Models and strategies for prioritizing the control of invasive exotic weeds in protected areas: theoretical and pragmatic challenges

The environmental value of protected areas is seriously threatened by the invasion of exotic weeds, particularly in countries like Australia. The value of these natural assets for biodiversity conservation, and for recreation and tourism, is reduced by the presence of weeds in these areas, and ecosystem services and functioning are undermined. Resources for the managing of these weeds are limited and therefore, it is important to establish priorities for their control. The chapter outlines economic and ecological models that may be (or have been) used for determining these priorities and assesses their limitations. The scope for applying social cost_benefit analysis and cost-effective analysis is explored, as well as less ambitious economic models. The use of ecological modelling based on the extent to which an invasive weed becomes established in protected areas is given particular consideration. This modelling is based upon the relevance of sigmoidal invasion curves. As pointed out, sometimes the implications of economic models for establishing priorities for weed control are at odds with policy conclusions drawn from ecological models. Actual processes for prioritizing weed control in some of Australia’s national parks are investigated. It is found that pressure groups can have a substantial influence on the determination of these priorities.