What is biodiversity?
We often think of biodiversity in the context of animals, such as those that are threatened or endangered; however, biodiversity is equally important among plants, which are found throughout South Dakota and in particular, in our rangelands. Biodiversity is defined as the variability among living organisms, and quite simply can be thought of as “the spice of life.” It can exist at multiple spatial scales, which means we can talk about biodiversity at small scales (species) or extremely large scales (across an ecosystem or landscape). Biodiversity is not static and can vary over time. Without biodiversity, our ecosystems across the world would look and function very differently, including those found in South Dakota.
Why is biodiversity important?
Aesthetics, economics, and ecosystem services are some of the key reasons why biodiversity is important. Most people appreciate the look of a rangeland covered in perennial grasses such as Western wheatgrass that is scattered with purple coneflower, scarlet globemallow, spiderwort, and milkweed, to name a few. This heterogeneous mix of plant species creates visual interest and is great to enjoy during recreational pursuits such as hunting or hiking. At the same time, there are direct benefits to having a heterogeneous or multi-species mix of plants. Benefits include food and fiber production, and forage for grazing animals, which have tangible economic benefits. Less obvious, but equally important benefits include the functioning of key ecosystem services such as mitigating climate and moderating weather, soil creation and stabilization, nutrient cycling, and water storage and purification. Further, a diverse array of cover, nesting sites, and food sources allow for several species – and therefore, diversity – of wildlife to co-exist. Ultimately, biodiversity is important for ecosystems and should be included in things to consider in managing rangelands and has been recognized as such by the Society for Range Management.
How does grazing influence biodiversity?
Livestock producers have a direct role in maintaining and creating biodiversity in grassland ecosystems, by choosing when, where, and how long to graze. The relationship between biodiversity and grazing is complex and has been evolving ever since grazing animals were on the landscape.
Grazing can create positive and negative effects on biodiversity. For example, continuous heavy grazing and trampling can result in rare plants being outplaced from a system. Indirect effects of heavy grazing can be felt by wide-ranging vertebrates, such as predators and carrion-eaters (i.e. scavengers), that are sometimes jeopardized by heavy grazing. In contrast, the short-grass steppe ecosystems that are the result of heavy grazing pressure provide the mountain plover with nesting habitat. Thus, livestock grazing can enhance the conservation of particular species.
Finding the balance between seeing grazing as the means to an end (livestock production) and a tool to increase the production, biodiversity, and resiliency of grassland systems requires some practice. Ranchers can alter the time, intensity, and duration of grazing, rest period length, and type of livestock to create different vegetation heights, and the kind and amount of plants. Moderate grazing and trampling, for example, can increase plant diversity by decreasing the ability of one species becoming dominant. In contrast, heavy grazing can shift native, perennial grass rangeland into range that is dominated by short-grass species such as buffalograss and Kentucky bluegrass, as the heavy grazing pressure will have pushed out the more ‘sensitive’ native grasses like Western wheatgrass and allowed the more ‘tough’ and competitive shortgrasses to take over. At the same time, however, heavy grazing can be a tool to create biodiversity in other scenarios. If you have a pasture dominated by a cool season, introduced grass like smooth brome and you would like to increase the diversity of that pasture, you could graze that pasture heavy and early in the season to decrease its competitiveness and give native perennial species an edge. Grazing in this scenario will create gaps in the plant community, making light, moisture, and nutrients more available for species that emerge slightly later like Western Wheatgrass, helping them get established. Increasing rest periods can result in greater vegetation height but requires flexibility within your operation to accommodate this.
Why should you care about plant biodiversity?
We can dig deeper into why plant biodiversity is important by thinking of factory workers. In a car factory, for example, there are workers who do the engine installation, workers who put the hood on, workers who put the wheels on the car and so on. The big picture is this: the car is not made and cannot function without each of those workers doing their part. If the car ends up with only 3 wheels, it will not function the same as it would if it had all 4 wheels on. The car could maybe hobble down the road, but it won’t get too much further than a block, and if it needs to change direction, it can’t. The same can be said of grassland systems – without a multitude of individual plants, the system will slowly move forward and then stop. With a variety of plants – grasses, forbs, and shrubs – the system can continually evolve and respond to change, such as drought or wildfire. Whether or not a system can respond to change is up to the driver’s decisions; so, consider your management decisions as a producer in the grand scheme of your goals and see if there’s room to use grazing as a tool to increase the production, biodiversity, and resiliency of your rangeland.
References:
- Society for Range Management. Biodiversity of rangelands: An issue paper. Hidinger L, editor. Denver (CO): Society for Range Management.
- Derner, J.D., D.J. Augustine, and E.J. Kachergis. 2014. Cattle as ecosystem engineers. Western Confluence: Natural Resource Science and Management in the West. Issue 01: 10-13.
