USGS Science Supports Management of Invasive Species
Invasive species can harm ecosystems, increase wildfires, damage forests, and outcompete native species. The US Geological Survey's Southwest Biological Science Center conducts research that provides our federal and state partners, cooperators and land managers with the tools, data and strategies to enhance biosecurity management.
Scroll down through the information below to read about different projects that focus on invasive species research.
Reducing the extensive impacts of invasive plants and animals can be daunting, but USGS science helps illuminate new tactics for preventing, detecting, and controlling biological invasions.
Predicting the next high-impact insect invasion:
Increased global connectivity and trade have increased the risk of non-native, tree-feeding insect introductions. Forest ecosystems and urban trees are increasingly threatened by these invasive insects.
Most of these insects have little impact, but some, around 5%, become catastrophic invaders, causing billions of dollars in damage to North American forest ecosystems each year.
The question is, how do we predict the next high-impact insect invader?
To improve forest biosecurity and target management priorities, forest managers and pest inspectors need a way to enhance forecasts of the impact invading non-native tree-feeding insects might have. To counter this threat, a group of USGS, Forest Service, and university scientists have developed a suite of predictive models and an online tool, called the i-Tree Pest Predictor (iTPP), to assess the potential impact of non-native tree-feeding insects and predict the impact of insects that have not yet arrived in North America.
The group incorporated the models into the i-Tree Pest Predictor, which enables prediction of the potential impact of a new invading tree-feeding insect on over 360 hardwood and 50 conifer trees native to North America.
The models differ by whether the invading insect feeds mainly on conifers as a sap feeder, feeds mainly on hardwoods and is a bark beetle (Scolytidae) or feeds on both hardwoods and conifers. One important factor that predicts insect impact is the evolutionary history between an invading insect’s native host tree and its novel North American host. In other words, the more closely related the tree species, though geographically separated, the more impact an invasive pest can have.
Having probability estimates of the potential for a newly invading non-native tree-feeding insect to be high impact will fill a critical need to identify insects and commodities to prioritize for prevention and biosecurity efforts.
Such information can help direct policymaking and allocation of limited resources for USDA Animal and Plant Health Inspection Service (APHIS) regulatory risk assessments, inform priority actions at ports-of-entry, support forest managers in urban and natural settings to determine management actions, and enhance early detection, rapid response programs to prevent new invasions more effectively. Ultimately, these models, tools, and predictions can be used for a nation-wide risk assessment for North American trees and the ecosystems in which they reside.
Innovative eDNA technology—A game changer in the fight against aquatic invasive species:
The Southwest Biological Science Center (SBSC) is partnering with Bureau of Reclamation, U.S. Forest Service, U.S. Fish and Wildlife Service, and the National Park Service in the use of environmental DNA (eDNA), an emerging technology, to detect aquatic invasive species in rivers and reservoirs in the southwestern US.
This technique analyzes genetic material shed into aquatic systems—essentially providing a snapshot of the organisms present in a water body without the need for direct capture. It minimizes stress to aquatic species, is especially valuable for identifying elusive organisms or those residing in hard-to-reach habitats and allows early detection of nonnative species—essential for preventing their establishment and proliferation.
Responding quickly to non-native species introductions before populations become large and established is the least expensive and most effective way to control non-native species. eDNA enables scientists and resource managers to collect water samples and DNA extracted from cells collected in the environment in which an organism lives, rather than directly from the animals themselves. This reduces or eliminates fish handling and stress, which addresses Tribal concerns, and allows managers to detect species at the early stages of expansion, species with low susceptibility to capture, or species residing in habitats outside the range of standard sampling methods. As such, the use of eDNA is becoming a reliable and cost-effective tool that resource managers can use to detect rare non-native species prior to population expansion.
Warm-water invasive fish species, invertebrates, parasites, and pathogens currently present in rivers like the Colorado River are a fraction of the potential taxa that could establish, particularly if fish like smallmouth bass pass through a dam from an upstream reservoir into a river reach. These new, emerging threats have the potential to affect fish and wildlife populations and human health in river segments used by the recreational angling and boating community.
In 2025, the SBSC will enhance its efforts by utilizing an eDNA autosampler to automate the collection of water samples downstream from Glen Canyon Dam. This cutting-edge device will facilitate year-round monitoring, allowing for regular assessments of aquatic invasive species every few days, regardless of field trips. The project is collaborating with the USGS Rapid Environmental (e)DNA Assessment and Deployment Initiative & Network (READI-Net), aimed at revolutionizing eDNA as a standard practice for detecting aquatic biological threats.
The water samples will be analyzed using a novel AIS biochip developed by the U.S. Forest Service National Genomics Center for Wildlife and Fish. This tool will provide species-specific screening, giving valuable insights into the presence and relative abundance of very high risk or high-risk species, informing effective management and eradication strategies for water bodies associated with federal lands. Detection of new species or expanded coverage of existing species will be provided to federal and state agency staff to inform management and eradication decisions.
The SBSC's continued commitment to high-quality cutting-edge science supports our partners efforts to safeguard our waterways from invasive species, ensuring the health of our ecosystems and wellbeing of the communities that rely on them.
Strategies to stop smallmouth bass from spreading throughout the Colorado River:
Smallmouth bass were introduced into Lake Powell in the 1980s and now are one of the most abundant fishes in the reservoir. Until recently, smallmouth bass were extremely rare in Grand Canyon, downriver of Glen Canyon Dam. Smallmouth bass have caused native fish declines in the Upper Colorado River Basin. In the Yampa and Green Rivers in Colorado and Utah, for example, smallmouth bass have proliferated and decimated native fish populations.
Historically, the section of Colorado River between Lake Powell and Lake Mead has been insulated from smallmouth bass. Glen Canyon Dam served as a barrier to their movement from Lake Powell into the Grand Canyon, and cold water in this section of the river prevented smallmouth bass from reproducing.
Long-term drought in the Colorado River basin meant that surface water levels in Lake Powell are lower and closer to Glen Canyon Dam’s turbines. Smallmouth bass live in the warmer epilimnion waters, which are the top thermal layer of the reservoir. In 2022, the water dropped low enough so that smallmouth bass passed through the dam into the Colorado River. This led to the first records of reproduction of smallmouth bass below the dam.
This increase in smallmouth bass is being driven by record low lake levels in Powell, which does 2 things: 1) increases the probability of passing fish through the dam and 2) warms the water in the river so that smallmouth bass can spawn.
The Grand Canyon segment of the Colorado River, located downstream of Lake Powell, is the stronghold for threatened humpback chub, which are recently experiencing some recovery success. If reservoir levels remain low for an extended period of time, smallmouth bass can pose a continued threat to the recovery of humpback chub.
To assist managers concerned about this invasion, USGS, through a directive by the Glen Canyon Dam Adaptive Management Program, developed models that:
- Predict smallmouth bass passage through dam turbines (entrainment) rates for different reservoir elevations,
- Assess how various reservoir water storage and operational strategies, water temperatures, and smallmouth bass population dispersal and recruitment affect population growth rates, under different climate and management scenarios, and
- Assist managers to assess the effectiveness of mitigation efforts to help humpback chub continue their path to recovery.
USGS modeling results are currently being used by the Bureau of Reclamation for National Environmental Policy Act (NEPA) analyses.
Using USGS and partner assessments, several management strategies have been implemented, including mechanical removal of smallmouth bass, and water storage and dam operations designed to decrease release temperatures to reduce the risk of reproduction, growth, and establishment.
RestoreNet improves restoration management and invasive species detection:
RestoreNet is a research network co-produced by researchers and land managers that systematically tests dryland restoration treatments across environmental gradients in the Southwest. The USGS and partners examine the effects of native seed mixes and restoration treatments, including those to reduce invasive species, on restoration outcomes.
The results produced by the program contribute to knowledge on cutting edge ecological restoration methods for use in the southwestern United States to benefit land managers, landowners, and restoration practitioners.
Successful restoration of ecosystems, especially after disturbances or incursion of invasive species, leads to more resilient ecological communities, soil integrity, habitat protection for wildlife, and improved ecosystem services such as water retention, reduced erosion, and improved landscapes for recreation.
Learn more at:
RestoreNet: Distributed Field Trial Network for Dryland Restoration | U.S. Geological Survey
and
Southwest Energy Exploration, Development, and Reclamation (SWEDR) | U.S. Geological Survey
Background photo: USGS Biologist Sarah Costanzo monitors a RestoreNet plot within a sea of invasive cheatgrass (Bromus tectorum) and tall tumblemustard (Sisymbrium altissimum) in western Colorado.
Is Phragmites common reed invasive in Grand Canyon?
The USGS is working on a study that evaluates the distribution and extent of native and nonnative common reed (Phragmites australis) populations in the Glen and Grand Canyon regions.
Common reed is a native species around the world, but different lineages occur depending on location. For example, there are two native lineages of common reed in North America (spp. americanus and spp. berlandieri). There is an invasive lineage of common reed that came from Europe and spread across the eastern U.S. (ssp. australis). In wetlands and rivers across the U.S., the arrival and expansion of the nonnative lineage has led to major changes to wetland diversity and structure. It's considered one of the worst wetland invasive species since it quickly overtakes open areas and native plants.
Common reed has expanded along the Colorado River between Glen Canyon Dam and Lake Mead, particularly since 2009. This expansion is likely due to dam operations but could also have been related to the arrival of an invasive lineage. The definitive method to identify whether common reed is native or nonnative is to perform genetic testing. The USGS has tested over 70 sites in Glen Canyon National Recreation Area and Grand Canyon National Park, and we have confirmed that there are currently only two locations of the invasive reed — both near the mouth of the Paria River, at Paria Beach and Paria Riffle.
Why is this important?
Finding that the vast majority of common reed in the Grand Canyon region is native is very rare. Most parts of the United States know common reed ONLY as a nonnative, invasive species that is nearly impossible to eradicate. Along the Colorado River though, it is a valued and important species that is worth protecting and caring for. And uniquely, Glen Canyon Dam operations have promoted the expansion of the native common reed along the Colorado River.
Common reed is a culturally important species to the Tribes traditionally affiliated with this region. It plays a role in multiple emergence stories, is used in a wide variety of ceremonies, and has had many utilitarian uses. Plants along the sacred Colorado River in the uniquely powerful location of the Grand Canyon can take on a special status even within their own species. Management of this culturally important species along a sacred river is conducted in close collaboration with regional Tribes.
Best practices to control invasive Buffelgrass in the desert Southwest:
Buffelgrass (Pennisetum ciliare) is a highly invasive, non-native, perennial bunchgrass from Africa that was brought to Arizona in the 1930s for erosion control and has expanded rapidly across the desert. It is highly invasive in the Sonoran Desert of the southwest U.S., where it threatens desert ecosystems by out-competing native plants and altering fire regimes.
Buffelgrass spreads rapidly and reduces wildlife habitat and biodiversity of native ecosystems by outcompeting native plants. Left unchecked, it will dominate the desert landscape and could cause regular, fast-moving wildfires.
Desert landscapes naturally have gaps between vegetation. Buffelgrass fills in those spaces, providing a fuel source and carrying fire across a landscape, which increases the frequency and intensity of wildfires. Buffelgrass invasion and subsequent fire can alter ecosystem structure and function and kill iconic species like the saguaro (Carnegiea gigantea), which is not adapted to fire. It has the potential to transform the Sonoran Desert ecosystem from a diverse assemblage of plants to a non-native grassland monoculture.
To counter this threat, NPS' Saguaro National Park carries out chemical and mechanical removal treatments.
A team of researchers from the USGS Southwest Biological Science Center, Arizona-Sonora Desert Museum, and Saguaro National Park examined the effectiveness of a decade (2011 - 2020) of chemical and mechanical (manual removal) treatments to reduce buffelgrass with the goal of improving treatment success and invasive management. They assessed how the stage of buffelgrass invasion, treatment type and intensity, and environmental variables influenced reductions in cover.
Results of the studies showed that early detection and conducting both manual removal and chemical treatments every 3 years or less are crucial for eradicating buffelgrass. By targeting new infestations and treating affected areas regularly, managers can protect these desert landscapes.
Smallmouth bass expansion downstream of Glen Canyon Dam
RestoreNet: Distributed Field Trial Network for Dryland Restoration
Predicting the Next High Impact Insect Invasion
Invasive species can harm ecosystems, increase wildfires, damage forests, and outcompete native species. The US Geological Survey's Southwest Biological Science Center conducts research that provides our federal and state partners, cooperators and land managers with the tools, data and strategies to enhance biosecurity management.
Scroll down through the information below to read about different projects that focus on invasive species research.
Reducing the extensive impacts of invasive plants and animals can be daunting, but USGS science helps illuminate new tactics for preventing, detecting, and controlling biological invasions.
Predicting the next high-impact insect invasion:
Increased global connectivity and trade have increased the risk of non-native, tree-feeding insect introductions. Forest ecosystems and urban trees are increasingly threatened by these invasive insects.
Most of these insects have little impact, but some, around 5%, become catastrophic invaders, causing billions of dollars in damage to North American forest ecosystems each year.
The question is, how do we predict the next high-impact insect invader?
To improve forest biosecurity and target management priorities, forest managers and pest inspectors need a way to enhance forecasts of the impact invading non-native tree-feeding insects might have. To counter this threat, a group of USGS, Forest Service, and university scientists have developed a suite of predictive models and an online tool, called the i-Tree Pest Predictor (iTPP), to assess the potential impact of non-native tree-feeding insects and predict the impact of insects that have not yet arrived in North America.
The group incorporated the models into the i-Tree Pest Predictor, which enables prediction of the potential impact of a new invading tree-feeding insect on over 360 hardwood and 50 conifer trees native to North America.
The models differ by whether the invading insect feeds mainly on conifers as a sap feeder, feeds mainly on hardwoods and is a bark beetle (Scolytidae) or feeds on both hardwoods and conifers. One important factor that predicts insect impact is the evolutionary history between an invading insect’s native host tree and its novel North American host. In other words, the more closely related the tree species, though geographically separated, the more impact an invasive pest can have.
Having probability estimates of the potential for a newly invading non-native tree-feeding insect to be high impact will fill a critical need to identify insects and commodities to prioritize for prevention and biosecurity efforts.
Such information can help direct policymaking and allocation of limited resources for USDA Animal and Plant Health Inspection Service (APHIS) regulatory risk assessments, inform priority actions at ports-of-entry, support forest managers in urban and natural settings to determine management actions, and enhance early detection, rapid response programs to prevent new invasions more effectively. Ultimately, these models, tools, and predictions can be used for a nation-wide risk assessment for North American trees and the ecosystems in which they reside.
Innovative eDNA technology—A game changer in the fight against aquatic invasive species:
The Southwest Biological Science Center (SBSC) is partnering with Bureau of Reclamation, U.S. Forest Service, U.S. Fish and Wildlife Service, and the National Park Service in the use of environmental DNA (eDNA), an emerging technology, to detect aquatic invasive species in rivers and reservoirs in the southwestern US.
This technique analyzes genetic material shed into aquatic systems—essentially providing a snapshot of the organisms present in a water body without the need for direct capture. It minimizes stress to aquatic species, is especially valuable for identifying elusive organisms or those residing in hard-to-reach habitats and allows early detection of nonnative species—essential for preventing their establishment and proliferation.
Responding quickly to non-native species introductions before populations become large and established is the least expensive and most effective way to control non-native species. eDNA enables scientists and resource managers to collect water samples and DNA extracted from cells collected in the environment in which an organism lives, rather than directly from the animals themselves. This reduces or eliminates fish handling and stress, which addresses Tribal concerns, and allows managers to detect species at the early stages of expansion, species with low susceptibility to capture, or species residing in habitats outside the range of standard sampling methods. As such, the use of eDNA is becoming a reliable and cost-effective tool that resource managers can use to detect rare non-native species prior to population expansion.
Warm-water invasive fish species, invertebrates, parasites, and pathogens currently present in rivers like the Colorado River are a fraction of the potential taxa that could establish, particularly if fish like smallmouth bass pass through a dam from an upstream reservoir into a river reach. These new, emerging threats have the potential to affect fish and wildlife populations and human health in river segments used by the recreational angling and boating community.
In 2025, the SBSC will enhance its efforts by utilizing an eDNA autosampler to automate the collection of water samples downstream from Glen Canyon Dam. This cutting-edge device will facilitate year-round monitoring, allowing for regular assessments of aquatic invasive species every few days, regardless of field trips. The project is collaborating with the USGS Rapid Environmental (e)DNA Assessment and Deployment Initiative & Network (READI-Net), aimed at revolutionizing eDNA as a standard practice for detecting aquatic biological threats.
The water samples will be analyzed using a novel AIS biochip developed by the U.S. Forest Service National Genomics Center for Wildlife and Fish. This tool will provide species-specific screening, giving valuable insights into the presence and relative abundance of very high risk or high-risk species, informing effective management and eradication strategies for water bodies associated with federal lands. Detection of new species or expanded coverage of existing species will be provided to federal and state agency staff to inform management and eradication decisions.
The SBSC's continued commitment to high-quality cutting-edge science supports our partners efforts to safeguard our waterways from invasive species, ensuring the health of our ecosystems and wellbeing of the communities that rely on them.
Strategies to stop smallmouth bass from spreading throughout the Colorado River:
Smallmouth bass were introduced into Lake Powell in the 1980s and now are one of the most abundant fishes in the reservoir. Until recently, smallmouth bass were extremely rare in Grand Canyon, downriver of Glen Canyon Dam. Smallmouth bass have caused native fish declines in the Upper Colorado River Basin. In the Yampa and Green Rivers in Colorado and Utah, for example, smallmouth bass have proliferated and decimated native fish populations.
Historically, the section of Colorado River between Lake Powell and Lake Mead has been insulated from smallmouth bass. Glen Canyon Dam served as a barrier to their movement from Lake Powell into the Grand Canyon, and cold water in this section of the river prevented smallmouth bass from reproducing.
Long-term drought in the Colorado River basin meant that surface water levels in Lake Powell are lower and closer to Glen Canyon Dam’s turbines. Smallmouth bass live in the warmer epilimnion waters, which are the top thermal layer of the reservoir. In 2022, the water dropped low enough so that smallmouth bass passed through the dam into the Colorado River. This led to the first records of reproduction of smallmouth bass below the dam.
This increase in smallmouth bass is being driven by record low lake levels in Powell, which does 2 things: 1) increases the probability of passing fish through the dam and 2) warms the water in the river so that smallmouth bass can spawn.
The Grand Canyon segment of the Colorado River, located downstream of Lake Powell, is the stronghold for threatened humpback chub, which are recently experiencing some recovery success. If reservoir levels remain low for an extended period of time, smallmouth bass can pose a continued threat to the recovery of humpback chub.
To assist managers concerned about this invasion, USGS, through a directive by the Glen Canyon Dam Adaptive Management Program, developed models that:
- Predict smallmouth bass passage through dam turbines (entrainment) rates for different reservoir elevations,
- Assess how various reservoir water storage and operational strategies, water temperatures, and smallmouth bass population dispersal and recruitment affect population growth rates, under different climate and management scenarios, and
- Assist managers to assess the effectiveness of mitigation efforts to help humpback chub continue their path to recovery.
USGS modeling results are currently being used by the Bureau of Reclamation for National Environmental Policy Act (NEPA) analyses.
Using USGS and partner assessments, several management strategies have been implemented, including mechanical removal of smallmouth bass, and water storage and dam operations designed to decrease release temperatures to reduce the risk of reproduction, growth, and establishment.
RestoreNet improves restoration management and invasive species detection:
RestoreNet is a research network co-produced by researchers and land managers that systematically tests dryland restoration treatments across environmental gradients in the Southwest. The USGS and partners examine the effects of native seed mixes and restoration treatments, including those to reduce invasive species, on restoration outcomes.
The results produced by the program contribute to knowledge on cutting edge ecological restoration methods for use in the southwestern United States to benefit land managers, landowners, and restoration practitioners.
Successful restoration of ecosystems, especially after disturbances or incursion of invasive species, leads to more resilient ecological communities, soil integrity, habitat protection for wildlife, and improved ecosystem services such as water retention, reduced erosion, and improved landscapes for recreation.
Learn more at:
RestoreNet: Distributed Field Trial Network for Dryland Restoration | U.S. Geological Survey
and
Southwest Energy Exploration, Development, and Reclamation (SWEDR) | U.S. Geological Survey
Background photo: USGS Biologist Sarah Costanzo monitors a RestoreNet plot within a sea of invasive cheatgrass (Bromus tectorum) and tall tumblemustard (Sisymbrium altissimum) in western Colorado.
Is Phragmites common reed invasive in Grand Canyon?
The USGS is working on a study that evaluates the distribution and extent of native and nonnative common reed (Phragmites australis) populations in the Glen and Grand Canyon regions.
Common reed is a native species around the world, but different lineages occur depending on location. For example, there are two native lineages of common reed in North America (spp. americanus and spp. berlandieri). There is an invasive lineage of common reed that came from Europe and spread across the eastern U.S. (ssp. australis). In wetlands and rivers across the U.S., the arrival and expansion of the nonnative lineage has led to major changes to wetland diversity and structure. It's considered one of the worst wetland invasive species since it quickly overtakes open areas and native plants.
Common reed has expanded along the Colorado River between Glen Canyon Dam and Lake Mead, particularly since 2009. This expansion is likely due to dam operations but could also have been related to the arrival of an invasive lineage. The definitive method to identify whether common reed is native or nonnative is to perform genetic testing. The USGS has tested over 70 sites in Glen Canyon National Recreation Area and Grand Canyon National Park, and we have confirmed that there are currently only two locations of the invasive reed — both near the mouth of the Paria River, at Paria Beach and Paria Riffle.
Why is this important?
Finding that the vast majority of common reed in the Grand Canyon region is native is very rare. Most parts of the United States know common reed ONLY as a nonnative, invasive species that is nearly impossible to eradicate. Along the Colorado River though, it is a valued and important species that is worth protecting and caring for. And uniquely, Glen Canyon Dam operations have promoted the expansion of the native common reed along the Colorado River.
Common reed is a culturally important species to the Tribes traditionally affiliated with this region. It plays a role in multiple emergence stories, is used in a wide variety of ceremonies, and has had many utilitarian uses. Plants along the sacred Colorado River in the uniquely powerful location of the Grand Canyon can take on a special status even within their own species. Management of this culturally important species along a sacred river is conducted in close collaboration with regional Tribes.
Best practices to control invasive Buffelgrass in the desert Southwest:
Buffelgrass (Pennisetum ciliare) is a highly invasive, non-native, perennial bunchgrass from Africa that was brought to Arizona in the 1930s for erosion control and has expanded rapidly across the desert. It is highly invasive in the Sonoran Desert of the southwest U.S., where it threatens desert ecosystems by out-competing native plants and altering fire regimes.
Buffelgrass spreads rapidly and reduces wildlife habitat and biodiversity of native ecosystems by outcompeting native plants. Left unchecked, it will dominate the desert landscape and could cause regular, fast-moving wildfires.
Desert landscapes naturally have gaps between vegetation. Buffelgrass fills in those spaces, providing a fuel source and carrying fire across a landscape, which increases the frequency and intensity of wildfires. Buffelgrass invasion and subsequent fire can alter ecosystem structure and function and kill iconic species like the saguaro (Carnegiea gigantea), which is not adapted to fire. It has the potential to transform the Sonoran Desert ecosystem from a diverse assemblage of plants to a non-native grassland monoculture.
To counter this threat, NPS' Saguaro National Park carries out chemical and mechanical removal treatments.
A team of researchers from the USGS Southwest Biological Science Center, Arizona-Sonora Desert Museum, and Saguaro National Park examined the effectiveness of a decade (2011 - 2020) of chemical and mechanical (manual removal) treatments to reduce buffelgrass with the goal of improving treatment success and invasive management. They assessed how the stage of buffelgrass invasion, treatment type and intensity, and environmental variables influenced reductions in cover.
Results of the studies showed that early detection and conducting both manual removal and chemical treatments every 3 years or less are crucial for eradicating buffelgrass. By targeting new infestations and treating affected areas regularly, managers can protect these desert landscapes.