Mission Areas

Ecosystems

Mission Areas L2 Landing Page Tabs

Filter Total Items: 562
Date published: May 1, 2018
Status: Active

Pollution in Aquatic Ecosystems

USGS scientists quantify and describe functional relationships among aquatic species and habitats to characterize aquatic community structure, function, adaptation, and sustainability.

Date published: May 1, 2018
Status: Active

Bird Banding Laboratory

The Bird Banding Laboratory (BBL) is an integrated scientific program established in 1920 supporting the collection, archiving, management and dissemination of information from banded and marked birds in North America.  This information is used to monitor the status and trends of resident and migratory bird populations. Because birds are good indicators of the health of the environment, the...

Date published: May 1, 2018
Status: Active

Invasive Species and Disease

USGS provides fisheries research information to restore and enhance fish habitat and understand fish diseases. Endangered species and those that are imperiled receive special research interest. Aquatic Invasive Species research is aiding in early detection and control measures, as well as understanding impacts these invaders have on aquatic environments.

Date published: May 1, 2018
Status: Active

Land and Water Management

USGS research in advanced technologies, use of remote sensing, and research and monitoring in large river systems across the U.S. uniquely positions the USGS Fisheries Program to contribute to practical applications of landscape science.

Date published: May 1, 2018
Status: Active

Drought and Ecological Flows

As part of the USGS Fisheries program, ecological flows, or the relationships between quality, quantity, and timing of water flows and ecological response of aquatic biota and ecosystems; and related ecosystem services are being investigated. 

Date published: May 1, 2018
Status: Active

Climate Change and Aquatic Ecosystems

Climate change is an additional stressor in a complex suite of threats facing freshwater ecosystems. Climate change is already stressing many freshwater species by warming water temperatures, shifting streamflow regimes, increasing extreme events (e.g., floods, drought, wildfire), and facilitating species invasions.

 

USGS fisheries scientists study the complex...

Date published: May 1, 2018
Status: Active

Energy Development and Aquatic Ecosystems

USGS is advancing science on the impacts of energy development on aquatic ecosystems.

Date published: April 26, 2018
Status: Active

Fish and Aquatic Ecology

USGS scientists conduct studies to understand how aquatic species interact with each other and their environment in a wide range of aquatic habitats, including streams, rivers, lakes, wetlands, and coastal areas. USGS scientists quantify and describe functional relationships among aquatic species and habitats to describe aquatic community structure, function, adaptation, and sustainability....

Date published: April 26, 2018
Status: Active

Vulnerability Assessments of Aquatic Species

The USGS Fisheries Program develops valuable tools for assessing species’ vulnerability to environmental stressors, focusing on 3 critical elements: exposure (magnitude of change), sensitivity (likelihood of adverse impacts), and adaptive capacity (species’ ability to cope with change). For example, our scientists develop the tools and science to help water managers evaluate tradeoffs in...

Date published: April 26, 2018
Status: Active

Aquatic Toxicology

The USGS investigates pathogens and other environmental factors that affect aquatic organism health to  support the management, conservation, and restoration of aquatic species.

Date published: April 26, 2018
Status: Active

Fish Health

USGS investigates pathogen discovery, causes, and drivers; researches disease ecology and immunology; and develops advanced tools for surveillance, risk assessment, and control of diseases that impact aquatic organism health to support the management, conservation, and restoration of aquatic species.

Date published: April 26, 2018
Status: Active

Fish Physiology and Behavior

USGS research focuses on fish physiology and behavioral characteristics, vulnerability assessments, and development of indicator tools that can be used to inform decisions with the goal of sustaining and enhancing fisheries resources in concert with human uses.

Filter Total Items: 69
Date published: February 8, 2017

The North American Breeding Bird Survey, Results and Analysis 1966 - 2015

This website presents population change information for more than 400 species of North American birds, as estimated from the North American Breeding Bird Survey. Estimates of trend (interval-specific estimates of population change), annual indices of abundance, and maps of abundance and population change for these species are presented for a variety of regions.

Date published: February 8, 2017

North American Amphibian Monitoring Program (NAAMP) anuran detection data from the eastern and central United States (1994-2015)

The North American Amphibian Monitoring Program (NAAMP) was a collaborative citizen science effort between the US Geological Survey (USGS) and 26 Partners (state agencies, universities, and nonprofits) for monitoring calling amphibian populations over much of the eastern and central United States.

Date published: February 2, 2017

A Multiscale Index of Landscape Intactness for the Western United States

Landscape intactness has been defined as a quantifiable estimate of naturalness measured on a gradient of anthropogenic influence. We developed a multiscale index of landscape intactness for the Bureau of Land Management’s (BLM) landscape approach, which requires multiple scales of information to quantify the cumulative effects of land use.

Date published: February 2, 2017

North American Aquatic Macroinvertebrate Digital Reference Collection (NAAMDRC)

Aquatic invertebrates are a key component of freshwater ecosystems, and an understanding of aquatic invertebrate taxonomy is central to freshwater science. The North American Aquatic Macroinvertebrate Digital Reference Collection (NAAMDRC) was created by the USGS Aquatic Experimental Lab (AXL) to provide users with high-quality digital microscopy photographs.

Date published: January 30, 2017

Field Guide to the Nonindigenous Marine Fishes of Florida

The purpose of this field guide is to provide information on nonindigenous (i.e., non-native) fishes that have been observed in Florida’s marine waters.

Date published: January 27, 2017

Mean of the Top Ten Percent of NDVI Values in the Yuma Proving Ground during Monsoon Season, 1986-2011

This study uses growth in vegetation during the monsoon season measured from LANDSAT imagery as a proxy for measured rainfall. NDVI values from 26 years of pre- and post-monsoon season Landsat imagery were derived across Yuma Proving Ground (YPG) in southwestern Arizona, USA.

Date published: December 1, 2016

DATA RELEASE - TsezhinBii Field and Summary Data, Navajo Nation, Arizona, 2004

These data provide the locational coordinates, soil texture characteristics, plant species occurrence and cover, and vegetation summary characteristics for the Tsezhin bii region in the south-central area of the Navajo Nation.

Date published: October 31, 2016

USGS Dam Removal Information Portal (DRIP)

The Dam Removal Information Portal is a Web site that serves information about the scientific studies associated with dam-removal projects. It is a visualization tool, including a map and interactive charts, of a dam-removal literature review designed and developed by a working group at the USGS John Wesley Powell Center for Analysis and...

Date published: October 1, 2016

Approved Data Releases

This public folder contains approved data release products produced by the USGS Western Ecologial Research Center. This folder also includes metadata that will be harvested and displayed by the USGS Science Data Catalog ( http://data.usgs.gov/datacatalog) to improve access and discovery. 

Date published: July 14, 2016

Diamondback Terrapins in Chesapeake Bay, 2002 Beach Survey

The survey was conducted in summer 2002 to assess the presence of terrapins in the Maryland portion of the Chesapeake Bay. Results are spatial locations of evidence related to nesting.

Date published: May 2, 2016

Evidence of Absence Webinar

This video describes a statistical software package called "Evidence of Absence" that can be used to provide evidence of compliance with incidental take permits. It will be useful to wildlife managers and wind energy operators to estimate, with reasonable certainty, that a certain number of birds or bats have been killed at wind energy facilities, even when no carcasses are found.

Date published: April 27, 2016

South Florida Information Access (SOFIA)

South Florida Information Access (SOFIA) was established to provide coherent information access in support of research, decision-making, and resource management for the South Florida ecosystem restoration effort.

Filter Total Items: 2,285
Year Published: 2018

Raptor interactions with wind energy: Case studies from around the world

The global potential for wind power generation is vast, and the number of installations is increasing rapidly. We review case studies from around the world of the effects on raptors of wind-energy development. Collision mortality, displacement, and habitat loss have the potential to cause population-level effects, especially for species that are...

Watson, Richard T.; Kolar, Patrick S.; Ferrer, Miguel; Nygård, Torgeir; Johnston, Naira; Hunt, W. Grainger; Smit-Robinson, Hanneline A.; Farmer, Christopher J; Huso, Manuela; Katzner, Todd
Watson, R.T., Kolar, P.S., Ferrer, M., Nygard, T., Johnston, N., Hunt, W.G., Smit-Robinson, H.A., Farmer, C., Huso, M.M., Katzner, T.E., 2018, Raptor interactions with wind energy- case studies from around the world: Journal of Raptor Research, v. 52, no. 1, p. 1-18, https://doi.org/10.3356/JRR-16-100.1.

Year Published: 2018

Biological and ecological science for Wisconsin—A Great Lakes and Rivers State

Wisconsin and natural resources go hand-in-hand. Tourism, which generates $19 billion annually and sustains about 200,000 jobs, depends on an abundance of lakes, rivers, shorelines, and woodlands for fishing, hunting, boating, and other outdoor recreation. Rivers and floodplains in the Upper Mississippi Basin, including the Mississippi River, are...

Attribution: Ecosystems
U.S. Geological Survey, 2018, Biological and ecological science for Wisconsin—A Great Lakes and Rivers State: U.S. Geological Survey Fact Sheet 2018-3004, 2. p., https://doi.org/10.3133/fs20183004.

Year Published: 2018

Modeling intrinsic potential for beaver (Castor canadensis) habitat to inform restoration and climate change adaptation

Through their dam-building activities and subsequent water storage, beaver have the potential to restore riparian ecosystems and offset some of the predicted effects of climate change by modulating streamflow. Thus, it is not surprising that reintroducing beaver to watersheds from which they have been extirpated is an often-used restoration and...

Dittbrenner, Benjamin J.; Pollack, Michael M.; Schilling, Jason W.; Olden, Julian D.; Lawler, Joshua J.; Torgersen, Christian E.
Dittbrenner, B.J., Pollack, M.M., Schilling, J.W., Olden, J.D., Lawler, J.J., Torgersen, C.E., 2018, Modeling intrinsic potential for beaver (Castor canadensis) habitat to inform restoration and climate change adaptation: PLoS ONE, v. 13, no. 2, p. e0192538, https://doi.org/10.1371/journal.pone.0192538.

Year Published: 2018

Fire and grazing influence site resistance to Bromus tectorum through their effects on shrub, bunchgrass and biocrust communities in the Great Basin (USA)

Shrubs, bunchgrasses and biological soil crusts (biocrusts) are believed to contribute to site resistance to plant invasions in the presence of cattle grazing. Although fire is a concomitant disturbance with grazing, little is known regarding their combined impacts on invasion resistance. We are the first to date to test the idea that biotic...

Condon, Lea A.; Pyke, David A.
Condon, L.A., Pyke, D.A., 2018, Fire and grazing influence site resistance to Bromus tectorum through their effects on shrub, bunchgrass and biocrust communities in the Great Basin (USA): Ecosystems, p. online, https://doi.org/10.1007/s10021-018-0230-8.

Year Published: 2018

Golden Eagle Monitoring Plan for the Desert Renewable Energy Conservation Plan

This report describes options for monitoring the status and population trends of the golden eagle (Aquila chrysaetos) within the Desert Renewable Energy Conservation Plan (DRECP) area of Southern California in maintaining stable or increasing population in the planning area. The report profiles the ecology of golden eagles in the region and...

Wiens, David; Kolar, Patrick; Katzner, Todd
Wiens, J.D., Kolar, P.S., Katzner, T.E., 2018, Golden Eagle Monitoring Plan for the Desert Renewable Energy Conservation Plan: California Energy Commission Publication number: CEC-500-2018-008, p. 99.

Year Published: 2018

An analytical framework for estimating aquatic species density from environmental DNA

Environmental DNA (eDNA) analysis of water samples is on the brink of becoming a standard monitoring method for aquatic species. This method has improved detection rates over conventional survey methods and thus has demonstrated effectiveness for estimation of site occupancy and species distribution. The frontier of eDNA applications, however, is...

Chambert, Thierry; Pilliod, David S.; Goldberg, Caren S.; Doi, Hideyuki; Takahara, Teruhiko
Chambert, T., Pilliod, D.S., Goldberg, C.S., Doi, H., Takahara, T., 2018, An analytical framework for estimating aquatic species density from environmental DNA: Ecology and Evolution, p. online, https://doi.org/10.1002/ece3.3764.

Year Published: 2018

A simplified field protocol for genetic sampling of birds using buccal swabs

DNA sampling is an essential prerequisite for conducting population genetic studies. For many years, blood sampling has been the preferred method for obtaining DNA in birds because of their nucleated red blood cells. Nonetheless, use of buccal swabs has been gaining favor because they are less invasive yet still yield adequate amounts of DNA for...

Vilstrup, Julia T.; Mullins, Thomas D.; Miller, Mark P.; McDearman, Will; Walters, Jeffrey R.; Haig, Susan M.
Vilstrup, J.T., Mullins, T.D., Miller, M.P., McDearman, W., Walters, J.R., Haig, S.M., 2018, An simplified field protocol for genetic sampling of birds using buccal swabs: The Wilson Journal of Ornithology, p. online, https://doi.org/10.1676/16-105.1.

Year Published: 2018

Assessment of distribution and abundance estimates for Mariana swiftlets (Aerodramus bartschi) via examination of survey methods

We described past and present distribution and abundance data to evaluate the status of the endangered Mariana Swiftlet (Aerodramus bartschi), a little-known echolocating cave swiftlet that currently inhabits 3 of 5 formerly occupied islands in the Mariana archipelago. We then evaluated the survey methods used to attain these estimates via...

Johnson, Nathan C.; Haig, Susan M.; Mosher, Stephen M.
Johnson, N.C., Haig, S.M., Mosher, S.M., 2018, Assessment of distribution and abundance estimates for Mariana swiftlets (Aerodramus bartschi) via examination of survey methods: The Wilson Journal of Ornithology, p. online, https://doi.org/10.1676/16-106.1.

Year Published: 2018

Effect of cattle exclosures on Columbia Spotted Frog abundance

Livestock grazing is an important land use in the western USA and can have positive or negative effects on amphibians. Columbia Spotted Frog (Rana luteiventris) often use ponds that provide water for cattle. We conducted a long-term manipulative study on US Forest Service land in northeastern Oregon to determine the effects of full and partial...

Adams, Michael J.; Pearl, Christopher; Chambert, Thierry; Mccreary, Brome; Galvan, Stephanie; Rowe, Jennifer
Adams, M.J., Pearl, C.A., Chambert, T., McCreary, B., Galvan, S.K., Rowe, J.C., 2018, Effect of cattle exclosures on Columbia spotted frog abundance: Wetlands Ecology and Management, p. online, https://doi.org/10.1007/s11273-018-9596-9.

Year Published: 2018

Improving estimation of flight altitude in wildlife telemetry studies

Altitude measurements from wildlife tracking devices, combined with elevation data, are commonly used to estimate the flight altitude of volant animals. However, these data often include measurement error. Understanding this error may improve estimation of flight altitude and benefit applied ecology.There are a number of different approaches that...

Poessel, Sharon; Duerr, Adam E.; Hall, Jonathan C.; Braham, Melissa A.; Katzner, Todd
Poessel, S.A., Duerr, A.E., Hall, J.C., Braham, M.A., Katzner, T.E., 2018, Improving estimation of flight altitude in wildlife telemetry studies: Journal of Applied Ecology, p. online, https://doi.org/10.1111/1365-2664.13135.

Year Published: 2018

Greater sage-grouse science (2015–17)—Synthesis and potential management implications

Executive SummaryThe greater sage-grouse (Centrocercus urophasianus; hereafter called “sage-grouse”), a species that requires sagebrush (Artemisia spp.), has experienced range-wide declines in its distribution and abundance. These declines have prompted substantial research and management investments to improve the understanding of sage-grouse and...

Hanser, Steven E.; Deibert, Patricia A.; Tull, John C.; Carr, Natasha B.; Aldridge, Cameron L.; Bargsten, Travis D.; Christiansen, Thomas J.; Coates, Peter S.; Crist, Michele R.; Doherty, Kevin E.; Ellsworth, Ethan A.; Foster, Lee J.; Herren, Vicki A.; Miller, Kevin H.; Moser, Ann; Naeve, Robin M.; Prentice, Karen L.; Remington, Thomas E.; Ricca, Mark A.; Shinneman, Douglas J.; Truex, Richard L.; Wiechman , Lief A. ; Wilson, Dereck C.; Bowen, Zachary H.
Attribution: Ecosystems
Hanser, S.E., Deibert, P.A., Tull, J.C., Carr, N.B., Aldridge, C.L., Bargsten, T.C., Christiansen, T.J., Coates, P.S., Crist, M.R., Doherty, K.E., Ellsworth, E.A., Foster, L.J., Herren, V.A., Miller, K.H., Moser, Ann, Naeve, R.M., Prentice, K.L., Remington, T.E., Ricca, M.A., Shinneman, D.J., Truex, R.L., Wiechman, L.A., Wilson, D.C., and Bowen, Z.H., 2018, Greater sage-grouse science (2015–17)—Synthesis and potential management implications: U.S. Geological Survey Open-File Report 2018–1017, 46 p., https://doi.org/10.3133/ofr20181017.

Year Published: 2018

Mercury concentrations in multiple tissues of Kittlitz's murrelets (Brachyramphus brevirostris)

Mercury (Hg) is a non-essential, toxic metal that is distributed worldwide. Mercury biomagnifies in food webs and can threaten the health of top predators such as seabirds. The Kittlitz's murrelet (Brachyramphus brevirostris) is a seabird endemic to Alaska and the Russian Far East and is a species of conservation concern in the region. We...

Kenney, Leah A.; Kaler, Robb S.; Kissling, Michelle L.; Bond, Alexander L.; Eagles-Smith, Collin A.
Kenney, L.A., Kaler, R.S., Kissling, M.L., Bond, A.L., Eagles-Smith, C.A., 2017, Mercury concentrations in multiple tissues of Kittlitz's murrelets (Brachyramphus brevirostris): Marine Pollution Bulletin, p. online, https://doi.org/10.1016/j.marpolbul.2017.10.055.

Filter Total Items: 538
Bats hibernating in cave
December 31, 2017

Bats hibernating in cave

Bats hibernating in a cave. 

Attribution: Ecosystems
USGS
December 31, 2017

Hoary Bat (Lasiurus cinereus) Echo Call

Bats produce a variety of vocalizations that are used for navigation, feeding, and social communication. Most vocalizations are pitched well above the range of human hearing and are referred to as ultrasonic. These calls are often known as echolocation calls since bats use the echoes produced when a sound bounces off a bug or a building to determine what is in the area. 
 

Sea Lamprey Larvae in Hand 2
December 31, 2017

Sea Lamprey Larvae in Hand 2

This image shows sea lampreys in their larvae phase.

Slower sea lamprey growth rates during the larval phase of development may increase the odds of sea lampreys becoming male, according to a USGS study. Sea lampreys are an invasive, parasitic species of fish damaging the Great Lakes.

Hibernating little brown bat
December 31, 2017

Hibernating little brown bat

little brown bat (Myotis lucifugus) with white-nose syndrome hibernating in a Virginia cave during late spring of 2016. Patches of the fungus that causes white-nose syndrome can be seen growing out of the skin (white areas) near the nose and across the folded wing skin of this bat.  Spherical drops of water condensation coat the bat's outer fur, a normal condition that...

Monarch on Joe Pyeweed plant
December 31, 2017

Monarch on Joe Pyeweed plant

Monarch butterfly on a Joe Pyeweed plant.

USGS
December 31, 2017

Hoary Bat (Lasiurus cinereus) Social Call

Bats produce a variety of vocalizations that are used for navigation, feeding, and social communication. Most vocalizations are pitched well above the range of human hearing and are referred to as ultrasonic. These calls are often known as echolocation calls since bats use the echoes produced when a sound bounces off a bug or a building to determine what is in the area. 
 

Brown bears (Ursus arctos) and Chum Salmon (Oncorhynchus)
December 31, 2017

Bear predation on salmon can be high in many Alaskan rivers.

Bear predation on salmon can be high in many Alaskan rivers.  Brown bears Ursus arctos and Chum Salmon Oncorhynchus keta are managed concurrently in McNeil River State Game Sanctuary by Alaska Dept. of Fish and Game to benefit the salmon, bears, commercial fishers, and provide unparalleled close-up bear viewing and photography opportunities for the public.

Phragmites rhizome
December 31, 2017

Phragmites rhizome

Phragmites rhizome, or a belowground stem that puts up new shoots, dug up in a coastal marsh of Lake Erie in northern Ohio. Phragmites' belowground biomass can exceed that of its aboveground biomass. 

Monarch on hairy puccoon
December 31, 2017

Monarch on hairy puccoon

A monarch butterfly on a hairy puccoon plant.

USGS
December 31, 2017

Yuma myotis (Myotis yumanensis) Call

Bats produce a variety of vocalizations that are used for navigation, feeding, and social communication. Most vocalizations are pitched well above the range of human hearing and are referred to as ultrasonic. These calls are often known as echolocation calls since bats use the echoes produced when a sound bounces off a bug or a building to determine what is in the area. 
 

Brown bears (Ursus arctos) and Chum (Salmon Oncorhynchus)
December 31, 2017

Brown bears (Ursus arctos) and Chum (Salmon Oncorhynchus)

Bear predation on salmon can be high in many Alaskan rivers.  Brown bears Ursus arctos and Chum Salmon Oncorhynchus keta are managed concurrently in McNeil River State Game Sanctuary by Alaska Dept. of Fish and Game to benefit the salmon, bears, commercial fishers, and provide unparalleled close-up bear viewing and photography opportunities for the public. ...

Southeastern Bat with P. destructans Fungus
December 31, 2017

Southeastern Bat with P. destructans Fungus

This southeastern bat (Myotis austroriparius) from Alabama shows signs of infection from the Pseudogymnoascus destructans fungus that causes white-nose syndrome in bats. The USGS National Wildlife Health Center later confirmed white-nose syndrome in this animal, marking the first time that WNS was found in a southeastern bat. As of June 2017, the species joins eight other hibernating bat...

Filter Total Items: 313
Date published: December 13, 2017

Taking the Bait: Majority of Prairie Dogs Are Consuming Plague Vaccine

About 70 percent of wild prairie dogs successfully ingested baits containing an oral sylvatic plague vaccine, or SPV, that were distributed throughout their habitats, according to a new U.S. Geological Survey study.

Date published: December 12, 2017

Saving Salamanders: Vital to Ecosystem Health

Amphibians—the big-eyed, swimming-crawling-jumping-climbing group of water and land animals that includes frogs, toads, salamanders and worm-like caecilians—are the world’s most endangered vertebrates. 

Date published: December 4, 2017

Avian Flu From Abroad Can Spread in North American Poultry, Wild Birds

Some avian influenza, or bird flu, viruses that are able to enter North America from other continents through migrating birds can be deadly to poultry and can infect waterfowl populations, according to a recently published U.S. Geological Survey study.

Date published: November 24, 2017

Serene Sirens: USGS Sea Cow Science

It may be hard to believe the legend that sailors long-at-sea once considered manatees to be mermaids. The manatee nickname – the “Sea Cow” – which comes from the herbivores’ affinity for grazing on vegetation and their slow, ambling way just makes more sense. But a U.S. Geological Survey video reveals that while they may be cow-like, they also have more than a bit of the magical mermaid to them.

Attribution: Ecosystems
Date published: October 27, 2017

California Condor Behavior Unresponsive to Lead Exposure

Scavenging birds are at risk of lead poisoning from consuming carcasses of animals killed with lead ammunition. Methods to identify lead exposure typically require capturing an animal to collect a blood sample; however, USGS and U.S. Fish and Wildlife Service researchers sought to design a less costly, noninvasive behavioral test to identify lead exposure in California condors.

Date published: October 25, 2017

Biologist starting over after Hurricane Irma damages home, office, research site

Coral reef expert Caroline Rogers was the only USGS employee in the Virgin Islands when the Category 5 storm hit.

Date published: October 23, 2017

Trick or Treat? The Frightening Threats to Bats

Written by Marisa Lubeck and Ethan Alpern

Date published: September 29, 2017

Annual Southern Sea Otter Survey: Despite Small Population Dip, Species Moves a Step Closer to Recovery

According to data released Friday by the U.S. Geological Survey and partners, the three-year average of the total counts of southern sea otters was down from last year’s high, although it still exceeded the U.S. Fish and Wildlife Service’s delisting threshold for a second straight year.

Date published: September 27, 2017

Research to Recover Threatened Waterfowl: USGS Cooperative Fish and Wildlife Research Unit Supervisor Receives Prestigious U.S. Fish and Wildlife Service Recovery Champion Award

USGS scientist James “Barry” Grand, Ph.D., has been named a 2016 U.S. Fish and Wildlife Service Recovery Champion (Region 7) for his exemplary long-term research on two formerly threatened species, the spectacled eider and Alaska-breeding Steller’s eiders.

Date published: September 19, 2017

Emerging Disease Further Jeopardizes North American Frogs

A deadly amphibian disease called severe Perkinsea infections, or SPI, is the cause of many large-scale frog die-offs in the United States, according to a new study by the U.S. Geological Survey