The tough, tangled roots of sedges, shrubs and trees provide structure to stream banks and reduce soil loss to the stream.
Riparian zones supply water to underground reservoirs. We call this process groundwater recharge. Well vegetated areas trap the overland flow of water, allowing it to infiltrate the soil and percolate downward. Underground stores provide the primary and sometimes only source of water for streams during dry periods. Without this supply, the aquatic ecosystem would collapse. Recharge is equally crucial for humans who depend on groundwater for drinking and other purposes.
As surface runoff flows through the riparian zone to the stream, vegetation traps much of the sediment it carries which reduces turbidity levels in the stream. Riparian vegetation also pulls nutrients out of the soil before they can reach the stream.
Riparian zones serve as reservoirs for flood waters. The vegetation and soil absorb overbank flow then releases it over time. This decreases the amount and energy of water flowing through the stream at any one time. People who live in floodplains benefit from the regulating effect of healthy upstream riparian zones.
Riparian zones concentrate water and nutrients form the stream and the surrounding uplands. In response, the vegetation grows dense and structurally complex- it takes on a variety of shapes and sizes. This greater complexity translates into more niches for organisms to fill.
- The diversity and production of riparian zones surpass all other terrestrial (land) ecosystems.
- Riparian zones in the Southwestern United States have a higher breeding diversity of birds than all other western habitats combined.
- Aquatic organisms are just as dependent upon riparian zones for their survival. The leaves, sticks and bark that into the water may provide up to 99% of the energy for organisms in a small headwater stream (the other 1% comes from photosynthesis).