperatures to record highs and intensify extreme weather.

Lead author Dr Flossie Brown, of ETH Zurich, emphasized that the problem extends well beyond the flames themselves. Forest fires do not just release carbon dioxide when they burn, she explained; they also contribute to the rise in ground-level ozone, a pollutant that damages the leaves of surviving trees and reduces their ability to keep absorbing carbon afterwards. According to the study, this hidden effect is equivalent to around a quarter of the carbon released by the fires themselves — a significant loss to the Amazon’s carbon budget that had not previously been considered. In other words, every hectare of burned forest inflicts a further, largely unmeasured penalty on the intact forest around it, eroding the region’s capacity to recover the carbon that has been lost.

The drought years examined in the study each left a distinct signature in the data, but the most recent event stands out starkly. Ozone damage during the 2023/24 drought nearly doubled compared with the average of the previous decade, a jump that coincided with record fire activity across the basin. Dr Brown warned that, given a comparably strong El Niño appears to be developing again this year, the researchers are concerned that history could repeat itself. Forecasters have indicated that the emerging El Niño has the potential to become one of the most intense on record, raising the prospect of another major spike in this hidden carbon loss. If drought conditions and fire activity mirror those of 2024, the ozone-driven suppression of photosynthesis could once again strip a substantial fraction of the Amazon’s remaining carbon uptake capacity at precisely the moment it is most needed.

The mechanics of this damage are rooted in the chemistry of the tropical atmosphere. Wildfires release a cocktail of precursor gases, including nitrogen oxides and volatile organic compounds, which react under the intense sunlight of the tropics to produce ozone near the ground. Unlike the stratospheric ozone layer that shields the Earth from ultraviolet radiation, ground-level ozone is a pollutant. In plants, it enters through stomata — the tiny pores on leaf surfaces that regulate gas exchange — and triggers oxidative stress that damages cellular machinery. Stressed trees may close their stomata to limit ozone uptake, but doing so also restricts the influx of carbon dioxide, directly reducing photosynthesis. Over large areas and extended periods, this physiological impairment translates into measurably lower carbon uptake across the forest, compounding the losses from drought stress and fire mortality.

What makes the new findings particularly consequential is that the ozone effect operates on surviving forest rather than burned land. Conventional carbon accounting for wildfires focuses on the immediate emissions from combustion and the slower losses from tree death and decomposition. The ozone penalty, by contrast, is invisible in satellite images of smoke and scorched earth, yet it accumulates across vast swathes of intact forest downwind of burning areas. By combining long-term observational records with a global vegetation model, the researchers were able to isolate this signal and express it in carbon budget terms, showing that the atmosphere suffers significantly more damage from each Amazon fire season than direct emissions alone would suggest.

There is, however, a clear and actionable message embedded in the research. Almost all fires in the Amazon are started by people, whether through deliberate land clearance or through agricultural burning that escapes into standing forest. The worst ozone damage is concentrated in the so-called Arc of Deforestation, the frontier zone where agricultural land is expanding into the rainforest. Professor Stephen Sitch, of the University of Exeter, stressed that this means the extra ozone damage described in the study is largely preventable. Reducing deforestation and forest degradation would cut direct fire emissions, but the study shows it would also protect the Amazon from this secondary, invisible source of carbon loss. The same policy lever, in other words, addresses both problems at once.

Co-author Dr Alexander Cheesman, of James Cook University, argued that the findings demonstrate why air pollution, land-clearing and climate change cannot be treated as separate problems when determining the future of the Amazon. These impacts interact and need to be considered together, he said, but that interaction also means solutions may deliver multiple benefits. Policies that tackle deforestation and degradation address both the carbon dioxide released directly by fires and the ozone pollution quietly eroding what is left of the forest’s ability to soak that carbon back up. In a region where the margin between sink and source grows thinner with each drought, such co-benefits could prove decisive.

As the developing El Niño raises the specter of another record fire season, the study serves as a timely reminder that the true climate cost of Amazon fires is greater than the smoke plumes suggest. The research was funded by the Natural Environment Research Council, partly via the GW4+ Doctoral Training Partnership, and the underlying paper is entitled Fire-derived ozone and intensifying droughts undermine the Amazon carbon sink. Its central conclusion is stark: every fire season in the Amazon now carries a hidden surcharge, paid not in flames but in the diminished photosynthesis of the trees that survive. Protecting the world’s largest rainforest, the authors make clear, requires confronting not only the fires themselves but the polluted air they leave behind.

Subject of Research: Fire-derived ground-level ozone pollution and drought reducing carbon uptake in the Amazon rainforest

Article Title: Wildfire ozone pollution weakening Amazon's ability to absorb carbon

Article References: Wildfire ozone pollution weakening Amazon's ability to absorb carbon. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Amazon rainforest, ozone pollution, wildfires, carbon sink, El Niño, drought, deforestation, climate change, photosynthesis, Communications Earth & Environment, Arc of Deforestation, ground-level ozone

The central question the researchers set out to answer is deceptively simple: can political leaders influence whether society complies with legal requirements simply through what they say? Brazil offers an ideal testing ground for this question because it contains the largest share of the Amazon rainforest, the world’s most extensive tropical forest and a critical reservoir of biodiversity and carbon. During the first months of Bolsonaro’s term, he and members of his cabinet repeatedly made derogatory remarks about the protection of this ecosystem, creating a natural experiment in how elite signaling might alter behavior at the forest frontier.

To measure deforestation with precision, the team drew on data from the initiative MapBiomas Alerta, which reviews and validates deforestation alerts from multiple satellite-based sources covering the whole of Brazil. This validation process gives researchers a high-quality record of where and when forest loss actually occurred, rather than relying on raw, unverified alerts. On the other side of the analysis, the researchers examined more than 3,600 Twitter posts that Bolsonaro and his ministers of agriculture, environment, and foreign affairs published in 2019. From this large corpus, they identified 38 posts that signaled a lower enforcement risk for infringements against environmental laws, such as statements criticizing conservation policy or downplaying the likelihood of punishment for illegal clearing.

A crucial insight guiding the study’s design is that political messages are only effective if they are heard. A tweet from the president does not automatically reach a farmer deciding whether to clear a remote plot of land. The researchers therefore estimated the Twitter reach of government messaging across 578 municipalities in the Amazon region. Their proxy for exposure was local Twitter activity: they analyzed how many tweets relating to the topic of forest were posted by citizens in each municipality between 2015 and 2018. The logic is straightforward. The higher the pre-existing Twitter activity in a municipality, the greater the likelihood that relevant tweets from the government would be seen there, whether directly or through secondary diffusion.

That diffusion mechanism, the authors argue, likely extends well beyond the platform itself. As Dr. Gustavo Magalhães de Oliveira, a postdoctoral researcher at the Institute for Food and Resource Economics at the University of Bonn, explains, the team assumes such messages spread through word of mouth. Supporters share them, critics share them, and they are discussed locally until they reach the people who actually make decisions about deforestation. Those decision-makers, whether landholders, speculators, or intermediaries coordinating illegal clearing, view the statements as a political signal about how the federal government will treat environmental crime.

The empirical results show a direct and far-reaching response to that signal. In the regions with the greatest exposure to the government’s messaging, deforestation increased significantly in the months when Bolsonaro and his ministers had published posts opposing forest conservation. Importantly, the researchers checked whether this pattern was an artifact of Twitter alone. It was not. As Oliveira notes, the impacts were not limited to Twitter; the same pattern emerges when the team analyzes other forms of exposure, such as television. This convergence across communication channels strengthens the interpretation that the underlying driver is the political signal itself rather than any quirk of one medium or its user base.

One of the most striking findings concerns what did not change. The researchers found that the government statements had no influence on municipal environmental fines or on deforestation bans. In other words, the actual machinery of enforcement on the ground, the inspections, the penalties, and the legal restrictions, remained the proximate context in which landholders operated. What shifted was something more subtle: expectations. According to Oliveira, the analysis indicates that, as a result of the messages, people changed their expectations of the extent to which they would be prosecuted for breaking the law. The effect is thus not attributable to any changes in the local enforcement of forest conservation laws, but to the perceived risk of punishment, which elite rhetoric could lower even as formal rules stayed on the books.

The study also reveals that the phenomenon appears to be driven by economic incentives rather than political loyalty. If the mechanism were simply that Bolsonaro’s base felt emboldened to follow his lead, the effect should have been strongest in municipalities with high levels of support for the president. The data show no such pattern. Instead, the effect was stronger in areas where agricultural returns are high and where nature conservation policy had restricted deforestation in the past. This makes economic sense: rhetoric lowering the perceived cost of illegal clearing matters most where the potential profits from cleared land are large and where accumulated pressure from conservation rules had created pent-up demand for conversion. Where the economic payoff is small, even a permissive political climate does not move the needle.

The magnitudes involved are substantial. The researchers estimate that, in 2019 alone, between 190 and 1,700 square kilometers of forest fell victim to the statements by the Bolsonaro government. The upper bound of that range, nearly 1,700 square kilometers, is almost double the area of Berlin, a comparison that underscores how a handful of social media posts from senior officials can translate into landscape-scale environmental damage. It is worth emphasizing that this estimate is additional to the deforestation driven by the broader weakening of Brazil’s environmental authorities during Bolsonaro’s term, which the study treats as a separate channel. Even setting aside institutional erosion, the perception of a low risk of punishment was itself a relevant driver of forest loss.

Beyond its immediate findings for Brazil, the study carries a broader warning about the power of political language. It provides evidence of how influential words can be when they come from people holding great political power, and it is quite possible that the effect extends beyond forest conservation and the context of the Brazilian Amazon. Wherever compliance with law depends partly on citizens’ beliefs about enforcement, leaders who signal tolerance for rule-breaking may erode that compliance without changing a single regulation. The research was a collaboration between the University of Bonn, the University of Texas at Dallas in the United States, and Wageningen University in the Netherlands, funded by the Bonn SDG Fellowship Program, the German Federal Ministry of Food and Agriculture, the German Research Foundation as part of the German Excellence Strategy, and the EU program Horizon. For scientists and policymakers alike, the message is sobering: in the digital age, the pen, and the tweet, can be mightier than the chainsaw, and protecting forests may require defending not only institutions but the credibility of the rules themselves.

Subject of Research: The effect of political rhetoric on Amazon deforestation and environmental law compliance in Brazil

Article Title: How Bolsonaro’s statements destroyed the rainforest

Article References: How Bolsonaro’s statements destroyed the rainforest. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Amazon rainforest, deforestation, Jair Bolsonaro, political rhetoric, environmental enforcement, Brazil, Twitter, The Journal of Politics, University of Bonn, MapBiomas Alerta, deterrence, land use