Revised 7 January 1997
Remove all of the fences on public lands leaving no trace of their existence (no fence, fence posts, or holes in the ground) and about 75% of those fence lines could be located to within 10 centimeters of the actual fence line. How? What I call "the fence line effect". The fence line effect is quite simple really. The grass is greener on the other side.
Fences keep cattle from being able to eat the grass on one side of the fence. This has striking consequences. On the side of the fence with cows, there is often a lot of bare ground interspersed with clumps of scrub grass, while the side without cows is a developed grassland with grass sometimes reaching knee height or taller. Using this disparity, it is possible to locate fence lines from as far as 80 km (50 miles) away when visibility permits.
This is important because it powerfully depicts the destructiveness of cows in arid climates. Unlike elk and deer, cows will remain in one general location for long periods of time. Because of this, they over-forage areas. Basically, cows will stay in one spot until they have eaten everything that is edible there, then move on. This translates to cattle having a large (negative) impact on those areas. Because of the extensive loss of vegetation, the soil is much more prone to erosion. Erosion that starts in these areas almost invariably spreads beyond the area directly effected by the cattle. Anyone who knows about the "Great Dust Bowl" in the Midwest knows about the dangers of soil erosion.
(NOTE: A derivative of the fence line effect is that there would be no need for fences on within tracts of public land if there were no cows on those lands.)
Since the fence line effect is my own little concept, it is not covered by anyone else that I know of, so a refutation of it isn't possible at this point. If you would care to write a rebuttal, feel free to send it to me and I'll post it here.