This chapter discusses a rationale regarding why we need to conduct environmental assessment by Data Envelopment Analysis-Enviromental Assessment (DEA-EA). Our description will serve as a conceptual basis for preparing various DEA and DEA-EA formulations and applications for environmental protection and sustainability enhancement. Such underlying concerns will be analytically explored in the remaining chapters of this book. To precede our discussion, this chapter starts with concepts on sustainable development for economy and environmental protection, often referred to as the practice of Environmental, Social and Governance (ESG) and Sustainable Development Goals (SDGs). The United Nations (UN) has gradually developed these principles. Many countries around the world continue to promote its coordinated developments in accordance with the principles of ESG and SDGs under the UN leadership. This chapter considers that ESG indicates “investment” opportunities at all levels of entities (e.g., counties and firms) and SDGs focus upon 17 sustainability goals, including environment protection, over time. Both are closely related each other in conducting environmental protection and sustainability enhancement. We also consider that both need a long run perspective (so, time series). The use of DEA-EA methodologically serves as an analytical tool to measure the level of ESG and SDGs enhancements. This chapter starts with reviewing what ESG and SDGs practically imply for our current and future life. The review on the two concepts provides us with the methodological importance (along with strengths and drawbacks) of DEA and DEA-EA in applying them for the measurement of global sustainability development.