Global wetlands range from moss-dominated artic peatlands to seasonally-flooded tropical floodplains, and exhibit significant differences in both hydrology and species composition. However, rather than concentrating on the detailed characteristics of specific wetland types, this concise textbook emphasizes their universal environmental and biological features. A combination of hydrology, low oxygen levels, and dense plant canopies are the major defining features of wetland habitats. Due to the slow diffusion of oxygen in water, oxygen in wetland soils and water columns is often very low or absent. The adaptations of wetland micro-organisims, invetebrates, plants, and vetebrates to anaerobic conditions (and ther functional consequences) are a major theme of this book. Plant canopies create complex gradients of light, temperature and oxygen that change daily and seasonally. The book demonstrates how these shifting environmental gradients are responsible for the distribution of algae, invertebrates, and vertebrates in wetlands. Another major focus is on water level fluctuations and how they can affect the flora, fauna, and functions of wetlands.The future of wetlands is also examined, including the potential impacts of global climate change and efforts to restore wetlands.