Riparian zone

October 27, 2011, 11:23 am

This article was researched and written by a student at Texas Tech University participating in the Encyclopedia of Earth's (EoE) Student Science Communication Project. The project encourages students in undergraduate and graduate programs to write about timely scientific issues under close faculty guidance. All articles have been reviewed by internal EoE editors, and by independent experts on each topic.

Introduction

caption Riparian zone on the New River. (Source: U.S. National Park Service)

Riparian zones are ecosystems located along the banks of rivers, streams, creeks, or any other water networks. Usually riparian zones are narrow strips of land that line the borders of a water source. Riparian flora and fauna are often distinctly different from those found in adjacent communities because of the water-rich soils found in the riparian zone. Healthy riparian zones provide a variety of important ecosystem services and they are often important habitats for wildlife.

Characteristics

Abiotic

caption Before and After. South Fork of the Crooked River in Oregon. Left, Unhealthy riparian area in 1976. Right, healthy riparian area, 1986. (Source: [U.S. Bureau of Land Management]; Photos: Wayne Elmore)

Undisturbed riparian zones typically have steep and vertical stream banks. The flow of streams flowing through healthy riparian zones changes only moderately during a year. Streams flowing through healthy riparian zones are typically shaded. The water flowing through these streams is typically clear (low sediment load) but still have natural organic input such as leaves, branches, and even fallen logs. Riparian zones that have been damaged have undercut banks, experience periodic flooding, and have muddy water in the streams (high sediment load) that are exposed to direct sunlight.

Biotic

Because rivers and streams flow through a variety of geologic and climatic regions, it is not surprising that riparian vegetation varies widely from place to place. Common riparian vegetation include riparian forests, marshes, and desert washes. In addition to having a diverse plant community, a healthy riparian zone will contain a variety of aquatic and terrestrial wildlife.

Ecosystem services

Even though the actual area covered by riparian zones is relatively small (they typically make up much less than 1% of land area) they are an extremely important component of most ecosystems. Riparian zones provide a variety of ecosystem services including (1) sediment filtering, (2) bank stabilization, (3) water storage and release, and (4) aquifer recharge. In addition, riparian zones provide important habitat for wildlife.

Fish habitat

Streams flowing through healthy riparian zones are superior habitat for fish because (1) the riparian trees provide shade and buffer temperatures, (2) inputs of woody debris creates fish habitat, (3) inputs of organic matter via leaf fall provides food sources for invertebrates and fish, and (4) invertebrates that fall into the stream from the surrounding riparian vegetation provides food for other organisms. In addition, the riparian zone can improve the water quality of the stream by filtering out nutrients that would otherwise enter the stream.

Wildlife habitat

The abundance and diversity of wildlife in an area is influenced by the availability of water, the productivity (amount of carbon fixed by photosynthesis) and habitat diversity. Riparian zones provide reliable sources of water for wildlife and the greater productivity allowed by the high moisture content of the soil allows for more potential food for wildlife. In addition, the habitat diversity of riparian vegetation provides many potential niches for wildlife to fill. Not surprisingly, the diversity and abundance of wildlife in riparian zones is higher than in adjacent communities, particularly in arid regions.

Threats to riparian zones

caption Heavily impacted riparian zone due to unrestricted grazing. (Source: U.S. Fish and Wildlife Service)

Riparian zones are threatened by a variety of factors including (1) overgrazing, (2) logging, (3) agriculture, (4) building dams, and (5) human development.

Conservation and restoration

Currently, maintaining and restoring riparian zones is an important conservation goal. Managers attempt to maintain this natural buffer within the floodplain by reducing the threats listed above. In addition, there are many efforts to restore ecosystem function of healthy riparian zone by replanting native riparian vegetation.

References and Further Reading

Glossary

Citation

Freitag, A. (2011). Riparian zone. Retrieved from http://www.eoearth.org/view/article/155754

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