The art and science of rangeland grazing

Rangeland management involves assessing soil types, vegetation composition, land use history and other variable environmental conditions, and then and working with lessee ranchers or permittees on each season’s grazing schedule.

 Grazing livestock on native rangeland is a high-profile issue—especially grazing on public lands. Some say that livestock are to blame for degradation of natural resources. Others say that livestock grazing improves range by reducing dead grasses and keeping invasive non-native plants in check.

So which is it? And the answer is—it depends.

Over-grazing is a function of timing—number of animals, grazing duration, and the condition of the lands. Range can be grazed heavily for short periods of time under the appropriate conditions, and remain healthy; however, that level of grazing is not sustainable for long periods. If extreme grazing occurs in a single year, it is unlikely to degrade if appropriate recovery time is allowed (possibly multiple growing seasons).

Decisions regarding rangeland ecology are based in science. They consider environmental conditions such as soil types, moisture regimes, vegetation composition, invasive species, land use history, current weather and more. In Eastern Washington, our limiting factors for vegetation communities typically are precipitation and soil types—lighter sandy soils versus clay or heavy soils, and everything in between. Historical overgrazing in some areas also has negatively affected some state trust lands. It takes much longer to bring an ecosystem back to health after it has crossed that threshold into a severely degraded state in which invasive annual plants dominate.

However, nature is too dynamic to limit decisions to a hard and fast set of protocols year after year. This is where rangeland management becomes both a science and an art. The art involves assessing all these variable conditions and working with the lessee ranchers or permittees on the season’s grazing schedule.

What then determines the timing to start grazing livestock, and for how long? DNR writes a flexible grazing schedule in the lease agreement to allow for annual environmental changes. The key factors are the soil moisture conditions and determining when key species are able to sustain and recover from grazing. Soils need to have dried out enough to not risk compaction from livestock, and dominant forage species need to have developed enough photosynthetic material to allow recovery from grazing.

As an example, spring 2011 conditions in the Columbia Basin resulted in a grazing season that was about three weeks behind an “average” year due to later than normal precipitation and cooler temps. If a specific turnout date were required by the lease agreement, grazing could occur when there is very little new growth on the range, or the soils too wet and vulnerable to damage, resulting in livestock grazing below the potential production levels of that year or causing damage. Having a flexible schedule allows timing for maximum livestock benefits, and will still allow enough recovery time for vegetation.

And for early season grazing, research shows that use levels of less than 50 percent have little effect on root systems. Often, at flowering, distinguishing which plants have been grazed early is nearly impossible because they have recovered completely. Early season grazing also prevents livestock from grazing when the plants are at their most vulnerable stage, before flowering and seeds set. This is why we have strict standards for grazing during this critical period—only on one out of every three years.

This discussion is just the tip of the information iceberg when it comes to grazing livestock on rangeland. A balance of science and an understanding of the ecological driving mechanisms are required when planning a grazing strategy. DNR, in partnership with our lessees, strives to maintain mutually beneficial relationships resulting in healthy rangelands and good stewardship of state trust lands for current and future generations.

By Mike Johnson, Grazing Lands Manager, Southeast Region