This work delivers ideas, comments and projects on energy, communications, transport, management, human resources, and financial and legal issues which macroengineering can contribute towards the solution of the Earth's environmental problems. Some 20 engineers and scholars identify problems in the next century whose solutions call for international policy planning and a more collaborative, peaceful and prosperous world order. Imaginative concepts employ forward thinking for applying technology in revolutionary projects. The book presents results of research on a triple helical turbine capable of extracting vast amounts of energy from slow-moving water, an invention which could harness rivers and ocean currents, rendering high dams (with their political, social and ecological implications) redundant. These turbines are already in mass production in the USA for use in the Gulf Stream to produce energy and hydrogen fuel, and can also be used to harness power from the wind. Another project, for which the technology is already available, will harvest solar energy by satellites stationed beyond our atmosphere and beam it to the Earth; and yet another calls for planetary defence of Earth against asteroid collisions. The environmental section discusses large projects for changing our climate, planning and costing for a sub-Mediterranean aqueduct connecting the River Rhone in France with Algeria, and plans for intensive fish farming of the oceans. The role of satellites includes telemedicine, and there are Swiss plans for further tunnelling through the Alps. Project management sections include the formation of a military-civilian conservation corps, financial and legal issues, macro-projects in China, and a forecast of 21st century macro-problems.