If only you, and the teabagger, knew what you were talking about:
http://www.fao.org/docrep/t0389e/t0389e02.htm
Civilizations began where farming was most productive. When farm productivity declined, usually as a result of soil mismanagement, civilizations also declined - and occasionally vanished entirely.
Of the three requisites for a thriving civilization: fertile soil, a dependable water supply and relatively level land with reasonable rainfall which would not cause erosion, it is likely that the third factor was most important, and evidence is mounting that soil degradation has toppled civilizations as surely as military conquest. In countries bordering the Mediterranean, deforestation of slopes and the erosion that followed has created man-made deserts of once productive land. Ancient Romans ate well on produce from North African regions that are desert today.
A recent study of the collapse in Guatemala around 900 AD of the 1700 year-old Mayan civilization suggests that it fell apart for similar reasons. Researchers have found evidence that population growth among the Mayans was followed by cutting trees on mountainsides to expand areas for farming. The soil erosion that resulted from growing crops on steeper and steeper slopes lowered soil productivity - both in the hills and in the valleys - to a point where the populations could no longer survive in that area. Today only empty ruins remain.
The same process of soil degradation which destroyed civilizations in the past are still at work today.
Firstly, billions of tons of soil are being physically lost each year through accelerated erosion from the action of water and wind and by undesirable changes in soil structure.
Secondly, many soils are being degraded by increases in their salt content, by waterlogging, or by pollution through the indiscriminate application of chemical and industrial wastes.
Thirdly, many soils are losing the minerals and organic matter that make them fertile, and in most cases, these materials are not being replaced nearly as fast as they are being depleted.
Finally, millions of hectares of good farmland are being lost each year to nonfarm purposes; they are being flooded for reservoirs or paved over for highways, airports, and parking lots. The result of all this mismanagement will be less productive agricultural land at a time when world population is growing and expectations are rising among people everywhere for a better life.
