The health stakes are considerable. The 2018 Lancet Commission on pollution and health identified air pollution as the largest environmental cause of disease and premature death globally, accounting for roughly 16 percent of all deaths. Particulate matter is a complex mixture of nitrates, sulfates, polycyclic aromatic hydrocarbons, endotoxins, and metals, and exposure to it is linked to cardiovascular and respiratory damage. Urban environments are particular hotspots, yet the exact extent of health effects at the city level remains largely unknown, a gap that is especially alarming in a heavily urbanized country like the United States, where urban sprawl expanded by 11 percent between 2001 and 2011.

Mosses have a long pedigree in pollution science. Researchers have used them for more than five decades to estimate atmospheric heavy metal deposition, and since 1990 an ongoing moss survey has mapped spatial and temporal trends in metal pollution across Europe. Bryophytes are ideal biomonitors for several reasons: they are small, they survive in highly polluted areas, they lack true roots and instead acquire nutrients directly from wet and dry deposition, and they tolerate many substances that are toxic to other organisms. Because they accumulate particles over time, they integrate pollution levels in a way that a single air sample cannot, effectively acting as living recorders of long-term exposure.

The Chicago study, led by researchers working in collaboration with local volunteers and the Field Museum, took advantage of two well-established biomonitoring strategies: passive monitoring with naturally growing moss and active monitoring with transplanted moss. The team chose the active approach, deploying standardized one-gram samples of Sphagnum in small mesh bags hung at strategically chosen sites. Two moss sources were used, a commercially purchased Sphagnum squarrosum and Sphagnum fallax collected in Maine, and the material was carefully cleaned of invertebrates and debris, air-dried, screened, and washed in three sequential treatments of Chicago tap water before deployment.

The site selection read like a map of hypothesized urban pollution sources. Moss bags were placed near a metals recycling facility, at Indian Ridge Marsh adjacent to industrial and transportation infrastructure, at the Des Plaines railroad station, and in a semi-natural reference area in Lake County. In a particularly eye-catching experiment, bags were also taped to the exhaust of a 2006 Ford F-350 diesel truck. Control samples were kept at the Field Museum under both sealed and exposed conditions, and bags were retrieved after one, three, and four weeks of exposure during June and July 2024.

Analysis relied on a Bruker Tracer 5 portable X-ray fluorescence spectrometer. Retrieved moss was frozen with liquid nitrogen, ground into a homogeneous powder, packed into sample cups sealed with a thin Prolene membrane, and measured with identical instrument settings across all samples. The researchers reported results as ratios of exposed sample counts to unexposed control counts, an approach that normalized differences between the two moss sources. Six replicate analyses on two to three bags per location yielded twelve to eighteen measurements per element per site, providing a reasonable statistical footing for an exploratory pilot.

The results showed clear location-specific patterns. The metals recycling facility, as expected for a multi-metal emission source, showed elevated levels of all measured elements. Indian Ridge Marsh, wedged next to industrial and transportation facilities, showed significantly increased iron and nickel. The railroad station exhibited elevated iron, plausibly reflecting particulate generation from steel rail infrastructure, a finding consistent with earlier studies linking rail transport to metal particle emissions. Most strikingly, even the semi-natural Lake County site showed elevated nickel, likely attributable to its proximity of less than one kilometer to a major highway, a demonstration of how far transportation-related emissions can reach.

The vehicle-mounted bags delivered a lesson in temporal dynamics. After just three days on the diesel truck, significant increases were recorded in iron, zinc, copper, titanium, and manganese compared with controls. But after four days, metal levels dropped, coinciding with significant rainfall in the Chicago area, suggesting that rain washed accumulated particulates off the moss. This observation underscores how strongly meteorological factors shape biomonitoring outcomes and points to the need for moss bag designs that mitigate wash-off, as well as standardized exposure durations and the incorporation of weather data into future protocols.

The broader implications extend beyond Chicago. North America lacks the kind of established moss survey network that Europe has maintained for decades, and this study addresses that gap while indicating strong potential for adoption in other US cities. Perhaps most compelling is the prospect of community-based monitoring: because moss bags and portable XRF instruments are inexpensive and accessible, resource-limited communities that are disproportionately affected by pollution could document contamination themselves and advocate for remediation. The authors also suggest that historical herbarium moss specimens could be retrospectively analyzed with pXRF, opening a window onto past pollution profiles and the effectiveness of remediation efforts.

The study is candid about its limitations. Sample sizes and temporal coverage were limited, systematic meteorological evaluation was not conducted, and commercially sourced moss may introduce baseline contamination variability compared with locally gathered material. The washing water and even the newspaper used for drying are potential contamination sources, and pXRF provides semi-quantitative results with detection limits that may be unsuitable for low-level contamination. Still, as a proof of concept, the work makes a persuasive case: standardized Sphagnum moss bags coupled with portable X-ray fluorescence offer a practical, cost-effective, and community-accessible tool for urban air pollution biomonitoring, one that could help cities and their residents see, quite literally in green, the metallic fingerprints of the air they breathe.

Subject of Research: Moss-based biomonitoring of urban metal air pollution using portable X-ray fluorescence in Chicago

Article Title: Green guardians: Mosses as potential low-cost biomonitors of air pollution in urban Chicago

Article References: Green guardians: Mosses as potential low-cost biomonitors of air pollution in urban Chicago. (n.d.). https://doi.org/10.3897/biorisk.24.180507

Image Credits: AI Generated

DOI: 10.3897/biorisk.24.180507

Keywords: air pollution, biomonitoring, moss, Sphagnum, portable X-ray fluorescence, heavy metals, particulate matter, Chicago, urban pollution, environmental justice, pXRF, bryophytes

The research, led by Anne Y. Yusuf of RMIT University in Melbourne together with colleagues from RMIT, the University of Southern Queensland, Griffith University, and the University of Melbourne, focused on peatlands in the Bogong High Plains of the Australian Alps. The team compared three sites: one degraded peatland and two intact ones, all located within Victoria’s Alpine National Park, where soils were collected under a research permit issued by the Victorian Department of Environment, Land, Water and Planning. Alpine peatlands are rare and ecologically precious in Australia, and they face mounting pressure from historical drainage, livestock grazing, and fire — the same disturbance trifecta that threatens peatlands worldwide.

To understand how degradation reshapes the underground world, the researchers profiled the microbial communities living at different depths in the peat profile and related them to two critical environmental variables: the position of the water table and the chemical composition of the peat’s organic carbon. The carbon chemistry was characterized in terms of functional groups — the molecular building blocks such as alkyl, N-alkyl, O-alkyl, di-O-alkyl, aryl, O-aryl, and ketone structures — which together describe how labile, or easily decomposed, versus recalcitrant, or chemically stubborn, the peat’s carbon reservoir really is. This combination of microbiology and organic geochemistry allowed the team to ask not just who lives where, but why.

The results revealed a striking pattern. In the intact peatlands, microbial communities were strongly stratified: fungal and prokaryotic — bacterial and archaeal — communities differed markedly depending on depth in the profile and on their position relative to the water table. This vertical heterogeneity is exactly what one would expect in a healthy peatland, where the upper, aerated layer hosts a very different cast of organisms than the saturated, anoxic depths. The intact peats also showed strong associations between community structure and bulk indicators of carbon quality, particularly the total carbon concentration and the carbon-to-nitrogen ratio, suggesting that the microbial residents there are organized around the overall nutritional landscape of the peat.

In the degraded peatland, that orderly structure largely fell apart. The strong depth-dependent and water-table-dependent patterns in fungal and prokaryotic communities were markedly weaker or absent altogether. Instead of being arranged in coherent layers tied to oxygen availability, the microbial communities of the degraded site appeared shuffled, their organization decoupled from the hydrological architecture that normally governs it. At the same time, the chemistry signal changed: variation in the degraded peat’s microbial communities was linked more to specific carbon functional groups — the labile and recalcitrant molecular fractions — than to the bulk carbon and nitrogen measures that mattered in intact peats. In other words, degradation seems to rewrite both the physical structure of the microbial habitat and the chemical language through which microbes and organic matter interact.

Diversity itself told a story as well. The intact peats supported higher prokaryotic diversity and evenness, meaning more distinct microbial types present in more balanced proportions. Degradation, by contrast, was associated with a less diverse and less even prokaryotic community — a signature familiar from many disturbed ecosystems, where a handful of tolerant or opportunistic taxa come to dominate while specialists disappear. Because microbial diversity underpins the full suite of decomposition pathways, from slow anaerobic fermentation to methane production, losses of this kind can ripple through the entire carbon cycle of a peatland.

Why does this matter for the climate? The mechanism is rooted in redox chemistry. When a peatland’s water table is high, the deep peat stays anoxic, and decomposition proceeds slowly through anaerobic pathways, allowing carbon to accumulate faster than it is released. When drainage or degradation lowers the water table, oxygen floods into previously sealed layers, aerobic microbes switch on, and ancient carbon begins to oxidize into carbon dioxide. The new findings suggest that degradation does not merely flip this switch; it dismantles the entire regulatory apparatus. If the tight coupling between water table position and microbial community structure is lost, the ecosystem may lose a key buffer that would otherwise restrain decomposition when conditions fluctuate. A degraded peatland, in effect, may have fewer microbial safeguards standing between its carbon store and the atmosphere.

The shift in which chemical variables best explain microbial community structure is equally significant. Bulk carbon concentration and carbon-to-nitrogen ratio are coarse-grained descriptors; carbon functional groups are fine-grained ones. A community whose composition tracks specific functional groups such as O-alkyl carbohydrates or aryl aromatic structures is one that is responding to the molecular availability of its substrate — potentially indicating that decomposition in the degraded peat is being driven by which compounds are chemically accessible rather than by the broad nutritional context. Such a regime could favor the rapid consumption of labile carbon pools while leaving recalcitrant fractions exposed to slower attack, a dynamic that would progressively erode the peat’s capacity to hold carbon over centuries.

The study also carries a geographic wake-up call. Much of what the world knows about peat microbiology comes from the vast boreal and tropical peat domes of the Northern Hemisphere and Southeast Asia. Alpine peatlands in Australia are small by comparison, but they perform outsized functions: they act as alpine sponges, regulating water flow into major river systems, and they harbor distinctive Sphagnum-associated microbiomes. The Bogong High Plains sites, sampled with support from Australian Government and Parks Victoria scholarships, show that the microbial signatures of degradation are not unique to any one continent. Wherever drainage, grazing, and fire intersect with peat, the same architectural collapse of the microbial–carbon–water table relationship appears to follow.

For conservationists and land managers, the implications point toward restoration with a microbial lens. Rewetting drained peatlands is the flagship intervention, and this study adds a mechanistic rationale: restoring the water table may do more than slow aerobic decay — it may allow the depth-stratified microbial communities that regulate carbon storage to reassemble. Whether that reassembly is possible after severe degradation, and how long it takes, remains an open question that the authors’ framework is well suited to test. What is already clear is that peatland carbon storage is not a passive geological accident but an actively maintained biological system, one that depends on an intricate interplay of water, chemistry, and life. Degrade that interplay, and the planet’s most carbon-rich soils begin, microbe by microbe, to give back what they have spent thousands of years keeping out of the air.

Subject of Research: The effects of peatland degradation on microbial community composition, carbon chemistry, and water table interactions regulating soil carbon storage in alpine peatlands

Article Title: Peatland Degradation Alters the Microbial–carbon–water Table Interactions that Regulate Carbon Storage

Article References: Yusuf, A. Y., Krohn, C., Birnbaum, C., Hearn, K., Treby, S., Ball, A. S., Chapman, J., & Grover, S. (2026). Peatland Degradation Alters the Microbial–carbon–water Table Interactions that Regulate Carbon Storage. Microbial Ecology. https://doi.org/10.1007/s00248-026-02891-3

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02891-3

Keywords: peatlands, microbial ecology, carbon storage, water table, soil carbon, fungal communities, prokaryotes, carbon functional groups, Australian Alps, peatland degradation, Sphagnum, climate

The story begins with a sediment core recovered from the Amundsen Sea during an expedition of the research icebreaker Polarstern. In 2020, the same international team, led by marine geologist Dr Johann Klages of the Alfred Wegener Institute, stunned the scientific community when they announced in the journal Nature that the core contained an extraordinarily well-preserved forest soil dating back roughly 90 million years, complete with abundant pollen, spores and a dense network of fossil roots. During the Cretaceous, tectonic conditions placed this temperate rainforest even farther south than the drill site itself, a mere 900 kilometres from the geographic South Pole. Today, average annual temperatures at that location hover around minus 30 degrees Celsius, and the entire region lies beneath an ice sheet several kilometres thick.

The climate that supported such a forest was shaped by greenhouse conditions unlike anything in the recent geological past. Atmospheric carbon dioxide concentrations during the warmest interval of the Cretaceous were four to six times higher than preindustrial modern levels, and the average annual temperature in the West Antarctic rainforest reached around 12 degrees Celsius, roughly two degrees warmer than present-day Germany. Rainfall was plentiful but strongly seasonal: dry periods regularly gave way to monsoon-like rainy seasons. For about four months of each year, the forest endured the continuous darkness of the polar night, yet conifers and tree ferns thrived, and dinosaurs roamed through the misty swamplands. It was this combination of warmth, abundant moisture and pronounced seasonality that set the stage for the fires the team has now documented.

In the new study, the researchers re-examined the same core using a broader suite of analytical methods, and the evidence of fire proved unmistakable. Throughout the Late Cretaceous section of the sediment sequence, the team identified microscopic charcoal particles, the diagnostic residue of vegetation burned in situ or transported short distances by water and wind. Critically, the abundance of these charcoal particles increased steadily in the younger sediments, indicating that fires became more frequent as the ecosystem evolved. The particles themselves carried chemical and structural signatures showing that the fuel was mainly soft conifer wood burned at relatively low temperatures, a pattern typical of surface fires that creep through undergrowth and ground litter without climbing into the forest canopy.

Fire left its mark in more than charcoal. The sediments also yielded amber, the fossilised form of tree resin, appearing in a configuration that suggests the resin flowed over fire-damaged areas of tree trunks and hardened into a protective seal, much as living conifers today exude resin to wall off wounds. Together, the charcoal and amber record a forest that was burned and healed, burned and healed again, over an extended stretch of Late Cretaceous time. Because volcanically active areas lay at least 400 kilometres away from the site during that period, the researchers conclude that the most plausible ignition source was not lava or volcanic ash flows but lightning strikes from thunderstorms, a conclusion consistent with the strongly seasonal, storm-prone climate inferred from the broader sedimentological and palaeontological evidence.

Perhaps the most consequential discovery in the core concerns what grew back after the fires. The sediments contain countless spores of peat moss of the genus Sphagnum, the same group of plants that dominates raised bogs across the modern Northern Hemisphere. These spores provide evidence of some of the earliest raised bogs known, and their rise was closely intertwined with the recurrence of fire. According to the scenario the researchers developed from their data, the temperate and very swampy Antarctic rainforest, with its alternating dry and monsoon seasons, gradually silted up and transitioned into a peatland dominated by peat mosses. Wildfires, growing ever more frequent, played a decisive role in that transition by keeping the vegetation open, preventing the re-establishment of dense forest, and creating the conditions under which waterlogged, moss-dominated ground could persist and expand.

Once the peat bog had formed, fire did not disappear from the system. Instead, it changed character. Ground-level smouldering fires occurred repeatedly within the peat itself, burning slowly through damp, carbon-rich material rather than racing through standing forest. Co-first author Prof. Dr Ulrich Salzmann of Northumbria University draws a direct line from that ancient process to the present day, noting that such smouldering ground fires resemble those that have become increasingly common in German peatlands in recent years, where prolonged drought has lowered water tables and left once-saturated peat vulnerable to slow, persistent combustion. The Antarctic core thus preserves a complete natural experiment in how fire, hydrology and vegetation interact during the birth and maturation of a peatland, conducted under greenhouse conditions far warmer than today’s.

The climate significance of that experiment is difficult to overstate. Peatlands are among the most effective long-term carbon stores on Earth, accumulating partially decomposed plant material over thousands to millions of years because waterlogged conditions slow decay to a crawl. Co-first author Prof. Dr Thorsten Bauersachs of RWTH Aachen University emphasises that peatlands played a key role in the climate system then as now, precisely because of this capacity to lock away carbon over long periods. Paradoxically, the Cretaceous record suggests that in a warm climate, where wetlands dry out more quickly and fires that suppress forest development occur more frequently, conditions can actually favour the formation of new peatlands, allowing carbon-rich plant matter to accumulate even as the world warms. Fire, in other words, was not merely a destructive force in this ancient ecosystem but an architect of one of the planet’s most durable carbon sinks.

For the research team, the parallels between the Cretaceous Antarctic and today’s high latitudes were among the most surprising findings of the study. Dr Johann Klages, co-first author of the paper, describes the team’s astonishment at finding evidence in the core of an early Antarctic ecosystem that, in many respects, resembled today’s Arctic raised bogs and also experienced regular fires. Modern raised bogs in Arctic and boreal regions face acute threats from climate change and increasing drought, and the fate of the carbon they store is a major uncertainty in projections of future warming. The West Antarctic record demonstrates that peat formation and fire can coexist and even reinforce one another under greenhouse conditions, but it also shows how sensitive these systems are to the balance between moisture and burning, a balance that human-driven warming is now shifting across the northern peatlands.

The study also underscores how much remains hidden beneath the Antarctic ice. A single sediment core, drilled through the seafloor of the Amengen Sea region, has now yielded a rainforest soil, a fire history and the trace of the earliest polar peatlands, all from a time when the South Pole itself was green. As analytical methods grow more sensitive, existing cores continue to surrender new secrets, and each one refines the picture of how Earth’s most extreme greenhouse intervals functioned. Ninety million years ago, lightning-lit fires crackled through swampy conifer forests under a polar night, and from those ashes rose the bogs that would bury carbon for geological time. Understanding that ancient dance between flame and moss may prove essential to anticipating what a warming world will do to the peatlands that still guard vast reservoirs of carbon today.

Subject of Research: Cretaceous wildfires and early Sphagnum peatland formation near the South Pole

Article Title: Evidence of ancient wildfires near the South Pole

Article References: Evidence of ancient wildfires near the South Pole. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Antarctica, wildfires, Cretaceous, peatlands, Sphagnum, paleoclimate, charcoal, amber, carbon storage, West Antarctica, sediment core, climate change