The main emphasis in this edition is systematic analysis of natural and man-made world encompassing various scientific, economic, social and ethical aspects. Human impacts leading to large scale degradation of environment have aroused global concern on environmental issues in the recent years. Thisedition is reclassified into four units. Unit I covers introduction of environment, ecology and ecosystem, human activities like food security, economic, social security etc., effects of various human activities on environment, environmental impact assessment and sustainable development. Unit II covers natural resources and energy. Unit III discusses environmental pollution and current environmental issues of importance. Unit IV covers environmental protection and initiatives at various levels. In this book basic concepts of environment and ecology have been introduced and analyzed in a simple manner strictly as per the syllabus recommended for its undergraduate and graduate classes in all disciplines by the UP and other State Technical Universities..