Can Cows And Fish Coexist?

Managed Grazing By Cattle And Other Livestock Can Have Positive Or Negative Impacts To Surface Waters And Fish

Montana’s abundant clean water and thriving populations of trout and other fishes are revered worldwide. Enjoying these amenities is a wonderful benefit to citizens and visitors of our state. Ensuring that land stewardship sustains and enhances these incredible resources is a tremendous responsibility of Montana landowners. Grazing land stewards rely on Best Management Practices (BMPs) to keep Montana’s water clean and to keep Montana’s riparian areas (i.e., land adjacent to water bodies) healthy. Grazing by cattle, horses, sheep, llamas, alpacas and other livestock can either harm or enhance the health of Montana streams, lakes, and reservoirs and the fish and other aquatic life that inhabit them. Livestock grazing BMPs are research-proven practices that enable grazing land stewards to maximize positive and minimize negative effects. Appropriate livestock grazing BMPs in riparian areas address 1) when the grazing occurs; 2) how often the grazing occurs; 3) how much vegetation is consumed; and 4) how to keep livestock from congregating in riparian areas.

When to Graze/Not Graze?

Livestock grazing effects in riparian areas depend primarily upon when the grazing occurs. Therefore, a good first step in developing a riparian grazing plan is to determine the critical period(s) of a riparian area. Each stream or shoreline segment tends to have its own critical period, or time within a year, when it is particularly vulnerable to grazing damage. Critical periods are likely to be either in late springearly summer, when streambanks are more easily broken down by trampling; or late summer- early fall, when excessive browsing may weaken shrubs that are needed to help armor streambanks against erosion. Most impairment of water quality by livestock grazing can be prevented by limiting livestock access to surface waters when streambanks and shorelines are overly wet and susceptible to trampling and sloughing.

How Often to Graze/Not Graze?

Livestock grazing can be applied every year if grazing does not occur during critical time periods, but livestock grazing during critical periods should occur no more often than once every three or four years. Riparian vegetation is especially resilient to grazing because moisture is usually available to help plants regrow and regain vigor after grazing. An area can be grazed more than once per growing season if moisture and temperature conditions enable plant regrowth. Recovery periods of at least 30 to 60 days are needed before re-grazing within the same growing season. Sloughing and erosion of streambanks and shorelines can contribute large amounts of sediment and other contaminants into surface waters. Stable and overhanging streambanks and shorelines are also important for fish habitat. The longer that livestock have access to streambanks or shorelines, the more likely that bank damage will occur. Grazing more often and for shorter time periods (up to 3 weeks at a time) is preferable to fewer grazing periods that are longer. In Montana, the first sign of inappropriate livestock grazing in riparian areas is usually excessive physical disturbance to streambanks and shorelines.

How Much Vegetation to Consume/Leave?

Excluding livestock grazing may help some degraded riparian sites recover where previous livestock grazing was excessive, but the benefits of exclusion are usually short-lived. This is because riparian plants grow more and reproduce more when stimulated by moderate livestock grazing. Riparian plants are healthier in moderately grazed areas than in ungrazed areas, and moderate grazing during late spring-early summer increases plant densities that, in turn, reduce the transport of sediment and other contaminants into surface waters. Moderate livestock grazing also limits weeds, especially Canada thistle, that often invade and dominate ungrazed riparian areas. To sustain the plants that protect water quality and provide optimal fish habitat, moderate livestock grazing should remove 40 to 60% of the current year’s aboveground plant growth of grasses, forbs, and shrubs. These levels of use translate into post-grazing residual stubble heights of three to four inches for most grasses and sedges, but two inches for Kentucky bluegrass.

Providing an alternative source of drinking water will usually keep livestock from congregating on streambanks and shorelines. Herding livestock to upland areas can be effective on larger acreages. Supplemental salt, minerals, or feed also can be placed strategically to lure livestock away from riparian areas, provided these supplements are located at least 300 feet from surface waters. Having access to a barn or shed will decrease the need for livestock to seek shelter near riparian shrubs and trees.

Fencing is often the most effective way to control riparian livestock grazing, especially on smaller acreages. However, fencing is not a cureall. A wellplaced fence can be invaluable, but a fence situated in the wrong place can make things worse by causing livestock to congregate in sensitive areas. Fencing is expensive to build and maintain, may inhibit the movement of some wildlife species, can interfere with human recreation, and may detract from aesthetics.

Ungrazed vegetative buffer strips (i.e., bands of vegetation adjacent to surface waters that remove contaminants from runoff before reaching surface waters) are not usually necessary to prevent livestock grazing from impairing water quality. One notable exception, however, is wherever large amounts of livestock feces and urine are being deposited in or immediately adjacent to surface waters. In these situations, fences should be built at least 10 to 20 feet away from streambanks or shorelines to enable buffer strips to filter contaminants from runoff.

So, can cows and other livestock coexist with fish? Absolutely — and the thriving riparian ecosystems and fish populations across Montana provide resounding proof! Continued success and improvement will require that Montana’s grazing land stewards continue to hone their skills and continue to implement livestock grazing BMPs that protect water quality.