Photo: Salt Cedar & Giant Cane along the Rio Grande. © 2017 Delena Norris-Tull
Economic and Ecological Costs of Invasive Plants
Research summary and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020, updated November 2024.
The Invasive Species Specialist Group (Lowe, et al., 2009) reports that, “Today, alien invasion is second only to habitat loss as a cause of species endangerment and extinction. Safeguarding the earth’s diversity is the best way to maintain our life support system. There is evidence to suggest that the biosphere acts as a self-regulating whole and that diverse systems may be more resilient. Island ecosystems, which have evolved in isolation often have relatively fewer plants, herbivores, carnivores and decomposers to maintain essential processes and are more vulnerable to invasion. On islands around the world species extinction is increasing at an unprecedented rate.”
Rural areas in the Western United States have some similarities with island populations. Like islands, many ecosystems in the West are isolated from each other. Mountain ranges and desert basins create many localized climatic systems that have resulted in ecosystems isolated from distinct ecosystems just a few miles away. High altitude locations in the West, with very short growing seasons and often desert-like conditions, are isolated from other such locations. And Western deserts create unique ecosystems unlike those found in the eastern United States.
Invasive plants have had a significant negative economic impact on agriculture and ecological systems. For example, Leistritz, Bangsund, & Hodur, 2004, point out that, “Leafy spurge has become a serious problem for ranchers and land managers in the northern Great Plains region. A bioeconomic model was developed to estimate the economic impacts of leafy spurge on grazing land and wildland in a four-state region (Montana, North Dakota, South Dakota, and Wyoming). Leafy spurge infestations on grazing land were estimated to result in a loss in regional grazing capacity sufficient to support a herd of 90,000 cows. Direct economic impacts on stock growers, landowners, and agribusiness firms were estimated to exceed $37 million annually, whereas secondary impacts throughout the regional economy totaled almost $83 million. Impacts on wildland were smaller but still substantial.”
Invasive plant species are estimated to have an economic cost to agriculture of approximately two billion dollars annually in the United States. In the 2017 report on Washington State, Economic Impact of Invasive Species, the authors conclude that, “The direct impact of invasive species [both invasive plants and animals] on crops grown in Washington is estimated to be $239.5 million per year…. The direct economic impact of invasive [plant] species on the livestock industry is estimated to be $120.1 million annually…. The direct economic impact of invasive [plant and insect] species on the timber industry is estimated to be $124.8 million…. The direct economic impact to recreational activities [including hunting, fishing, and boating] from invasive species is estimated to be $20.5 million per year.” The report includes the estimated economic costs for each of twelve noxious weed species.
As another example of the damages caused by invasive plant species, Herron, et al., 2001, point out that in the northwestern US and Canada, spotted knapweed (Centaurea maculosa) has “altered plant community composition and reduced forage value, wildlife habitat, and species diversity. [It] displaces perennial grasses and increases bare ground, surface water run-off, and stream sedimentation.”
The following data comes from the Montana Department of Transportation, Statewide Integrated Roadside Vegetation Management Plan: 2018-2024:
“The impact of weeds on biological communities, ecosystem processes, and the agricultural economy is well documented in Montana. Studies have shown that replacement of native bunchgrasses with taproot weeds such as spotted knapweed can increase surface water runoff and soil erosion by 56% and 192% respectively… Weeds have been shown to influence wildlife by reducing forage, modifying habitat structure—such as changing grassland to a forb-dominated community—or changing species interactions within the ecosystem… Non-native plants also threaten biological diversity of native plant communities by displacing native species… and can threaten the survival of rare and sensitive plants….
“The cost of spotted knapweed and leafy spurge to Montana’s economy is substantial…Total impact from spotted knapweed infestations were estimated at $42 million per year…The impact of leafy spurge to Montana’s economy was estimated at $18.6 million per year.”
The total of all invasive species (including plants, arthropods, and vertebrates) has an estimated annual cost to the United States of $120 billion annually (Pimentel, Zuniga, & Morrison, 2004). The cost to the US economy of invasive plants alone is in the billions. Worldwide the cost of all invasive species has been in the trillions of dollars.
In 2011, the U.S. Department of the Interior spent $120 million on invasive species management (US Fish & Wildlife, January 2012). In 2015, Montana-based Federal Agencies jointly spent nearly $9 million on invasive species management (including both plants and animals), and disbursed an additional $2 million to various Montana State entities. Montana State Agencies spent $7.5 million in 2015, and disbursed $3.4 million to other entities, primarily local and county governments (Creative Resource Strategies, 2016).
References:
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Research summary and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020, updated November 2024.
The Invasive Species Specialist Group (Lowe, et al., 2009) reports that, “Today, alien invasion is second only to habitat loss as a cause of species endangerment and extinction. Safeguarding the earth’s diversity is the best way to maintain our life support system. There is evidence to suggest that the biosphere acts as a self-regulating whole and that diverse systems may be more resilient. Island ecosystems, which have evolved in isolation often have relatively fewer plants, herbivores, carnivores and decomposers to maintain essential processes and are more vulnerable to invasion. On islands around the world species extinction is increasing at an unprecedented rate.”
Rural areas in the Western United States have some similarities with island populations. Like islands, many ecosystems in the West are isolated from each other. Mountain ranges and desert basins create many localized climatic systems that have resulted in ecosystems isolated from distinct ecosystems just a few miles away. High altitude locations in the West, with very short growing seasons and often desert-like conditions, are isolated from other such locations. And Western deserts create unique ecosystems unlike those found in the eastern United States.
Invasive plants have had a significant negative economic impact on agriculture and ecological systems. For example, Leistritz, Bangsund, & Hodur, 2004, point out that, “Leafy spurge has become a serious problem for ranchers and land managers in the northern Great Plains region. A bioeconomic model was developed to estimate the economic impacts of leafy spurge on grazing land and wildland in a four-state region (Montana, North Dakota, South Dakota, and Wyoming). Leafy spurge infestations on grazing land were estimated to result in a loss in regional grazing capacity sufficient to support a herd of 90,000 cows. Direct economic impacts on stock growers, landowners, and agribusiness firms were estimated to exceed $37 million annually, whereas secondary impacts throughout the regional economy totaled almost $83 million. Impacts on wildland were smaller but still substantial.”
Invasive plant species are estimated to have an economic cost to agriculture of approximately two billion dollars annually in the United States. In the 2017 report on Washington State, Economic Impact of Invasive Species, the authors conclude that, “The direct impact of invasive species [both invasive plants and animals] on crops grown in Washington is estimated to be $239.5 million per year…. The direct economic impact of invasive [plant] species on the livestock industry is estimated to be $120.1 million annually…. The direct economic impact of invasive [plant and insect] species on the timber industry is estimated to be $124.8 million…. The direct economic impact to recreational activities [including hunting, fishing, and boating] from invasive species is estimated to be $20.5 million per year.” The report includes the estimated economic costs for each of twelve noxious weed species.
As another example of the damages caused by invasive plant species, Herron, et al., 2001, point out that in the northwestern US and Canada, spotted knapweed (Centaurea maculosa) has “altered plant community composition and reduced forage value, wildlife habitat, and species diversity. [It] displaces perennial grasses and increases bare ground, surface water run-off, and stream sedimentation.”
The following data comes from the Montana Department of Transportation, Statewide Integrated Roadside Vegetation Management Plan: 2018-2024:
“The impact of weeds on biological communities, ecosystem processes, and the agricultural economy is well documented in Montana. Studies have shown that replacement of native bunchgrasses with taproot weeds such as spotted knapweed can increase surface water runoff and soil erosion by 56% and 192% respectively… Weeds have been shown to influence wildlife by reducing forage, modifying habitat structure—such as changing grassland to a forb-dominated community—or changing species interactions within the ecosystem… Non-native plants also threaten biological diversity of native plant communities by displacing native species… and can threaten the survival of rare and sensitive plants….
“The cost of spotted knapweed and leafy spurge to Montana’s economy is substantial…Total impact from spotted knapweed infestations were estimated at $42 million per year…The impact of leafy spurge to Montana’s economy was estimated at $18.6 million per year.”
The total of all invasive species (including plants, arthropods, and vertebrates) has an estimated annual cost to the United States of $120 billion annually (Pimentel, Zuniga, & Morrison, 2004). The cost to the US economy of invasive plants alone is in the billions. Worldwide the cost of all invasive species has been in the trillions of dollars.
In 2011, the U.S. Department of the Interior spent $120 million on invasive species management (US Fish & Wildlife, January 2012). In 2015, Montana-based Federal Agencies jointly spent nearly $9 million on invasive species management (including both plants and animals), and disbursed an additional $2 million to various Montana State entities. Montana State Agencies spent $7.5 million in 2015, and disbursed $3.4 million to other entities, primarily local and county governments (Creative Resource Strategies, 2016).
References:
- CAI. (Jan., 2017). Economic impact of invasive species: Direct cost estimates and economic impacts for Washington State. Seattle: Community Attributes, Inc (CAI).
- Creative Resource Strategies. (March, 2016). Montana Management Assessment of Invasive Species. Montana Invasive Species Advisory Council.
- Herron, G.J., Sheley, R.L., Maxwell, B.D., & Jacobsen, J.S. (Sept, 2001). Influence of nutrient availability on the interaction between spotted knapweed and bluebunch wheatgrass. Restoration Ecology, 9 (3): 326-331.
- Leistritz, F.L., Bangsund, D.A., Nancy M. Hodur, N.M. (2009).Assessing the Economic Impact of Invasive Weeds: The Case of Leafy Spurge (Euphorbia esula). Weed Technology, 18, Invasive Weed Symposium: 1392-1395.
- Lowe, S., Browne, M., Boudjelas, S., & De Poorter, M. (2000). 100 of the World’s Worst Invasive Alien Species: A Selection From The Global Invasive Species Database. Published by the Invasive Species Specialist Group, a specialist group of the Species Survival Commission of the World Conservation Union. University of Auckland, Auckland, New Zealand.
- Montana Department of Transportation. (2019). Statewide integrated roadside vegetation management plan: 2018-2024. Helena, MT: Montana Department of Transportation.
- Pimental, D., Zuniga, R. & Morrison, D. (December, 2004). Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecological Economics: 52 (2005), 273– 288.
- US Fish & Wildlife Service. (January, 2012). Fact sheet: The Cost of Invasive Species. US Fish & Wildlife Service.
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