What ecological effect do cattle actually have on grasslands?
Grazing is actually very important for grasslands! Just like I prefer to eat pizza over hamburgers, grazers may prefer one type of plant over another. By eating their preferred meal, grazers give the less yummy plant a break so that the playing field becomes more even. Thus, grazers’ eating habits help maintain greater biodiversity on the plains. Grazers assist the ecosystems in other ways as well, such as through the cycling of nutrients (Blair et al.).
If grazing is so good, why do we regulate how much livestock can graze on public lands?
Like all things, grazing is good in moderation. Just as too little grazing would deprive the grasslands of much needed ecological benefits, too much or overgrazing can wreak havoc on a grassland ecosystem. The selective eating that is so good at intermediate intensity causes extinction and endangerment of plants at high levels, causing intense ripple effects throughout the rest of the food web (Blair et al.). Additionally, the nutrient cycling that cattle do so effectively at high volumes causes excess nutrient runoff that can lead to a wide range of downstream effects including algal blooms and dead zones (Center for Biological Diversity). Too many cattle can also lead to the compaction of soil, making it difficult for plants to grow roots. Thus fewer plants can survive in compacted soil and the rich topsoil that they would have been keeping in place is now free to blow away with the wind.
So, what do we do?
Effective management is the key to maintaining grassland biodiversity. We must find the sweet spot where we are grazing just enough cattle to take advantage of the economic goods and services that grasslands provide for humans, while not grazing so many cattle that the grasslands are suffering biodiversity loss (Bureau of Land Management).
“Grassland Ecology” by John Blair, Jesse Nippert, and John Briggs
Fact Sheet on the BLM’s Management of Livestock Grazing by The Bureau of Land Management
Grazing by Center for Biological Diversity