Soil

In the United States the health of wild places is often reflected in the quality of a region’s soil health. Flourishing food systems and ecologically intact landscapes require healthy soil. As a result, a new wave of attention is focusing on soil health and how heavy tillage, grazing and pesticide use have affected the land. Overly heavy cattle grazing caused much of the damage to soil and watersheds in need of repair. Yet despite the degradation caused by grazing, the beef industry is illogically calling for more grazing as the solution.

Biological crusts of the Earth, or “biocrusts” — the living skin of the Earth — are common throughout grassland ecosystems and play a critical role in ecosystem health and function. Biocrusts can decrease the germination of large-seeded annual grasses that are degrading grasslands and increasing fire frequency in grasslands and steppe habitats. By inhibiting annual grasses, biocrusts help the perennial grass species thrive. In arid landscapes, biocrusts cover the soil between the spaces in bunchgrass communities and keep other plants from germinating and competing for limited nutrients and water. The hooves of nonnative ungulates like cattle harm biocrust and are not only unnecessary but inhibit the ability of soil and vegetation to thrive

Clearing land for pasture or feed crops creates a mass release of soil carbon and a loss of natural carbon sinks. Agricultural soils often contain 25% – 75% less soil organic carbon than undisturbed ecosystems. This fact has led many in the conservation and scientific communities to call for a rewilding of lands where possible to restore ecosystem health and our global ability to mitigate climate change. Converting lands that aren’t very productive for growing food to forests and perennial land use is another option. A third is advocated by the livestock industry: using cattle to help sequester carbon. But soil organic carbon and aboveground sequestration is higher in undisturbed grasslands without livestock in many cases. In other words, while cattle can help sequester carbon, other options are often better at doing so.

Healthy soils are loose and well-aerated to allow for movement of water, nutrients, roots and insects. Cattle trampling causes compaction of soils and damages plant roots, which leads them to concentrate near soil surfaces, hindering plants from needed resources. Many studies that have reviewed the effect of hooves on soil infiltration have shown that a thousand-pound cow compacts soil, diminishing the space between soil particles, which reduces water penetration and increases water runoff. For example, a spring cow can weigh 1000 pounds, with 250 pounds distributed through each hoof, distributing weight to 300-500 pounds when walking. The pressure is intensified depending on non-rotational grazing, soil moisture, and location (cattle tend to gather densely by water sources, where moist soil worsens the compacting effect under the weight of herds of cattle). With a herd of 200 cattle, that creates a magnitude of pressure on the ground.

Just as native plants help protect ecosystems, provide shelter and reduce runoff, wind and water erosion is exacerbated by cattle eating vegetative cover. By eating vegetation to its roots, grazing cattle can also take a big bite out of the carbon sequestered in the soil. Lower soil organic carbon in the roots degrades soil quality, which worsens soil erosion. Although untreated manure and urine are often highlighted in building organic soil reserves and increasing water retention and structural stability, the opposite is generally true. The resulting stream degradation and manure contamination of waterways is further linked with erosion. 

Grazing cattle in pastures with high concentrations of manure can overwhelm plant life with nitrogen. Plants are able to take up a limited amount of nitrogen, but the high concentration in manure, and especially in urine, can harm the ecosystem. The effects of fertilizer, manure and urine on nitrogen cycling shows that nitrogen returned to the soil surface as urine or manure is lower than grass-clover pastures receiving no nitrogen fertilizer. Where a manure pile covers less than 1 square foot, a urine spot can cover 4 to 7 square feet, while the soil under each manure pile or urine spot may receive the equivalent of up to 500 to 1,000 pounds of nitrogen per acre. Where the nitrogen in manure is released more slowly than in urine, the latter takes a heavy toll on the health of local plant life.

Cattle grazing can also harm wildlife and wetlands by causing stream sedimentation. A study assessing the effects of grazing management on sediment, phosphorus, and pathogen loading of streams in cool-season grass pastures found cattle shedding disease (bovine enterovirus) into runoff, along with fecal pathogens (including bovine coronavirus and bovine rotavirus). For example, Arizona’s Verde River has been heavily damaged by cattle under the watch of the U.S. Forest Service, according to a report from the Center for Biological Diversity, which sued the Forest Service for allowing producers to endanger wildlife and violate contracts and management plans. Damage from cattle was found on nearly three fourths of 143 stream miles surveyed. 

While some management practices can reduce densely congregating of cattle on waterways, such ecologically damaging behavior is common in cattle and harder to manage with larger herds. Reducing herd sizes — along with other environmental protections — is key to a reasonable and resilient protection against stream sedimentation.

Agricultural practices that are considered “regenerative” focus on regenerating soil health, increasing biodiversity, and enhancing ecosystem integrity. Such practices aim to reduce climate change impacts by restoring degraded soil, sequestering carbon and improving water cycles.

One of the critical aspects of regenerative grazing is the use of cattle to restore soils (often degraded from the impact of cattle in the first place) and store carbon. Origins of these claims can often be traced back to Allan Savory and his theory of holistic management as the cure to damage caused by cattle operations. Savory is the founder of the Savory Institute and has claimed that cattle grazing is necessary to reverse climate change. More livestock grazing, this theory goes, will significantly reduce global greenhouse gases. While this overstated claim has received significant media attention, and led many well-intentioned food producers and advocates astray, it has been roundly debunked by scientists. Attempts to confirm or replicate Savory’s claims have failed, instead showing that holistic management is, at best, not scalable and, at worst, leads to declines in biodiversity and soil health.

Furthermore,  cattle are a leading contributor of GHG, in both methane and carbon. While it is true that significant amounts of carbon are stored in the soils of rangelands, the ability to capture and transfer additional atmospheric carbon to grassland soils is small. Most arid grasslands have low productivity, meaning minimal capacity to store new sources of carbon. 

In some ecosystems, soil crust disruption can contribute to biological regeneration — within limits. However, research shows the trampling and other behaviors of cattle can destroy soil crusts and negatively impact nutrient cycling, soil stability, and water infiltration, particularly in arid landscapes that did not evolve to support grazing from nonnative bovines. 

To compare the impacts of grazing on soil health, vegetation and biodiverse ecosystems, one might compare grazed land to one of the national parks where grazing has not been permitted to note stark differences in biodiversity. Often, pastures heralded as regenerated grasslands, for example, do not contain the biodiversity needed for a fully cycling ecosystem.       

Improving soil health and its ability to sequester carbon is good for everyone. Grazing proponents point to soil impacts from the trampling, pawing and wallowing of nonnative cattle on fragile western ecosystems and suggest that these impacts break up soil, incorporate seeds, and contribute to nutrient cycling by depositing nitrogen from urine and feces into the soil. While cattle grazing of well-managed and smaller herds in some regions and landscapes may have a role to play in the future of sustainable agriculture, it’s important not to overstate the science on grazing benefits for soil health nor downplay the harms, particularly to wildlife and watersheds, that large amounts of grazing cattle will inevitably create.  

It’s time to be realistic about cattle grazing impacts, acknowledging that the more environmentally beneficial methods only work at small scale and not in tandem with most western lands. Meanwhile, policymakers, researchers and producers can emphasize the need for widescale reduction in consumption so that smarter climate and environmental policy can produce more sustainable and resilient agriculture.