In this chapter, ecosystems are summarized as energetic systems and ecosystem health is discussed in relation to changes in structure, organization, and functional capacity as explained by changes in emergy, empower, and transformity. The living and nonliving parts and processes of the environment as they operate together are commonly called ecosystems. Examples are forests, wetlands, lakes, prairies, and coral reefs. Ecosystems circulate materials, transform energy, support populations, join components 90 in network interactions, organize hierarchies and spatial centers, evolve and replicate information, and maintain structure in pulsing oscillations. Energy drives all these processes and energetic principles explain much of what is observed.