NOTE: The notation (su3) means that the data is used in the document analyzing the sustainability of the productivity of the world's food, fiber and water supply systems. (See elsewhere in this website.)

(Sections (6-A), -B) and -C) define terminology and units used below.)

What most people don't realize is that much (e.g. 50% in Africa's Sahel) rainfall comes from moisture that evaporated from soils and plants further upstream in weather-flow patterns, rather than from oceans. Hence loss of vegetation from over-grazing and loss of water-holding capacity from soil erosion produces less evaporation and hence less rainfall further down-stream. This creates a downward spiral of over-grazing causing less precipitation causing less grass-growth causing further over-grazing - a positive-feedback loop.

Human population pressures on land and government subsidies are causing higher-quality (higher-rainfall) grazing lands to be converted to low-quality croplands (a primary reason for the increasing wind erosion on croplands); lands normally considered to be shrub desert are becoming low-quality grazing lands, and forests are being converted to grazing lands at 600,000 km²/ decade. Most of this is tropical forestland. These tropical grazing lands last for about 8 years before they must be abandoned for 20-30 years to restore soil nutrients. Grazing lands (grasslands) are typically a factor of five less productive, in terms of dollar-value of human-food production, than rain-fed croplands. This is due mainly to the greater aridity of grasslands and also to the fact that human stomachs can't digest lignocelluloses (grass etc.), and ruminants can convert lignocelluloses into high quality protein that humans need, but feeding humans via the intermediary, livestock, is a low efficiency (10-20%) process.

The world's natural environment is deteriorating in numerous ways. But few of these ways can even begin to compare in scale to the degradation of the world's grazing lands. The world's rivers that drain grazing lands are choked with sediments that flow down the arroyos and gullies running through active and abandoned grazing lands and into streams (and former streams) whose riparian habitats bear little resemblance to their pre-grazing days. Sediment per unit drainage-basin area of these rivers is typically several times that from average rivers. Grasslands that aren't overgrazed lose topsoil at a gross rate of about 100 tonnes/ km²/ year - about the rate of topsoil creation on grass lands. Topsoil erosion characterized by phenomena like gullies and arroyos lose soil at typical rates of 40,000 tonnes/ km²/ year, though as significant portion of this is subsoil. Typical grassland topsoil inventories are on the order of 400,000 tonnes/ km².

Some grazing lands have been overgrazed for centuries; many are former grasslands that have been reduced to barren wastelands populated, at best, by toxic and inedible grass and shrubs. The great majority of the most arid rangelands, where precipitation is 10-30 cm/ year, have been moderately to severely overgrazed for 50+ years. The UNEP Global Assessment of Soil Degradation Survey reveals that 12 million km² (11% of the Earth's vegetated land) have been seriously degraded since 1945 (including a loss of 1 million km² to deserts). Overgrazing by livestock accounts for 35% of this degraded land. The rate of abandonment of dryland due to degradation is 0.9-1.1 million km²/ decade. Degradation rates seem to be accelerating, particularly in "developing" countries.

Utilizing the last few bits of unused grasslands, savanna and shrub desert doesn't change the picture significantly - nor does distribution of animal products more "equitably". Vegetarianism has been examined in some detail, but doesn't get us very far because most grazing lands cannot function as productive croplands, and wind erosion can wipe out this productivity in a few years. Converting forest land to grazing land reduces forest productivity, and causes floods that can destroy existing croplands and grazing lands - besides opening the possibility of reducing the non-soil biomass of the Earth's land surface by over 50%.

The scale of grazing-land degradation has become so extreme that the word "desertification" has been devised to describe mainly it. Grazing animal populations tend to expand in parallel with human populations, doubling every 5 decades. Carrying capacity of grazing lands decrease in parallel with topsoil loss. Topsoil losses increase with increased bare-soil and water-runoff. Runoff increases with soil compaction by animal hooves. Grazing land degradation rates are at least proportional to the difference between grazing-animal population and carrying capacity. Hence degradation rates must continually accelerate until action is taken. "Free-market economics" offers no solution to the problem because:

• So many costs are not internalized;
• There are so many government subsidies that work in the opposite direction of cost-internalization,
• "Discounting" of future harvests of natural resources is fully accepted practice in economic circles

Replacement of nutritious grasses by toxic and inedible plants as a result of a combination of "globalization" and overgrazing should also be viewed as part of the overall grazing land degradation process.

Even in the US, where large-scale over-grazing is only about 14 decades old, the US SCS estimates that less than 50% of the West's original rangeland topsoil remains. In 1980 the US Dept. of Agriculture estimated that the vegetation on more than 50% of all western rangelands was deteriorated to less than 40% of potential productivity, and to less than 60% of potential productivity on more than 85% of these rangelands. Things are even worse in riparian (stream-side) zones on US rangelands. These zones typically represent 2-5% of rangelands but supply up to 80% of forage used by cattle. Riparian zone losses on US rangelands fall in the range of 60-90% of original inventory. In Africa, centuries of overgrazing have converted most rangelands to annual grasses that are largely unpalatable.

The politics of grazing land degradation is equally depressing. Much of this degradation would not occur if it were not government-subsidized. Most information on this topic comes from the US, but what little additional information is available indicates that grazing-land politics are much the same the world over. Numerous books have been written on the subject, but perhaps none more recent, complete and compelling than Ref. (91J1). No law outlaws overgrazing, or its side effects, on private rangelands, even though US society endures billions of dollars in annual costs inflicted by erosion and other problems resulting from overgrazing. Western US grazing interests, even though few in number, dominate western politics through "cowboy mystique" and "campaign contributions" and get whatever they want in national politics by horse-trading.

Public land grazing is only a little better than private land grazing even though it would be expected to be worse due to the fact that public grazing lands are more arid than private grazing lands. Any public land manager can easily get himself fired (as many have) by suggesting too openly that the barren wasteland in his charge might violate policies and laws against overgrazing. Recent proposed legislation argues that such public land managers should be liable to be sued personally for making such suggestions, regardless of how truthful the allegations are, or how timidly they are made. And it's not just a matter of power-corrupted ranchers. The history of public-land grazing in the western US is filled with examples of massive government bungling and incompetence that have often forced over-grazing on ranchers even when ranchers found it distasteful (Ref. (94O1)).

Absolute power corrupts absolutely, so it's little wonder that western US ranchers should push for more than just "keeping government off their backs". Over the decades they have been able to extract massive subsidies from federal, state, and local taxpayers. The most recent estimate (91J1) is that taxpayers subsidize the average public-land-grazed cow by $400-$800/ year (perhaps $1/ lb. of beef). Privately-grazed cattle may draw somewhat less. Public-land ranchers make something on the order of 2-4% return on their investment, so clearly, much public-land ranching would probably not exist as an economically viable enterprise were it not for taxpayer-financed subsidies. Australian and Brazilian ranchers also receive subsidies for desecrating public land.

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