Because wetlands have poor drainage, the area is characterized by sluggish or standing water that can create an open-water habitat for wildlife. Highly productive and complex ecosystems, wetlands help to regulate the water cycle, filter the water supply, and prevent soil erosion. More significantly, however, wetlands serve as spawning and feeding grounds for nearly one third of the endangered animal and plant species in the United States, and their ecological value in most other countries is comparable. The VEQI used wetland loss as a measure of ecosystem-level change. Wetland loss has been included in several indexed measures of environmental quality.
Wetlands act as buffers from and filters of pollution.
Wetlands also reduce flooding, contribute to the groundwater supply recharge and provide excellent habitat for fish, shellfish, birds and insects. Both shores of the Chesapeake Bay have extensive estuarine wetlands. Many wetlands were destroyed by urban growth and farming before their value was recognized. More than half of U.S. wetlands in the lower 48 states have been lost since colonial times. Virginia Environmental Quality Index.