Ecological Grazing Rejuvenates Native Prairie

Conservationists and cattle producers are working together to restore native prairie in the Last Mountain Lake National Wildlife Area in south-central Saskatchewan. Using an ecological grazing system, cattle from nearby pastures are helping to control the spread of exotic species and reintroduce a diversity into the ecosystem that existed years ago when bison roamed the prairies.

Environment Canada's Canadian Wildlife Service and Agriculture and Agri-Food Canada's Prairie Farm Rehabilitation Administration (PFRA) launched the project six years ago in response to a steady decline in habitat quality and biodiversity in the area. Left idle for decades, the land was succumbing to a takeover by alien plant species, which were choking out native plants and diminishing the variety of habitat available to birds, invertebrates, and other animals.

Scientists have recognized for several decades that both fire and grazing need to be reintroduced to the prairie landscape, since both played a significant role in its formation. Prescribed burning is used at Last Mountain Lake, but is costly and complex. Burning also requires specific weather and environmental conditions, so it is not always possible to carry out burns as planned or required.

Enter cattle. The ecological grazing project uses a system of rotational cattle grazing that biologists believe closely mimics historic bison grazing patterns, which were brief but intensive. When roaming herds happened upon the shores of a lake or river, they had a significant impact on the environment and then left, allowing the land to recover. This created the kind of open habitat many bird species require during molting and migration.

To replicate this bison grazing pattern, scientists modified the intensive rest-rotation grazing commonly used by farmers to allow pastures to recover from the pressures of livestock. Through the use of gates, electric fences, and other barriers to control their movement, cattle are directed to a specific site, allowed to graze for several weeks, and then directed to another site—making it possible to cover large tracts of land over the course of the season.

At Last Mountain Lake, cattle are left to graze long enough to reduce the existing growth to a height of two to five centimetres, and then moved. They are also only allowed access to a certain percentage of shoreline area in a given year. This treatment is applied three years in a row, and then the land is allowed to rest for three to six years.

This year, each grazing unit was divided in half, with half receiving the three-year grazing treatment and the other half being rested to allow litter and growth to build up. Creating a patchwork of smaller mosaics in this way will create more structural complexity and variability in the vegetation in a given area. This will provide more habitats for a wider variety of bird and invertebrate species, as well as assist in the pollination, flowering, and seed production of native plant species.

Environment Canada gathered data on bird and other species populations in each segment of the wildlife area before the cattle were introduced, and is closely monitoring the changes that have since taken place. So far, in areas that have been subjected to ecological grazing, the growth and seed production of exotic species, which are not accustomed to being grazed, have been eliminated or greatly reduced. This has helped level the playing field for native grasses, which originally took root when grazing and grass fires were a natural part of their lifecycle. These native species are gaining ground and may eventually take over in areas where the two now compete.

The PFRA also benefits greatly from managing the cattle and assisting with range monitoring. Access to the wildlife area's rangeland is helping to rest and rejuvenate over-stressed community pastures, as well as providing cattle with an abundant source of high-quality forage. Since the project started, calves grazed on the wildlife area have gained an average of 50 pounds more than those grazed on the community pasture.

In ensuring the long-term sustainability of native prairie habitat and biodiversity, and improving productivity for private cattle producers, the ecological grazing system project is creating a template for others to follow in managing our valuable natural resources.

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