The recently proposed new, universally applicable, rigorously derived and reality-based concept of dynamic complexity provides a unified basis for the causally complete understanding of any real, multi-component and multi-level system of interacting entities, including the case of earth system and global civilisation development. This crucial extension with respect to other existing notions of complexity is obtained due the unrestricted, universally nonperturbative analysis of arbitrary interaction process leading to the new, rigorously derived concept of dynamically multivalued (redundant) entanglement of interacting components. Any real system with interaction is described as a sequence of autonomously emerging "levels of complexity", where each level includes unceasing, dynamically random change of multiple system configurations, or "realisations", each of them resulting from dynamic entanglement of interaction components coming, generally, from lower complexity levels. Dynamic complexity as such is universally defined as a growing function of the number of those explicitly obtained system realisations (or related rate of their change). Mathematically rigorous, realistic and universal nature of unreduced dynamic complexity determines its unique role as a basis for theoretical ecology. This conclusion is confirmed by several directions of universal complexity application to global change understanding and monitoring. They include the rigorously substantiated necessity of civilisation transition to the superior level of complexity involving new, intrinsically unified and causally complete kind of knowledge (initiated by the "universal science of complexity"), qualitatively new kind of material production, social structure, and infrastructure. We show why that new level of civilisation development is intrinsically "sustainable", i. e. characterised by creative, complexity-increasing interaction between "production" and "natural resources" that replaces current contradiction between them.
