Ecosystem to regional impacts of introduced pests and pathogens: historical context, questions and issues

An introductory overview is presented of the many different impacts of introduced pests and pathogens, from the ecosystem scale to the regional scale. A historical context for the assessment of these impacts is provided. Species introductions can seriously reduce native species populations, resulting in profound ecological and evolutionary disruption. In addition, introduced pest species may drastically alter forest composition, structure, and microenvironments, with impacts on nutrient cycling, nutrient retention, and a host of other important processes. Several important case studies of introduced pests and pathogens in the US are reviewed. Questions that must be addressed by future research are examined.