Changing relationships among biodiversity, management, and biosecurity in managed and unmanaged forests

Natural forest ecosystems have long been, and continue to be greatly influenced by human activities, particularly through tree harvest, development and conversion of land for agriculture, suppression of natural disturbances such as fire, and environmental pollution (e.g., Carey, 2003a; Fuller et al., 1998; Hannon et al., 2000; Kanowski et al., 2003; Litvaitis, 2003; Moretti & Barbalat, 2004; Williams, 2003). Tropical forests are suffering the fastest rates of deforestation, and unfortunately also support the highest levels of species endemism and richness (Hall, Harris, Medjibe, & Ashton, 2003; Kellman & Tackaberry 1997; Thiollay, 2002). Forest ecosystems can be disrupted by spatial effects resulting from fragmentation by roads, power lines, and urban development (Fahrig, 2003; Godefroid & Koedam, 2003; Spellerberg, 1998). The nature of forest ecosystems is modified further when humans manipulate stand composition, such as by establishing native trees of uniform age and introducing exotic tree species (e.g., Brockerhoff et al., 2003; Ohsawa, 2004), or creating artificial ecosystems de novo, as in the case of many urban forests. With increasing urbanization worldwide and decimation of natural habitats (United Nations, 2003), it is essential that methods be developed for managing natural and man-made forests to sustain economic productivity and/or aesthetic quality while conserving biodiversity.