The Challenge of Modelling and Mapping the Future Distribution and Impact of Invasive Alien Species

Invasions from alien species can jeopardize the economic, environmental or social benefits derived from biological systems. Biosecurity measures seek to protect those systems from accidental or intentional introductions of species that might become injurious. Pest risk maps convey how the probability of invasion by an alien species or the potential consequences of that invasion vary spatially. These maps inform strategic and tactical decisions for invasive species management. Pest risk modellers must contend with the challenges of developing models that forecast the course or consequence of invasions and are more meaningful than could be obtained by chance, of demonstrating the validity of those models and of portraying results on maps in ways that will be useful for decision makers. Frequently, these forecasts depend on extrapolations from limited information to project how a species might be affected, for example, by changes in commerce, exposure to novel environments or associations with new dispersal vectors, or how these species might affect resident species or ecological processes. Consequently, pest risk maps often focus on one phase of the invasion process: arrival, establishment, spread or impact. Risk assessors use different analytical tools and information sources to address each phase. To be certain that pest risk models and maps are fully fit for purpose, models and maps must be critically evaluated at each stage of the development process. Invariably, errors will be revealed. The International Pest Risk Mapping Workgroup has offered a number of suggestions to improve the development of pest risk models and maps. In addition, short-term improvements are likely to be achieved through critical, objective assessments of model performance and greater transparency about model development.