Abstract: There is much present need for a knowledge source that presents an authoritative,comprehensive and integrated approaches to the science,technology and management of four essential natural resources necessary for life support:water,energy,environment and food & agriculture. Not only are these natural resources, together with air and land,necessary for life support on our planet;they must be orchestrated and enhanced through human engineering efforts to ensure that the resulting resources are truly sustainable and that they can be utilized for life quality enhancement. The Encyclopedia of Life Support Systems (EOLSS) is a source document for this knowledge,as well as document that contains encompassing discussions on the interactions and interplay in human activities,and associated infrastructure needs,that results in sustainable life support systems. As a source book for students,researchers and professional practitioners in efforts related to integrated approaches to sustainable development through systems management of natural and human engineered resources,the EOLSS will satisfy five critical needs.