Hierarchy of Ecological Homeostasis as a Principle of Systemology

— The broad concept of “homeostasis” in relation not only to organisms, but also to populations, ecosystems, and socio–ecological and economic systems (in the context of sustainable development) is discussed. Sustainability is the major quality of systems. The following mathematical formalizations and examples of various definitions of sustainability are discussed: according to Lyapunov (stability), Lagrange (steadiness), Poisson (periodic stability), Svirezhev (hierarchical stability), Holling (elasticity), Fleishman (vitality), and Gnedenko (reliability).