Climate Change and...
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Invasive Plants and Climate Change
Preparer: Robin J. Tausch; Grasslands, Shrublands, and Deserts; Rocky Mountain Research Station.
Newer (2012) version of this paper is available here.
Because they are often highly competitive, invasive plant species are altering the plant composition of ecosystems and changing their structure and function over large landscape areas. In addition, the fine fuels they often add increases fire frequency in many areas and leads to increased dominance by invasive species and further degradation. Climate change is exacerbating these changes by altering the amount and seasonal distribution of precipitation seasonal temperature patterns in ways that often favor the invasive species. These types of changes, to which ecosystems are highly sensitive, will have a substantial regional impact in many areas.
We use models to predict how expected climate change will change the distribution of individual plant species. Predictions for individual species, however, are not sufficient to help us predict how their cumulative effects may drive changes in ecosystems, particularly changes in ecosystem structure and function. Changes in weather and climate can also have both individual and cumulative effects on ecosystems that can further facilitate the expansion and abundance of invasive plant species. Increases in invasive plant species usually results in a loss of services from the affected ecosystems. In many cases, these changes could even lead to ecosystem collapse over large landscape areas over the long term. Because so little is known about how climate change will facilitate invasive plants and their subsequent impact on ecosystems, it is only through adequate, detailed monitoring that we will be able to follow and recognize these changes.
In the West, in particular, a warming climate will often lead to an upward elevational migration of plant species. Because of the rapidity of expected changes in climate, individuals of a native plant species may be lost from their lower-elevation limits faster than they will be able to migrate upward and establish into newly created habitat. This will result in stressed communities with fewer plant species distributed over large areas of the landscape. As ecosystems become simplified, their trophic levels are truncated and their trophic interactions reduced.
Such ecosystems potentially have an increase in the quantity of unused resources. These stressed communities thus become more open and their resources more available for the invasion and establishment of invasive plant species. These invaders may also be better adapted than native species to the new environmental conditions resulting from climate change. An exception might be native species of plants that can migrate from adjacent areas or regions into locations where they previously were excluded by climate as the new locations become more suitable. The greater the change, the more likely this facilitation of invasives will be. In addition to climate change are the species of invaders involved, the effects of the interactions of their species composition on the ecosystems, and the disturbance patterns those ecosystems are experiencing. On landscape scales, these ecosystem spatial and temporal variabilities have major effects on ecosystem susceptibility to invasive species. Climate change and associated vegetation change interacting with invasive species are also increasingly leading to large wildfires that can further facilitate the establishment of additional invasive plant species.
Options for Management
The most important option for management is early detection of ecosystem changes that result from climate change. This requires detailed, regularly scheduled monitoring. The next step is to actively prevent the spread of invasive plant species into ecosystems recognized as having become more susceptible. Prevention first requires an awareness of invasive species that pose a threat. These are not the same as native plant species that need to migrate to new locations to survive. Second, it requires recognition of what ecosystems are likely to become susceptible to invasion by these species as climate changes. Because of our current lack of understanding of just how climate change is going to change ecosystems and change their susceptibility to particular invasive species, our ability to recognize susceptible ecosystems and potential invasive plant species beforehand is limited.
Devising means to prevent the spread and establishment of invasive species will also be limited. Prevention may often not be possible because we will not know to which plant species a particular ecosystem has become susceptible to until after it has arrived. To prevent these species from becoming a problem, early detection, followed by a rapid response to eradicate these initial infestations, will be necessary. This will be possible only if these infestations are located as a result of regular, detailed monitoring.
Once invasive plant species have become established, a strategic approach for control and management becomes necessary. Successful control or management efforts for invasive species require an active program of restoration or rehabilitation. Because each situation is unique, each site will require a program designed for its unique landscape characteristics to successfully accomplish the needed restoration or rehabilitation.
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