Cows and Sand: Effects of Livestock Overgrazing
by Moses Seenarine 12/15/17
Worldwide, livestock overgrazing practices are substantially reducing many grasslands' performance as carbon sinks. Overgrazing occurs on 33% of all range-land, and often, marginal range-lands are used intensively when historically productive adjacent range has become overgrazed and unproductive. The cycle of overgrazing, soil degradation, topsoil erosion and loss of vegetation is rapidly expanding on all continents.
The chief ecological impacts of overgrazing are (i) the loss of biodiversity, (ii) irreversible loss of topsoil, (iii) strengthening of turbidity in surface waters, and (iv) greater flooding frequency and intensity. Overgrazing of pastureland leads to a decrease in long-term grazing productivity. In Botswana, for example, farmers' common practice of overstocking cattle to cope with drought losses made ecosystems further vulnerable and risked long-term damage to herds by depleting scarce biomass.
Globally, 70% of all grazing land in dry areas is considered degraded, mostly because of overgrazing, compaction and erosion attributable to livestock activity. Worldwide, overgrazing can be considered the major cause of desertification in arid dry-lands, tropical grasslands, and savannas. On top of that, in arid and semi-arid dry-lands around the globe, overgrazing is the major cause of desertification.
Placement of high densities of livestock on a grassland removes biomass at a rapid rate, which produces a series of accompanying effects. For instance, (i) the residual plants decline in mass density, and (ii) surface water infiltration is reduced. Then (iii) there is a dwindling away of fungal biomass that relies on grasses. Ground surface temperatures rise, which exaggerates the amount of (iv) evaporation and (v) transpiration, and this leads to (vi) a build up in aridity. In addition, overgrazing has a characteristic effect of (vii) reducing root depths. With impeded water uptake from the soil, a positive feedback loop of growth retardation is established.
At least 25% of the world's biodiversity lives underground where the earthworm is a giant alongside tiny organisms such as bacteria and fungi. These organisms act as the primary agents driving nutrient cycling, and they help plants by improving nutrient intake, which in turn supports above-ground biodiversity.
Removing livestock, and better soil and land management that supports healthy soil organisms can boost the soil's ability to absorb carbon and mitigate desertification. This could result in greater quantities of carbon being sequestered, thus helping to offset agriculture's own emissions of GHGs. A four-year survey of the northern China plains concluded that by reducing grazing pressure to half can deliver improved ecosystem services like lower GHGs and improved grassland composition. Early summer rest maintained the best grassland composition.
In the US, removing livestock from public lands would reduce CH4 discharges, with attendant benefits for climate mitigation. This climate action would also mirror federal nutrition policy, particularly the recommendation to eat less cow flesh. Much of the degraded environmental conditions on public lands and waters caused by grazing farm animals would end. This would enable improvement or even recovery of vulnerable areas. And, undertaking this policy shift makes fiscal sense by saving taxpayer dollars.
Excerpt from "Meat Climate Change: The 2nd Leading Cause of Global Warming," by Dr. Moses Seenarine.
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