Small farm dams, wastewater ponds and mine pits generally form lake-like environments, common in humid and semi-arid climates world-wide. Nutrient inputs vary greatly depending on purpose and surrounding land uses. They are often warm and shallow, and biological productivity and diversity vary widely depending on the cover and state of fringing vegetation, with the most diverse examples rivalling equivalent natural wetlands. Aquatic plants, plankton, algae and waterbugs may dominate in the shallows, supporting amphibians, turtles, fish, and waterbirds.