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Research about United States

Source-linked reports with geographic coverage including United States.

At least 1,351 records · Page 75Linked to original sources
USGS2025

Characterizing projected future droughts for south Florida (2056–2095)

Balance anomalies, defined as the deviation of monthly precipitation minus reference evapotranspiration from their long-term monthly historical means (1950–2005), were computed for regions in south Florida and temporally averaged over 6- and 12-month timescales to identify meteorological drought events during a historical (1950–2005) and future (2056–2095) period of interest for 40 CMIP5 general circulation models (GCM) and scenario combinations downscaled by the Multivariate Adaptive Constructed Analogs method. Under the assumption of stomatal resistance ( r s ) remaining constant at the historical standard value (70 s/m), 81% of models project declines in monthly balance anomalies in the future compared to historical, with multimodel ensemble mean declines of 3.7 in/year under RCP4.5 and 8.7 in/year under RCP8.5. Drought events were identified from the downscaled model projections, their characteristics (duration and intensity) extracted, and their historical joint distributions validated against those derived from historical observational datasets. The future joint distributions of drought characteristics were compared across models using hierarchical clustering. A climate model summary plot and table were developed based on these methods to guide climate model selection for hydrologic modeling in support of water-supply planning at the South Florida Water Management District (SFWMD). The model summary plot for the entire SFWMD shows that 35% of GCM/training-dataset combinations have historical joint distributions of drought characteristics that are significantly different at the 10% level from those derived from observational gridded data, whereas 39% of GCM/scenario/training-dataset combinations have future joint distributions that are significantly different from historical. A sensitivity analysis was performed assuming r s increasing with increasing CO 2 .

Florida↗
USGS2025

Increased soil greenhouse gas emissions from the combined use of cover crops and no‐tillage in producer‐ managed fields

Cover crop adoption offers multiple benefits and climate mitigation potential for agroecosystems, but is still an underutilized conservation practice. Recently, the combined use of cover cropping plus no-tillage (CCNT) has been increasingly promoted to achieve its synergistic effectiveness. Yet, how this combined practice affects soil greenhouse gas (GHG) emission remains a topic of debate. Existing studies are predominantly based on research-managed settings and often fail to assess all three major GHGs of carbon dioxide (CO 2 ), nitrous oxide (N 2 O), and methane (CH 4 ). To address these knowledge gaps, this study conducted a 30-month monitoring from producer-managed fields to quantify the soil greenhouse gas responses to CCNT compared to no-tillage (NT) alone. The findings showed that CCNT increased the soil global warming potential (GWP) by 15.2% relative to NT. CO 2 is the main contributor, accounting for over 91.7% of the total GWP. On average, the daily fluxes of CO 2 , N 2 O, and CH 4 were increased by 16.2%, 32.3%, and 55.6% under CCNT, respectively. Meteorological variables explained 85.3% of the CO 2 increase and 46.1% of the N 2 O increase associated with CCNT. Furthermore, two types of CCNT practices differed in GHG emission responses, though both strategies significantly reduced nitrogen losses. These quantitative results, derived from actual production systems, provide informed decision-making among local producers regarding the adoption of cover crops. Moreover, this field-based evidence offers a robust empirical foundation for future modeling efforts aimed at assessing the ecological benefits of cover crops under varying climatic and soil conditions.

Indiana↗
USGS2025

Alternating movement strategies of a tropical raptor

The majority of raptor species reside in the tropics, yet very little is known about their movement ecology. However, quantifying movement behavior can provide otherwise elusive information on resource needs, habitat selection, and ecological constraints, which is important for understanding ecological patterns and the management of species of conservation concern. On the Island of Hawai‘i, Hawai‘i, USA, the endemic ‘Io, or Hawaiian Hawk ( Buteo solitarius ), is a species of conservation concern that little is known of their movement ecology, yet they are dependent on a fragmented and rapidly changing environment. We tracked 15 individuals for up to 18 months across a diverse landscape on the eastern side of the island. We found that all ‘Io occupied a relatively small geographic area, their place of residency, where they spent all or most of their time. However, 10 individuals also exhibited an alternative movement pattern, where individuals repeatedly commuted back and forth between their place of residency to another, geographically disjunct location. These commuter periods, which could last from 24–180 days, were characterized by frequent (9–259) movements, with individual trips lasting 4–77 h away from their place of residency and 12–47 h in between commuter trips. In most cases, individuals went to the same non-contiguous commuting destination, even across multiple commuting sessions, indicating high fidelity to commuting locations. The ‘Io is a forest adapted Buteo but occurs across a diverse landscape from forest to agriculture lands to urban areas. Habitat selection analysis indicated high individual variation among different birds, but generally a preference for forest patches at localized levels. The discovery of the alternative commuting strategy for many ‘Io represents a cryptic movement pattern in the species, demonstrating the power of small, long-lived Global Position System tracking devices to track movement and providing important insights into the ecology of a tropical island raptor.

Hawaii↗
USGS2025

Young explosive eruptions from the Clear Lake volcanic field

The Clear Lake volcanic field is the northernmost and youngest field in a chain of volcanic fields in and near the California Coast Range mountains. For 2 million years, numerous eruptions have happened around (and through) Clear Lake. The most recent period of activity in the Clear Lake volcanic field probably started around 40,000 years ago and was mainly explosive eruptions concentrated on and near faults in and around the lake. The combination of hot magma and groundwater created explosive releases of hot steam. The craters, called maars, threw out volcanic ash, pumice, and lava fragments, which fell back to the ground and draped the surrounding landscape. The deposits are visible in many places around the southeast end of the lake.

California↗
USGS2025

Effects of climate on temporal variability in streamflow and salinity in the Upper Colorado River Basin

Study Region The Upper Colorado River Basin, a critical water source for more than 40 million people in the western United States. Study Focus Potential decreasing streamflow and elevated salinity concentrations threaten this resource. Climate variability has a large and well-studied effect on streamflow in the basin; however, the effect on salinity loading is less understood. This study investigates how snowpack dynamics, precipitation volume, and air temperature affect both streamflow and salinity at the basin scale from water years 1986–2021. New Hydrological Insights for the Region Climate variables explained 54 % of streamflow variability and 40 % of salinity variability across the basin. Both streamflow and salinity yields have declined in response to climate variability, but their response occurs on different timescales. Streamflow is more sensitive to snowpack, whereas salinity yields respond more strongly to antecedent precipitation. The delayed response of salinity yields may obscure the effects of both climate variability and salinity control measures. Residual analysis identified subbasins where the climate-salinity relation deviated from basin-wide patterns, suggesting that possible anthropogenic or other watershed processes may influence salinity loading in these areas. These novel findings underscore the importance of accounting for climate variability when evaluating long-term trends in streamflow and salinity.

Arizona, Colorado, New Mexico, Utah, Wyoming↗
USGS2025

Two million years of climate-driven cave-sediment aggradation and valley incision in the southern Ozark Plateau from Fitton Cave, northern Arkansas, USA

Landscape evolution in karst terrains affects both subterranean and surface settings. For better understanding of controlling processes and connections between the two, multiple geochronometers were used to date sediments and speleothems in upper-level passages of Fitton Cave adjacent to the Buffalo River, northern Arkansas, within the southern Ozark Plateau. Burial cosmogenic-nuclide dating of coarse sediments indicates that gravel pulses washed into upper passages at 2.2 Ma and 1.25 Ma. These represent the oldest epigenetic cave deposits documented in this region. Associated sands and clay-rich sediments mostly have reversed magnetic polarity and thermally transferred optically stimulated luminescence dates of 1.2 to 1.0 Ma. Abandonment of these upper passages began before 0.72 Ma, when coarse sediment was deposited in a passage incised below older sediment. Maximum U-series dates of 0.7–0.4 Ma for flowstones capping clastic deposits mark the stabilization of older sediments and a change to vadose conditions that allowed post–0.4 Ma stalagmite growth. Resulting valley incision rates since 0.85 Ma are estimated at 27 m/Ma. Coarse cave-sediment pulses correlate to Laurentide glacial tills about 300 km to the north, suggesting climate influence on periglacial sediment production. Dated cave sediments also may correlate with undated older strath terraces preserved at similar heights above the Buffalo River.

Arkansas↗
USGS2025

Spatially explicit power analyses to inform occupancy‐based multi‐species wildlife monitoring programmes

1. Current and accurate information on wildlife populations is integral to successful biodiversity management and conservation globally. Nevertheless, many monitoring programs fail in their attempts to accurately monitor populations of interest due to interlinked issues including insufficient sample sizes, inappropriate duration, lack of reproducibility, and lack of clearly stated objectives. These common pitfalls could be avoided through the elicitation of explicit monitoring objectives and the a priori use of simulations to inform minimum sampling design requirements to meet said objectives. 2. Here, we provide a blueprint for using spatially explicit power analyses to inform the design and implementation of multi-species monitoring programs on landscape-scales. As a demonstration, we used spatially explicit simulations to devise a suitable sampling regime to meet clearly specified monitoring objectives in New York State: to use annual occupancy-based monitoring to be able to detect 25% and 50% changes in abundance of populations over five- and ten- year periods for all species of management interest in New York State, USA. We focused our simulation efforts on three challenging focal species (black bear, Ursus americanus, bobcat, Lynx rufus, and American marten, Martes americana) that differ notably in their morphology, life histories, space use, detection probability, habitat suitability, and population sizes/trajectories, and thus provide extremes in the challenges presented when it comes to sampling appropriately to detect changes in abundance. 3. Our simulations demonstrate variable context dependent trade-offs in sampling designs (i.e. number of sites [J] and number of sampling occasions [K]), and identify necessary minimum detection probabilities that must be attained to achieve statistical power to detect changes of varying magnitudes in populations of varying sizes in the three focal species. The simulations also highlight that monitoring population increases is likely beyond the reach of occupancy-based monitoring programs for wide-ranging or locally abundant species. 4. Synthesis and applications : We combine the results from the single-species simulations to produce a multi-species sampling design that meets the specified objectives for all three species. While the case study is centered on developing a multi-species sampling regime for New York State, it provides a reproducible step-by-step framework using established methods for wildlife managers and other practitioners to inform their own context- and objective- specific multi-species occupancy-based monitoring programs.

New York↗
USGS2025

Interacting sea-level rise, sea-ice loss, storm flooding, erosion, and permafrost thaw threaten ecosystems, wildlife, and communities on the Yukon-Kuskokwim Delta

The Yukon-Kuskokwim Delta has the largest intertidal wetland in North America, is a globally critical breeding area for waterbirds, and is home to the largest regional indigenous population in the Arctic. Here, coastal tundra ecosystems, wildlife, and indigenous communities are highly vulnerable to sea-ice loss in the Bering Sea, sea-level rise, storm flooding, erosion, and collapsing ground from permafrost thaw caused by climate warming. These drivers interact in non-linear ways to increase flooding, salinization, and sedimentation, and thus, alter ecosystem trajectories and broader landscape evolution. Rapid changes in these factors over decadal time scales are highly likely to cause transformative shifts in coastal ecosystems across roughly 70% of the outer delta this century. We project saline and brackish ecotypes on the active delta floodplain with frequent sedimentation will maintain dynamic equilibrium with sea-level rise and flooding, slightly brackish ecotypes on the inactive floodplain with infrequent flooding and low sedimentation rates will be vulnerable to increased flooding and likely transition to more saline and brackish ecotypes, and fresh lacustrine and lowland ecotypes on the abandoned floodplain with permafrost plateaus will be vulnerable to thermokarst, salinization and flooding that will shift them toward brackish ecosystems. This will greatly affect bird nesting and foraging habitats, with both winners and losers. Already, some Yup'ik communities are facing relocation of their low-lying villages. The societal challenges and consequences of adapting to these changing landscapes are enormous and will require a huge societal effort.

Alaska↗
USGS2025

Using bioavailability modeling to refine copper treatments for zebra mussel control and better understanding risks to non-target species

Copper can be toxic to aquatic organisms at high concentrations and has been previously used successfully to control zebra mussels ( Dreissena polymorpha ). Because copper’s toxicity changes with water chemistry, using the same copper concentration in different waterbodies could yield different outcomes. We demonstrate how measuring water chemistry parameters and using the Biotic Ligand Model (BLM) and multiple linear regression (MLR) models can predict a suitable, site-specific copper concentration for management. We exposed zebra mussel adults and non-target organisms to varying concentrations of copper over 10 d in a mobile laboratory. We found that one non-target species, Daphnia magna , had a 50% chance of survival at 9.50 µg Cu/L (i.e., the 50% lethal concentration, LC 50 ), within our BLM-predicted range of 3.38–16.95 µg Cu/L LC 50 values. In the future, managers could make similar predictions and tailor their copper concentrations to their management goals. We also measured zebra mussel larvae mortality at copper concentrations ranging from 0 to 191 µg Cu/L. While those results were inconclusive, we present the results of this work as a foundation for future projects. Our study underscores the importance of developing site-specific copper concentration recommendations and demonstrates the potential utility of the BLM and MLR approaches for informing those recommendations.

Minnesota↗
USGS2025

Salting behaviors influence urban stream conductivity in Boston, Massachusetts (USA)

Freshwater salinization is a major concern in temperate climates where road salt is used as a deicer to manage snow and ice on roadways. In urban and suburban areas, wastewater, weathering of infrastructure, and salting on parking lots and sidewalks can also contribute to salt contamination, but little is known about how well these sources explain variation in stream conductivity and what factors may mitigate high conductivity in streams. We collected specific conductance samples seasonally over 1 y at 100 stream sites in the greater Boston (Massachusetts, USA) metropolitan area, which reflected a gradient of land use/cover and sociodemographic variables. We also continuously monitored specific conductance over 1 y (November 2021–December 2022) at 3 streams with different levels of impervious cover. Baseflow conductivity from grab samples was best explained by % impervious cover (positive relationship) and season (highest median conductivity in summer and early autumn) ( r 2 = 0.47, p < 0.001). At high impervious cover, watersheds with higher housing vacancy had lower conductivity, suggesting that resident salting behavior may affect conductivity. Continuous conductivity varied with discharge, with spikes in conductivity coincident with increases in discharge in the winter, likely due to the influx of road salt into waterways. In the summer, higher discharge was linked with sharp decreases in conductivity, suggesting that storm flows dilute high baseflow conductivity, although combined sewer overflows caused secondary conductivity pulses. Overall, conductivity was highest during winter storm pulses, but elevated conductivity levels persisted throughout the year, especially in more impervious watersheds. Our research suggests that reduced salt application and street sweeping may reduce conductivity but will not prevent continued salinization. Temporal patterns of conductivity highlight the importance of seasonal road-salt application (winter), seasonal climate (low-flow summers), and precipitation (storm events, droughts) in influencing stream conductivity and can guide monitoring design, policymaking, and management decisions under climate uncertainty.

Massachusetts↗
USGS2025

Remote sensing of chlorophyll a and temperature to support algal bloom monitoring in Blue Mesa Reservoir, Colorado

We present methods to reconstruct historical chlorophyll a and surface water temperatures from satellite-based remote sensing products for Blue Mesa Reservoir, Colorado, to support algal bloom monitoring. A machine learning model was trained to construct chlorophyll a concentrations from Sentinel-2 satellite imagery and in situ measurements of chlorophyll a concentrations (out of bag RMSE = 1.9 μg/L, R 2 = 0.63) and reconstruct summertime chlorophyll a concentrations over the entire reservoir from 2016 through 2023. Concurrently, we developed an approach to retrieve remotely sensed water temperatures from the Landsat collection 2 provisional surface temperature product (MAE = 0.6°C) and reconstructed summertime surface water temperature records from 2000 through 2023. Finally, we demonstrate how the reconstructed chlorophyll a and temperature records can yield insight on reservoir dynamics. The chlorophyll a records indicate that algal blooms have a consistent spatial pattern across multiple years, initiating in the eastern end of the reservoir and spreading to the west over time. Water temperatures increased at a linearized rate of 0.3°C per decade from 2000 through 2023 and were inversely proportional to reservoir water surface elevation. Finally, mean summer remotely sensed chlorophyll a concentration had a moderately positive correlation with mean summer remotely sensed water temperature.

Colorado↗
USGS2025

Temporal associations between ambrosia beetles and ʻōhiʻa (Metrosideros polymorpha) artificially inoculated with Ceratocystis lukuohia

Wood boring ambrosia beetles play a central role in the spread of Ceratocystis wilt of ‘ōhi‘a, a fungal disease caused by Ceratocystis lukuohia that kills the bioculturally important ‘ōhiʻa ( Metrosideros polymorpha ) tree. Beetles contribute to the spread of the disease by extruding fungus-infected wood particles (frass). Disease mitigation can benefit from knowledge of ambrosia beetle life-history and fungal survival in affected ‘ōhi‘a. We investigated temporal associations among tree death, the timing and duration of beetle attacks, and the persistence of viable C. lukuohia within intentionally infected (inoculated) ʻōhiʻa at three sites that approximate the elevational range of the disease on the Island of Hawaiʻi. Beetles most frequently attacked inoculated trees at the time when foliage first showed symptoms of infection (yellow leaves; n = 9) although some attacks were observed during earlier (green leaf; n = 3) and later (brown leaf; n = 3) stages of symptom progression. On average, beetles initiated new attacks for nearly one year after trees were inoculated. We tracked active galleries of Xyleborinus saxesenii , Xyleborus ferrugineus and Xyleborus simillimus and found they produced frass with viable C. lukuohia propagules for 122.8 ± 40.0, 275.8 ± 32.7 and 304.2 ± 53.4 days, respectively. Infected ʻōhiʻa felled from our mid-elevation site at the end of the study revealed viable fungal propagules and the presence of X. ferrugineus over two years after trees first appeared symptomatic of infection, suggesting that Ceratocystis wilt of ʻōhiʻa remains a threat to spread from infected trees long after trees succumb to the disease.

Hawaii↗
USGS2025

Landsliding follows signatures of wildfire history and vegetative regrowth in a steep coastal shrubland

Five years after the deadly and destructive 9 January 2018 Montecito debris flows (Santa Barbara County, California, USA), an atmospheric river storm on 9 January 2023 triggered widespread landsliding that affected many of the same drainages in the Santa Ynez Mountains. Using high-resolution aerial imagery, we identified >10,000 landslides over an ∼160 km 2 area. Most of the landslides were shallow (<1 m in depth) translational debris slides that initiated on steep (∼40°), south-facing hillslopes, with the highest incidence of landsliding in a sandstone-dominated bedrock unit. The landslides mobilized into debris flows and delivered substantial quantities of sediment downstream, which contributed to costly infrastructure impairments. We detected order-of-magnitude differences in landslide density across the study area that could not be attributed to variations in geomorphology (topographic aspect and slope), geology (bedrock type), or hydrology (seasonal antecedent rainfall, peak hourly storm rainfall intensity, total storm rainfall), which are usually considered relevant factors for shallow landsliding. Rather, we found that vegetation regrowth following wildfire was likely a relevant factor associated with the highly variable landslide densities. Hillslopes with less and different types of vegetation regrowth after fire appear to have been more susceptible to shallow landslides. We identify a possible vegetation control on postfire landsliding, which highlights an opportunity for hypothesis testing using more advanced techniques to track the evolution of vegetation cover and vegetation type in steep shrubland environments following wildfire.

California↗
USGS2025

The U.S. Geological Survey National Water Quality Network—Surface Water, 2024

The U.S. Geological Survey (USGS) National Water Quality Network for surface water (NWQN-SW) was established in 2013 to develop long-term, comparable assessments of surface-water quality in support of national, regional, State, and local needs related to water-quality management and policy. Water-quality samples are collected at each site and measured for a variety of constituents. In 2024, the NWQN-SW consisted of 105 sites, each of them paired with a streamgage, operated by the USGS or other agencies that provide continuous information on streamflow conditions. The water-quality data and the streamflow information from the NWQN-SW are then used to assess the status and trends of water-quality conditions and potential impacts on human and aquatic health.

General Information Product↗
USGS2025

Mammalian scent lures fail to increase detections of invasive Burmese pythons (Python bivittatus)

Burmese pythons ( Python bivittatus ) are large constricting snakes native to Southeast Asia that have invaded the Greater Everglades Ecosystem in South Florida, USA. Pythons have caused precipitous declines in native mammals and are exceedingly difficult to detect using traditional methods such as scout snakes, detection dogs, and visual surveys. Live mammal lures have previously been used to attract pythons, with rabbits outperforming rodents in increasing detection. While live mammal lures can increase python detection and identify hotspots of python activity, ensuring animal welfare and logistical challenges limit their utility. As part of this study, field experiments were conducted to determine if mammalian lures, derived from rabbits (feces, urine, and hair) could replace live mammals and increase the detection of pythons. We ran trials for 84 days from June to September 2022 for 21 paired plots across three study sites in the Greater Everglades. We monitored two groups, the treatment (i.e., rabbit scent) and control (i.e., soil) with camera traps on a 1-minute time lapse. We detected 11 pythons during our study, but there was no difference between controls with soil ( n = 7) and treatments (n = 4). However, we did find that scent lures increased native snake detection. This pattern was best explained by an increased number of rodents at the scent lures. Our experiment indicates that mammalian scent lures alone are insufficient to attract pythons. Since live mammals can attract pythons, but scent lures cannot, future studies could examine if a multi-faceted lure combining several stimuli (i.e., heat, visual, movement) might increase python detection.

Florida↗
USGS2025

Decoupling the roles of corticosterone in mediating effects of methylmercury and chytrid fungus on amphibian survival

Amphibians have suffered widespread declines caused by many interacting factors whose effects are often difficult to isolate. We used complementary analyses to decouple effects of methylmercury (MeHg) and amphibian chytrid fungus (Bd) on survival of Columbia Spotted Frogs ( Rana luteiventris ) during a 5-year capture-mark-recapture study. We also evaluated whether effects on apparent survival were mediated through physiological responses (corticosterone, CORT). While Bd was unrelated to frog survival, geometric mean MeHg bioaccumulation in our population (164 ng/g) reduced survival by ~20%. Baseline CORT was negatively associated, and stress-induced CORT was positively associated with higher MeHg, suggesting that MeHg dysregulated glucocorticoid physiology. Survival was positively associated with higher baseline CORT, whereas survival was negatively associated with higher stress-induced CORT. Our results provide rare evidence linking CORT and long-term survival of wild vertebrates and that environmentally relevant concentrations of MeHg can influence survival of free-ranging amphibians, and these effects may be mediated by CORT.

Montana↗
USGS2025

Dynamic feedbacks between river meandering and landsliding in northwestern Washington glacial terraces

Landsliding in river valleys poses unique risks for cascading hazards and can damage infrastructure and cause fatalities. In postglacial valleys, many landslides are posited to occur in relation to lateral river erosion, but the dynamics of fluvial-hillslope interactions are not well understood. Here, we investigate a section of the Nooksack River in western Washington State where the channel is flanked by landslide-prone glacial terraces similar to those that failed in the 2014 State Route 530 “Oso” landslide. We map 216 landslides through time across 17 aerial imagery data sets (1933–2022) and analyze them in relation to river meandering and curvature. We observe dynamic feedbacks between lateral river meandering and valley-adjacent landsliding. Terrace lateral retreat rates of up to 25 m/year owing to combined fluvial erosion and slope failure occur on pinned, outer meander bends immediately downstream from peaks in river curvature (>0.0075 1/m); these locations are predisposed to both shallow and deep-seated landslides. Deep-seated landslides extending 17%–32% of the active valley width into the floodplain can displace the river away from the floodplain margin and change the channel planform. River-displacing landslides relocate meanders up- or downstream, thereby conditioning the location of subsequent landslides. This conceptual model of coupled landslide-driven meander displacement and valley-adjacent landsliding is exemplified across western Washington river systems. The distance between up- and downstream valley-adjacent landsliding scales with valley width, meander wavelength, and terrace height. Our results can advance our understanding of the river-hillslope interface in landscape evolution and can be used to inform hazard management in river corridors.

Washington↗