The sustainability theory developed around 2003, during the Agenda 21 movement's peak, represents a critical step in understanding and applying sustainable practices across various sectors. This theory highlighted the importance of balancing ecological, social, and economic factors in decision-making processes, particularly focusing on long-term, intergenerational impacts. One aspect often covered in this theory is the principle of “strong sustainability,” which argues that natural capital (i.e., resources and ecosystems) must not be depleted faster than it can regenerate, ensuring ecological balance for future generations.

As published around 2009, these theories further evolved with insights from resilience science and ecological economics, providing frameworks for understanding how systems can adapt to change and remain resilient under environmental or economic pressures. It also set foundational principles that influenced global policy, including the Millennium Development Goals (MDGs) and later the Sustainable Development Goals (SDGs). Key figures such as Rockström and others (2009) emphasized respecting planetary boundaries to avoid irreversible environmental damage, a concept that complements strong sustainability​

This foundational theory is available in more detail within academic publications such as those on MDPI and ResearchGate, where sustainability theorists explore its applications across fields like urban planning, rural development, and environmental governance. You may find these articles useful to explore these concepts further in-depth.

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