Within this boundary all water flows or drains to a common point. This is called a watershed scale and provides a manageable area with definite boundaries and common characteristics. Ecosystems change constantly. Changes in species composition , structure and function occur through succession , a slow, orderly sequence of development of structure and complexity over many years. Change also occurs due to random disturbances and recovery from fire, drought, flood and insect damage and due to human-induced impacts.
Natural disturbances are common and extremely important to a healthy ecosystem .
Disturbance and recovery from disturbance regulate energy flow and nutrient cycling and maintain age, species, genetic and structural diversity in an ecosystem. Efforts to reduce disturbance from fire, flood and insects have reduced biodiversity , ecosystem health and natural ability to recover from these outbreaks. However, these disturbances are often in direct conflict with human perceptions and expectations such as economic goals. Ecosystem management attempts to integrate knowledge of how ecosystems work into management practices that preserve or restore the environment while simultaneously providing goods and services demanded by humans. The study of ecology tells us that everything is related to everything else - or that everything depends on something else for its survival.