Invasive species are impacting biodiversity, degrading ecosystem function, and creating new risks to communities across the United States. At the same time, changing environmental conditions like rising temperatures, shifting seasonality, more variable precipitation, and more frequent extreme events like wildfire and floods make ecosystems more vulnerable to invasions. In some places, warmer conditions allow invaders to move to areas where they couldn’t survive before. In others, environmental changes help them grow faster or stick around longer. For example, longer growing seasons allow established invasive pests to emerge earlier in the spring and persist longer into the fall, allowing them to outcompete native species and spread further. In other places, shifting transportation routes, like new shipping routes opened by melting sea ice, make it easier for invasive species to reach areas that were previously difficult to access. Globally, human transportation is the leading driver of invasive species spread, whether through accidental stowaways on ships, planes, cars, or trucks, or through intentional introductions that later become invasive.  

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Between 1960 and 2020, invasive species cost the United States at least \$1.22 trillion in damages, resource losses, and management costs. Invasive species outcompete, prey upon, and displace native species, interfering with how ecosystems work and reducing the benefits that humans get from surrounding ecosystems. They fuel more frequent wildfires, disrupt how nutrients and water move through the landscape, and spread new diseases. These disruptions can weaken ecosystem stability and resilience and undermine the many ways that ecosystems support human communities. Invasive species also pose a threat to national security: Combined with the impacts of extreme weather and other global pressures, invasive species can reduce the supply of natural resources, destabilize economies, and strain agricultural, water, and food systems. They can also harm human health, driving up medical and insurance costs.   

Timely management actions can reduce the environmental and economic damage caused by invasive species. However, as development and changes in climate alter when, where, and how invasives spread, some traditional management strategies are becoming less effective. For example, prescribed burns, a typically reliable approach for managing invasive grasses, are becoming harder to safely implement as fire seasons become longer, more intense, and less predictable. Even containment and quarantine strategies can fall short when invasive species spread faster than monitoring programs or regulations can – for instance, zebra mussels may spread into watersheds previously too cold to support them, where monitoring programs may not yet be in place. 

Invasive species can have serious, far-reaching impacts on infrastructure, damaging critical facilities, driving up maintenance costs, and putting communities at risk. Some invasives affect the built environment: For example, English Ivy, can weaken the structural integrity of buildings by destroying grout between masonry, while giant African land snails, mice, and rats can eat through building materials like concrete and stucco. Invasive plants can also undermine roads, bridges, and culverts, while burrowing animals can weaken levees and flood control systems. Other invasives disrupt essential services. Snakes and ants can cause power outages, while invasive mussels and aquatic weeds can clog dams, pipes, and cooling systems. Whether damaging buildings, utilities, or transportation networks, invasive species increase costs and strain infrastructure. 

Changing climate conditions are driving invasive species into new areas and intensifying their impact on infrastructure. The process of repairing and maintaining infrastructure after extreme weather events can also contribute to their spread. As natural hazards become more frequent and severe, emergency repairs to roads or power lines can unintentionally spread invasive species when soil and roadsides are disturbed or if equipment and materials are not properly cleaned between uses.  

CASC scientists are working across the country to help natural resource managers better understand and prevent these impacts – ensuring infrastructure planning, hazard response, and recovery efforts account for the growing risks posed by invasive species.  

Wildfires are both a cause and a consequence of species invasions across ecosystems. Invasive grasses are especially problematic, as they act as fast-drying, continuous fuel that increases the likelihood, intensity, and frequency of wildfires, fundamentally changing fire regimes, nutrient cycling, and soil processes. Fire-adapted invasive grasses also recover quickly after fire, creating a self-perpetuating cycle. These new wildfire patterns are often unsuitable for native plants, leading to a loss of biodiversity and even local extinctions. 

In a recent national-scale study, CASC scientists showed that the threat of fire caused by invasives is widespread in the U.S. They examined 12 non-native invasive grasses across 29 U.S. ecoregions and found that eight increased fire occurrences by as much as 230% and six more than doubled fire frequency. These effects spanned a wide range of ecosystems and vegetation types, from pine savannahs to wetlands, deserts, and temperate forests. 

The CASCs are uncovering how fire interacts with invasive species and changes in climate to develop solutions and tools that aim to reduce the risk and impacts of invasive-fueled wildfires. 

Invasive species are creating major challenges for livestock grazing and the health of rangelands. Invasive weeds, pests, and diseases are spreading faster than ever, competing with valuable forage plants, disrupting food webs, and introducing new management hurdles for ranchers.  

When invasive plants crowd out native grasses, livestock can lose access to the high-quality forage they depend on. At the same time, invasive pests and diseases can also harm native plants and wildlife, further limiting the food and space available for livestock. Shifting weather patterns and increasing droughts and wildfires are adding to these pressures and helping invasives spread into new areas. As a result, some areas are experiencing degraded soils, a decrease in the ability of rangeland to support livestock, and rising management costs.  

Thriving rangelands are critical for economic and food security. Just as managers must plan for water availability and changing weather, they also must control invasive species to maintain productive rangelands. To help manage these risks, the CASCs partner with land managers to identify adaptive strategies, develop monitoring tools, and restore healthy native plant communities to support productive rangelands.    

Invasive species and changes in temperature and precipitation are altering aquatic ecosystems across the United States and threatening fisheries that support recreation, economies, and cultural traditions. In 2022, commercial and recreational fisheries supported 2.3 million jobs, and contributed \$149 billion to the U.S. gross domestic product (GDP). But recreational, commercial, and subsistence fisheries are at increasing risk from warming waters, shifting stream flows, longer growing seasons, and invasive species – factors that interact to degrade habitats, disrupt food webs, reduce native fish survival, and enable invasives to expand into new waters.  

With CASC support, scientists are studying invasive aquatic species, building models, and mapping vulnerable ecosystems to help managers anticipate future risks to valuable fisheries. CASC science is evaluating the risks that invasive carp pose to native fish and billion-dollar fisheries; how invasives affect stream ecosystems from the Northeast to the Pacific Islands; and developing tools for early detection of aquatic invasives before they become established. This work is guiding strategies such as targeted removals and habitat restoration to protect fisheries and slow or prevent the negative effects of invasive species.    

Forests across the United States are increasingly under pressure from the combined threats of invasive species and climate change, both of which disrupt ecosystems and carry serious economic and social consequences. Invasive insects, plants, and pathogens can decimate native tree populations, reduce timber quality, reduce biodiversity, and alter critical forest functions like nutrient cycling, hydrology, and soil stability. These disturbances often create conditions that leave forests even more vulnerable to future invasions. At the same time, stressors such as hotter, drier conditions and more extreme storms and wildfires further weaken trees, damage ecosystems, and open pathways for invasive species to move in.

The forestry industry depends on healthy, productive forests for timber, furniture, and paper products. In 2022, the forest products sector produced over half a trillion dollars’ in goods and directly employed over 1.3 million workers. In addition to the products provided by forestry, the growing field of agroforestry, which integrates trees with other crops or livestock, provides food for communities and diversified income streams for producers, while also improving soil and ecosystem health. However, across the country, invasive pests such as the emerald ash borer, the hemlock woolly adelgid, and the coconut rhinoceros beetle have already killed millions of trees, leading to lost timber yields, lost food production, increased management costs, and degraded recreational and cultural resources.  

CASC science supports efforts across the country to respond to invasive threats to forestry, agroforestry, and the communities that depend on them. Our science is helping managers navigate uncertainties, plan effective management strategies, and sustain the forests that underpin biodiversity, agricultural systems, and economic resilience.  

Collectively, the impacts of invasive species can strain national stability: critical infrastructure failures undermine disaster response, readiness, and community stability; wildfires threaten military installations, evacuation routes, energy grids, and homes, while endangering public health; and degraded rangelands, fisheries, and forests compromise food security and economic prosperity.  

The U.S. Department of Defense manages nearly 27 million acres of land across the U.S. and its territories, much of it vulnerable to invasive species. The threat is especially urgent across military installations in the Pacific, where invasives are already damaging critical infrastructure, compromising equipment, and endangering personnel safety – all of which threatens operational readiness. In Guam, brown tree snakes short out power grids and disrupt shipping due to costly cargo inspections to intercept stowaway snakes. In Hawai‘i, invasive grasses increase wildfire risk and can cause erosion around critical infrastructure. On Wake Atoll, invasive rats chew through electrical wiring in drones and jets, damage supplies, contaminate food, and spread diseases—creating hazards, mission delays, and health risks for personnel. 

As military presence expands in the Pacific, so too does the movement of people and materials. This increases opportunities for invasives to spread among islands that often lack sufficient biosecurity infrastructure and to potentially jump from islands to the U.S. mainland. 

CASC-supported activities and partnerships are advancing rapid response tools and interagency coordination to reduce invasions after severe storms and natural disasters. Healthy ecosystems, including forests, fisheries, and coral reefs, are key to economic and national resilience. The Pacific Islands CASC is helping strengthen island biosecurity through research, planning, and knowledge-exchange.