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Invasive plants and animals

This map shows forest pests from the Forest Service's Aerial Detection Surveys for the year 2014.

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This map shows forest pests from the Forest Service's Aerial Detection Surveys for the year 2014.

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Invasive plants and animals

What Are Invasive Species??
“Invasives” are species recently introduced to new ecosystems that cause or are likely to cause significant harm to the environment, economy, or human health. Invasives compete with native plants and wildlife for resources, disrupt beneficial relationships, spread disease, cause direct mortality, and can significantly alter ecosystem function. Some of the more common invasives in Massachusetts may already be familiar - problematic invasive plants include purple loosestrife (Lythrum salicaria), Japanese barberry (Berberis thunbergi), glossy buckthorn (Frangula alnus), multiflora rose (Rosa multiflora Thunb), Japanese knotweed (Fallopia japonica), garlic mustard (Alliaria petiolata) and black locust (Robinia pseudoacacia). Invasive animals include forest pests such as the hemlock woolly adelgid (Adelgis tsugae), Asian longhorn beetle (Anoplophora glabripennis), and the emerald ash borer (Agrilus planipennis). The zebra mussel (Dreissena polymorphais a particularly detrimental aquatic invasive species that has recently been detected in Western Massachusetts. For more on specific species, impacts and distributions visit the National Invasive Species Information Center or the Invasive Plant Atlas of New England.

Invasive Species and Climate Change
The impacts of invasive species may interact with those of climate change, magnifying the negative impacts of both threats. Furthermore, due to the very traits that make them successful at establishing in new environments, invasives may be favored by climate change. These traits include tolerance to a broad range of environmental conditions, ability to disperse or travel long distances, ability to compete efficiently for resources, greater ability to respond to changes in the environment with changes in physical characteristics (phenotypic plasticity), high reproductive rates, and shorter times to maturity.

To become an invasive species, the species must first be transported to a new region, colonize and become established, and spread across the new landscape. Climate change may impact each stage of this process. Globally, climate change may increase the introduction of invasive species by changing transport patterns (if new shipping routes open up), or by increasing the survival of invasives during transport. New ornamental species may be introduced to Massachusetts to take advantage of an expanded growing season as temperatures warm. Aquatic invasives may survive in ships' ballast waters with warmer temperatures. Extreme weather events or altered circulation patterns due to climate change could also allow the dispersal of invasive species to new regions via transportation of seeds, larvae and small animals.

Species may shift their ranges north as the climate warms and be successful in regions they previously had not colonized. Invasives may also be able to spread more rapidly in response to climate change, given their high dispersal rates and fast generation times. These faster moving species may be at a competitive advantage if they can move into new areas before their native competitors.

Purple loosestrife, an invasive plant species of wetlands. Photo credit: Scott Jackson
Purple loosestrife, an invasive plant species of wetlands. Photo credit: Scott Jackson

Here in the Northeast, warming conditions may be particularly concerning for some invasives because species ranges in temperate regions are often limited by extreme cold temperatures or snowfall. There is concern that aquatic species, such as hydrilla (Hydrilla verticillata) and water hyacinth (Eichhornia crassipes), may be able to survive and overwinter in Massachusetts with increased temperatures and reduced snowfall. Nutria (Myocastor coypus), large non-native, semi-aquatic rodents that are currently established in Maryland and Delaware, are likely to move north with warming temperatures, perhaps as far as Massachusetts.

Extreme winter temperatures are also critical limiting factors for many forest pests, and warming is expected to increase their survival and lead to expansions and outbreaks. For example, in Massachusetts, it’s likely that winter temperatures have been limiting the impact of hemlock wooly adelgid (Adelges tsugae), as many infested forest stands are surviving while in more southerly ranges there is near complete mortality from this pest. But the adelgid has already expanded its range with warming winter temperatures and is likely to have increased survival and higher reproductive rates in the northern portion of its range as temperatures warm, likely leading to more significant impacts on forests.

Of particular concern to human health are species like the Asian tiger mosquito (Aedes albopictus). This invasive mosquito, originally from southeast and subtropical Asia has moved through the Eastern U.S. and has recently arrived in Massachusetts. Capable of spreading West Nile Virus, Equine Encephalitis and numerous other tropical diseases, this aggressive mosquito is likely range-limited by cold winter temperatures, suitable landscape conditions (it prefers urban areas), and variation in moisture. As winter temperatures increase the species is likely to become more prevalent in Massachusetts and throughout the Northeast, increasing the risk of serious illness for residents in summer months.

Invasive species? are often able to thrive or take advantage of areas of high or fluctuating resource availability such as those found in disturbed environments. For example, for invasive plants, insect outbreaks or storms often free up space in the forest allowing light to penetrate and nutrients and moisture balances to change, allowing invasive plants to move in. Climate change is likely to create these types of opportunities through increased disturbances such as storms and floods, coastal erosion and sea level rise.

Invasives may also be better able to respond to changing environmental conditions that free up resources or create opportunities. For example, greater plasticity in response to their environment may allow some invasive plants to respond faster to increases in spring temperature than native plants. These invasives are able to leaf-out earlier in warmer years, taking up available space, nutrients, and sunlight, and achieving a competitive advantage against native species. Increased carbon dioxide in the atmosphere may also benefit some weedy plant species, allowing them to compete for other resources (like water) more effectively than their native counterparts.

Species roles may change as the climate changes, further complicating the management and policy response. As species ranges shift and existing inter-species relationships are broken, there is the potential that some species, including native species, may become pests because the interspecies interactions (e.g., predation, herbivory) that used to keep their population numbers in check are no longer functional.

References

1. Bradley, B.A., D.M.Blumenthal, R. Early, E.D. Grosholsz, J.J. Lawler, L.P. Miller, C. J.B. Sorte, C.M. D’Antonio, J.M. Diez, J.S. Dukes, I. Ibanez, and J.D. Olden. 2012. Global change, global trade, and the next wave of plant invasions. Frontiers in Ecology and the Environment 10:1, 20-28.

2. Carey, M.P., B.L. Sanderson, K.A. Barnas, J.D. Olden. 2012. Native invaders — challenges for science, management, policy, and society. Frontiers in Ecology and the Environment. 10:373-381.

3. Dukes, J.S. and H.A. Mooney. 1999. Does global change increase the success of biological invaders? Trends in Ecology & Evolution.14: 135–139.

4. Hellmann, J.J., J.E. Byers, B.G. Bierwagen, J.S. Dukes. 2008. Five potential consequences of climate change for invasive species. Conservation Biology. 22: 534–543.

5. Kerns, B., Q. Guo. 2012. Climate Change and Invasive Plants in Forests and Rangelands. U.S. Department of Agriculture, Forest Service, Climate Change Resource Center.www.fs.usda.gov/ccrc/topics/invasive-plants/

6. Lodge, D.M., S. Williams, H.J, Macisaac, K.R. Hayes, B. Leung, S. Reichard, R.N. Mack, P.B. Moyle, M. Smith, D.A. Andow, J.T. Carlton, A. McMichael. 2006. Biological invasions: recommendations for U.S. policy and management. Ecological Applications. 16: 2035-2054.

7. Pimentel, D., R. Zuniga, D. Morrison. 2005. Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecological Economics. 52:273–288.

8. Rochlin, I., D.V. Ninivaggi, M.L. Hutchinson, and A. Farajollahi. 2013. Climate change and the range expansion of the Asian tiger mosquito (Aedes albopictus) in Northeastern USA: Implications for Public Health Practitioners.

9. Rustad, L., J. Campbell, J.S. Dukes, T. Huntington, K.F. Lambert, J. Mohan, N. Rodenhouse. 2012. Changing Climate, Changing Forests: The Impacts of Climate Change on Forests of the Northeastern United States and Eastern Canada. U.S. Forest Service Northern Research Station General Technical Report NRS-99. 48 pp.

10. Theoharides, K.A., and J.S. Dukes. 2007. Plant invasion across space and time: factors affecting nonindigenous species success during four stages of invasion. New Phytologist 176:256-273.

11. Willis, C.G., B.R. Ruhfel, R.B. Primack, A.J.Miller-Rushing, J.B. Losos, C.D., Davis. 2010. Favorable climate change response explains non-native species' success in Thoreau's Woods. PLoS ONE, 5: e8878.

Click link above to view references.

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