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USGS2026

Fifteen years of WRTDS for advancing water-quality science: A critical review of methodological developments and global applications

Contamination by nutrients, major ions, and metals poses a major threat to global water sustainability. Understanding how these pollutants vary across time and space requires long-term monitoring and robust statistical approaches. Traditional methods, however, often struggle to account for streamflow variability, seasonality, and nonlinear responses. Introduced in 2010, the Weighted Regressions on Time, Discharge, and Season (WRTDS) method offers a flexible, data-driven framework that generates both observed and flow-normalized estimates of concentration and load. Over the past 15 years, WRTDS has become a state-of-the-art tool for water-quality science and management, with applications spanning a wide range of hydrologic, climatic, and policy contexts─including major watersheds across North America, Europe, Asia, Australia, and the Arctic. In this review of WRTDS, we document the method’s major advancements, examine its expanding geographic and thematic applications, and summarize its relevance to water-quality management programs and policies worldwide. We also discuss its performance relative to other regression and machine-learning approaches. Finally, we identify key priorities for future development to support the continued evolution of WRTDS as a trusted and practical tool for scientists and managers working to protect and sustain water resources.

Environmental Science and Technology↗
USGS2026

Towards affordable wetland evapotranspiration monitoring using the Variance-Bowen Ratio method: Insights from three contrasting wetlands

Accurate measurement of evapotranspiration (ET) is essential for sustainable water management. Standard methods such as eddy covariance (EC) are costly, while alternatives such as surface renewal are cheaper but require calibration and complex data processing. This study evaluates the utility of the Variance-Bowen Ratio (VBR) method for estimating ET across three California’s wetlands. Using data from 2023, half-hourly latent heat flux (λE) and daily/monthly ET from VBR were compared with EC at one non-tidal (site A) and two tidal (sites B and C) wetlands. λE VBR consistently underestimated λE EC , with root mean squared errors (RMSE) of 61.2 W m -2 at sites A, 106.1 W m -2 at site B, and 137.2 W m -2 at site C, largely due to storage fluxes across sites. Temporal integration improved VBR’s performance at tidal sites, where compensating water heat storage errors yielded low daily and monthly biases (site B: RMSE = 0.78 mm/d and 12 mm/month; r = 0.93; site C: RMSE = 0.90 mm/d and 13 mm/month; r = 0.93), with reduced major axis (RMA) regression slopes of 0.98 and ~0.91. In contrast, biomass heat storage at site A caused persistent biases (RMSEs = 0.97 mm/d and 23 mm/month; daily and monthly RMA slopes ~0.75; r = 0.85). These results highlight VBR’s limitations in environments with substantial storage fluxes. Despite this, VBR is cost-effective for estimating daily and monthly ET, with sensor costs at least tenfold lower than EC and simpler setup, making it suitable for ET monitoring in resource-limited and hard-to-access regions.

California↗
USGS2026

The interplay of habitat quality and temperature shape demographic patterns of mule deer (Odocoileus hemionus) in North America

Mule deer ( Odocoileus hemionus ) are declining in abundance across their broad distribution in western North America. Identifying drivers of mule deer demography could inform habitat restoration. However, linking habitat quality to vital rates is challenging and often done indirectly using proxy metrics. We combine habitat selection with climate-related effects to identify synergistic influences affecting mule deer age ratios (fawn:doe). We used location data from 1473 female deer over 22 years in Wyoming to fit seasonal resource selection models, predict habitat suitability, and model age ratios as a function of drought conditions, winter severity, and seasonal habitat. Here we show temperature had the largest effect on mule deer recruitment with age ratios declining following hotter summers and colder winters. Age ratios increased with higher proportions of habitat with high-quality summer habitat of particular importance. Given the likely increases in summer temperatures and extreme winter weather events, populations may struggle to increase recruitment over the next half-century. Targeted management supporting forage quantity and quality, especially on summer range, could buffer the effects of decades-long drought conditions. Our findings also indicate mule deer avoid areas with high densities of oil and gas development. By delineating important mule deer habitat, we offer spatial tools for development siting and mitigation in Wyoming and a framework for broader application across the western United States.

Wyoming↗
USGS2026

Global glacier mass change in 2025

Glaciers lost 408 ± 132 Gt of mass during the hydrological year 2025, equivalent to 1.1 ± 0.4 mm sea-level rise. Since 1975, glacier mass loss has totalled 9,583 ± 1,211 Gt, equivalent to 26.4 ± 3.3 mm of sea-level rise, with six of the highest mass-loss years on record occurring in the past seven years.

Nature Reviews Earth and Environment↗
USGS2026

Nutritional and reproductive dynamics of moose near their southern range limit

Understanding the relationships between nutrition and life-history characteristics can provide insight into the factors limiting populations. Moose ( Alces alces ) at their southern range periphery are subject to nutritional constraints because of marginal climatic and habitat conditions, but how these limitations influence vital rates remains a point of uncertainty. We examined the nutritional and reproductive dynamics of moose at the fringes of their range in southeast Wyoming, USA. We used an individual-based approach to evaluate the nutritional condition (i.e., body fat) of female moose by recapturing the same individuals each autumn and spring to measure body fat, pregnancy, recruitment of offspring, and survival. Like other temperate ungulates, we anticipated that moose would accumulate body fat over summer and use those reserves to support survival and reproduction over winter. Throughout the annual cycle, we expected that body fat, an integrated measure of energetic gains and losses, would influence pregnancy, recruitment, and adult survival. Contrary to expectations, body fat varied by less than 1.5 percentage points between autumn and spring. Despite relatively low seasonal fluctuations, body fat was positively associated with probability of pregnancy and adult survival but did not influence recruitment of young. Moreover, age influenced probability of pregnancy and overwinter survival. We demonstrate clear signs of nutritional limitation and unexpectedly absent relationships between body fat and recruitment that may be unique to moose living at the fringes of their range, highlighting environmental constraints on reproduction at distributional limits. By investigating the connections between nutrition and reproduction in southern moose, we provide insight into how vital rates can be used to monitor demographic performance for at-risk populations.

Wyoming↗
USGS2026

Between quiescence and crisis: Hawaiian Volcano Observatory communication and response strategies on the Island of Hawaiʻi

Over the past two centuries, eruptions of Mauna Loa volcano have damaged infrastructure and destroyed several communities on the Island of Hawaiʻi. Future eruptions will impact existing population centers and critical infrastructure, which continue to grow each year. The U.S. Geological Survey Hawaiian Volcano Observatory has developed and practiced methods to promote eruption preparedness in communities on the Island of Hawaiʻi, particularly over the past three decades during which Mauna Loa was quiescent while Kīlauea volcano erupted frequently. Here, we summarize the observatory’s efforts to increase awareness of hazards associated with Hawaiian volcanoes and describe how lessons learned during responses to past volcanic crises on Kīlauea were applied prior to and during the 2022 Mauna Loa eruption, highlighting new response communication challenges encountered during the event. Additionally, we identify potential avenues for future communication/outreach on the Island of Hawaiʻi, such as expanding efforts in communities located in high-hazard areas and striving to be more culturally and linguistically inclusive in our communication techniques.

Hawaii↗
USGS2026

First vertebrate assemblage from the middle member of the Fremouw Formation (Lower Triassic) of Antarctica

The Fremouw Formation of the Central Transantarctic Mountains preserves the southernmost record of Early to Middle Triassic terrestrial ecosystems that developed in the aftermath of the end-Permian mass extinction. Although the well-studied vertebrate fossil assemblage in the lower member of the Fremouw Formation provides a detailed snapshot of subpolar ecosystems immediately following the end-Permian mass extinction, the nature of how long these earliest Triassic communities persisted at the southern extremes of Pangaea is virtually unknown. Importantly, the timing and extent of the major faunal turnover between the lower and upper members of the Fremouw Formation have been obscured by the paucity of fossil specimens historically recovered from the middle member. Here, we describe the first vertebrate assemblage from the middle member of the Fremouw Formation, including occurrences of procolophonids (including Procolophon trigoniceps ) and archosauromorphs (including Prolacerta broomi ), as well as infilled vertebrate burrow casts referrable to the ichnogenus Reniformichnus . We also summarize and expand on lithostratigraphic shifts between the lower, middle and upper members of the Fremouw Formation. Although the sample size of vertebrate body fossils is small compared to the lower and upper members of the Fremouw Formation, we discuss the evidence for a taphonomic shift between the lower and middle members of the Fremouw Formation that favours preservation of smaller-bodied taxa and individuals in the latter. Together, these preliminary data add crucial context to the persistence of subpolar vertebrate communities in the earliest Mesozoic.

Antarctic Science↗
USGS2026

Permafrost thaw controls iron flux from wetlands and sulfide-bearing rocks to Arctic rivers and streams

Recent warming has caused widespread iron mobilization into Arctic waterbodies that degrades ecosystems and threatens natural resources. Yet, understanding where and when iron flux occurs remains limited. Here, we investigate iron loading across regional to local scales in Arctic Alaska using climate, water chemistry, and borehole data together with mapped geology and permafrost presence. We show that both anoxic microbial iron reduction and acid rock drainage from iron-sulfide oxidation mobilize iron. Iron influx is strongly associated with lowland wetlands, sulfide-rich upland bedrock, and near-surface permafrost. Acid rock drainage chemistry correlates very strongly with the depth of seasonal thaw above permafrost from the previous year, indicating a one-year lag. These findings clarify the spatial and temporal dynamics of Arctic river rusting, provide a mechanistic understanding of the phenomenon, and may allow anticipation of its occurrence and assessment of its implications for aquatic ecosystem health and subsistence resources under ongoing climate change.

Alaska↗
USGS2026

When is a parasite a problem?

A parasite’s perceived societal impact depends on the disease it causes and the perception of the affected host species. For instance, doctors and veterinarians have a mission to treat parasites that infect humans or that impact host species that have some utilitarian or aesthetic value for society. Marine scientists have different concerns than doctors. Although the number of parasites that marine scientists should be concerned about may vary, only 13% of parasites and 6% of host–parasite links might be considered “problematic” in a kelp forest food web. With regard to the many threats to marine ecosystems, these percentages suggest that most parasites and infectious diseases are inconsequential. A related issue is the common expectation that parasites and the impacts that they cause are increasing under stress as ocean environments across the globe degrade. Yet, reports of disease have not increased due to human impacts on the marine environment, where the factors that influence parasitism are more complex. Thus, the expectation that marine parasites create problems, and that the diseases they cause are getting worse, is more likely the exception than the rule.

Book chapter↗
USGS2026

Growth, movement, and survival of precocial shorebird chicks are constrained by their environment.

Young animals are often less mobile than adults, while also having high energetic demands. They may therefore be more vulnerable to local-scale changes in environmental conditions. In particular, when 1 sex must grow more rapidly than the other to achieve a larger adult size, that sex may experience especially dramatic reductions in growth and survival in the face of suboptimal environmental conditions. In order to investigate the flexibility of individuals in response to local-scale environmental variation during development, we studied the sex-specific growth, movement, and survival of Hudsonian Godwit ( Limosa haemastica ) chicks—a sexually dimorphic, precocial shorebird that breeds in the sub-Arctic and exhibits a male-skewed adult sex ratio. We found that female chicks—which must grow to a larger adult size—reached their maximum growth rates at a later age, but had similar growth rates to males before that and survived equally well to 21 days. We also found that, irrespective of sex, chicks had reduced movement rates when they were young and/or temperatures were cold, and only weakly increased their movement rates when invertebrate abundances remained low across an entire week. Early in life, godwit chicks may therefore be constrained from increasing their foraging efforts by local environmental conditions, forcing females to sustain higher growth rates late in the season past the local resource peak. Such sex-specific vulnerabilities could lead to lower early-life survival and, in turn, skewed adult sex ratios, which have important implications for population dynamics and persistence.

Behavioral Ecology↗
USGS2026

Social influences complement environmental cues to stimulate migrating juvenile salmon

Background The large-scale seasonal migrations undertaken by many species require complex navigational and timing decisions. Animals migrating in groups might benefit from collective decision making, especially if the environment has large local variation rather than smooth gradients in, for example, salinity or temperature, or is unpredictable, or if the migrants cannot rely on individually acquired information. We focus on juvenile salmon whose downstream migration is timed to match suitable conditions for growth and survival at sea. While the environmental and physiological factors that influence the timing of migration have been well studied, the influence of social interactions on migration timing is poorly understood. Method We compiled data on two species of juvenile salmon, collected at traps over 19 years, during their downstream seaward migration in three rivers in Washington state along with relevant environmental data. We developed state space statistical models to estimate the influence of hatchery-produced salmon in stimulating the downstream migration of wild salmon, while also incorporating potential environmental stimuli. Results Our results are consistent with the “pied-piper” hypothesis that large numbers of migrating hatchery-origin salmon provide a social cue stimulating migration of co-occurring wild salmon. The increase in the number of hatchery salmon counted at the trap was a strong predictor of the increase in wild sub-yearling Chinook salmon in the Dungeness, Puyallup, and Skagit rivers and yearling coho salmon in the Puyallup and Skagit rivers. Migration timing was also associated with abiotic factors related to temperature, river flow, and time of year. Conclusions Our findings highlight the potential for social cues to affect migration timing of downstream migrating salmon, in concert with environmental factors. Incorporating social information into timing decisions may allow animals to benefit from collective decision-making strategies and better time their migrations. Moreover, understanding the effects of large-scale hatchery releases on wild salmon migration may provide valuable insights for planning the timing and duration of hatchery releases.

British Columbia, Washington↗
USGS2026

Drought resistance is greater in montane conifers compared to coastal conifers in northern California

Frequent and intense droughts are rapidly altering stand dynamics in western North American forests. The ecological and geographical diversity of northern California provides a unique opportunity to measure these responses across species, habitat types, and levels of competitive pressure. This study used dendrochronological techniques and linear mixed-effects models to assess growth responses to drought in four montane and two coastal conifer species across 54 study sites (nine sites per species, 526 trees total) in northern California. Montane species included Abies magnifica var. shastensis , Picea breweriana , Pinus lambertiana , and Pinus monticola ; coastal species included Picea sitchensis and Tsuga heterophylla . Growth was evaluated from 2002 to 2018 and the drought period was from 2013 to 2015. There were significant differences among species and environments (coastal vs montane) in growth, drought resistance and resilience, and annual latewood proportion. Growth in montane species was generally positively related to moisture availability (Palmer Drought Severity Index) and negatively related to tree competition. The four montane species maintained relatively stable drought resistance, resilience, and latewood proportion across the study period. In contrast, growth in the two coastal species was influenced more by tree size and crown ratio than moisture availability or competition. As the 2013–2015 drought proceeded, coastal species showed marked reductions in drought resistance and resilience and increases in latewood proportion. Across the six conifer species, mean reductions in growth during and after the drought were generally less than 20% and never exceeded 40%. Compared to montane species, the lower resistance measured in coastal species suggests greater risk for increased stress and mortality in the event of more severe, prolonged, and/or frequent droughts.

California↗
USGS2026

Important geographies for migrating and wintering waterfowl

This chapter identifies and describes the most important geographic regions for migrating and wintering waterfowl across North America. Although breeding habitats have historically been the focus of waterfowl conservation, this chapter emphasizes that the non-breeding period plays a critical role in shaping population dynamics. The authors use expert judgment, survey data, and conservation planning frameworks to designate regions that support large numbers of waterfowl or provide essential habitat functions. Organized primarily by flyway, these regions are described in terms of their physiography, climate, habitat resources, species assemblages, and conservation concerns. Particular attention is given to habitat loss, hydrological alteration, development pressure, and climate change, all of which pose ongoing threats to waterfowl populations. While limitations in data are acknowledged, this chapter represents one of the most comprehensive reviews of non-breeding waterfowl geographies to date and underscores the need for coordinated, annual cycle conservation strategies to sustain healthy waterfowl populations across the continent.

Book chapter↗
USGS2026

Long-term monotonic trends in water budget components in the contiguous United States: Insights from two hydrologic models

Characterizing changes to water availability for domestic, industrial, agricultural, and other uses is essential to support water management. To better quantify these changes, the U.S. Geological Survey and National Science Foundation National Center for Atmospheric Research produced two hydrologic models simulating water budget components from 1980 to 2021 over the contiguous United States (CONUS). Both hydrologic models were driven by a common atmospheric forcing dataset and aggregated to common spatial and temporal scales, which enables a novel evaluation of congruency between the models. We present annual and seasonal trends in six water budget components (precipitation, evapotranspiration, streamflow, groundwater recharge, soil saturation, and snow water equivalent) based on the Mann–Kendall test for monotonic trend and Theil-Sen slope estimate for the water year 1983–2021 period for ~86,000 catchments in CONUS. Additional components and metrics from our analysis pipeline are available in an associated published dataset, which contains more than 46 million trend results. The water budget trends showed broad agreement with prior observational and modeling studies that indicate increasing trends in the northeast and decreasing trends in southwestern CONUS. We found the seasonal variability in water budget trends was greatest in the southern, central, and northwest CONUS. These findings support integrated trend assessments when coupled with trends in water quality and use.

Contiguous United States↗
USGS2026

The 2025 Puerto Rico and Virgin Islands U.S. National Seismic Hazard Model Update: Ground motion model selection and comparison

We evaluate, select, and describe the ground-motion models (GMMs) used in the 2025 update of the U.S. National Seismic Hazard Model (NSHM) for Puerto Rico and the U.S. Virgin Islands (PRVI). We identify the most appropriate models that align with GMM selection criteria for use in the PRVI region to improve the accuracy of seismic hazard assessments. The update incorporates globally applicable GMMs suited for the active crustal and subduction earthquakes in the region. We include region-specific adjustments to these GMMs derived from local site response analyses derived from ground motion records. The unadjusted and regionally-corrected GMMs are combined to create a robust model for predicting median ground motion. The model integrates epistemic uncertainty through a median ground motion logic tree that accounts for variations in magnitude and distance. This study compares the GMMs selected for the 2025 PRVI NSHM, including both as-provided and regionally adjusted NGA-West2 and NGA-Subduction models, with those used in the 2003 PRVI NSHM. We evaluate how changes in model selection, weighting, aleatory variability, and epistemic uncertainty influence seismic hazard estimates. Trends with distance, magnitude, and spectral period are analyzed to evaluate how the scaling behavior of the newer GMMs differs from that of earlier models. Relative to the GMMs used in the 2003 NSHM for this region, the 2025 models generally predict lower ground motions. Comparisons with additional GMMs indicate that the adjustments applied for PRVI are consistent with regional-specific modifications developed elsewhere globally. The increase in aleatory variability and epistemic uncertainty in the 2025 update results in a notable increase in hazard levels from these wider uncertainty bounds. These changes can result in as much as a 10%–20% variation in probabilistic ground motion at the 2% in 50 years exceedance level for hazard maps computed across the region for representative site classes and periods.

Puerto Rico, Virgin Islands↗
USGS2026

An ecosystem-scale model of PFAS dynamics in stream-to-riparian food webs

Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants in aquatic ecosystems, where they bioaccumulate and trophically transfer through food webs. We derived an ecosystem-scale model assessing Σ 12 PFAS partitioning, bioaccumulation by larval aquatic insects, bioamplification by adult aquatic insects, and trophic transfer from aquatic insects to riparian spiders using data collected across five streams in a mildly impacted watershed. Partitioning involved the greatest PFAS enrichments (range in posterior median log 10 k d values = 1.5–2.1), with lesser concentration increases from particulates to larval aquatic insects and from larval to adult aquatic insects, and Σ 12 PFAS concentration decreases from adult aquatic insects to spiders. Among the 12 compounds, PFOS had the largest proportional contribution to Σ 12 PFAS concentrations for all sample types, with consistently increasing concentrations from surface water to adult aquatic insects. Σ 12 PFAS concentrations (5.4–51 ppb wet weight), body burdens (0.44–5.2 ng per individual), and bioamplification factors (0.15–4.9) differed considerably among five common aquatic insect taxa. This study presents a robust modeling framework for PFAS trophodynamics and offers insights into the biological controls that contribute to the context dependency of PFAS at the interfaces of aquatic and terrestrial food webs.

Connecticut, Massachusetts↗