Much has been written about the effects of increased UV radiation caused by stratospheric ozone depletion on the weather, but there has been a dearth of publications on the role of UV on ecosystems as a whole. Now that much more is known about the effects of UV radiation at the organism level, we are gaining an understanding of how this impacts on specific ecosystems. From microbial to plant ecosystems, the book examines how changes in UV radiation, caused by anthropogenic ozone depletion, as well as changes in radiation levels throughout the evolution of life on Earth, can alter species composition and interspecies competitiveness. Two foci of the book are the evolutionary aspects of the effects of UV and also the various synergistic interactions of UV radiation with other environmental factors. Because our knowledge of UV effects on whole ecosystems is still at a relatively early stage, an important part of each chapter is an overview of future research directions and indications of where new data and knowledge are needed.