Invasion by exotic forest pests : a threat to forest ecosystems

Summary: For millions of years, the distribution of the world's biota has been restricted by oceans and other natural barriers. During the last 100 years, human activities, especially international travel and trade, have circumvented these barriers, and species are invading new continents at an increasing rate. Biological invasions of insect, plant, and fungal pest species often cause substantial disturbance to forest ecosystems as well as severe socioeconomic impacts. Case histories are presented that illustrate the invasion process via details of the arrival, spread, impact, and management of selected exotic forest pests.