"This book discusses ultraviolet (UV) radiation, its effects on ecosystems, and the likely evolutionary consequences of changed UV radiation environments, past, present, and future. The first two chapters examine the history of the UV radiation climate of the Earth and the factors that determine organismal and ecosystem exposure. Their purpose is to give the reader a physical perspective on UV radiation and an understanding of the constantly changing UV environment that ecosystems are exposed to over time. Variations in the UV radiation environment occur at the local level (such as boundary layer and plant canopy effects) through to global-scale changes (such as alterations in the column abundance of UV-B protecting ozone). UV radiation regimes also vary over temporal scales. These alterations occur on time scales of seconds (the movement of clouds and plant canopies) to literally billions of years (gross long-term changes in the composition of Earth's atmosphere)."--BOOK JACKET.