Why do wetlands have high biodiversity?

High Biodiversity. Wetlands have been called “biological super systems” because they produce great volumes of food that support a remarkable level of biodiversity. In terms of number and variety of species supported, they are as rich as rainforests and coral reefs. read more

Wetlands have the water and land biotopes overlapping. For instance, a bird species that use the sea for foraging may use the wetland for its nests. Then, the wetland can contain a species which do not actually consume food resources in the wetland. read more

My best guess would be the high availability of all necessary nutrients. If you aren't limited you tend to burn hot, remove the interspecific competition at most niche levels and nothing is losing out and giving way to the best competitor. Couple that with something else you see in wetlands which is highly defined gradients in habitat. read more