Riparian areas, commonly referred to as wetlands, are generally considered to be the belt of vegetation along the edge of a body of water. These areas, although they only account for a small percentage of land in the United States, tend to be one of the most active and biologically diverse ecosystems on the planet. Currently, over half of the riparian zones in the coterminous 48 states have been destroyed, and very few remain in their original, pristine condition.
It is the actions of man that put these resources in danger. There location along rivers and lakes make them very susceptible to degradation from human activities such as the clearing of land for farming and development. Unrestricted livestock has also taken a toll on riparian areas over the years.
In order to help minimize the destruction of riparian areas, landowners must realize the importance of buffering their land. A proper riparian buffer will filter out excess nutrients from the water due to agricultural run off, provide bank stability minimizing land loss, as well as provide habitat for many species of birds, mammals, and aquatic organisms. The importance of riparian areas must be recognized before this valuable resource has vanished.
Due to their location in flood plains, more than half of the riparian areas in the lower 48 states have been destroyed and very few of them remain undisturbed (Manci, 1989). The location riparian areas put them at human’s disposal because so many of our activities affect them. These activities include urbanization, the manipulation of stream flow, development of roads, pipelines, recreational areas, and especially clear-cutting for agricultural uses. Together they result in erosion and a loss of natural diversity among these ecosystems. Something must be done if we want to save these valuable resources.
Riparian areas are the green belt of abundant vegetation associated with waterways, riverbanks, lakes, and low wet areas. They are usually associated with an abundance of diverse macro and micro flora and fauna (Lium, 2001). Native riparian areas are disappearing rapidly so we must keep them maintained. This is a serious problem in the southwest United States due to the lack of water. Manipulations of stream flow in the form of dams, reservoirs and channelization projects have resulted in a loss of about 120,000 acres of riparian vegetation each year (Manci, 1989).
Figure 1 presents a before and after picture of a riparian area. The picture on the left was taken before the restoration project, the picture on the right was taken two years later.
Figure 1. Before and After (Lium, 2001).
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According to the 1992 report, restoration is defined by the National Research Council as "the return of an ecosystem to a close approximation of its condition prior to disturbance" (EPA, 2002). What other condition would be more appropriate? In order to receive the benefits of a healthy riparian system, restoration projects like the one seen in figure 2 need to be conducted. After all, without the intertwining roots of diverse plants binding the soil together and creating structural protection, running water erodes river banks easily. In addition, without vegetation, fisheries and wildlife habitat are adversely affected. Degraded riparian systems are clear sign of potential erosion and loss of property (Lium, 2001).
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It is easy to tell if a riparian area is healthy or not if you know what to look for. An unhealthy system often has a low water table and low forage production (Malheur Experiment Station, 2000). They experiences little shade from lack of surrounding vegetation. This warms the water to the point that it is no longer good fish habitat. The lack of vegetation also results in low species diversity and unstable stream banks. A healthy system on the other hand, will have a much higher water table, increased storage compacity, and a high forage production. Plenty of shade make for much cooler water and better fish habitat. In addition to good fish habitat, wildlife habitat is more diverse. A healthy stream is also be well protected by the complex root system on its banks, so there will be little evidence of erosion.
Due to the location of riparian areas on flood plains, there condition associated with the activities of humans. Any development at all can be devastating. Currently, over half of the riparian zones in the coterminous 48 states have been destroyed, very few remain unhampered (USGSa, 1989). In the southwest region of the country, riparian ecosystems are dwindling fast. This is due mainly to expanded agriculture, livestock grazing, and groundwater depletion. Low groundwater levels don't impact these zones directly but drive us to alter stream flow by constructing dams, channelization projects and reservoir construction. Along the Colorado River alone, more than 1,200 ha/year of riparian vegetation is being removed each year (USGSa, 1989).
In the Pacific Northwest, erosion is a major issue due to lack of proper riparian vegetation. Logging and farming have increased surfaced runoff causing higher than normal water levels. These high waters breakdown stream banks quickly. Approximately 10 tons of sediment erode from stream banks each year in Oregon and Washington alone (USGSa, 1989).
When it's added up, riparian habitats represent less than 1 percent of the total acreage of public lands in all the 11 western states. About 72% of all reptiles, 77% of all amphibian species, 80% of all mammals, and 90% of all bird species which occur regularly in the Colorado Plateau region routinely use riparian areas for food, water, cover or migration routes (Northern Arizona University, 1999). Yet the development of farm land has caused many of the major rivers in the region to be altered for irrigation and flood control, destroying what little habitat remains. It's the same in the mid west. Within the 600-mile stretch of the Mississippi river between the Gulf of Mexico and Cape Girardeau, Missouri, there are over 2,000 miles of levees and about 40,000 acres of pits left over from where the levee material was borrowed (USGSa, 1989), all because of the need for irrigation. The problem is every where. Estimates place Iowa's soil erosion rates at 6 to 7 tons per acre per year on farmland with some areas running up to an amazing 25 tons a year (Isenhart, 1999).
Riparian area degradation is not just a local issue but a national concern that all land owner must recognize. Everyone from the President on down is becoming aware of the problem. In Bill Clinton's State of the Union Address in February 1997, the American Heritage Rivers Initiative was announced (Oklahoma Cooperative Extension Service, 1998). This is a program designed to study and protect all of America's rivers. In addition, Secretary of Agriculture Dan Glickman announced that same spring that 2,000 miles of river would be targeted for a conservation reserve program (Oklahoma Cooperative Extension Service, 1998). Plus, the U.S. Army Core of Engineers had decided to rethink their structure-oriented floodplain policy (Oklahoma Cooperative Extension Service, 1998). It is very clear that a concern for riparian areas is growing.
Disturbances
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Clearing riparian areas for rural and urban purposes is by far the most common destructive disturbance. Many landholders and developers should learn the benefits of retaining and maintaining such important ecosystems. Another problem caused by a natural force is a channel change. This is simply a rerouting of a stream and can include bed and bank erosion as well as sediment on the floodplain. Although this is a natural process, things can certainly be sped up by human activities such as development, redirection of flow, and livestock access.
Unrestricted livestock access to a stream or river is a big problem by itself. Stock grazes upon and tramples vegetation denying regeneration. Their grazing compacts the soil and creates pathways along and across river beds impacting the natural balance as seen in figure 3. They also contribute extra nutrients and bacteria to the water through their urine and feces. Other animals like goats, pigs and rabbits can have similar affects. They eat young vegetation and damage the essential under story necessary for a good buffer.
Vehicles and public access can also result in severe damage especially if the activities are prolonged or are inappropriate. Often there are secondary effects that occur as a result of these activities such as: creation of tracks or paths, trampling of vegetation, disposal of rubbish and garden waste, and the lighting of fires. In some places, such as Australia, vegetation is adapted to deal with the effects of fire but unfortunately, this is not always the case. Sometimes the effects fire can reduce the likelihood of a successful regeneration.
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Figure 3. Top Degradation caused by grazing livestock. Bottom The result of decades of erosion (USGSb, 1999).
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Here are a few practices to be avoided in order to preserve riparian areas.
- Indiscriminate burning and/or removal of riparian shrubs, trees and other vegetation reduce shoreline soil stability, increase water erosion and decrease groundwater storage.
- Channelization and brush clearing along creeks and rivers increases the speed of water flow, causing erosion and flooding which can severely damage upstream property.
- Destroying riparian areas by cultivating to the edge of the creeks, slough and potholes removes important vegetation, increasing the volume of contaminated agricultural run-off reaching dugouts, ponds and groundwater reserve.
- Cultivating temporary water-runs in crop land causes severe soil erosion, reducing long-term productivity. Water-eroded soil is often carried into streams and sloughs, lowering water quality.
- Concentrating livestock in riparian areas for long periods results in overgrazing that reduces forage productivity and encourages expansion by unpalatable plant species. This increases erosion potential and lowers water quality.
- Activities using heavy equipment, such as road construction, agricultural production or timber harvesting, compact riparian soils and damage shorelines. Recreational all-terrain vehicles cause similar impacts.
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Riparian Buffers
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Having a proper riparian buffer is an excellent way to keep erosion to a minimum. The ideal system for maintaining stream banks would consist of an interweaving network of the roots of small trees and brush (Figure 4). In fact, A two-inch deep root mat resists erosion up to 20,000 times better than a bare soil stream bank (USGSb, 1999). This combined with grassy vegetation will bind the soil together helping to maintain steam stability. It is important to realize that small trees are the most efficient. Larger trees will prohibit under story growth, a very crucial part of a healthy system, eventually leading to their collapse leaving the bank unprotected once again.
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Figure 4. Riparian trees play a large role in maintaining the river ecosystem (Parson, 2002).
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All buffers are built for different reasons, so it is important to make sure the size of the vegetation matches the land use and topography of the site. Consider the following:
- A buffer is much more important to the quality of water in sites that receive a lot of runoff and less important on land that tips away from the water. The steeper the slope, the faster moving runoff and therefore the need for a wider buffer to absorb pollutants. It is also important to take notice of the path a meandering stream takes at high water or during a flood.
- A soils ability to absorb pollutants and nutrients also depends on the type of soil, its depth, and its relation to the water table (Tarbuck and Lutgens, 2000). Clays, wet soils, and extremely dry soil absorb much less efficiently. This kind of soils present are very important to note.
- The kind of vegetation used to build a buffer is influenced by the intent of the buffer. Larger trees and shrubs tend to be preferred in urban areas because they are efficient at catching runoff associated with parking lots and residential lawns in addition to providing habitat for small animals, especially birds. Shrubs and grasses can provide the same results between crop lands and waterways without shading crops but trees can still be used on the north side of fields. After all, trees do seem to have several advantages over other plants. It is obvious that they provide much better habitat for larger wildlife but they also greatly benefit small aquatic ecosystems by providing shade. Underground, trees have much larger root systems and are much more resistant to erosion as well.
- The buffer width is another important consideration to keep in mind when you are buffering your own land. Is the purpose to keep the water clean, provide habitat for fish and wildlife or satisfy human demand for land (Figure 5)?
Figure 5. Buffer Width (Conn. River Joint Commission, 2000).
- Bank Stabilization – On smaller streams, good erosion control may require covering the bank with shrubs and trees, and a 35' managed grass buffer. If there is active bank erosion, or on larger streams, going beyond the bank at least 50 feet is necessary. Severe bank erosion on larger streams requires engineering for proper protection but this can be done with plants. For better stabilization, use more of the shrubs and small trees.
- Fisheries Habitat – Buffer width depends on the fish community. If the fish like cold water, the stream should be shade completely. Warm water fish do not require as wide a buffer, therefore not as much shade. However, all fish benefit from the cleansing a buffer provides. Studies show that at least up to 100', the wider the buffer, the healthier and more active the aquatic food web.
- Nutrient Removal – A width of up to 100' or more may be necessary on steeper slopes to allow run off to soak in sufficiently, and for microbes to work on the nutrients and pesticides. If you are building on a less permeable surface like clay, your buffer will have to be much wider, as wide as 500'.
- Sediment Control – For slopes gentler than 15%, most sediment settling occurs within a 35' buffer of grass. More with is needed on steeper slopes, for shrubs and trees, where sediment loads are higher.
- Flood Control – Smaller streams may require only a narrow width of trees and shrubs. Larger streams my require a buffer that spans almost the entire flood plain
- Wildlife Habitat – The proper buffer width depends on species but 300' is considered a bare minimum. Much larger stream side forest buffers are needed for wildlife habitat purposes rather than for water quality. The larger the buffer, the more valuable it is to animals.
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Riparian Areas as Fish and Wildlife Habitat
Figure 6. A deer is looking for a drink at the waters edge. (Anonymous, nd).
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Due to an abundance of water, shelter and food, riparian areas are very important and attractive to all sorts of wildlife, even large mammals (Figure 6.) (Saskatchewan Wetland Conservation Corporation, 1998). In largely cultivated zones, riparian areas provide the only suitable option. Damage can prove to be devastating to these populations.
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The presence of water and forest provide two habitats in close proximity, this is called a transition zone (Tarbuck and Lutgens, 2000). Transition zones like riparian areas, usually produce abundant and diverse populations of wildlife. Nomadic animals and especially migrating birds make these areas their home away from home during certain times of the year.
In Vermont, diverse and productive communities of amphibians, reptiles, waterfowl, raptors, songbirds, and mammals, especially furbearer species like mink and otter, will thrive in this transition zone (Vermont Agency of Natural Resources, nd). Streamside and lake shore vegetation also creates corridors that are vital for wildlife passage within and between habitats (Vermont Agency of Natural Resources, nd). Birds and certain mammals rely on these corridors to move between different seasonal habitats to obtain food, cover, and nesting areas (Vermont Agency of Natural Resources, nd).
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In addition to land animals, riparian areas are also crucial to fish and other aquatic life. In fact, the suitability of a stream for a given species is often determined by the condition of the surrounding riparian vegetation. Insects falling from overhanging vegetation provide a principal summer food source for many fish species (Vermont Agency of Natural Resources, nd). Fallen leaves provide an important food source for many aquatic insects which in turn, are also eaten by fish (Vermont Agency of Natural Resources, nd). The tree and shrub growth at the waters edge provide overhanging branches and stable undercut banks providing cover for all fish species. The growth of shrubs and trees also keep the water cooler during summer months by providing shade. The shade limits the growth of algae and helps to maintain higher oxygen levels in the water and better fish habitat (Figure 7).
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Figure 7. Rainbow trout are dependant on cool, highly oxygenated waters (University of Wisconsin Sea Grant Institute, 1998).
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Riparian areas don't just provide for wildlife, they protect the water that is essential to all life, including us.
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References
American Rivers, 2002. Recipe for a Healthy River: Riparian Areas. Retrieved the 6th of May 2002 from http://www.amrivers.org/aboutrivers/riparian.htm.
Anonymous, nd. no title. Retrieved the 5th of May 2002 from www.lakevermilion.com/ moods/pxs/deer.html.
Association for Temperate Agroforestry, nd. Riparian Forest Buffers Protect North America’s Surface Water Resources. Retrieved the 5th of March 2002 from http://www.missouri.edu/~afta/About_AF/RB1.htm.
Connecticut River Joint Commissions, 2000. Introduction to Riparian Buffers for the Connecticut River Watershed. Retrieved the 1st of March 2002 from http://www.crjc.org/buffers/Introduction.pdf.
EPA, Office of Water, 2002. River Corridor and Wetland Restoration – Definitions and Distinctions. Retrieved the 28 of January 2002 from http://www.epa.gov/owow/wetlands/restore/defs.html.
Green, Charles N., 1998. no title. Retrieved the 1st of February 2002 from http://www.cayuganet.org/owla/riparian/.
Isenhart, Tom, 1999. Riparian Buffer Systems: The Basics. Retrieved the 2nd of May 2002 from http://www.ent.iastate.edu/ipm/icm/1999/6-14-1999/riparian.html.
Lium, Bruce, 2001. American Water Resources. Retrieved the 10th of February 2002 from http://www.americanwaterresources.com.
Malheur Experiment Station, 2000. Riparian Areas. Retrieved the 30th of April 2002 from http://www.cropinfo.net/ripiarian.htm.
Manci, Karen M. 1989, Riparian ecosystem creation and restoration: A literature summary. U.S. Fish and Wildlife Service Biological Report 1989. Retrieved the 24th of March from http://www.npwrc.usgs.gov/resource/literatr/ripareco/ripareco.htm#contents.
Northern Arizona University, 1999. Degradation and Loss of Riparian Areas on the Colorado Plateau. Retrieved the 5th of May 2002 from http://www.cpluhna.nau.edu/Biota/riparian_degradation.htm
Oklahoma Cooperative Extension Service, Division of Sciences and Natural Resources, 1998. Riparian Area Management Handbook. Retrieved the 2nd of May 2002 from http://www.agweb.okstate.edu/pearl/e952/e-952.pdf.
Parsons, David, 2002. "Autumn in Vermont." Retrieved the 5th of May 2002 from http://www.amrivers.org/aboutrivers/riparian.htm.
Saskatchewan Wetland Conservation Corporation.1998. A Saskatchewan Riparian Project. Retrieved the 12th of March 2002 from http://www.agr.gc.ca/pfra/land/stream/stream1f.htm.
Tarbuck, Edward J. and Fredrick K. Lutgens, 2000. Earth Science, Ninth Edition. Prentice Hall, New Jersey, 672 pages.
USGSa, 1989. Riparian Ecosystem Creation and Restoration: A Literature Summery. Retrieved the 7th of April 2002 from http://www.npwrc.usgs.gov/resource/literatr/ripareco/intro.htm.
University of Wisconsin Sea Grant Institute, 1998. Identification Tips for Trout and Salmon. Retrieved the 5th of May 2002 from http://seagrant.wisc.edu/greatlakesfish/brooktrout.html.
USGSb, 1999. Riparian Areas of South Dakota. Retrieved the 30th of April 2002 from http://www.npwrc.usgs.gov/resource/1999/ripsd/ripfound.htm.
Vermont Agency of Natural Resources, nd. The Value of Riparian Buffers. Retrieved the 5th of May 2002 from http://www.anr.state.vt.us/dec/waterq/Rivers/benefitsriparian.pdf.
Western Resource Management Associates Ltd. 1999. Riparian Areas: An Undervalued Saskatchewan Resource. Retrieved the 28th of April, 2002 from http://www.agr.gc.ca/pfra/pub/riparian.htm.
