At present and over the next few years, large-scale windfarms are being installed far off the coast of Germany in the North and Baltic Sea, making a major contribution to electricity generation from renewable energy sources. One of the German government’s aims is to ensure the environmentally sound and sustainable development of offshore wind energy. Germany’s first offshore test site, alpha ventus, was therefore accompanied from the construction phase to the first years of operation by an intensive environmental research programme, the StUKplus project, financed by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety and coordinated by the Federal Maritime and Hydrographic Agency. Marine and ecological aspects have been researched there for more than five years to improve the level of knowledge about the ecological impacts of offshore windfarms. This book provides a broad, richly illustrated overview of applied and new research methods and monitoring techniques. It summarises the key research findings on the impacts on benthic communities, fish, marine mammals and birds, also taking into account underwater sound and sediment measurements. Interpreting the results in the sense of lessons learned, new challenges and perspectives are discussed for future sustainable offshore development in German waters.