The core value of forestry is the long-term sustainability of forests. Sustainability can be accomplished only if we understand ecological processes and respect them; then we can creatively protect and shape forests to satisfy the needs of future generations. In the early days of American forestry, a primary duty of foresters was to protect against destructive disturbances, particularly forest fires, insect outbreaks, and disease infestations. Reforestation of disturbed areas also was a high priority. While protection and reforestation are still major activities of foresters, the field has become much more wide-ranging and diversified as landowner objectives have broadened, society has demanded more input into forest management, budgetary limitations and other economic concerns have increased, and technologies have become more complex and sophisticated.