The relaunch is more than a change of infrastructure. It reflects a deliberate strategy by TIBS to position the journal for growth in a publishing landscape that has been transformed over the past decade. The society, a non-profit founded in 2001 to support the study, understanding, communication and application of biogeography, established the journal’s vision and mission, subsidises its running costs, appoints its chief editors, who serve without payment alongside the rest of the editorial board, and oversees its performance through a newly established publications committee reporting to the TIBS board.

Founded in 2009, Frontiers of Biogeography began as an open-access forum for syntheses, perspectives and discussion, with its first volume containing profiles, commentaries, book reviews and announcements alongside early research contributions. Over seventeen volumes the journal has evolved into a more conventional format, with empirical Research Articles now forming the majority of published papers, complemented by Perspectives, Reviews, Correspondence, Book Reviews and occasional Editorials. The journal accepts work on any taxon, across temporal scales from short to deep time, and across spatial scales of analysis, spanning pure and applied schools of thought within biogeography.

A significant milestone accompanies the relaunch. Clarivate has selected Frontiers of Biogeography for inclusion in the Web of Science, with articles published from 2022, beginning with volume 14, indexed in the Emerging Sources Citation Index, Zoological Record, Biological Abstracts and BIOSIS Previews. The journal’s current Scopus CiteScore of 4.3, recorded for 2023, offers one existing measure of the attention its published work is already receiving. Inclusion in major citation and listing systems enhances connectivity and ease of discovery, an expectation in modern scientific publishing that the journal has now formally met.

The transition to Pensoft also changes the journal’s publication model in a fundamental way. Rather than appearing in four issues per year, Frontiers of Biogeography now operates on a continuous publication schedule, meaning each paper is published in final form as soon as possible after acceptance and proofing are complete. Volume 16, the last produced via the e-Scholarship platform, was closed after its first two issues, and all subsequent 2024 papers form volume 17. Thereafter, each new volume will begin at the start of each calendar year, aligning the journal with contemporary practices in rapid, article-level publication.

Pensoft’s strengths in biodiversity data publishing were a key factor in the decision. The publisher is a leader in facilitating the publication of biodiversity data into the Global Biodiversity Information Facility (GBIF), and its marine counterpart, the Ocean Biodiversity Information System (OBIS). These systems use and develop international standards for data and metadata, allowing thousands of datasets to be integrated into a single searchable infrastructure. Researchers can query and download information on any selected taxa, places or time periods in a standard format, removing the need to reformat data and making it far more reusable than data deposited merely as supplementary material.

For a discipline like biogeography, which depends fundamentally on the distribution of organisms across space and time, this data infrastructure is transformative. The integration of large volumes of data on the distribution of hundreds of thousands of species opens new analytical possibilities, from modelling range shifts under climate change to reconstructing historical biotic exchanges. The journal’s editorial team argues that while depositing data in supplementary files may technically constitute open data, it avoids the standards and protocols that make data genuinely interoperable and reusable, a distinction that matters increasingly as large-scale synthetic studies become the norm.

The economics of open-access publishing also shaped the relaunch. The open-access model shifts the financial burden of publication from readers to authors, potentially limiting the ability of researchers without institutional funding to publish in many journals. Article processing charges (APCs) in scientific publishing often exceed $2,000 per paper and can be significantly higher. TIBS is committed to low-cost, gold open-access publishing for biogeographers and provides a financial subsidy for the journal’s running costs. The publications committee will review the journal’s APC, discounts and waivers policy annually, seeking to balance the costs to the society of subsidising the journal while minimising financial barriers for society members.

Because the budget available for APC subsidies and waivers is finite, the journal encourages authors who do not require discounts to pay the default APC, enabling TIBS to support more discounts and waivers for those who lack appropriate funding sources. Any changes to these policies will be announced towards the end of the year and will apply to papers submitted in the following calendar year. This approach reflects a broader tension in scientific publishing between the ideals of open access and the practical realities of sustaining a journal without excluding early-career researchers or those in less-funded institutions and regions.

The chief editors, writing on behalf of The International Biogeography Society, have invited all members of the biogeographical community, whether society members or not, to submit manuscripts to the relaunched journal. The success of the venture, they note, depends on researchers submitting strong papers and on the willingness of the editorial board and reviewer community to provide the scrutiny and constructive input needed to ready papers for publication. With its new platform, continuous publication model, Web of Science inclusion and integrated data publishing infrastructure, Frontiers of Biogeography enters its seventeenth volume with the ambition of becoming a leader in the field it serves.

Subject of Research: Scientific publishing and open access

Article Title:  Frontiers of Biogeography relaunched with Pensoft Publishers

Article References: Whittaker, R. J., Franklin, J., & Costello, M. J. (2024). Frontiers of Biogeography relaunched with Pensoft Publishers. Frontiers of Biogeography, 17, Article e132542. https://doi.org/10.21425/fob.17.132542

Image Credits: AI Generated

DOI: 10.21425/fob.17.132542

Keywords: Frontiers of Biogeography, Pensoft Publishers, International Biogeography Society, open access, biodiversity data, GBIF, Web of Science, scientific publishing, Frontiers, Biogeography, relaunched, Pensoft

The research team, led by scientists at the University of Liège, set out to answer two questions that have long frustrated conservationists. First, which environmental conditions actually determine where Japanese giant salamanders can live? Second, how will those conditions shift as the planet warms? To do this, they deployed species distribution models, a cornerstone tool of modern macroecology, over an area of 282,916 square kilometres covering the entirety of Honshu, Shikoku and Kyushu islands. The models compared 477 high-resolution occurrence records, gathered from field surveys and published studies dating back to 1970, against seven remote-sensing environmental predictors spanning climate, topography and land use.

The occurrence data required careful preparation. The team collected 1,228 presence records in total, but to avoid spatial autocorrelation and overfitting, they thinned the dataset so that no two points fell within one kilometre of each other, a distance chosen because it matches the grid scale of the environmental data and the typical migratory range of the species. The result was a robust set of 477 presence points on which to train the models. Environmental predictors were selected based on the salamander’s ecology: four bioclimatic variables from the WorldClim dataset, including mean temperature of the wettest and warmest quarters and precipitation of the warmest and coldest quarters, alongside mean slope, agricultural area and urban area, all at a one-square-kilometre resolution.

The modelling itself used MaxEnt, a presence-background method that compares the environmental conditions at species locations with those available across the landscape. To ensure the model captured conditions specific to the salamander’s actual range, the team restricted the background to the known distribution during training, then projected the model across all of Japan to explore potential suitability beyond it. They corrected for sampling bias using a bias grid built from a minimum convex polygon around occurrence points buffered by 50 kilometres, and partitioned the data spatially into four folds to improve transferability across space and time. Model calibration tested 36 parameter combinations of feature classes and regularisation multipliers, with the optimal model selected using corrected Akaike Information Criteria and validated against null models built from 100 iterations.

The findings are striking. Climatic variables dominated the distribution model, contributing 76.21 percent of the total, with precipitation of the warmest quarter alone accounting for 36.73 percent. The salamanders favour areas with moderate precipitation during cold and wet seasons and mild summer temperatures, with the highest probability of presence at average air temperatures around 20 to 24 degrees Celsius. Excessive precipitation proved detrimental, with suitability dropping sharply above 500 millimetres in the wettest quarter, likely because strong currents and prolonged flooding threaten larvae and disrupt the submerged nests that males guard. Slope also mattered, with suitability rising up to a mean of 17 percent before declining in steeper terrain, while land-use variables contributed relatively little.

Perhaps the most unexpected result concerns geography. The current habitat suitability map reveals highly suitable areas both within and beyond the species’ known range. In the northern part of Honshu Island, far from any confirmed salamander populations, the model identified 42,508 square kilometres of high-suitability habitat. Yet the salamanders cannot reach them. The Japanese Alps, a mountain chain bisecting Honshu, form an impassable natural barrier for a fully aquatic species that cannot climb terrestrial environments outside of riverine areas. The team’s analysis suggests that climatic differences between northern and southern Japan do not explain the species’ absence in the north; rather, it is the biogeography of the Alps that has confined the salamander to the south-western regions of the island.

Within the current distribution range, which covers 59,193 square kilometres, the picture is already mixed. Thirty percent of the area was identified as unsuitable, 37 percent as low suitability, 22 percent as moderate and just 11 percent as high suitability. The projections for the future are more alarming. Considering the extent of the current range, more than 50 percent of the geographic area is expected to lose habitat suitability at any point between 2050 and 2090, under both the optimistic SSP126 scenario and the pessimistic SSP370 scenario. The most severe loss, affecting 64.5 percent of the area, is predicted for 2090 under the pessimistic scenario. Gains in suitability do occur, reaching 14.5 percent of the area in 2070 under the optimistic scenario, but they are insufficient to offset the losses.

The mechanisms behind these projected losses are rooted in the salamander’s physiology. Japanese giant salamanders prefer relatively cold mountainous streams with high levels of dissolved oxygen, which promotes cutaneous respiration. Rising air temperatures raise water temperatures and reduce dissolved oxygen concentrations, a critical parameter for survival. Heavy and sustained rainfall is also expected to increase across Japan, raising the frequency of flooding events that particularly affect larval stages and nesting sites. A study on the North American giant salamander, or hellbender, showed that a two-degree increase in water temperature decreased immune function and growth rate while increasing physiological stress, offering a sobering parallel for what warming may mean for the Japanese species.

The conservation implications are complex. The species was reassessed from Near Threatened to Vulnerable on the 2022 IUCN Red List, but many populations are declining and the salamander’s long life expectancy makes the true status of populations difficult to assess. Habitat fragmentation from dams, built for agriculture and flood control, blocks movement along waterways and reduces breeding microhabitat availability. Without connectivity between habitats, even the suitable areas identified by the models would be inaccessible to the salamanders. Interestingly, the declining human population in rural Japan may offer some relief, as unmaintained agricultural dams eventually burst and restore connectivity, though new flood-control infrastructure linked to climate change threatens many habitats.

The study calls for new surveys based on the projected maps, particularly on Shikoku and Kyushu islands where distribution data remain sparse, and for fine-scale research on disturbances to aquatic habitats. Environmental DNA surveys could identify previously unknown populations, followed by visual confirmation at positive sites. Because giant salamanders act as top predators structuring aquatic communities, protecting their habitat may benefit other species relying on the same streams, an umbrella effect that amplifies the conservation value of every stream saved. As climate change tightens its grip on the cold, clear waters these ancient creatures depend upon, the race is on to understand and preserve what remains of their world before the living fossil becomes a fossil in fact.

Subject of Research: Projected climate-driven loss of habitat suitability and distribution range of the endangered Japanese giant salamander

Article Title: Loss of habitat suitability and distribution range of the endangered Japanese giant salamander under climate change

Article References: Duret, C., Bartet, T., Hambuckers, A., Kishida, O., Okada, S., Taguchi, Y., Takahashi, M. K., & Denoël, M. (2025). Loss of habitat suitability and distribution range of the endangered Japanese giant salamander under climate change. Frontiers of Biogeography, 18, Article e133105. https://doi.org/10.21425/fob.18.133105

Image Credits: AI Generated

DOI: 10.21425/fob.18.133105

Keywords: Japanese giant salamander, Andrias japonicus, climate change, species distribution models, MaxEnt, habitat suitability, amphibian conservation, biogeography, Japanese Alps, habitat fragmentation, Frontiers of Biogeography, freshwater megafauna

The research, led by scientists studying Totternhoe Quarry, an 8.9-hectare Site of Special Scientific Interest managed by the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire, deployed a network of 131 temperature data loggers across the reserve’s remarkably heterogeneous landscape. Medieval quarrying left behind steep slopes of every aspect, patches of bare chalk, grasslands of varying heights, and encroaching scrub, all within a small area. By recording temperatures at 1 cm, 5 cm and 50 cm above the soil from May 2018 to August 2019 and again from May to August 2022, the team captured six heatwave events, including the summer that produced the highest air temperatures ever recorded in the UK.

The scale of local thermal variation was striking. Across more than 629,000 hourly recordings, microclimate temperatures ranged from −16.0 °C to 63.0 °C, while the nearby Met Office weather station at Woburn, roughly 16 kilometers away, recorded macroclimate temperatures between −7.1 °C and 39.3 °C. During heatwaves, microclimate temperatures spanned from 17.2 °C below ambient to a staggering 36.0 °C above ambient. Perhaps most tellingly, more than 3,000 recordings exceeded 40 °C, higher than the maximum air temperature the weather station ever logged, and over half of those extreme readings occurred outside officially defined heatwave events. Species in these habitats, the study suggests, may be encountering lethal temperatures far more frequently than heatwave statistics imply.

Using random forest classification models trained on 500 decision trees, the researchers ranked environmental variables by their ability to predict whether a microhabitat would become a heat trap, with temperatures above ambient, or maintain cool refugia, with temperatures below ambient. Macroclimate temperature itself proved the most influential variable, followed by vegetation type, topographic aspect, and degree of shelter, with slope steepness ranking last. When the 2022 data were analysed separately with two additional variables, vegetation height emerged as the strongest environmental predictor while percentage of bare ground ranked lowest. Every environmental variable tested improved the model’s predictive accuracy, confirming that landscape structure genuinely shapes the temperatures organisms experience at fine scales.

The strongest buffering capacity belonged to encroaching scrub on north-facing slopes. Ranked combinations of environmental structures showed that north-facing slopes with scrub produced a coefficient of just 0.017, meaning microhabitat temperatures rose by only 0.017 °C for every 1 °C increase in air temperature, keeping local conditions remarkably close to ambient. At the opposite end of the spectrum, south-facing slopes with short grass showed the strongest heat amplification, with a coefficient of 0.328. Intermediate slopes, low percentages of bare ground, and tall vegetation also increased the probability of maintaining cool refugia. Notably, the degree of shelter did not alter the scrub effect, implying that even low-density scrub can provide sufficient shade and shelter to buffer high temperatures, a finding with significant implications for grassland management.

Height above the ground emerged as a critical axis of thermal experience. A linear mixed effects model revealed a significant change in microclimate offsetting with distance from the soil (χ² = 11.082, p < 0.001). At 50 cm above the ground, temperatures closely tracked the macroclimate recorded by the weather station, whose thermometer sits at 1.25 m, and remained relatively stable even as air temperatures climbed. Near the ground, at 1 cm and 5 cm, temperatures deviated increasingly from ambient conditions and became progressively warmer as air temperatures rose. Several processes likely drive this ground-level amplification: surfaces absorb solar radiation and heat the air in contact with them by conduction, reflected radiation warms near-ground air pockets, and complex topography and vegetation reduce air mixing, trapping air that varies more in temperature than the well-mixed air higher up.

The segmented analysis uncovered a thermal breakpoint with profound consequences. At a macroclimate temperature of 7.24 °C ± 0.07, confirmed by the Davies test (p < 0.001), the relationship between air temperature and microclimate offsetting changed direction. Below this threshold, microclimates became marginally cooler relative to the macroclimate as air temperatures increased, possibly because cold air sinks and lingers in complex topography and vegetation, creating a lag behind the exposed weather station. Above 7 °C, microclimate temperatures became warmer and more variable relative to ambient conditions as air temperatures climbed. This breakdown implies that cool refugia become increasingly rare and unpredictable precisely when species need them most, during hot weather. The authors caution that no combination of environmental structures they measured could consistently maintain temperatures below ambient during heatwaves.

For the reserve’s celebrated butterfly fauna, including the regionally rare Duke of Burgundy (Hamearis lucina) and the chalkhill blue (Polyommatus coridon), these findings carry weight. Small ectothermic organisms are acutely sensitive to temperature, which alters metabolism, oxygen demand, immune functioning, and hormone production, effects that cascade to behaviour, phenology, distribution, and survival. Species living close to the ground, such as caterpillars and many ground-dwelling insects, face the most amplified temperatures, while flying adults or insects that climb into tall vegetation can escape to cooler strata. The study suggests patches of tall herbaceous vegetation, maintained through grazer exclusion or reduced mowing, could provide vertical escape routes, though what would benefit strictly surface-dwelling organisms remains unclear.

The evolutionary dimension adds urgency. Extreme temperature events impose truncation selection, where only individuals with thermal tolerance above a threshold survive and reproduce, a form of strong selection that can raise extinction risk. Yet the innate unpredictability and scarcity of such events erodes adaptation, particularly for short-lived species, returning populations to phenotypes suited to averages rather than extremes. Microclimatic refugia may therefore be critical for persistence irrespective of adaptation. The study’s authors note that species may have been experiencing extreme near-ground temperatures for longer than previously suspected, potentially allowing more time to adapt, but that increasingly rare and unpredictable refugia may force species assemblages to reorganise according to species’ capacity to locate and compete for suitable microclimates.

The practical recommendations are actionable. Because topography is difficult to manipulate, landscapes containing north-facing slopes should be highly valued for future conservation, and the authors point to artificial topographies already being constructed by the RSPB, Butterfly Conservation, and the Wildlife Trust as emerging mitigation methods on flat land. Vegetation is more easily managed: retaining some scrub, allowing grass to grow long, protecting areas from grazers, or pausing mowing during the hottest months could all support refugia. Yet the study delivers a sobering caveat. Macroclimate temperature had a substantially weaker impact on microhabitat offsetting than any environmental variable, meaning there is only so much local structure can achieve. As ambient temperatures rise, many microhabitats will amplify rather than mitigate the effects of climate change, and weather stations will increasingly underestimate the temperatures species actually endure. Understanding when and where microclimates provide genuine refugia, and when they become heat traps, will be essential for predicting biodiversity’s fate under a warming climate.

Subject of Research: Local microclimates can both amplify and mitigate extreme temperatures associated with climate change

Article Title: Local microclimates can both amplify and mitigate extreme temperatures associated with climate change

Article References: Ashe-Jepson, E., Turner, E. C., & Bladon, A. J. (2025). Local microclimates can both amplify and mitigate extreme temperatures associated with climate change. Frontiers of Biogeography, 18, Article e164843. https://doi.org/10.21425/fob.18.164843

Image Credits: AI Generated

DOI: 10.21425/fob.18.164843

Keywords: microclimate, climate change, heatwaves, biodiversity, ecology, insects, conservation, Frontiers of Biogeography, Local, microclimates, both, amplify

The research team assembled a dataset of 3,570 occurrence points, drawing on 2,611 records from their own quantitative fieldwork and 959 records from GBIF, each one painstakingly verified against photographs of herbarium specimens to ensure that species identifications were correct. Specimens collected before 1980 were excluded because their georeferencing was considered unreliable in an era before GPS devices and accurate maps became available. Records with known coordinate problems or insufficient precision were also removed, and a spatial thinning step ensured that no two occurrences were closer than 450 metres, reducing the sampling biases that plague continental-scale biodiversity data.

What emerged from this cleaned dataset was a set of species distribution models built with three complementary statistical approaches: Generalized Linear Models, Gradient Boosting Models, and Random Forest models. Each method was trained on 70 percent of the occurrence data and tested on the remaining 30 percent, with performance evaluated using two independent accuracy metrics. The ensemble models that combined all three approaches achieved exceptionally high scores, with True Skill Statistics exceeding 0.78 and ROC values above 0.95 for every species, indicating that the predicted distribution maps captured the real geographic patterns with remarkable fidelity.

The single most powerful predictor across all eighteen species was soil base cation concentration, a measure of the availability of nutrient cations such as calcium, magnesium, and potassium that plants need for growth. This variable appeared in every single species model and was the most important predictor for many of them. Understory temperature and elevation were also included in all models but carried less weight. Cation exchange capacity, a soil property that is more readily available in global databases, proved far less informative, appearing in only half of the models. This finding carries a practical warning for the field: relying on easily accessible but ecologically imprecise soil variables can systematically underestimate the true importance of soil chemistry in shaping plant distributions.

When the researchers classified the modelled distribution patterns, six distinct types emerged, each corresponding to a specific combination of soil and climate preferences. In order of increasing range size, these were Guianan, Andean, southern, circum-Amazonian, bimodal, and widespread. The five species with the smallest ranges were confined to the Guianas, the Andean forelands, or the southern margin of the rainforest biome. Three species displayed a doughnut-shaped circum-Amazonian pattern, absent from the central-western core but present around most of the perimeter. Four species showed a bimodal distribution, occupying both the Andean foothills and the Guianan region while skipping the intervening central and southeastern Amazonia. The remaining five species spanned nearly the entire basin.

The link between these spatial patterns and soil chemistry was unambiguous. The Andean species, whose ranges hug the young, nutrient-rich sediments deposited by rivers flowing down from the mountains, showed occurrence probabilities that dropped essentially to zero on soils with base cation concentrations below 1 cmol(+)/kg. The bimodal species shared similarly high cation optima but avoided both the impoverished soils of central Amazonia and the seasonal climates of the south. In stark contrast, the five most widespread species all had the lowest base cation optima of the entire dataset, thriving on the infertile, highly weathered soils that dominate much of the Amazon basin. Because infertile soils cover such vast areas, species adapted to them can spread almost everywhere, while species requiring nutrient-rich substrates are confined to the geologically young western forelands.

Climate variables told a complementary story. No single climatic measure dominated across all species, but seasonal variability emerged as more critical than averages. Mean diurnal temperature range, temperature seasonality, and precipitation seasonality were selected in more than half of the species-specific models, while total annual precipitation was the most important climatic factor for only one species. This pattern aligns with what is known about fern physiology: these plants are highly sensitive to desiccation and reach their greatest abundance and diversity where water scarcity is not a limiting factor. The circum-Amazonian and southern species, which occupy the more seasonal margins of the biome, were the ones best adapted to these fluctuating conditions.

The forward-looking projections are sobering. Using two shared socio-economic pathways from the CMIP6 climate modelling framework, with consensus bioclimatic variables averaged across five global climate models, the researchers modelled range shifts for the 2030s, 2050s, and 2070s. Under the extreme SSP5-8.5 scenario, fourteen of the eighteen species were predicted to suffer a net loss of suitable habitat by the 2070s. Eight species would lose more than half of their currently suitable area, and five of these hardest-hit species are among the most widespread and abundant in the entire genus. Only three species were projected to gain new suitable area exceeding 20 percent of their current range, and the sole species predicted to expand by more than 50 percent was Adiantum tetraphyllum, whose distribution already extends beyond Amazonia into the drier biomes to the south.

These findings challenge an earlier assumption that widespread species are inherently more resilient to climate change. On the contrary, the very species that dominate the core rainforest understory, adapted to stable, humid, nutrient-poor conditions, appear most vulnerable as temperatures rise and rainfall patterns shift. The researchers note that their models did not explicitly account for deforestation, fragmentation, fire, or dispersal barriers, meaning the true losses will likely be even greater than projected. Ferns are generally efficient dispersers, but whether they can colonise new suitable habitat fast enough to keep pace with the deterioration of their current ranges remains an open and troubling question.

Beyond the immediate fate of eighteen fern species, the study carries a broader message for tropical biogeography. Because all plants respond to the same fundamental gradients of temperature, moisture, and nutrient availability, the six distributional types identified here are unlikely to be unique to Adiantum. Similar patterns almost certainly characterise other understory herbs, shrubs, and even some tree lineages across Amazonia. As climate change pushes the basin toward hotter and more seasonal conditions, the forests of the future may increasingly resemble the dry forests that today fringe their southern and eastern edges. Whether the species capable of surviving that transition can actually reach the new habitats in time is one of the most consequential unknowns facing Amazonian biodiversity in the coming decades.

Subject of Research: Amazon-wide distribution patterns and climate change vulnerability of understory fern species

Article Title: Amazon-wide distribution patterns of understory plants: Effects of soils and changing climate

Article References: Gupta, R., Zuquim, G., Moulatlet, G. M., Lehtonen, S., Sirén, A., Alonso, A., Cárdenas, G. G., & Tuomisto, H. (2026). Amazon-wide distribution patterns of understory plants: Effects of soils and changing climate. Frontiers of Biogeography, 19, Article e188764. https://doi.org/10.21425/fob.19.188764

Image Credits: AI Generated

DOI: 10.21425/fob.19.188764

Keywords: Amazonia, Adiantum, ferns, species distribution models, soil base cation concentration, edaphic niche, climate change, understory plants, biogeography, SSP5-8.5, habitat loss, Frontiers of Biogeography

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

The research, carried out by Dr. Axel Arango Garcia and Professor Chaitanya S. Gokhale of the Chair for Computational and Theoretical Biology at Julius-Maximilians-Universität Würzburg, has been published in the journal Frontiers of Biogeography. The two scientists set out to resolve a debate that stretches back to the mid-twentieth century. In 1946, the influential ornithologist Ernst Mayr proposed that the icterids originated in South America and subsequently spread northwards in a stepwise fashion, colonising Central and then North America. That view remained broadly influential for decades, until a 2015 study by Barker and colleagues challenged it by pointing instead to a North American origin for the family. That later study, however, left a crucial question unanswered: once the family had arisen in the north, how and when did its descendants fan out across the rest of the hemisphere?

To answer that question, Arango Garcia and Gokhale assembled a comprehensive dataset covering 104 of the 106 species currently recognised within the Icteridae. Their analysis combined information on the geographic distributions of these species with evolutionary trees that describe how the different lineages are related to one another and how long ago they diverged. Onto this framework they applied a range of statistical models from the field of parametric biogeography, each of which attempts to reconstruct the most probable sequence of colonisation events that could have produced the present-day pattern of species ranges. By comparing the fit of competing models to the observed distributions, the researchers were able to identify the scenario that best explains the family’s history, together with approximate dates for each major dispersal event.

The winning scenario is one of slow, stepwise southward expansion. According to the reconstruction, the ancestors of today’s blackbirds most likely originated in North America and then moved progressively south over millions of years. Around 7.5 million years ago, the birds reached Mesoamerica and the Caribbean. Amazonia was colonised approximately 6.1 million years ago, with the Andes reached shortly afterwards. Southern South America followed around 4.8 million years ago, and the final frontier, Patagonia, was reached roughly 2.7 million years ago. Taken together, these dates sketch a picture of a family that did not conquer the hemisphere in a sudden burst, but rather through a long, gradual process of dispersal and establishment that unfolded across the late Miocene, Pliocene and Pleistocene epochs.

One of the most striking findings concerns the timing of the family’s arrival in South America. The model indicates that the first dispersal into that continent occurred around six million years ago, roughly three million years earlier than previous studies had suggested for this group of birds. That timing matters because of the geology of the region. The Isthmus of Panama, the narrow land bridge that today connects Central and South America, had not yet fully formed when the blackbirds’ ancestors made their move. The birds therefore cannot simply have walked south across a continuous corridor of land. Instead, the researchers suggest, they may have crossed stretches of open water, or used existing islands and temporary or partial land connections that preceded the fully formed isthmus. The scientific paper discusses both overwater dispersal and pre-isthmian or proto-isthmian land connections as plausible routes for this early crossing.

The environment of South America at the time may also have played a role in welcoming the newcomers. Around the same period that the blackbirds arrived, open, grass-dominated habitats were expanding across parts of the continent. Many icterids, including meadowlarks, cowbirds and several grackles, are strongly associated with open country, grasslands and savannas rather than closed forest. Arango Garcia notes that the spread of the birds into South America appears to coincide with the expansion of these open habitats, raising the possibility that the birds followed suitable environments as they spread southwards. He is careful, however, to draw a firm line between correlation and causation: the study cannot demonstrate that these environmental changes actually drove the birds’ southward expansion. The coincidence in timing is suggestive, but establishing a causal link would require additional lines of evidence.

The study also delivers a surprising verdict on the question of why so many icterid species exist in the first place. A natural assumption might be that each new region the birds colonised triggered a burst of species formation, as isolated populations adapted to new conditions and diverged from their relatives. The analysis shows that this is not the whole story. Colonisation of new regions alone does not explain the emergence of new species; instead, many species arose within regions that had already been colonised, as lineages diversified in place. Moreover, the calculated rates of speciation were broadly similar in North and South America, suggesting that no single continent offered an exceptional engine of diversification for the family. Geography, in other words, set the stage, but something else wrote the play.

What those other factors might be remains an open question, and the authors are explicit about the limits of the current analysis. They point to a set of candidate mechanisms that could explain why some lineages produced more new species than others: specialisation on particular foods and habitats, the complex social behaviour for which many icterids are known, and mate choice, including the striking plumage differences and song variation that characterise the family. Future studies could incorporate such traits directly into biogeographic and evolutionary models, allowing researchers to test more precisely whether ecological specialisation, social behaviour or sexual selection shaped the diversification of the group. Such work would move the field beyond mapping where and when species arose, toward explaining why the family’s evolutionary tree has the shape it does.

There is a pleasing irony in how the project came about. Arango has used the Icteridae for years as a teaching example, drawing on the family to illustrate macroecological rules, to walk students through phylogenetic data analysis, and to show how phylogenetic information can be managed and interpreted. The analysis that ultimately became the published paper took shape while he was preparing course material for a workshop on parametric biogeography, an effort funded by a grant from the Bayerische Hochschulzentrum für Lateinamerika, or BAYLAT, an institution that fosters academic cooperation between Bavaria and Latin America. A family of birds that has long served to train the next generation of biologists has now, thanks to that teaching, become the subject of a substantive contribution to biogeographic science in its own right.

For Arango, the results retain their capacity to surprise even after years of working with the group. He describes it as striking to discover that the lineages of these familiar birds reached South America long before the land bridge between the continents closed, and to be able to trace the exact dispersal routes they used to spread all the way to Tierra del Fuego. The study thus resolves a decades-old biogeographic debate in favour of a North American origin, while opening new avenues of inquiry into the mechanisms of diversification and the role of ancient environmental change in shaping one of the Americas’ most widespread and beloved families of songbirds. As the grasslands expanded and the isthmus slowly rose from the sea, the blackbirds were already on their way south, and their descendants now sing from nearly every corner of two continents.

Subject of Research: The historical biogeography and diversification of New World blackbirds (Icteridae) across the Americas

Article Title: How New World blackbirds conquered the Americas

Article References: How New World blackbirds conquered the Americas. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: New World blackbirds, Icteridae, biogeography, phylogenetics, South America, North America, Isthmus of Panama, speciation, dispersal, ornithology, evolution, Frontiers of Biogeography