Geology topics

Research about United States

Source-linked reports with geographic coverage including United States.

At least 1,117 records · Page 62Linked to original sources

USGS2025

Reconciliation of geochronology and paleozoogeography for Quaternary marine terraces, San Luis Obispo Bay area, California, USA

In the San Luis Obispo Bay area of central California, interpretations of marine terrace ages have been hampered by inconsistent results from geochronological indicators (U-series ages of corals and correlations using amino acid racemization of mollusks) and seemingly contradictory paleozoogeographic aspects of fossil faunal assemblages. New U-series ages of corals, amino acid data from mollusks, and detailed analyses of fossil mollusk assemblages are presented that reconcile many of the apparently discordant results from previous studies. The two lowest-elevation terraces are Q1 (lower) and Q2 (upper); both are thought to date from high-sea stands of marine isotope stage (MIS) 5, the last interglacial complex. A combination of U-series dating and amino acid racemization results indicates that the Q1 terrace probably dates to the ∼80 ka high-sea stand of MIS 5a. U-series analyses of corals from the Q2 terrace show open-system histories, but consideration of two alternative open-system histories indicates that this terrace likely hosts corals dating to the high-sea stands of MIS 5c (∼105–95 ka) and MIS 5e (∼130–115 ka). Amino acid ratios in the fossil bivalve Leukoma staminea (Conrad, 1837) support the age differences between the two terraces and the open-system models suggested by the U-series data. Alkenone studies along much of the coast of California have shown that sea surface temperatures (SSTs) of the eastern Pacific Ocean were warmer than present during MIS 5e. During MIS 5c, on the other hand, SSTs were either similar to the present or cooler, but in either case, much cooler than during MIS 5e. The paleozoogeographic aspects of the molluscan faunas from the Q2 terrace support an interpretation that these deposits contain a mixture of fossils from both the MIS 5c and 5e high-sea stands. Fossils from the Q2 terrace include southern or southward-ranging species (likely dating to MIS 5e) and northern or northward-ranging species (likely dating to MIS 5c). A mixture of MIS 5e and MIS 5c fossils on the Q2 terrace is consistent with similar data reported for other localities in California. This phenomenon is explained by glacial isostatic adjustment (GIA) processes, which brought about a higher-than-present sea level during MIS 5c. GIA processes, combined with a low uplift rate, allowed mixing of MIS 5e fossils during the MIS 5c high-sea stand through capture of an MIS 5e terrace that had experienced minimal uplift in ∼20,000 years. Terrace reoccupation and fossil mixing such as that in the San Luis Obispo Bay area can be expected along any part of the Pacific Coast of North America that was affected by GIA processes and where uplift rates are low.

California↗

USGS2025

Exploring the use of non-invasive drone-based Ground Penetrating Radar (GPR) to characterize biogenic gas dynamics in subtropical peat soils

Peat soils are a critical component of the global carbon cycle as natural producers of biogenic greenhouse gases (e.g., methane and carbon dioxide) that accumulate within the soil matrix and are episodically released to the atmosphere. Previous studies have showed the unique ability of ground-based minimally-invasive geophysical methods like ground-penetrating radar (GPR) to characterize carbon dynamics in peat soils. However, the GPR methods are still limited by the scale of measurements and soil disturbance potentially altering biogenic gas releases during deployment. Here we explore the potential of drone-based GPR for identification of hot spots and hot moments of gas accumulation and release in subtropical peat soils. We collected drone-based GPR datasets across two grids (~ 17,500 m2) in the Florida Everglades during January, September, and November of 2023 to characterize peat thickness and seasonal variability of gas content. Results show that drone-based GPR is effective and efficient for: 1) capturing the temporal variation of in-situ biogenic gas content in peat soils with changes between 1-25% volumetric gas content over repeatable grids; 2) inferring peat thickness from discrete measurements ranging between 0.8-1.2 m; and 3) estimating methane flux releases of 63 and 135 mg CH4 m-2 day-1 for specific locations and time periods that are strikingly consistent with our coincident gas trap measurements. This work also indicates that (1) spatial distribution of gas content in the Everglades is strongly controlled by landscape morphology such as ridges and sloughs and (2) the temporal variation of gas content is seasonal with increased gas production during the wet season.

Florida↗

USGS2025

High-precision earthquake catalog for Minto Flats fault zone, central Alaska, reveals complex and conjugate faulting

The Minto Flats fault zone (MFFZ) in central Alaska is a left‐lateral strike‐slip fault system situated between the continental‐scale right‐lateral Denali and Kaltag‐Tintina faults. The MFFZ has the potential to generate magnitude 7 earthquakes, and it hosted a magnitude 6 earthquake in 1995. It has also produced exotic events, such as very‐low‐frequency earthquakes and nucleation signals. We use network‐matched filtering and relative earthquake relocation techniques to derive a detailed catalog of earthquake locations for the MFFZ. The catalog spans from August 2014 to December 2019, a time period including 13 temporary seismic stations in the region. Our results provide the most complete catalog for the MFFZ and include deeper events, clusters of shallow seismicity, and a complex and segmented fault structure not observed in the original regional catalog. We document right‐lateral strike‐slip faulting, conjugate to the main northeast‐striking left‐lateral faults of the MFFZ. Below Nenana basin, the relocated seismicity reveals northwest‐dipping left‐lateral faults, supporting the inference that deep crustal active faulting is associated with recent basin deformation.

Alaska↗

USGS2025

Achieving interpretable machine learning by functional decomposition of black-box models into explainable predictor effects

Machine learning (ML) models are often based on complex black-box architectures that are difficult to interpret. This interpretability problem can hinder the use of ML in fields like medicine, ecology, and insurance, and has boosted research in interpretable machine learning (IML). Here, we propose a novel approach for the functional decomposition of black-box predictions, which is a core concept of IML. This approach replaces the prediction function with a surrogate model consisting of simpler subfunctions, providing insights into the direction and strength of the main feature contributions and their interactions. Our method is based on a concept termed “stacked orthogonality”, which ensures that the main effects capture as much functional behavior as possible. To compute the subfunctions, we combine neural additive modeling with an efficient post-hoc orthogonalization procedure. Our method yielded plausible results in an analysis of stream biological condition in the Chesapeake Bay watershed (United States).

Chesapeake Bay watershed↗

USGS2025

A high-resolution late Paleocene–early Eocene organic-walled dinoflagellate cyst zonation of the United States Atlantic Coastal Plain

Over the past decades, many expanded sedimentary records from the US Atlantic Coastal Plain (ACP) have been studied in detail to assess causes and consequences of the Paleocene–Eocene Thermal Maximum (PETM; ∼ 56 Ma). In ACP sections, the PETM, which is globally marked by a distinct negative carbon isotope excursion (CIE) lasting ∼ 180 kyr following a large input of 13 C-depleted carbon into the ocean–atmosphere system, has been recorded near the base of the Marlboro Clay. However, truly detailed site-to-site correlations within the CIE interval remain difficult in view of the absence of suitable stratigraphic markers offering the required resolution. Here, augmenting earlier studies involving various other marine microfossil groups, we present a high-resolution regional organic-walled dinoflagellate cyst (dinocyst) zonation scheme covering the uppermost Paleocene to lowermost Eocene sediments of the Aquia and Marlboro Clay formations at six ACP localities. We propose five latest Paleocene (ACP Pv–Pz) and six earliest Eocene (all within the PETM interval; ACP E0a-E0f) regional informal dinocyst zones. In addition, we emend the genus Hystrichokolpoma and employ several new species, of which four, viz. Impagidinium witmeri sp. nov., Nematosphaeropsis elongatus sp. nov., Hystrichokolpoma heroldiae sp. nov., and Cannosphaeropsis frielingii sp. nov., are formally described. Furthermore, we calibrate the dinocyst zones against magneto-, bio-, and ecostratigraphic records to allow robust regional correlation and age assessments with an average time resolution of < 10 5 years for the late Paleocene and < 10 4 years within the PETM interval. The scheme provides new opportunities for portraying the environmental and sedimentological evolution across the US Atlantic Coastal Plain during the PETM in unprecedented detail.

Delaware, Maryland, New Jersey, Virginia↗

USGS2025

Dusky grouse seasonal resource selection in the Great Basin isolated mountain ranges of Nevada, USA

Dusky grouse Dendragapus obscurus are a montane forest grouse species with a paucity of information regarding their temporal and spatial resource use during critical times of high mortality and reproductive output. This lack of vital data may leave dusky grouse at risk of sub-optimal management in many areas of their distribution, especially in the isolated ‘sky island' mountain ranges of the Great Basin, where high elevation habitats are surrounded by sagebrush and salt desert shrubland flats. Many of these high elevation habitats are being altered and lost rapidly from increasing disturbance events and effects of climate change. Our objective was to evaluate dusky grouse resource selection in the Schell Creek, Duck Creek, and Egan ranges of White Pine County, Nevada, USA, during breeding, nesting, brood-rearing, and over winter to identify habitats of importance for concentrating conservation actions. We found that breeding male dusky grouse selected for aspen stands, nearness to water, and nearness to forest edges, while breeding female dusky grouse selected for mountain mahogany, aspen, and mountain shrub communities (i.e. sagebrush), and areas with high predicted probability of males. Nesting female dusky grouse selected for mountain shrub communities, intermediate elevation, low ruggedness, and high percent shrub cover. Brooding female dusky grouse selected for aspen and mountain shrub communities, nearness to water, high percent shrub cover, and intermediate elevation and ruggedness. Finally, wintering female dusky grouse selected for spruce–fir and pine conifer types, high elevation and ruggedness, and farther distances from forest edges, while selecting against high percent tree canopy cover. Our results suggest that dusky grouse presence may indicate aspen and conifer community health in the Great Basin mountain ranges. Conservation priority could be placed on these limited vegetation communities, especially given the slow regeneration and growth in the region due to the arid climate and xeric soils.

Nevada↗

USGS2025

Landsat-derived rainfed and irrigated-area product for conterminous United States for the year 2020 (LRIP30 CONUS 2020) using supervised and unsupervised machine learning on the cloud

Accurate maps of irrigated and rainfed croplands are crucial for assessing global food and water security. Irrigated croplands yield two to four times more grain and biomass than rainfed croplands. To meet rising food demand, the proportion of cropland that is irrigated must be increased globally. Because agriculture uses 80% to 90% of global fresh water, understanding changes in cropland extent, crop type, and irrigation is critical for meeting nutritional needs sustainably. The United States has one of the most productive rainfed and irrigated croplands in the world and is a leading producer and exporter of agricultural crops. Precise maps of irrigated and rainfed croplands in the United States are crucial for assessing the current and the future agricultural production capacity in supporting food security. We developed a 30-m resolution rainfed and irrigated area map for the conterminous United States derived from 2019 to 2021 multi-date Landsat-8 data (LRIP30 CONUS 2020). A total of 96 harmonized spectral bands comprising monthly median value composites of eight bands (blue, green, red, NIR, SWIR1, SWIR2, TIR, and enhanced vegetation index [EVI]) were used. A cropland mask was then applied, and reference data were sourced from various sources. A pixel based supervised random forest classifier, and pixel based unsupervised ISODATA clustering classifier were implemented on Google Earth Engine and the ERDAS Imagine workstation to classify, identify, map, and assess accuracies of irrigated and rainfed cropland areas. The LRIP30 CONUS 2020 product achieved an overall accuracy of 93.9%. The irrigated and rainfed classes had producer's accuracies of 90.2% and 95.7%, respectively, and user's accuracies of 90.8% and 95.4%, respectively. The total net cropland area was estimated at 139.4 million hectares (Mha), of which 94.9 Mha (68%) was classified as rainfed and 44.5 Mha (32%) was classified as irrigated. State level summaries highlight regional differences and their implications for national and global food and water security.

conterminous United States↗

USGS2025

Wangyanite, PdNi8S8, a new Pd end-member mineral of the pentlandite group from the J-M reef, Stillwater Complex, Montana, USA

Wangyanite (IMA2024-008a), ideally PdNi 8 S 8 , is a Pd end-member mineral of the pentlandite group that was discovered in the J-M reef of the Stillwater Complex, Montana, USA. Wangyanite occurs as anhedral-subhedral granular crystals 200–400 µm in size, associated with isoferroplatinum, braggite, pentlandite, and chalcopyrite interstitial to plagioclase grains within anorthosite. Wangyanite exhibits a yellowish brown color with a black streak and a metallic luster. It is brittle with uneven fractures, and has a calculated density of 5.14 g/cm 3 . The mineral does not show discernible pleochroism, bireflectance, or anisotropy. It has an average composition of 9.95 wt.% Pd, 31.95 wt.% Ni, 25.02 wt.% Fe, 0.57 wt.% Co, 31.74 wt.% S, totaling 99.23 wt.%. The empirical formula, based on eight sulfur atoms per formula unit, is (Pd 0.76 Co 0.08 ) Σ0.84 (Ni 4.39 Fe 3.60 ) Σ7.99 S 8 . Wangyanite has a cubic cell with a space group of Fm -3 m (#225), having lattice parameters of a = 10.1167(12) Å, V = 1035.4(4) Å 3 , and Z = 4. Its crystal structure has been solved by single-crystal three-dimensional electron diffraction study. The strongest X-ray diffraction lines of wangyanite are claculated at [ d in Å ( I %)( hkl )]: 5.841(14.03)(111), 3.050(100)(311), 1.947(29.16)(115,333), 1.264(11.66)(800), 3.577(8.79)(220), 2.920(20.82)(222), and 2.321(9.34)(331). Wangyanite shares the same crystal structure as pentlandite, but the octahedrally coordinated site is mainly occupied by Pd in wangyanite. Based on the textural features and previous experimental Pd-Fe-Ni-S phase system, wangyanite could form by peritectic reaction between braggite, pentlandite and sulfide liquid. These mineral associations are stable in a Ni-Pd-rich sulfide melt system at about 550 °C or even lower temperature. Therefore, wangyanite can potentially serve as an indicator of the presence of Pd-rich residual melts. The mineral is named in honor of Prof. Christina Yan Wang, a well-known researcher on platinum-group element (PGE) occurrences and enrichment mechanisms in mafic-ultramafic intrusions, notably those deposits related to the Emeishan large igneous province in China.

Montana↗

USGS2025

A spatiotemporal interrogation of hydrologic drought model performance for machine learning model interpretability

The predictive accuracy of regional hydrologic models often varies across both time and space. Interpreting relationships between watershed characteristics, hydrologic regimes, and model performance can reveal potential areas for model improvement. In this study, we use machine learning to assess model performance of a regional hydrologic model to forecast the occurrence of streamflow drought. We demonstrate our methodology using a regional long short-term memory (LSTM) deep learning model developed by the U.S. Geological Survey (USGS) and data from 384 streamgages across the Colorado River Basin region. Performance was assessed by clustering catchments using: (a) physical and climatological catchment attributes, and (b) streamflow drought signatures time series. We examined the association of USGS LSTM model error measures with clusters generated by both approaches to interpret meaningful spatial and temporal information about LSTM model performance. Clustering static catchment attributes identified elevation, degree of streamflow regulation, baseflow contribution, catchment aridity, and drainage area as the most influential attributes to model performance. Clustering gages by their drought signatures revealed that catchments with significant seasonal peak runoff between January and June generally exhibited better model performance. Additionally, a Random Forest classifier was trained to successfully predict LSTM model performance (F1 score of 0.72) based on physical and climatological catchment attributes. Low degree of flow regulation was identified as a key indicator of better LSTM model performance. These findings point to the opportunities for improving the USGS LSTM model performance in future hydrologic drought prediction efforts across regional and CONUS scales.

Arizona, California, Colorado, Idaho, Montana, Nev↗

USGS2025

Nodal seismic deployment on Mauna Loa volcano, Hawaii: Dataset and preliminary insights

Mauna Loa is the largest active volcano on Earth, comprising ∼51% of the Island of Hawai‘i’s landmass and posing significant risks to the island’s communities, infrastructure, and natural environment. Historical eruptions have produced lava flows that have reached the ocean in as little as 3 hr. The timing and location of such lava flows in the past 200 yr underscore how critical determination of the location and geometry of magma storage and structure is for volcanic hazard assessment and eruption forecasting. Now, after nearly 38 yr of volcanic quiescence, Mauna Loa has erupted again. On 27 November 2022, fissures initiated within the summit caldera and then migrated to the northeast rift zone, where they generated a large lava flow that threatened a major highway. To improve our understanding of the geometry of this magma system, we deployed a temporary nodal array on Mauna Loa in the summer of 2024. This increased our seismic coverage sufficiently to image this magmatic system. This nodal array consists of 33 seismometers distributed on and around the volcano and was deployed for over three months to record seismic signals. The primary objective of this project is to resolve the high‐resolution seismic velocity structure and characterize seismic features associated with magma storage and ascent pathways. In this article, we present an overview of the deployment, evaluate the quality of the data, and show example recordings to evaluate the suitability of the data set for future seismic investigations, including earthquake relocation, seismic tomography, and receiver function analysis. Comparisons with nearby permanent broadband and short‐period seismic stations demonstrate that the nodal array recorded high‐quality waveforms, making it a valuable resource for constraining the magmatic system beneath Mauna Loa at multiple scales.

Hawaii↗

USGS2025

Movements and survival of hatchery reared juvenile cisco (Coregonus artedi) in Saginaw Bay, Lake Huron

Background Cisco ( Coregonus artedi ) were historically abundant throughout Lake Huron, including Saginaw Bay, but only a few remnant populations remain in northern Lake Huron today. Reestablishment of cisco is an important component of management plans to restore sustainable fisheries in Lake Huron. Cisco restoration efforts have focused on the release of hatchery-reared fish, but the fate and behavior of stocked fish after release is unknown. Mortality due to predation and behavior of hatchery-reared fish after release may influence success of restoration stocking programs. Acoustic telemetry tags with predation sensors show promise for tracking movements and survival of juvenile fish; however, guidelines for designing receiver arrays to capture movements and determine the fate of juvenile fish are not well-established. Results We examined whether an acoustic receiver array with approximately 20 km 2 of coverage was sufficient to determine movements and fate of cisco during the first month after release. We implanted 26 juvenile cisco (mean total length = 161 mm) with acoustic tags equipped with a sensor to detect predation. Thirteen fish (50%) moved more than 4 km from the release location and out of the array, seven fish (27%) were consumed by predators while in the array within 17 days of release, and the fates of six fish (23%) were unknown. Of fish that left the array, 50% left between 4 and 7 days after release. No fish were detected after 17 days after release. Cisco moved with water currents during the first day after release, but this was not observed in subsequent days. Concurrent with fish release, detection range was estimated from stationary tags at three locations within the receiver array. Daily estimates of detection range were greater than 50% at 250 m during October 2021. Conclusions This study provides evidence that hatchery-reared juvenile cisco can move more than 4 km within 17 days of release but are vulnerable to predation. To fully quantify sources of mortality and spatial extent of movements by hatchery-reared cisco, future acoustic telemetry studies will require a receiver array designed to track movements of tagged fish and their predators over larger distances than monitored in this study.

Michigan↗

USGS2025

Application of fin tissue for nonlethal stable isotope analysis of small-bodied fishes

Stable isotopes are commonly used to characterize food web structure and resource use by aquatic organisms. White muscle is generally preferred for stable isotope analysis of fishes. However, obtaining white muscle tissue typically requires lethal take or invasive sampling techniques, which are undesirable for small-bodied species or those of conservation concern. We assessed the use of fish fin as a nonlethal alternative to muscle tissue for stable isotope analysis of four small-bodied fishes native to the upper Red River drainage of Texas and Oklahoma, USA: plains minnow Hybognathus placitus , prairie chub Macrhybopsis australis , Red River shiner Alburnops bairdi , and Red River pupfish Cyprinodon rubrofluviatilis . Fin isotope values were strong predictors of both δ 15 N and δ 13 C muscle isotope values (ANCOVA: δ 15 N: F 1,451 = 5312.09, P < 0.001; δ 13 C: F 1,451 = 7864.39, P < 0.001), although isotopic composition varied among species for δ 13 C ( F 3,451 = 4.29, P < 0.01). Species-specific regression models indicated positive linear relationships between fin and muscle isotope values (δ 15 N: P < 0.001, R 2 ≥ 0.80; δ 13 C: P < 0.001, R 2 ≥ 0.83) that did not vary significantly with body size or age of individuals. We suggest minimum total length thresholds for least destructive fin clipping at 70 mm, 62 mm, and 48 mm for plains minnow, prairie chub, and Red River pupfish, respectively. Nonlethal fin clipping may not be viable for Red River shiner within the size range reported here as multiple fins were required for routine analysis. Overall, we conclude that fin tissue may be used for δ 15 N and δ 13 C assessments to mitigate lethal take of imperiled, small-bodied fishes.

Oklahoma, Texas↗

USGS2025

Recovery of Delaware Bay horseshoe crabs following harvest reductions

Objective Horseshoe crabs Limulus polyphemus play a vital role in the Delaware Bay ecosystem. The migratory stopover of several shorebird species occurs during the horseshoe crab spawning season, and the eggs of horseshoe crabs provide an essential food source to fuel their northward migration to breeding areas. High commercial fishery use of horseshoe crabs as bait during the 1990s coincided with a decline in crabs and shorebirds, particularly the red knot Calidris canutus rufa , which has been listed as threatened under the U.S. Endangered Species Act since 2015. In response to the population decline of shorebirds, the Atlantic States Marine Fisheries Commission began reducing the harvest of horseshoe crabs in 2000 with a goal of rebuilding the population of horseshoe crabs and shorebirds that depend upon them. The objective of this analysis was to determine whether horseshoe crab harvest management in the Delaware Bay region has increased the abundance of the species in recent years. Methods We analyzed data from fisheries-independent trawl surveys of horseshoe crab relative abundance using a Bayesian hierarchical model to determine whether harvest management has resulted in the rebuilding of the horseshoe crab population to levels seen in 1990—a period before the overuse of horseshoe crabs and the decline in the population of red knots. Results Data from multiple surveys showed that the horseshoe crab population in Delaware Bay declined from the 1990s through approximately 2005, was relatively low and stable until 2010, and then increased through 2023, with a 0.38 probability of exceeding the 1990 level. Conclusions The results of this analysis support the effectiveness of management decisions related to horseshoe crabs in the Delaware Bay region. In response to harvest restrictions, the abundance of horseshoe crabs has neared levels observed in the early 1990s—a period prior to high commercial use and a decline in both horseshoe crabs and shorebirds that depend on them for food during annual migrations.

Delaware, Maryland, New Jersey↗

USGS2025

An automated compositing method for producing annual clear images from Landsat Collection 2 for annual NLCD production

Quality image input is fundamental to the quality of derived land cover products. Substantial time and effort are usually required to prepare images. Here, we present a novel and streamlined compositing algorithm that ingests Landsat Collection 2 Analysis Ready Data (ARD) and outputs cloud-free and gap-free composite imagery, which can be directly used for classification. This method leverages and improves the previous National Land Cover Database (NLCD) Virtual Median Value Point (VMVP) compositing method, the first part of the image preparation for NLCD 2019 operational production. The NLCD 2019 image preparation approach includes a second part, a residual cloud and cloud shadow detection and gap-filling method, to produce final cloud-free and gap-free composite imagery. The second part requires one clear reference image for each target year. Additional reference images are needed for producing reasonable observations for perennial ice/snow areas because Pixel QA (Quality Assessment) from ARD has difficulties differentiating ice/snow areas from clouds. Unlike the NLCD 2019 image preparation approach, our new compositing method, which is referred to as Automated VMVP (AVMVP), uses Landsat ARD as the only input and does not require reference images and extra steps. In this method, we developed new spectral filter criteria coupled with counts of clear observations using Pixel QA to identify potential cloud and cloud shadow observations on initially selected observations from the NLCD VMVP compositing algorithm. We also automate “gap-filling” using clear observations retrieved from a maximum of ±2 years around the target year when needed. Finally, a percentile-filtered compositing method was developed for the perennial ice/snow areas. All these steps are streamlined, pixel-based, and directly run on Landsat Collection 2 ARD. We have run successful tests on the conterminous United States (CONUS). Composite images derived from our innovative method were used to produce the CONUS Annual NLCD Collection 1 product suite that covers the period from 1985 to 2023.

conterminous United States↗

USGS2025

Control of a dominant predator influences the occurrence of a mesocarnivore of conservation concern

Context Interspecific interactions shape ecological communities, influence community dynamics, and drive co-evolution. Despite their ecological significance, predation and competition remain understudied in plains spotted skunks ( Spilogale interrupta ), a species of conservation concern. Clarifying how predator management influences their occurrence is crucial for effective conservation. Aims We investigated how coyote ( Canis latrans ) management affects the occupancy of plains spotted skunks and whether interspecific interactions with domestic cats ( Felis catus ) and striped skunks ( Mephitis mephitis ) influence plains spotted skunk occurrence. Methods We analysed live-trap data from east-central South Dakota collected in spring of 2021 and 2022. The study area encompassed portions of counties that implemented disparate predator management regimes, including one with systematic annual coyote removal and another without. We used single-species occupancy models to estimate detection and occupancy probabilities for plains spotted skunks, domestic cats, and striped skunks, incorporating environmental factors, including the site-specific predator control regime. We then applied conditional two-species occupancy models to test whether cats and striped skunks influenced plains spotted skunk occurrence. Key results Plains spotted skunks had the lowest occupancy, followed by domestic cats, and striped skunks. Our findings showed significant associations between coyote removal and occupancy probabilities for each mesocarnivore species. Plains spotted skunks had higher occupancy in areas where coyotes were annually removed. Spotted skunk occurrence was not conditional on either domestic cat or striped skunk occurrence. Conclusions In our study system, cats appear to pose less predation risk to spotted skunks than do other predators, reducing the likelihood that cats significantly influence spotted skunk occupancy. Defensive behaviours and use of spatial refugia by plains spotted skunks may further mitigate predation risk. In addition, co-evolutionary pressures may have led to trait adaptations that facilitate the independent co-occurrence of plains spotted skunks and striped skunks. Implications Our findings highlighted the ecological consequences of predator management and the importance of considering predator–prey dynamics in conservation and management planning. Strategies aimed at conserving plains spotted skunks should integrate predator control measures while considering broader mesocarnivore community interactions.

South Dakota↗

USGS2025

Causal analysis of fire regime drivers in California

Background Understanding the relative contribution of climate and human factors to wildfires is critical for managing risk across California’s diverse ecosystems, in the United States (US). Aims We propose a model that distinguishes between proximate and ultimate drivers of fire regimes and apply it to a century of fire and climate data to assess regional variation in causal mechanisms. Methods We analyzed fire statistics (1910–2021) alongside climate and weather data, stratifying the state by 10 ecoregions. Key results Northern forests had the strongest correlation with the proximate factor fuel aridity, ultimately due to climate. Fire rotation intervals exceeded 100 years, implicating woody fuel accumulation as an additional factor. Lightning ignitions occurred in decadal bursts, with dense strike events potentially overwhelming fire-fighting resources. Lower elevation/latitude foothill ecoregions experienced highest fire activity following wet winters and springs, implicating control by herbaceous fuel loads and a negative effect of global warming on future fires. Human ignitions dominate in these ecoregions, and population growth contributes to expansion of powerlines, a major ignition source. Conclusions While climate change may increase fire activity in forested ecoregions, its role is less pronounced in non-forested ecoregions, where human ignition sources are the dominant factor. Implications Different areas within ecoregions may require different management actions that reflect the specific proximate and ultimate factors at play.

California↗

USGS2025

Heat-driven functional extinction of Caribbean Acropora corals from Florida's Coral Reef

In 2023, a record-setting marine heat wave triggered the ninth mass coral bleaching event on Florida’s Coral Reef (FCR). We examined spatial patterns of heat exposure along the ~560-kilometer length of FCR and the mortality of two ecologically important, critically endangered reef-building corals. Sea surface temperatures were ≥31°C for an average of 40.7 days, leading to heat exposures 2.2- to fourfold higher than all prior years on record. In the Florida Keys and Dry Tortugas, 97.8 to 100% of the Acropora palmata and Acropora cervicornis colonies died. Mortality was lower offshore southeast Florida (37.9%), reflecting cooler temperatures in this region. Since the late 1970s, multiple stressors had already reduced the ecological relevance of Acropora in Florida, but the 2023 heat wave marks their functional extinction from FCR.

Florida↗

USGS2025

Wind pumping dominates landward salt transport in a weakly tidal estuary

In tidally energetic estuaries, salinity dynamics vary with tidal forcing as well as factors such as river discharge and bathymetry. However, in weakly tidal estuaries, mechanisms governing salt transport remain poorly understood. Here, we investigate salt transport processes in a weakly tidal estuary, Albemarle Sound on the U.S. East Coast, using a deterministic numerical model. In 2022, the volume averaged salinity of Albemarle Sound ranged from ∼2 to 10 psu. Although seasonal river discharge typically induces gradual salinity changes of less than 1 psu per month, four wind events caused sharp salinity increases of 1–2 psu within just a few days. We find that wind pumping, defined as the net salt transport due to temporal correlations between velocity and salinity associated with wind events, is the dominant mechanism contributing to these episodic increases in volume averaged salinity. In Albemarle Sound, wind pumping operates on timescales of several days, which is longer than the tidal timescale, and occurs intermittently throughout the year rather than following a regular repetitive pattern. Our analysis suggests that salt transport by wind pumping is typically an order of magnitude larger than by gravitational circulation and serves as the primary mechanism balancing salt loss from river flow. Isolating wind pumping requires averaging over variability of multiple days, longer than typical tidal averaging. Wind pumping likely also controls material exchange with coastal ocean, influencing biogeochemical processes in the estuary. This mechanism may be important in other systems with similar characteristics, particularly in coastal lagoons with multiple subembayments.

North Carolina↗