This textbook presents the fundamental principles of functioning of ecological systems and the biosphere as a whole, the problems of biosphere instability and the developing global environmental crisis. It examines global environmental issues such as demographics, natural resource depletion, and energy, which can be resolved only if humanity transitions to a sustainable development path. It provides a general overview of the principles and methods of protecting the biosphere from pollution and organizing environmental protection activities, including through international cooperation. The textbook is aligned with the curriculum of the "Ecology" discipline.