Invasive Species and Climate Change

Open-File Report 2006 −1153

U.S. Department of the Interior

U.S. Geological Survey
Invasive Species and Climate Change 

By Beth A. Middleton 

Open-File Report 2006-1153 

U.S. Department of the Interior 

U.S. Geological Survey 
 U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

P. Patrick Leahy, Acting Director 

U.S. Geological Survey, Reston, Virginia 2006 

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Suggested citation: 

Middleton, B.A., 2006, Invasive species and climate change: U.S. Geological Survey Open-File 

Report 2006-1153, 2 p. 

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endorsement by the U.S. Government. 
Invasive Species and Climate Change 

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By Beth A. Middleton

Invasive species challenge managers in their work of conserving and managing natural 

areas and are one of the most serious problems these managers face. Because invasive species 

are likely to spread in response to changes in climate, managers may need to change their 

approaches to invasive species management accordingly. 

An example of how the threat of an invasive species might change in response to climate 

is that of purple loosestrife (Lythrum salicaria). Purple loosestrife is an invasive species of 

northern wetlands; the species may be limited both by hot temperatures in the South and by cold 

temperatures in the North (Middleton, unpublished data). With climate change, the range of 

purple loosestrife may decrease in the South and expand in the North (Fig. 1). The immediate 

removal of newly invaded satellite populations before seeds are formed and populations establish 

may be an effective approach to curtailing the spread of invasive species in a changing climate 

because it is much easier to remove a species soon after it invades rather than after it establishes 

(Ashton and Mitchell, 1989; Middleton, in press). 

Figure 1. Purple loosestrife (Lythrum salicaria) at the northern limit of its range near Amos, Quebec, Canada. 

Pictured in the right foreground is Dr. Raja Sengupta of McGill University. 

 

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 U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Boulevard, Lafayette, LA 70506 
Managers at the edge of an invasive species’ range need to be especially aware that their 

activities might contribute to the spread of the species into new areas. Managers should 

aggressively treat invasive species of concern and reduce activities that might spread seeds. For 

example, to avoid the spread of seeds, roadside mowers should be cleaned of weed seeds 

between mowing different areas to prevent the spread of seeds into new areas. Managers who 

mow roadsides should give some thought to the manner in which they mow weeds so that they 

lessen the spread of seeds of invasive species. 

Dispersal is a key issue in invasive species, because most invasive species disperse 

readily. If climates change, then new invasive species may disperse into novel climate regions. 

Managers should be alert to new infestations along the fronts of species invasion, and they 

should target populations that are likely to spread readily. For example, the landscape pattern of 

invasive species dispersal in wilderness canyons is a key issue in the control of Chinese yam 

(Dioscorea oppositifolia). The aerial tubers of this species disperse downstream to spread the 

species vegetatively, so that controlling upstream populations may be the key to controlling the 

spread of this invasive species (Thomas and others, in press). In another example, the invasive 

scale insect Dactylopius ceylonicus presumably is wind dispersed, and these insects have spread 

to the mainland of North America via the Florida Keys on air currents (Simberloff and Stiling, 

1996). These scale insects kill cacti and were released on Nevis in the Caribbean in 1979 to 

control an invasive cactus. Because of its migration, this scale insect could negatively affect 

southwestern U.S. populations of cacti, so it is important for managers to control this species as 

it spreads across the Gulf of Mexico (Middleton, in press). Clearly, an understanding of the 

dynamics of dispersal aids in the understanding of the potential of invasive species to invade new 

regions during climate change. The manner in which an invasive species will respond to climate 

change will vary according to the life history requirements of the species, its current range, its 

ability to disperse, and the conditions under which it can regenerate. Managers need to be on the 

alert for new threats by invasive species if climates change, and they must be ready to respond to 

situations as they arise. 

References Cited 

Ashton, P.J., and Mitchell, D.S., 1989, Aquatic plants: patterns and modes of invasion, attributes 

of invading species and assessment of control programmes in Drake, J.A., Mooney, H.A., 

di Castri, F., Groves, R.H., Kruger, F.J., Rejmánek, M. and Williamson, M., eds., 

Biological invasions: a global perspective: Chichester, U.K., John Wiley and Sons, p. 111 

- 154. 

Middleton, B.A., in press, Invasive species, in Jørgensen, S.E., ed, Encyclopedia of ecology: 

Oxford, U.K., Elsevier. 

Simberloff, D., and Stiling, P., 1996, How risky is biological control?: Ecology, v. 77, p. 1965 - 

1974. 

Thomas, J.R., Middleton, B.A., and Gibson, D.J., in press, A landscape perspective of stream 

corridor invasion and habitat characteristics the exotic Dioscorea oppositifolia in 

southern Illinois: Biological Invasions.