Ecologism or Environmentalism represents a natural corollary of the doctrine of sustainable development. It seeks to redefine the relationship between human beings and nature, and between human beings themselves. It insists that human beings should no longer operate as the ‘masters’ of the natural world but as partners with other living organisms. The view that ecology, i.e. “the pattern and balance of relationships between plants, animals, people and their environment” is a self-sustaining system; that no damage should be done to this system for the satisfaction of human need or greed, as it would be injurious to everyone’s life. Ecologism calls for a review of the damage done to the nature in the course of unbridled industrialization, urbanization, and multiplication of human wants. This Chapter focuses on the interface between environment and development. Firstly, the concept of development is being analyzed, as well as the principles and dimensions of sustainable development, which is the dominant development policy, worldwide.