Macro-engineering involves the large-scale modification and manipulation of natural systems for the benefit of mankind. The primary goals of some Earth-based macroprojects described in this book are power production, land reclamation, food production, climate change, environment, water, transport and coastal protection. Other Earth or space projects considered here have a more futuristic ring, but our present-day technical skill makes their realization possible. Earth-based macroprojects usually combine different aspects and aims. They have a major impact on the ecology of a region and the inhabitant's means of living (like tourism, fishing, shipping). Its effects may be felt worldwide, like the rise in global sea level after the damming and evaporation of large ocean gulfs for power production, or the change in climate following the regional reduction of solar insolation. Each project will dramatically change the lives of the people affected. It can provide them with a better standard of living, at the cost of a rapid adaptation to a changed environment and a changed life style. This may provoke temporary geopolitical and social unrest. Macro-engineering contributes to sustainable progress, but it must first overcome the social, political and economical obstacles in its way.