The frontier images of America embrace endless horizons, majestic herds of native ungulates, and romanticized life-styles of nomadie peoples. The images were mere reflections of vertebrates living in harmony in an ecosystem driven by the unpre dictable local and regional effects of drought, frre, and grazing. Those effects, often referred to as ecological "disturbanees," are rather the driving forces on which species depended to create the spatial and temporal heterogeneity that favored ecological prerequisites for survival. Alandscape viewed by European descendants as monotony interrupted only by extremes in weather and commonly referred to as the "Great American Desert," this country was to be rushed through and cursed, a barrier that hindered access to the deep soils of the Oregon country, the rich minerals of California and Colorado, and the religious freedom sought in Utah. Those who stayed (for lack of resources or stamina) spent a century trying to moderate the ecological dynamics of Great Plains prairies by suppressing fires, planting trees and exotic grasses, poisoning rodents, diverting waters, and homogenizing the dynamies of grazing with endless fences-all creating bound an otherwise boundless vista. aries in Historically, travelers and settlers referred to the area of tallgrasses along the western edge of the deciduous forest and extending midway across Kansas as the "True Prairie. " The grasses thlnned and became shorter to the west, an area known then as the Great Plains."

The frontier images of America embrace endless horizons, majestic herds of native ungulates, and romanticized life-styles of nomadie peoples. The images were mere reflections of vertebrates living in harmony in an ecosystem driven by the unpre dictable local and regional effects of drought, frre, and grazing. Those effects, often referred to as ecological "disturbanees," are rather the driving forces on which species depended to create the spatial and temporal heterogeneity that favored ecological prerequisites for survival. Alandscape viewed by European descendants as monotony interrupted only by extremes in weather and commonly referred to as the "Great American Desert," this country was to be rushed through and cursed, a barrier that hindered access to the deep soils of the Oregon country, the rich minerals of California and Colorado, and the religious freedom sought in Utah. Those who stayed (for lack of resources or stamina) spent a century trying to moderate the ecological dynamics of Great Plains prairies by suppressing fires, planting trees and exotic grasses, poisoning rodents, diverting waters, and homogenizing the dynamies of grazing with endless fences-all creating bound an otherwise boundless vista. aries in Historically, travelers and settlers referred to the area of tallgrasses along the western edge of the deciduous forest and extending midway across Kansas as the "True Prairie. " The grasses thlnned and became shorter to the west, an area known then as the Great Plains."

processes; (3) ensure the integrity of ecosys- The theory and practice of ecosystem manage- tems; and (4) advocate the sustainable use of ment is pivotal to the debate over how to sustain the health and productivity of our envi- natural resources. In this book, each of these ronment. In particular, the role of ecosystems four topics is addressed by a set of eight key in preserving biological diversity, their contri- journal articles. The first article in each section bution to economic growth, and their influence provides an overview, followed by case histo- ries and a concluding paper which is a commen- on human well-being is highly controversial tary on the difficulty of the issue or assesses its (Lubchenco et al. 1991). Traditional resource management does not protect natural values future direction. An article by Risser provides a (Sax 1993) or provide for the sustainable pro- closing synthesis to this collection. duction of goods and services (Barnes 1993). The authors of the articles in Part 1-Under- Yet a number of researchers and managers stand Diversity - speak to the current problems further question the ability of science to pro- and directions in the conservation of biological vide sufficiently powerful tools for the under- diversity. Tilman and Downing argue that standing and implementation of ecosystem preservation of native biodiversity is essential management (Clark 1996).