Diversity of freshwater ecosystems and global distributions

Freshwater ecosystems are found on all continents comprising many different types and sizes; and defined and classified in different ways. The hydrologic regime influences the many physical and chemical features of freshwater ecosystems and has temporal and dynamic dimensions for flowing (rivers—lotic systems) and standing waters (lakes and ponds—lentic systems) and others that may experience permanent flooding or large fluctuations in water depths. The water balance is commonly used to understand a system's hydrology and provide insights into the key processes determining its functioning. Widely distributed, global mapping initiatives provide a general distribution of types, document latitudinal and longitudinal distribution, and provide a global coverage estimate of 12.5–14.4 × 106 km2. However, a comprehensive inventory and global map for these ecosystems still does not exist. Information on the specific features of rivers and streams, lakes and ponds, swamps and marshes, peatlands, and freshwater karst systems is provided.