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At least 1,297 records · Page 72Linked to original sources
USGS2026

Archean to Mesozoic–Cenozoic seismic crustal structure: Implications for geological and biological evolution

We use >4500 measurements of crustal structure to investigate the seismic structure of continental crust, Archean to Mesozoic–Cenozoic. The mean crustal thickness of continents, including their margins, is 36.5 km. We find that Archean, Paleoproterozoic, and Mesoproterozoic crust have similar mean crustal thickness (41 km), seismic velocities, Vp/Vs ratio, and density. Crusts of these ages span 3 Ga, from 4.0 to 1.0 Ga, and their similarity of physical properties (thickness, density, and seismic velocities) suggests that the process of crustal formation may have been similar during this time period, which covers 66% of Earth's history. Neoproterozoic crustal properties differ significantly from Mesoproterozoic and older crusts. The mean thickness of Neoproterozoic crust is 32 km, some 9 km thinner than the mean thickness of Archean, Paleoproterozoic, and Mesoproterozoic crust. A lithospheric root with a thickness of 150–200 km underlies Archean, Paleoproterozoic, and Mesoproterozoic crusts, and this root resists lithospheric rifting and crustal extension and thinning. Based on these observations, particularly the lithospheric thickness, we conclude that Archean, Paleoproterozoic, and Mesoproterozoic lithosphere are unique and together form the stable cratonic nuclei, defined as the thick (150–250 km), long-lived cores of continents. Higher mantle temperatures during the Archean, Paleoproterozoic, and Mesoproterozoic may have played a key role in the formation of the thick lithospheric roots. The second key finding is that the similarities of mean seismic properties indicate that the process of crustal formation operating in the Archean continued during the Paleoproterozoic and Mesoproterozoic. The thin (mean value < 135 km) lithospheric root beneath Neoproterozoic and younger crust may be related to the steady decrease in mantle temperature through time. Neoproterozoic and Paleozoic crust have similar physical properties, and these eras are characterized by pronounced biodiversification, including the renowned Garden of Ediacara, the Cambrian Explosion, and the Great Ordovician Biodiversification. Mesozoic–Cenozoic crust is the most diverse and reflects the current tectonic and magmatic processes of crustal formation.

Book chapter↗
USGS2026

Using quantitative polymerase chain reaction to assess phytoplankton and indicate eutrophication in freshwater rivers: A multiyear nationwide study across the United States

Phytoplankton are essential primary producers in fresh surface water that are critical to the health of ecosystems. However, phytoplankton overgrowth due to eutrophication threatens ecological, economic, and public health. Therefore, assessing phytoplankton is fundamental for understanding the productivity, health, and trophic status of freshwater ecosystems. Light microscopy and chlorophyll a assessment are common approaches for studying phytoplankton. They are easy to use, cost-effective, and reliable but have significant limitations. Microscopy has a low throughput and is time-consuming and labor-intensive. Chlorophyll a assessment does not reveal phytoplankton community composition and structure. For comparison, quantitative polymerase chain reaction (qPCR) is widely applied in quantifying microorganisms, offering multiple advantages, including high throughput, sensitivity, accuracy, and robustness. However, a research gap remains regarding the feasibility of using qPCR to assess phytoplankton and indicate trophic status of freshwater bodies. We conducted a nationwide, multiyear study in the United States to compare the performance of qPCR, microscopy, and chlorophyll a assessment in assessing phytoplankton and trophic statuses of multiple freshwater rivers. From early summer to late fall in 2017, 2018, and 2019, we assessed phytoplankton, chlorophyll a , pheophytin a , and the overall Trophic Level Index ( TLI Overall ) at the sampling sites in 12 large freshwater rivers in three regions (western, midcontinent, and eastern) across the United States. The seasonal summed abundance of four major phytoplankton taxa [Bacillariophyta (diatoms), Cyanobacteria (blue-green algae), Chlorophyta (green algae), and Dinoflagellates (Dinophyta)] ranged from 6.88 log 10 (GCN·L –1 ) (the Connecticut River, 2017) to 9.29 log 10 (GCN·L –1 ) (the Kansas River, 2019) (GCN: gene or genome copy number). qPCR- and microscopy-based phytoplankton abundance of eight phytoplankton taxa had a significant positive allometric or log-linear correlation (adjusted R 2 = 0.836, p -value < 0.001, n = 815). In addition, qPCR-based phytoplankton abundance had positive allometric or log-linear correlations with chlorophyll a (adjusted R 2 = 0.5437, p -value < 0.001, n = 164), pheophytin a (adjusted R 2 = 0.3378, p -value < 0.001, n = 164), and TLI Overall (adjusted R 2 = 0.4789, p -value < 0.001, n = 164). Therefore, qPCR is a promising alternative to microscopy and chlorophyll a for studying phytoplankton and trophic status in freshwater rivers. Moreover, phytoplankton abundance had limited temporal variation within each sampling season and over the three sampling seasons in 2017, 2018, and 2019 but showed clear spatial variation. The midcontinent sites had significantly higher phytoplankton abundance, chlorophyll a concentrations, pheophytin a concentrations, and TLI Overall values than those in the eastern and western rivers, reflecting the higher trophic statuses of the midcontinent rivers. This work also provides the thresholds of qPCR-based phytoplankton abundance for delineating trophic statuses in freshwater rivers. Overall, this work demonstrates that qPCR is a promising tool for studying phytoplankton and characterizing the trophic status of freshwater rivers.

Book chapter↗
USGS2026

Erosion and transport of sediments in watersheds of southwest Puerto Rico determined from strontium isotopes and mixing models

Sediment outflow from streams to coastal regions can adversely affect water quality and the health of ecosystems including Puerto Rico's southwestern carbonate platform with shallow marine communities. Knowledge of sediment provenance and erosional areas would aid effective restoration to reduce excessive sedimentation. Strontium (Sr) isotopic ratios ( 87 Sr/ 86 Sr) can be used to differentiate between sediment eroded into streams from different lithologies, or rock types, and used in mixing models to estimate proportions of source materials in downstream mixtures. The goal of this study was to use Sr isotopes to differentiate between river sediments in drainages with distinct geologies and present a case study where Sr isotope mixing models are used to identify sediment sourcing to Río Loco and Bahía de Guánica, a priority watershed of the U.S. Coral Reefs Task Force. For the Río Loco watershed, model results indicate that serpentinites in the uplands contributed approximately 71 % of sediment to Bahía de Guánica. About 21 % of sediment was from trachy-andesitic basalts in the foothills, and the remaining 8 % originated from sources on the coastal plain. Neither the uppermost headwater region of Río Loco, the Canal Principal De Riego Valle De Lajas, nor the tributary Quebrada Susúa appeared to be significant sources of sediment to Río Loco's mainstem or Bahía de Guánica at the time of the study. Our results demonstrate that sediment from the serpentinite-bearing areas of Río Loco watershed was effectively transported to the lowlands, which then discharge into Guánica Bay, and highlight the potential use of Sr isotopes as tracers of sediment provenance. This will, in turn, enable better science-based restoration efforts aimed at reducing terrestrial sediment erosion and impacts to marine ecosystems.

Puerto Rico↗
USGS2026

PFAS exposure suppresses leaf litter decomposition in a stream ecosystem

Decomposition of organic matter is critical to the biogeochemical cycling of carbon and nutrients in all ecosystems. In streams, decomposition can be influenced by anthropogenic impacts, including contaminants. Per- and polyfluoroalkyl substances (PFAS) are resistant to degradation and widespread in freshwater ecosystems, yet little is known about their influence on organic matter processing in streams. We paired an observational field study of a PFAS-impacted stream via food processing wastewater with a 28-day laboratory experiment to investigate PFAS effects on leaf litter processing using multiple lines of evidence. Leaf litter decomposition rates and microbial respiration were significantly lower downstream of the PFAS point-source compared to the paired upstream site. We hypothesized that PFAS suppressed microbial activity thereby resulting in slower decomposition rates. To investigate further and better isolate PFAS, we dosed aquatic mesocosms containing leaf packs with differing concentrations of perfluorooctane sulfonate (PFOS). Over the 28-day incubation, decomposition rates did not differ, but we observed lower respiration rates on day 28 and higher dissolved organic carbon (DOC) in PFOS-dosed mesocosms, suggesting that PFAS may suppress microbial activity and inhibit carbon processing. These results underscore that concerns regarding PFAS contamination extend beyond organismal toxicity to ecosystem-level effects. Further research is needed to understand the scale, implications, and mechanisms responsible for these changes.

Upper Mississippi River Basin↗
USGS2026

Global change and threats to waterbirds in the Asian flyways

Avian migration represents one of nature’s most spectacular phenomena, providing critical ecological services and acting as an indicator of environmental change. Flyways are geographical ranges through which migrating bird species move, and the flyway concept has been used to identify countries that share species to highlight their collective responsibility for conservation. Of the nine recognized global waterbird flyways, the Central Asian Flyway (CAF) and the East Asian–Australasian Flyway (EAAF) are among the most important areas in Eurasia, supporting millions of waterbirds across a vast network of habitats. We proposed this special issue in Avian Research entitled “Global Change and Threats to Waterbirds in the Asian Flyways” to synthesize recent findings from 12 papers covering a wide range of topics. The CAF stretches from the Siberian tundra through Central Asia including Mongolia, the Qinghai-Tibet Plateau, the Trans-Caucasus, and the Himalayas, extending south to the Indian subcontinent and parts of the Middle East. The EAAF spans eastern Siberia and Alaska to Southeast Asia, Australia, and New Zealand, including China, Japan, the Korean Peninsula, and the Russian Far East. These two flyways include 47 countries comprising critical wetlands, river basins, and coastal areas, which are vital breeding, stopover, and wintering grounds for waterbirds. Seasonal migration in these flyways is fundamentally influenced by climate and weather conditions, land cover dynamics, and anthropogenic activities, and contributes significantly to ecological processes such as pest control, nutrient cycling, and organism dispersal. However, migratory waterbirds and their habitats are undergoing enormous challenges. Changes in climate, habitat availability and connectivity, and human activities are altering the phenology, distribution, population dynamics, and health of the migratory bird populations. As migratory waterbirds travel across international boundaries, understanding their movements and responses to environmental change requires collaborative, cross-border research efforts that promote knowledge sharing and interdisciplinary approaches.

Avian Research↗
USGS2026

Wildfire smoke reduces the vocal activity of imperiled grassland birds in New York State

Smoke from new fire regimes driven by climate change may affect biodiversity in new regions of the world. Wildfires that occurred in eastern Canada in 2023 burned nearly 7.8 million hectares of forest, sending smoke throughout the northeastern United States. We leveraged passive acoustic monitoring to investigate real-time effects of wildfire smoke on vocalization behavior of globally imperiled grassland birds during the breeding season in open land covers across New York State. We determined an overall negative effect of elevated smoke levels on breeding grassland bird vocal activity. We observed the strongest vocalization responses in Bobolink ( Dolichonyx oryzivorus ) – a colonial breeding, grassland-obligate species; Bobolink vocal activity sharply dropped during intense smoke early in the breeding season, yet increased during a milder smoke event later in the breeding season. Our results indicate that wildfire smoke can present an additive stressor to already imperiled grassland bird species via potential fitness reductions from decreased communication. While some aspects of smoke exposure may be uncontrollable, our results suggest that increased attention to conservation practices that promote grassland birds in the Northeast could be prioritized to offset negative effects of increased smoke associated with global change.

New York↗
USGS2026

Where will the cat cross the road? Comparing camera and GPS-based models for identifying wildlife corridors

Designing effective wildlife corridors is a critical conservation challenge in fragmented landscapes. GPS-based step selection functions strongly predict dispersal corridors and connectivity, but GPS collaring can be expensive and invasive. Camera-based occupancy models are widely used for connectivity analyses but may involve trade-offs in data resolution. Despite widespread use of both approaches, few studies have directly compared them using concurrent datasets. We developed a stacked single-species, single-season occupancy model and a Circuitscape connectivity surface for mountain lions (Puma concolor) on Washington’s Olympic Peninsula, USA, and compared them with a connectivity surface from an existing integrated step selection function. Both models predicted mountain lion GPS locations well, with binned Spearman rank correlations of 1 for Circuitscape and 0.96 for the step selection function, though step selection better identified habitat use by dispersers. Connectivity predictions were moderately correlated across the landscape ( r = 0.26), but agreement was strongest in human-dominated areas most critical for corridor planning. We conclude that GPS-based approaches are advantageous when data collection is feasible and the focus is on dispersal or fine-scale movement. However, camera-based approaches may be preferable for multi-species monitoring, large spatial and temporal scales, noninvasive sampling, when resources are limited, or when fine-scale or dispersal-specific inference is not required.

Washington↗
USGS2026

Rhyolitic and basaltic reference materials for TC/EA analysis: Investigation of water extraction and D/H ratios

Increasingly, water and D/H ratios of silicic and basaltic glasses are used to investigate magmatic degassing and secondary hydration, as well as for study these parameters in the mantle and crustal magmas. The advent of the High Temperature Conversion Element Analyzer (TC/EA) continuous flow mass spectrometry made the determination of hydrogen isotopes relatively quick and precise (±0.04 wt% H 2 O and 1–3‰ δ 2 H). Many labs around the world have such systems, thus there is a need to develop both silicic and basaltic volcanic glass reference materials (RMs) that can be used for interlaboratory comparison by bulk and microanalytical methods. Here, we report results of such investigation run against solid RMs (USGS micas) and water RMs (including VSMOW) in three different labs and describe analytical protocols. We report on the effects of glass size fraction, the mass of aliquots measured, and yield dependency for two glasses: UOR (drill cutting of IDDP-1 rhyolite, Iceland) and UOB (an E -MORB basalt from the East Pacific Rise). Proposed RM values are: UOB rhyolitic glass ( n = 31): H 2 O = 1.84 ± 0.06 wt% (1 s.d.), and δ 2 H = −115.5 ± 2.6‰ (1 s.d.). UOB basaltic glass ( n = 60): H 2 O = 0.37 ± 0.03 wt% (1 s.d.), and δ 2 H = −82.1 ± 5.7‰ (1 s.d.). Glass reference materials are available in 100 mg quantities from the Stable Isotope Laboratory at the University of Oregon for a nominal fee.

Chemical Geology↗
USGS2026

Utilization of multiple geochronology techniques to constrain the age of laterization and mineralization of the world-class Mount Weld rare earth element deposit, Western Australia

Pervasive chemical weathering on stable cratons may form thick regoliths and elemental enrichment, but constraining the age of regolith formation is challenging. In this study we utilize multiple geochronological techniques on different minerals from the world-class Mount Weld rare earth element (REE) deposit, formed by lateritic weathering of a carbonatite, to constrain the age of formation and provide insight into landscape evolution. The oldest dates, ca. 100 to 38 Ma, are from Lu-Hf dating of churchite [HREE(PO 4 )·2(H 2 O)], a heavy REE phosphate mineral. Growth bands on individual minerals show a younging outwards. 40 Ar/ 39 Ar geochronology of cryptomelane [K(Mn 4+ ,Mn 2+ )₈O₁₆] yielded dates from ca. 40 to 27 Ma. Similarly, (U-Th)/He geochronology of goethite [FeO(OH)] yielded dates ranging from ca. 45 to 19 Ma. Integrating results into regional constraints, suggests 1) churchite formed by mineral saturation in a karst-like setting below the water table from ca. 100 to 40 Ma, 2) with minor uplift and erosion, cryptomelane and goethite formed at or near the water table between ca. 45 and 19 Ma, 3) after ca. 15 to 10 Ma chemical weathering within the profile had ended. Other studies document that the region experienced minimal uplift and a wet, warm climate from ca. 100 Ma to 15 Ma. These conditions and the high carbonate content of the carbonatite promote extensive chemical weathering, a deep weathering profile, and the preservation of the weathered section. This study highlights the use of multiple geochronological techniques utilizing different minerals to provide insight into how laterites form and to constrain the timing and history of the formation of this important mineral deposit.

Western Australia↗
USGS2026

Integrating detrital magnetite geochemistry and (U-Th)/He chronometry as a sediment provenance tool in geologic and metallogenic terranes

Magnetite is ubiquitous in porphyry Cu systems and in sediment sourcing both barren and mineralized regions, with potential as an indicator mineral in concealed and coarsely-mapped terranes. We develop and test a workflow for integrated geochemistry and (U–Th)/He (He) dating for inferring detrital magnetite (DMt) provenance in these settings. The ca. 70 Ma Taurus porphyry Cu–Mo(–Au) district in eastern interior Alaska serves as a test case. DMt from streams draining porphyry-related mineralization was characterized by geochemistry and mineral inclusion and microstructure observations, complemented by similar data for potential porphyry and host rock sources. Principal component analysis and clustering of DMt geochemical data resolve multiple populations in our samples geochemically and texturally compatible with derivation from metamorphic, porphyry-related hydrothermal, and igneous sources. Hydrothermal magnetite comprises ∼16–50% of DMt nearest porphyry mineralization but diminishes to ∼4% ∼15 km downstream. Subsampled grains within populations yield ∼160–110 Ma, ∼70 Ma, ∼55 Ma, and ∼20 Ma magnetite He date modes. Combined with provenance, He dates capture Early Cretaceous regional exhumation of metamorphic host rock and Late Cretaceous porphyry Cu mineralization. DMt grains showing partial hematite replacement yield ca. 55–20 Ma dates regardless of source, overlapping regional warm/wet climatic intervals. We interpret Cenozoic dates to reflect exhumation to near-surface oxidizing conditions and(or) supergene weathering. Magnetite is thus a promising target phase for (1) tracking the spatiotemporal distribution of porphyry systems, and (2) linking the formation and exhumation of these systems to a regional geologic history, both in Alaska and globally.

Alaska, Yukon↗
USGS2026

HyFlood: A surrogate-model-based framework for compound coastal flooding

Compound coastal flooding is a major threat to low-lying coastal regions and is expected to intensify under future climate change projections. However, modeling the joint interaction of waves, storm surge, tides, and rainfall remains computationally demanding, limiting the development of fast and reliable forecast tools. Here we present HyFlood, a hybrid statistical-numerical downscaling framework capable of computing and mapping high-resolution compound flood hazards while substantially reducing the computational cost compared with fully process-based hydrodynamic modeling. HyFlood combines statistical sampling and selection algorithms with a cascade of reduced-complexity surrogate models that emulate nearshore wave transformation, surf-zone hydrodynamics, and coastal, fluvial, and pluvial flooding. The surrogate models employ machine-learning and regression algorithms applied to a low-dimensional representation of the flooding outputs, obtained through statistical dimensionality reduction. The framework is demonstrated in southern O'ahu, Hawai'i, a region exposed to elevated sea levels driven by tides, waves, and storm surge along with frequent precipitation-driven flash flooding. Validation of the surrogates against the physics-based model outputs demonstrates that HyFlood accurately reproduces daily maxima of spatially distributed flooding depths. This hybrid approach offers a scalable and efficient tool to better quantify how changes in flooding drivers translate into hazard and impact assessments, and to support compound-flood risk assessments and climate-change adaptation planning.

Hawaii↗
USGS2026

Foraging benefits promote fitness in migratory mule deer

Although migration is widespread among ungulates, the fitness benefits associated with different migratory tactics have rarely been documented. Here, we evaluated a 9-year dataset on a migratory population of mule deer to test the hypothesis that long-distance migration provides access to seasonal forage which translates into demographic benefits. Mule deer that migrated long (>130 km) and medium distances (50–130 km) accessed higher forage quality and thus gained 1.3–2.7 times more fat over the growing season compared to mule deer that remained year-round as residents within a desert ecosystem. Elevated levels of fat translated to ∼20% higher probability of adult annual survival than residents. Mule deer that remained year-round in the desert portion of the study area were so resource-limited that they raised fawns at the expense of their own survival. Due to their higher levels of fat, annual survival, and fetal rates, migrants showed more robust population growth (λ = 1.03) compared to residents, which exhibited projected declines in population size over time (λ = 0.95). These results support the notion that migration translates into demographic benefits and highlight the urgent conservation work necessary to sustain diverse ungulate migrations amid habitat alteration due to climate change and an expanding web of linear barriers to movement.

Wyoming↗
USGS2026

Guidelines for producing integrated 210Pb and 14C age-models

Accurate reconstructions of past environmental changes are crucial in paleoecological research and require reliable chronologies of sedimentary archives. Establishing robust age-models and obtaining the most appropriate proxies for analysis is a complex scientific endeavor, requiring extensive resources and collaboration among specialists, including radiochronologists. Radiometric dating methods, such as 210 Pb and radiocarbon ( 14 C), are frequently employed to establish chronologies in aquatic sedimentary deposits and peat bogs. In this study, we review key aspects of sampling, analysis, and the principles underlying 210 Pb and 14 C age-models, focusing on methods for developing robust joint chronologies for paleoenvironmental research. Drawing largely from the authors' experiences and group discussions during and after a scientific workshop in 2022, we discuss important considerations for site selection, sampling strategies, and radiometric dating to construct integrated 210 Pb and 14 C age-models. Using expert consensus, this group – called Paleostats – aims to provide a set of best practices for other geochronologists with this methods paper. Among our conclusions, we emphasize the importance of accounting for site-specific factors such as prior information on sedimentation rates to establish appropriate sampling and analytical strategies. The use of appropriate coring devices can minimize disturbance to sediments and ensure the core surface remains intact and preserved until sectioning. Where excess 210 Pb is expected, sectioning at intervals of ≤1 cm provides an adequate sampling resolution for 210 Pb dating. Exceptions are possible, allowing for ~2–3 cm sections in areas with confirmed high sedimentation rates (e.g., > 1 cm yr −1 ). Recovering deeper core sections for 14 C dating with sufficient overlap allows for accounting errors in depth estimates made in the field. Special attention is advised during time intervals where validation proxies, such as the human-made radionuclides 137 Cs or post-bomb 14 C, are expected, and to determine the depth of secular equilibrium between 210 Pb and 226 Ra. Radiocarbon analyses are commonly performed by accelerator mass spectrometry, and age models are constructed mainly using Bayesian statistics with Markov Chain Monte Carlo techniques (e.g., Bacon ). A Bayesian approach ( Plum ) is now available for producing 210 Pb age-models, which infers the 210 Pb ex flux, eliminates the need for selecting an equilibrium depth, and allows dating cores with incomplete 210 Pb ex inventory. Plum offers improved chronologies by integrating raw 210 Pb and 14 C data, and these age-models can be enriched with other dating methodologies, such as identifying tephras and other well-recorded historical events. Harmonized reporting would contribute to making radiometric age-models reproducible, which would benefit from an international effort. Using 210 Pb and 14 C to produce integrated age-models may yield better insights into the interplay between natural and recent anthropogenic forcings on ecosystems. This can enhance our understanding of environmental processes and their impacts on climate change, ultimately supporting science-based assessments and decisions.

Earth-Science Reviews↗
USGS2026

Understanding the resource potential of natural hydrogen on Earth: Scientific gaps, uncertainties and recommendations

A comprehensive scientific research roadmap is essential to bridge knowledge gaps and deepen the understanding of key geological, geochemical, and geophysical aspects of natural hydrogen (H 2 ) as a potential new energy resource. This paper reviews major scientific uncertainties on natural H 2 , suggesting research priorities, as a guide for defining exploration strategies, techniques, and data interpretation. The uncertainties concern all phases of the natural H 2 cycle, from generation (source rocks) through migration (advection and diffusion) and accumulation (reservoir and cap rocks) to the application and interpretation of subsurface and surface geochemical and geophysical exploration techniques. Understanding H 2 sources and generation rates (the amount of H 2 generated by a given volume of rock over time) is crucial for determining whether a geological H 2 system operates as a short-term dynamic system with rapid H 2 production and release, or as a conventional gas system with long-term accumulations, analogous to petroleum reservoirs. Preliminary estimates for serpentinisation, radiolysis, and organic matter degradation suggest that H 2 generation is not inherently fast, especially for non-hydrothermal continental systems (crystalline basement of shields, ophiolites, peridotite massifs, sedimentary basins), and long-term accumulations, like those of fossil natural gas systems, represent the most likely scenario. The mechanisms of H 2 migration through geological formations require application of fundamental principles of fluid-flow physics, distinguishing advection and diffusion, as well as their forms (from gas-phase, bubble flows to aqueous solutions). Additional studies of H 2 accumulation and retention in subsurface reservoirs could improve understanding of mechanisms of H 2 migration by focusing on the rock fluid-bearing properties and the factors affecting H 2 preservation, such as the presence of cap rocks impermeable to H 2 , pressure conditions, residence times, and microbial or abiotic consumption. Advanced techniques, including reservoir modelling, flow simulations, 3D imaging (micro-CT) of H 2 -bearing rocks, and extraction and analysis of gas occluded in rocks, can provide insights into the stability and potential recoverability of H 2 accumulations. The interpretation of surface exploration techniques, including gas geochemistry, geophysics, and remote sensing, long employed in mineral and energy resource exploration, is now being adapted for natural H 2 studies, but challenges remain in the data interpretation. Distinguishing H 2 seepage due to geological degassing from H 2 produced near the surface by modern microbial processes or artificial sources, such as hammering or drilling for soil-gas sampling, drilling into aquifers, and corrosion in boreholes, is an essential step in exploration. The simple detection of H 2 in soils, even in morphological structures like sub-circular depressions or “fairy circles”, cannot be cursorily interpreted as a signal of natural H 2 seepage from a deep source. A holistic geochemical approach, including isotopic analyses of gases associated with H 2 , is recommended to distinguish among the variety of possible H 2 origins. Observations of H 2 in wells should be interrogated to rule out possible artifacts such as corrosion and drill bit metamorphism. The integration of multiple geophysical methods, including seismic, gravimetric, magnetic, and electro-magnetic surveys, is recommended to mitigate interpretation ambiguities regarding the structure of a subsurface H 2 system (source and reservoir rocks, including fluid and gas storage), due to the non-uniqueness of rock-specific physical properties.

Earth-Science Reviews↗
USGS2026

Estimating paleotemperature using stable isotopes of soil-formed phyllosilicates from paleosols: A review

Fossilized soils, or paleosols, contain soil-formed phyllosilicates whose stable isotopic compositions may be used to calculate paleotemperature and thus reconstruct ancient terrestrial environments. Though paleosols are common in the geologic record, the use of phyllosilicates as paleotemperature proxies is limited in the literature owing to difficulties with selecting optimal paleosols, isolation from non-clay minerals and organic materials, mixtures of phyllosilicates in natural samples, wide variations of chemical compositions for phyllosilicates, and limited to undefined equilibrium fractionation factors between phyllosilicates-water. Here, we address these challenges by examining and comparing methods used for sample selection, mineral isolation, pretreatments, mineral identification, conventional and developing methods for oxygen and hydrogen isotopic analyses, and determination of phyllosilicate-water equilibrium fractionation factors, concluding with recommendations for best approaches for paleotemperature estimation. Additionally, we discuss how to identify and avoid detrital phyllosilicates, the impacts of diagenesis, comparison of stable isotope and non-isotope paleosol paleotemperature proxies, and challenges and opportunities for broadly using paleosols as paleoclimate archives. With ongoing efforts to refine this multi-faceted paleotemperature approach, the stable isotope geochemistry of soil-formed phyllosilicates continues to be an invaluable proxy system, enhancing our understanding of terrestrial paleoenvironments and paleoclimate.

Kansas↗
USGS2026

Hierarchical mixture models and high-resolution monitoring data can inform siting and operational strategies to mitigate bat fatalities at wind turbines

Bats provide critical ecosystem services, but bat fatalities due to wind energy development may imperil some bat populations. Statistical models are used to estimate the total fatalities that occur based on carcasses observed during monitoring surveys. Current models often estimate fatalities aggregated across species, time, and/or turbines, but fall short of reliably informing siting and operational collision mitigation strategies that account for species-specific fatality patterns on a fine spatiotemporal scale. We developed a hierarchical mixture model for estimating species-specific covariate effects and total fatalities per species at each turbine on weekly intervals. We applied the model to a high-resolution dataset of bat carcasses found during turbine searches across nineteen wind facilities in Iowa over two years. Our model explains species-specific variation in bat fatalities at individual wind turbines according to turbine proximity to bat habitat, turbine design specifications, seasonal trends, and weather conditions such as nightly air temperature, air pressure, and wind speed. Turbines located on the edge of wind facilities had higher fatalities, and proximity to roosting and foraging habitat accounted for variation in species-specific fatality estimates. These insights into turbine placement effects can inform siting strategies. We also discovered species-specific relationships with average nightly wind speed and air temperature, among other weather conditions, that could inform operational mitigation strategies such as smart curtailment. Our model can transform observations of carcasses found during turbine searches across multiple facilities, years, and variable search efforts into estimates of total fatalities per species associated with species-specific spatial, temporal, and environmental covariate effects.

Ecological Informatics↗
USGS2026

Two-stage approach to automatic detection with machine learning for improved surveillance of the invasive Cuban treefrog

The Cuban treefrog ( Osteopilus septentrionalis ), as an invasive species in the southern United States, presents a need for effective surveillance. Automated detection expedites processing of audio data for large-scale surveillance and monitoring programs. However, current available methods commonly used for anuran species have not been sufficient to detect Cuban treefrogs. Here, we present results from a two-stage method for automated detection that employs both cross-correlation template matching and secondary supervised learning classifiers. In the first stage, audio data are screened for initial detections using template matching, in which the detections contain both true and false positives. In the second stage, the false positives are screened out using classifier algorithms. We used this method to process 139,985 audio recordings, consisting of 596,046 total minutes, collected at 13 locations in Louisiana and Florida from 2014 to 2022. From the stage 1 template matching, we detected 83,191 Cuban treefrog signals across recordings. The stage 2 machine learning model was able to identify stage 1 false positive detections with a testing accuracy of 98.46% and a testing false positive rate of 1.116%. After pruning false positive detections, a total of 20,271 individual Cuban treefrog detections remained, distributed mainly across 3 sites in an area with known presence. Locations with presumed absence had an easily verifiable number of false positive detections ( n = 109 across all other sites). The two-stage methodology utilizing both template matching and machine learning algorithms can be integrated into wildlife surveillance or monitoring programs for species with distinctive, conserved calls as an effective way to achieve sensitive species detection with a low incidence of false positives.

Florida, Louisiana↗
USGS2026

A site prioritization tool for invasive species management: Integrating diverse spatial data to improve decision making

Resource managers are tasked with protecting natural areas from invasive species with limited resources. Further, invasive management goals can vary greatly based on different management priorities specific to management agencies or taxa of interest. The site prioritization tool for invasive species management addresses these challenges by creating a platform to view and combine diverse spatial data layers to estimate cumulative invasion risk based on user-specific needs. For this tool, we developed a human transport risk layer, estimating invasion risk based on proximity to human population centers and transportation corridors, and created maps of non-native species richness across the conterminous United States. The tool also includes spatial layers showing projected changes in key climate variables through the end of the century to identify areas where invasion risk may shift. Users can explore these layers to prioritize sites based on the invasive taxa of interest, likely invasion pathways, and disturbances that may elevate invasion risk. This interactive tool will allow managers to make the spatial comparisons needed to focus efforts on areas that are highly susceptible to invasion and efficiently target monitoring and suppression efforts.

Ecological Informatics↗