interdependency

Interdependency refers to the mutual dependence of two or more entities for resources, outcomes, or functioning. Unlike simple dependence, interdependency implies reciprocal influence, where the state of each party affects the others.

In ecology, species often rely on each other for food, pollination, or habitat. In economic and social systems, firms, nations, and individuals form networks of trade, finance, information, and labor. Infrastructure and technology systems also exhibit interdependencies, for example electricity grids depend on data networks and vice versa. These connections can create coordinated behavior as well as shared risks.

Interdependencies are characterized by feedback loops, collaboration, and nonlinearity. They can contribute to resilience by distributing risk and enabling adaptive responses, but they can also propagate disturbances, creating systemic risk through cascading failures. The strength and structure of interdependencies influence how a disturbance spreads and how quickly a system can recover.

Analysts study interdependencies with network theory and systems thinking, using measures such as centrality, connectivity, and robustness. Policy and management aim to account for interdependencies in planning, governance, and risk assessment, through diversification, redundancy, and coordination mechanisms.

Examples include the climate–energy–water nexus, global supply chains, and urban infrastructure that integrates power, transportation, and communication systems. Recognizing interdependencies helps explain why actions in one domain can have ripple effects elsewhere and why cross-disciplinary collaboration is often essential for stability and sustainability.