Effects of Cattle Grazing in Riparian Areas of
the Southwestern United States

Riparian zones are the transition areas between terrestrial and aquatic ecosystems (Gregory et al. 1991).  Soil characteristics and plant communities in riparian areas indicate the presence of free, unbound water, associated with the margins of streams, rivers, ponds, lakes, springs and other wetlands (Swanson 1986 in Fitch and Adams 1998).   Riparian areas give rise to unique plant communities that depend on the river to maintain the water table at a depth accessible to their roots (Cohen 1997) and establish watershed function, provide diverse habitats for fish and wildlife, and a highly productive forage supply for livestock (Fitch and Adams 1998).  Livestock grazing in riparian areas is controversial.  Many riparian areas in the United States have been mismanaged and degraded by improper livestock grazing; however proper management practices can minimize the effects of grazing (Mosley et al. 1998).  Range livestock grazing has been a focal point of nearly two decades of debate in the western United States. This debate has given rise to remedial programs among federal and state agencies, which include fencing to exclude cattle from riparian areas. Most distressing to the livestock sector, various campaigns have been mounted to remove livestock altogether from public rangelands. Initiatives to reduce or remove livestock often relate to overuse and degradation of riparian areas. The riparian grazing issue has been characterized by deeply entrenched conflict among interest groups and legislated solutions (Fitch and Adams 1998).

Early Ranching and Range Science

European settlement brought with it sedentary grazing of the plains and foothills by domestic stock.  First during the brief period of open range grazing in the late 1800's, and later through the early ranching system with pasture units defined by barbed wire fences (Breen 1983). Guidelines for western ranchers were nonexistent.  Range science and the current philosophy of range management emerged as generations of ranchers observed natural processes and the impacts of their grazing animals, and learned from trial and error. The effect of long and intense grazing periods, and grazing impact on range productivity, was noted and quantified by early range studies (Smoliak in Breen 1983) as ranchers learned to imitate the natural system and implement more ecologically based grazing strategies.

A prevailing criticism of modern range science is that it has focused almost exclusively on management systems, condition, and productivity of upland terrestrial rangelands. Critics believe this is reflected in the United States where indices of range condition are increasing in uplands while the condition of riparian areas continue to decline (World Resources Institute 1994).  Less than 20% of the western riparian habitat of pre-settlement times still exists (Smith et al. 1991) today. 

Riparian Zones

In order to determine how livestock affect riparian zones it is important to understand the  development of riparian systems and their ecological function. Primarily, that streams and their watersheds function as units and are inseparable (Gregory et al. 1991). Structurally, riparian zones, are characterized by stream discharge, stream gradient, sediment load, resistance of banks and bed to movement of flowing water, vegetation, temperature and geology (Lane 1957 in Fitch and Adams 1997)  Also crucial to riparian areas and their maintenance, is the vegetation associated with them.  Riparian vegetation is an especially critical component of the watershed because it provides and estimated 99% of the nutrients in the aquatic food web (Doppelt et al. 1993) and because it provides a physical barrier to the effects of high water velocities and stream energy (Fitch and Adams 1997).

Riparian Degradation by Cattle Overgrazing

In the Southwestern United States, grazing has been a traditional use of federal lands which was completely unregulated until the 20th century.  For example, not until 1911 did a court hold that the direct cause of large amounts of nonpoint-source water pollution, causes the loss of riparian vegetation, and continues to have a major adverse impact on the integrity of riparian areas, including floodplains (Doppelt et al. 1993).

Grazing simplifies riverine-riparian ecosystems because livestock favor riparian vegetation over surrounding vegetation and tend to congregate in and along rivers, wetlands and streams (Doppelt et al. 1993).  Animals grazing in these areas trample and consume riparian vegetation, inhibiting the regeneration of natural plant communities and increasing sedimentation rates, which covers stream beds and kills aquatic organisms (Doppelt et al. 1993).  This can, in turn, deplete sources of large woody debris that are vital to channel stabilization and sinuosity.  Shade is reduced, which increases water temperature and leaves biotic organisms such as aquatic insects and fish vulnerable to predation .  Livestock also urinate and defecate in or near streams, increasing nutrient input beyond levels normal for natural aquatic communities (Fitch and Adams 1998, Mosley et al. 1998).

Riparian Management Plans

Without knowledge and tools to manage riparian systems, initial efforts for riparian recovery have involved fencing programs to permanently exclude livestock from riparian areas. While exclusion fencing can allow the rapid recovery of an area, it is expensive and a source of conflict and resentment in the ranching industry.  Exclusion fencing also conveys the notion that riparian areas and cattle are incompatible, and it falls short of a higher goal, that of complete river and landscape management (Fitch and Adams 1998).

Riparian grazing plans, according to Mosley et al. (1998) should be site-specific and based upon the best research and empirical evidence available. Recovery strategies should address the effects of overgrazing on riparian structure, riparian vegetation, and wildlife associated with riparian habitats.

Cattle access should be limited to surface water areas when adjacent to stream banks and cattle should generally avoid grazing in excessively wet areas.  To control the timing, frequency and intensity of cattle grazing, managers should consider creating smaller riparian pastures and adjusting for these aspects.  To protect banks and reduce impacts from cattle urine and feces buffer strips from 12.5 to 20 feet on the stream sides can be made (Mosley et al. 1997).  Because riparian vegetation is vital to ecosystem health and yet so easily degraded by cattle, one of the primary goals of new national riverine conservation approaches and policies must be the protection and restoration of riparian corridors especially on private and agricultural lands where riparian zones are more likely to be misused (Doppelt et al. 1993).

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Authored by Becky Wagner
May 2, 1999