Ecosystems

Ecosystems are dynamic complexes of living organisms (plants, animals, microorganisms) interacting with each other and their physical environment (air, water, soil, climate) as a functional unit. They include the flow of energy through the system, primarily via photosynthesis and predation, and nutrient cycling that recycles carbon, nitrogen, phosphorus, and other elements. An ecosystem's structure emerges from its community composition, species interactions, and physical conditions, and is characterized by properties such as biodiversity, productivity, and resilience.

Ecosystems range in scale from a pond to a forest biome. Broad categories include terrestrial ecosystems (forests, grasslands, deserts, tundra) and aquatic ecosystems (freshwater and marine), each with distinctive productivity and typologies. Within soils and water, organisms occupy niches and form food webs or networks. Key processes include primary production, trophic interactions, and decomposition by decomposers. Disturbances such as fire, drought, flood, storms, and human disturbance can reshape ecosystem structure and function.

Ecosystem services are commonly grouped into provisioning, regulating, supporting, and cultural benefits. Human activities such as land-use change, pollution, climate change, overexploitation, and invasive species can alter ecosystem structure and function, reducing services and causing losses in biodiversity. Some ecosystems show resistance and resilience to disturbances; others may cross thresholds into new states. Restoration ecology and conservation planning aim to recover degraded systems and maintain ecological integrity. Sustainable management relies on monitoring, adaptive practices, and the integration of ecological knowledge into policy.