developed. Indeed, one of the major challenges in investigating the interactive nature of climate 
change stressors is the incredible complexity of biological systems. Often, invasive species 
models account for climate change factors in isolation because of the challenges of complexity. 
For example, the most widely used models to predict invasibility may use temperature as the 
primary component, but in future modification and development of models, scientists should 
consider additional climate change parameters. 
1.7. CLIMATE CHANGE AND INVASIVE SPECIES DISTRIBUTION MODELS 
Models of invasive species introductions, distributions, spread, and establishment are key 
tools for both understanding the invasive-species problem and designing effective prevention and 
control techniques. Numerous types of models have been developed. In many cases, authors 
recommend that invasive-species managers be cognizant of specific factors (e.g., species 
interactions, climatic factors, spread vectors) in ecosystem management. Some offer clear, 
ready-to-use models and strategies for conservation managers. However, most models of species 
invasion currently do not explicitly account for climate change; this represents a research need 
that is discussed in sections 3.2.1 and 3.2.2, primarily in that scientists need to begin to build 
climate change variables and scenarios into these species invasion models. Initial steps include 
integrating climate change-related parameters such as salinity variations, temperature changes, 
and soil chemistry into these models and then examining future scenarios or projections. The 
outputs from models should help managers to better target and prioritize their prevention, 
monitoring, early detection, and rapid response programs under changing conditions. This 
section discusses some of the existing invasive-species distribution models and how climate- 
change information may be incorporated into them. Appendix E, Models for Invasive Species 
Introduction, Establishment, Spread, and Invasion provides additional examples. 
1.7.1. Models to Assess Climate-Change Impacts on Species Distributions 
Numerous ecological models have been developed to specifically address climate-change 
impacts on species distributions, but these models generally are not applied to invasive species. 
One of these types of models, the bioclimatic envelope model, is used to identify correlations 
between species’ distributions and climate-change factors to determine a species’ climatic 
boundaries. Based on this information, models predict how species’ distributions may change 
under predicted climate changes (Pearson and Dawson, 2003). Discriminant analysis is one 
method that has been used to explicitly evaluate climate-change impacts on invasive species. 
Mandrak (1989) uses discriminant function and principal component analyses to compare 
ecological characteristics of possible invading species to recently invading species to determine 
potential invaders’ response to climate change and found that nearly half of the potential species 
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