Understanding and Managing the Impacts of Invasive Vertebrates in Conservation Settings
Invasive vertebrates are a major cause of species loss and ecosystem disruption around the world. Consequently, the management of invasive vertebrates preoccupies much of the policy and management focus of conservation agencies in many countries, not least New Zealand and Australia. Using key wildlife management journals to track research activity on invasive vertebrates, reveals a sequence of changes in the way conservation agencies have integrated invasive vertebrate management into their efforts to achieve biodiversity outcomes. These changes reflect our increasing understanding of how invasive vertebrates interact with elements of indigenous ecosystems, and the consequential increase in the sophistication of management solutions sought. For example, in production settings, benefits are generally the inverse of simple damage functions that relate reductions in yield to prevailing pest density. However, in conservation settings, the benefits of pest control may occur at population, community or ecosystem levels. In each of these cases, benefits must be considered in the context of a range of other factors and processes (many of them stochastic) that influence the prevailing state of the population, community or ecosystem of interest. This requires explicit recognition of (1) a minimum acceptable state for the affected conservation value, and (2) an acceptable risk of the value declining below this state. A range of empirical modeling approaches can be used to link changes in these values to alternative vertebrate pest control strategies, in different conservation settings. I will use three case studies to illustrate these points, and to demonstrate a general approach that can be used to robustly link benefits and costs of vertebrate pest control in conservation settings.