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USGS2026

Seasonal migrations and other movements

In the past 25 years new information has been obtained on the migrations and movements of mountain sheep (bighorn [Ovis canadensis], thinhorn [Ovis dalli]). This chapter provides a comprehensive overview of mountain sheep migration and other movements across their broad distribution in western North America. Across the range of mountain sheep, migrations and other seasonal movements define a complex movement portfolio that relates to and supports all aspects of mountain sheep ecology. Bighorn and thinhorn species have examples of migratory behaviors that span the continuum between annual residents and long-distance migrants. Migratory behaviors can be characterized as low- or high-elevation residents; elevational migrations and other variants; and geographic migrants. Native populations that have been extant on the landscape without notable human intervention have greater migratory propensity and more diverse migratory portfolios due to the maintenance of migration through cultural learning and social transmission. Restored and augmented populations, where the population-level knowledge of migration has been lost or greatly reduced, are largely nonmigratory, although translocations show some ability to restore short-distance elevational migrations. Seasonal spring and fall migrations are less common in desert bighorn sheep (O. canadensis spp.) or bighorn sheep living in canyon or prairie breaks landscapes. Mineral lick visitation is important and common across the range of mountain sheep. Managing for migratory diversity can help to sustain migratory behavior in the face of climate change and other anthropogenic pressures, which can limit landscape connectivity between seasonal ranges or alter the spatiotemporal dynamics of regional phenology with cascading effects to other biotic and abiotic interactions such as the need to balance forage and predation risk or the spatial refugia with increased temperatures.

Book chapter↗

USGS2026

New methods provide a 300–year perspective on modern area burned in two wilderness areas of the southwest United States

Climate change, expanding human ignitions, and increased fuels from fire exclusion are driving increases in area burned and fire severity in dry conifer forests of the western United States. Increasing area burned is occurring against the backdrop of a large fire deficit caused by over a century of fire exclusion. A key land management question is whether historically frequent fire regimes can be restored. Accurate estimates of historical annual area burned (prior to circa 1900) are necessary to evaluate modern area burned (after circa 1900), but are difficult to derive, and have rarely been calibrated or validated against modern fires, leaving their accuracy uncertain. We developed new methods to use tree-ring fire scars to reconstruct historical annual area burned and compare it to modern annual area burned. We focused on two southwestern US wilderness areas—Saguaro National Park (SAGU) and the Gila Wilderness (GILA)—that have a long history of using prescribed and managed fires. The abundant modern low- and moderate-severity fires allowed us to (1) calibrate and validate the fire-scar models against mapped fires to derive the first uncertainty estimates of reconstructed annual area burned and (2) test whether active fire management can help restore annual area burned to historical levels. A multi-model ensemble consisting of 10 individual member models accurately estimated area burned of mapped modern fires with no consistent biases. Each member model had distinct strengths and assumptions that made them suitable for specific applications (e.g., the synchrony model is easily applied, and Thiessen polygons provide spatially explicit area burned estimates). The accurate reconstruction of modern area burned from relatively sparse fire-scar data at GILA suggests that dense grids may not be necessary for accurate reconstructions. Our findings reveal that despite the near absence of fire in the early 20th century, both annual and 20-year sums of area burned in recent decades are back within historical levels at GILA, and trending toward historical levels at SAGU. These results demonstrate that fire management can help restore the historically prevalent, ecologically important process of widespread, frequent, low-to-moderate-severity fire in dry conifer forests.

Arizona, New Mexico↗

USGS2026

Assimilation efficiency of rainbow trout fed natural diets

Assimilation efficiency is a critical assumption of stable isotope mixing models and bioenergetics models, yet few studies examine how assimilation efficiency influences modeling inferences. We conducted laboratory experiments to determine rainbow trout ( Oncorhynchus mykiss ) assimilation efficiencies. Assimilation efficiency averaged 55.8% (SE ± 0.90) and 64.5% (SE ± 1.98) at the 10% and 25% ration levels, respectively, and did not differ significantly. Caloric energy egested in feces was not significantly different between ration levels. Caloric energy excreted in ammonia and urea was significantly different between the ration levels, with a higher amount at the 25% ration level. Absorption efficiency was significantly greater at a higher ration level. Percent energy egested in feces was significantly greater at lower ration levels. Percent energy excreted as ammonia and urea was high compared to previous studies and did not differ significantly by ration level. Our estimates of assimilation efficiency of rainbow trout (56% and 65%) were lower than some previously reported estimates, and our estimates of energy losses (feces and ammonia) were higher than some previous estimates. As knowledge of species-specific assimilation efficiencies increases, our ability to draw strong inferences and improve the accuracy of model predictions will improve.

Environmental Biology of Fishes↗

USGS2026

Invasive grass influences on the fire cycle and treatment effectiveness to control their abundance in the Intermountain West, USA

Many non-native invasive grass species increase wildfire activity and regenerate more quickly than native species. This invasive grass–fire cycle has severe negative consequences for ecosystems, creating a need to understand how different invasive grass species alter fuel characteristics and fire behavior, as well as effective treatments to control their abundance. To address these needs and increase fire and natural resource management preparedness, we performed a review and meta-analysis of recent (1985 to 2023) scientific literature. We focused on the Intermountain West, USA, where six dominant invasive grass species have already transformed ecosystems, including winter annuals—cheatgrass ( Bromus tectorum L.), medusahead [ Taeniatherum caput-medusae (L.) Nevski], red brome ( Bromus rubens L.), and Mediterranean grass [ Schismus arabicus Nees and Schismus barbatus (Loefl. ex L.) Thell]; and summer perennials—buffelgrass [ Pennisetum ciliare (L.) Link] and Lehmann’s lovegrass ( Eragrostis lehmanniana Nees). Within the 204 selected articles, B. tectorum was the most well-studied species, treatment effectiveness was the most common study type, and more studies addressed fuel accumulation than fire characteristics. While initial reductions in B. tectorum following wildfire were followed by large increases, P. ciliare initially increased and then steadily declined, and other invasive grass species had no significant post-fire changes over time. Chemical treatments were more effective than other treatments for B. tectorum , P. ciliare , and Schismus spp., although T. caput-medusae had a greater reduction with chemical treatments compared with the other species. In many cases, treatment effectiveness was enhanced when treatment types were combined or repeat treatments were conducted. Both B. tectorum and T. caput-medusae increased to pretreatment conditions within 3 and 5 yr, respectively, although there were no detectable trends for other species. Our results provide comprehensive comparisons of the effect of invasive grass species on fuel and fire characteristics and much needed insight on effective strategies for reducing invasive grass impacts to ecosystems.

Intermountain West↗

USGS2026

Simulated ground motion dataset in the Azores Plateau, Portugal, on rock and soil sites

Building on a previously developed bedrock dataset, this study extends the Azores Plateau ground motion simulations to include soil-amplified records and introduces a comprehensive validation framework. Soil amplification is modeled using one-dimensional soil profiles. A stochastic source-based approach is employed to generate the dataset, incorporating randomization of input-model parameters to account for the aleatory uncertainty in seismic activity. The accuracy of the dataset is verified through a comprehensive validation framework, showing that the randomization effectively captures variance and inter-period correlation observed in records. This work provides a robust dataset for advancing seismic hazard and risk assessment in the Azores Plateau.

central and eastern Azores islands↗

USGS2026

Earthquake catalog for the Fairbanks region of central Alaska, 2014–2024, based on waveform cross-correlation

The Fairbanks region of central Alaska is part of a broad zone of intraplate crustal deformation, situated north of the Denali fault and north of the ongoing collision and flat‐slab subduction of the Yakutat oceanic plateau. Seismicity in the Fairbanks region occurs both in diffuse areas as well as in well‐defined lineaments, such as the left‐lateral Salcha fault, which hosted the 1937 M 8 7.3 earthquake. Starting with the regional seismicity catalog, we perform waveform cross‐correlation, network‐matched filtering, and relative relocation to obtain an enhanced seismicity catalog over the time period 2014–2024. Based on the relocated catalog, we interpret a set of 15 fault segments, including two conjugate faults and two new faults east of the previously documented fault system. Considering the combined seismicity in the Minto and Fairbanks regions, the median depth of seismicity decreases from east (6 km) to west (20 km). Our interpreted faults provide guidance for future tectonic modeling and assessment of seismic hazards in this region.

Alaska↗

USGS2026

Statistical facilitation in environmental science: Integrating results from complementary statistical analyses can improve ecological interpretations

Professionals working in biological conservation seek to understand, manage, and restore populations of native organisms using many techniques. A common approach for this discipline is using long-term data collections to inform decision making. However, several quantitative issues complicate statistical analysis of monitoring datasets and can reduce the utility of results for conservation decision making. Integrating results from multiple analyses applied to the same dataset (i.e., approaching the same biological problem using different techniques) is one way to address concerns related to field data that violate statistical assumptions. This process allows data analysts, researchers, and managers to assemble insights based on the weight of evidence. Here we tested whether three different statistical techniques [(1) multiple logistic regression on original data, (2) multiple logistic regression on standardized data (i.e., mean of 0 and standard deviation of 1), and (3) random forest analysis] identified a similar hierarchy for selecting natural and anthropogenic habitat regressors. Our examination of how environmental variables affected Plains Minnow ( Hybognathus placitus ), a state-threatened fish, is relevant to other taxa and locations. We gained useful information from redundancies (i.e., agreements across analyses). New directions also emerged by addressing ambiguities (i.e., disagreements among results across analyses). When multiple analyses were integrated into one ecological story, a clearer interpretation emerged. Viewing different statistical tests as facilitators that provide mutual advantages can advance the understanding and application of statistical analyses applied to non-experimental field datasets.

Kansas↗

USGS2026

Origins, evolutions, and future directions of Landsat science products for advancing global inland water and coastal ocean observations

In April 2020, the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center introduced a Level 2 provisional Aquatic Reflectance (AR) product for the Landsat 8 Operational Land Imager (OLI), marking the initial phase in developing a standardized global product for Landsat-derived surface water measurements. The goal of USGS EROS aquatic product research and development is to prepare for an operational processing architecture for Landsat Collection 3 in the late 2020s that will enable use of quality-controlled data for emerging Landsat aquatic science applications. To achieve this, we released a subset of the Landsat 8/9 provisional AR products (Crawford et al., 2025, https://doi.org/10.5066/P14MBBRM) and examined its general performance through the Science Algorithms to Operations (SATO) framework alongside quantitative assessment using community made inland water data records (GLObal Reflectance community dataset for Imaging and optical sensing of Aquatic environments, GLORIA) and radiometric coastal validation platforms (NASA’s Ocean Color component of the Aerosol Robotic Network, AERONET-OC). Variability within the validation datasets indicate that the performance of the Landsat 8/9 provisional AR retrieval is highly context-dependent; errors are minimal in optically simple waters (e.g., clear to moderately turbid coastal waters) but increase considerably in optically complex waters where factors such as elevated levels of turbidity, chlorophyll (Chl a ) concentrations, or colored dissolved organic matter (CDOM) dominate the water column. Additionally, this paper examines key algorithmic considerations for atmospheric correction, highlighting factors that influence accuracy, scalability, and computational efficiency necessary for collection processing in the operational Landsat Product Generation System (LPGS). This paper is intended to communicate with aquatic scientists, satellite oceanographers, and the broader Earth observation community on the origins, requirements, challenges, successes, and future objectives for operationalizing global AR data products for Landsat satellite missions.

Earth System Science Data↗

USGS2026

Metal induced chitinozoan malformations link the Mid-Ludfordian OAE to the venting of metalliferous hydrothermal basin brines into the Silurian Ocean

The mechanisms driving Silurian Ocean Anoxic Events (OAEs) and their impact on marine biota remain poorly understood. Previous studies linked chitinozoan (fossil zooplankton) malformations to heavy metal toxicity under expanding reducing oceanic conditions during the onset of some of these events. Importantly, these malformations represent in vivo reactions to changing paleoenvironmental stress and may serve as a sensitive indicator of marine metal loading and the geochemical processes driving Silurian extinction events. In the current study this hypothesis is tested for the prominent Mid- Ludfordian (upper Silurian) OAE. The onset of the event is examined using the thick and well preserved stratigraphic records in outcrop at Bodudd 1 (Gotland, Sweden). A bed-by-bed collection of 101 samples were analyzed for their whole rock geochemistry with chitinozoan malformations quantified in 66 samples. A total of 587.241 specimens were counted with 133 confirmed malformations and 87 potentially malformed, occurring in two intervals that correlate with Mn enrichments. Notably, malformations appear in the lowermost sample in the section, below the carbon isotope excursion, indicating that biotic stress preceded perturbations to the global carbon cycle. In addition to Mn, anomalies in Zn and Pb are present, alongside minor enrichments in Hg, Co, and Sb. The stratigraphic position of metal anomalies corresponds with an extraordinarily rapid rise in marine Sr isotope compositions. The pulsed nature of trace metal enrichments, the distinct elemental suite, and diagnostic spikes in radiogenic 87 Sr/ 86 Sr support the emerging model that episodic venting of metalliferous hydrothermal brines was the primary trigger for this and other Silurian OAEs.

Gotland↗

USGS2026

Living with wildfire in Funny River, Alaska: 2023 Data report

Homeowner wildfire risk mitigation and preparedness are important components of community wildfire readiness. This report describes the data collected through two efforts conducted in the Funny River, Alaska, study area: (1) parcel-level rapid wildfire risk assessments performed by trained assessors and (2) homeowner surveys in which respondents provided self-assessments of their parcel-level wildfire risk. This project was undertaken to support the Kenai Peninsula Borough Office of Emergency Management and Central Emergency Services to inform decisions about wildfire adaptation. The household surveys explored the social dimensions of wildfire, including understanding of wildfire risk, outreach or communication preferences, mitigation and evacuation preparedness activities, and perceptions of community risk reduction strategies. Overall, the study indicated a community that was engaged in preparing for and mitigating the risk of wildfire; however, more mitigation work with respect to defensible space and home hardening could help reduce overall wildfire risk.

Alaska↗

USGS2026

Living with wildfire in Santa Fe, New Mexico: 2024 data report

Community wildfire readiness includes homeowner wildfire risk mitigation and wildfire evacuation preparedness. This report presents results from a household survey distributed to homeowners in the study area around Santa Fe, New Mexico in 2024 which was a follow-up to a previous survey of homeowners of the same residences, consisting of mostly identical questions, that was conducted in 2021. This follow-up survey was motivated by the nearby 2022 Hermit’s Peak/Calf Canyon Fire. Comparison of results indicates general stability in the aggregated responses to most survey questions. As found previously, 2024 results indicate that Santa Fe survey respondents are engaged in preparing for wildfire, yet more could be done to reduce risk in study communities. Despite decreases between 2021 and 2024 in the acceptability of fuels treatment methods that concern the use of fire, respondents generally support multiple types of programs intended to reduce wildfire risk to the city, including most but not all types of fuels treatments on public lands.

New Mexico↗

USGS2026

Long- versus short-term changes in seafloor elevation and volume of the Upper Florida Keys Reef Tract: 1935–2002 and 2002–2016

Coral reefs provide immense ecosystem and economic value, supporting biodiversity, fisheries, tourism, and coastal protection worth billions annually. However, widespread degradation from thermal stress, storms, disease, and human impacts has caused significant coral cover and reef structure loss, increasing coastal vulnerability and economic risks. While coral loss is well-documented, degradation of underlying reef infrastructure and surrounding seafloor changes remain poorly understood. This study addresses this knowledge gap by quantifying seafloor elevation and volume changes across 234.2 km 2 of the Upper Florida Keys (UFK) reef tract using historical bathymetric and modern lidar (light detection and ranging) data collected from two periods with distinctly different disturbance regimes: 1935–2002 (frequent storms and major coral loss) and 2002–2016 (few storms and persistently low coral cover). Analysis of over 25,000 data points revealed substantial elevation and volume loss during 1935–2002 (−0.1 ± 0.8 m; 13.6 × 10 6 m 3 net loss), shifting to minimal gains by 2002–2016 (0.0 ± 0.3 m; 1.6 × 10 6 m 3 net gain). Despite this shift, benthic cover data showed continued declines in stony coral, with increases in macroalgae and octocorals, indicating that limited reef accretion persists even with reduced storm activity. Spatial analyses highlighted variable accretion and erosion patterns across habitats and subregions, underscoring the limitations of localized measurements for ecosystem-wide assessments. Our findings demonstrate the value of integrating historical and modern datasets for regional reef monitoring, establishing baselines for restoration planning, and emphasizing the need for continued high-resolution monitoring to guide adaptive management amid ongoing environmental change.

Florida↗

USGS2026

Environmental DNA pilot monitoring program for invasive species and biodiversity assessments on Santa Cruz Island: Interim report, September 2025

The U.S. Geological Survey (USGS) and Southern California Coastal Water Research Project supported Channel Islands National Park, The Nature Conservancy’s (TNC) Santa Cruz Island Preserve, and University of California San Diego (UCSD) researchers in using environmental DNA sampling to monitor for invasive Argentine ant ( Linepithema humile ) and to describe spatial biodiversity patterns in a freshwater stream on Santa Cruz Island that is colloquially known as Cañada del Puerto Creek (hydrologic unit code 12 number 180600140201). An eDNA autosampler was deployed May 27–June 02, 2025, which filtered and preserved four 2-L water samples every 12 hours (n = 48 samples). These samples were extracted by USGS and shipped to UCSD for targeted eDNA analyses of Argentine ant. Environmental DNA sampling kits were used to filter and preserve water samples at four sites along the creek spanning ~ 5 km of stream distance. Six 1-L samples were collected at each site May 27–28 and samples were analyzed for eDNA metabarcoding using a comprehensive panel, which encompasses species across the tree of life. In these samples, eDNA from 2,134 unique taxa spanning 30 taxonomic groups (e.g., amoebas, insects, plants) were found. These sampling efforts demonstrated how eDNA autonomous and manual sampling approaches can be applied by National Park Service, TNC, and partners at scale to provide otherwise difficult and expensive to acquire information about biological threats and biodiversity.

California↗

USGS2026

Origin of the Pd/Pt ratio of the J-M Reef, Stillwater Complex, Montana, USA

The J-M reef of the Stillwater Complex is characterized by a high Pd/Pt ratio (mean ~3.8 with a standard error of 0.03) with a homogeneous geospatial distribution at the deposit scale. In this contribution, we demonstrate that the Pd/Pt ratio of the reef is the product of equilibration of an immiscible sulfide liquid with a silicate melt rich in Pd relative to Pt. Despite the high tenors of the J-M reef sulfides (avg 2,700 ppm Pt and 770 ppm Pt), numerical modeling shows that the parental melts did not have extraordinary Pd and Pt concentrations. Instead, the initial composition of a plausible parental silicate melt can have Pd and Pt contents well within the expected range of a normal, mantle-derived partial melt (i.e., ~10–20 ppb for both Pd and Pt with Pd/Pt of ~1). The relative differences in the partitioning behavior of Pt and Pd between sulfide liquid and silicate melt are unlikely to produce a consistent Pd/Pt ratio across a wide range of silicate melt to sulfide liquid mass ratios (i.e., R factors). Instead, the pre-emplacement fractionation of Pt alloy from S-undersaturated silicate magma accounts for the homogeneous and high Pd/Pt ratio of the J-M reef. We show that batch equilibration of sulfide liquid with silicate melt can produce the high Pd/Pt ratios of the reef if the partition coefficients between sulfide liquid and silicate melt for Pd and Pt are extremely high (>10 6 ). In an alternative model, Pd enrichment could be achieved by sulfide upgrading in resident footwall mush even if the partition coefficients between sulfide liquid and silicate melt are relatively small (between 10 4 and 10 6 ) because the instantaneous mass ratio of silicate melt to sulfide liquid is small (R ≈ 100–700), so the partitioning behavior of Pt and Pd has little impact on the composition of sulfide liquid.

Montana↗

USGS2026

Frameworks for assessing tsunami hazard and risk

Tsunamis are multiscale phenomena resulting from a water column displacement that may be induced by multiple sources, and range from local scale inundation processes to ocean-wide scale wave propagation. Different strategies may be required to model tsunami evolution at different scales and to characterize various intensity measures. Research in tsunami hazard and risk has focused mostly on the tsunami effects such as the wave heights or flow depths. This chapter reviews the evolution of tsunami hazard and risk assessment methodologies, with particular emphasis on the development of probabilistic approaches. Building on advances in numerical modeling and uncertainty analysis, two main frameworks for Probabilistic Tsunami Hazard and Risk Analysis (PTHA/PTRA) are described. Framework 1 (FW1) focuses on quantitative methods, including fully simulation-based assessments (FW1A), integration of hazard with vulnerability and loss models (FW1B), consideration of dynamic processes such as tidal and sea-level variations (FW1C), and approaches using limited scenario sets (FW1D). Framework 2 (FW2) complements this by incorporating indicator-based vulnerability assessments, both physical (FW2A) and social, multi-dimensional (FW2B).

Book chapter↗

USGS2026

Prolonged cooling of andesitic-dacitic lava flows produces optimal groundmass material for 40Ar/39Ar dating

Organizing the eruptive histories and petrogenetic models that underpin hazard assessments at active volcanoes typically requires high-precision ages for late Pleistocene to Holocene lava flows. In this study, features of an existing 40Ar/39Ar dataset for andesitic-dacitic rocks from Ruapehu volcano, Aotearoa New Zealand, were interrogated with new microanalytical data to identify the optimal groundmass material for age determination. To understand the behavior of K and Ar within the cooling melt of lavas during their emplacement, we examined and compared the petrological features of samples from the ice-chilled margin and interior of a lava flow. The groundmass of the rapidly cooled sample comprises non-vesicular rhyolitic glass and microlites of plagioclase, orthopyroxene, and magnetite. The sample from the flow interior has minimal amounts of groundmass glass, and interstices are instead occupied by sanidine and tridymite. Modelling supports the interpretation that sanidine crystallized as a stable groundmass phase during slow cooling of degassed melt in the interior zones of lavas that were insulated behind their glassy margins. Our evaluation of the age data shows that sanidine contributed high yields of radiogenic argon during step-heating experiments for samples collected from lava interiors, which enabled high-precision 40Ar/39Ar ages to be determined. Using Ruapehu as an example of an arc volcano affected by lava-ice interaction, we provide a basic field guide for identifying lava flows that contain groundmass sanidine at the expense of glass. Target outcrops also offer opportunities for reconstructing geomagnetic dynamics and volcano–climate relationships during the Pleistocene and Holocene.

Ruapehu volcano↗

USGS2026

Drinking water arsenic, urinary arsenic biomarkers, and cognitive impairment in the REGARDS study

Background There are several pathways by which inorganic arsenic (iAs) exposure can affect cognition among adults. Few epidemiologic studies evaluate iAs in water and inter-individual differences in urinary arsenic toxicokinetics. We aimed to estimate the association between individual-level urinary arsenic biomarkers, county-level iAs in drinking water, and cognitive impairment in a cohort of Black and White Americans. Methods We evaluated the association between county-level iAs in water and urinary iAs metabolites with incident cognitive impairment in REasons for Geographic and Racial Differences in Stroke (REGARDS). Participants were linked to county-level concentrations of arsenic in public water (n = 15,516) and county-level probabilities of private well arsenic exceeding 10 μg/L (n = 20,448). In addition, urinary concentrations of iAs, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) were measured in a subset of participants (n = 1,013). Cognitive impairment was determined by the Six Item Screener (SIS) and the Enhanced Cognitive Battery (ECB). We used multivariable logistic regression to estimate odds ratios. Results Approximately 9 % of participants in REGARDS developed incident cognitive impairment on the SIS over 10 years of follow-up. County-level public water iAs concentrations and private well iAs probabilities were not associated with increased odds of cognitive impairment. Higher concentrations of MMA (OR: 1.74 [95 % CI: 1.22, 2.49]) and iAs (OR: 1.58 [95 % CI: 1.12, 2.22]) in urine were associated with greater odds of cognitive impairment on the SIS. Results for the ECB were similar. Conclusions iAs exposure may be associated with cognitive impairment. Our findings highlight the importance of considering multiple measures of iAs exposure.

Environmental Research↗

USGS2026

Hakalau’s moving castle: How climate change and restoration are shifting an island fortress for forest birds

Hakalau Forest Unit of the Big Island National Wildlife Refuge Complex (hereafter, Hakalau) protects the largest area with the highest endemic forest bird diversity in Hawaiʻi, including four federally listed species. Hakalau’s higher elevation montane forest provides refuge from avian malaria ( Plasmodium relictum ), a primary driver of Hawaiian honeycreeper extinctions. However, recent declines in Hakalau’s birds at lower elevations could indicate that conditions have become suitable for disease vector Culex quinquefasciatus . We evaluated the statuses of Hakalau’s bird populations in the context of recent climatic changes using new survey data from point-transect distance sampling, producing abundance estimates from 1999 to 2024. We stratified our analysis across four elevation ranges (<1500 m, 1500–1700 m, 1700–1900 m, and >1900 m) and assessed trends for each species using state-space models (SSMs). We constrained population trajectories to be biologically realistic by incorporating population dynamic models within the SSMs. We observed highly species-specific abundance trends below 1500 m, predominantly stable to upward trends within 1500–1700 m, stable trends within 1700–1900 m, and upward trends above 1900 m. Declines in Hawaiʻi ʻamakihi ( Chlorodrepanis v. virens ) and endangered ʻakiapōlāʻau ( Hemignathus wilsoni ) abundance coincided with lengthening warm seasonal temperatures indicative of shrinking disease-free habitat below 1700 m. Above 1900 m, however, increases in nearly all species indicate that reforestation has likely restored disease-free habitat since 1999. While most species were stable to increasing overall, surveillance for mosquitoes and disease at lower elevations, documenting changes in habitat, and continuing bird population monitoring can help to gauge their long-term persistence at Hakalau.

Hawaii↗