infertile land include: Droughts such as the "Dust Bowl" of the Great Depression in the US turned farmland into desert. Each year, arable land is lost due to desertification and human-induced erosion. Improper irrigation of farmland can wick the sodium, calcium, and magnesium from the soil and water to the surface. This process steadily concentrates salt in the root zone, decreasing productivity for crops that are not salt-tolerant. Rainforest deforestation: The fertile tropical forests are converted into infertile desert land. For example, Madagascar's central highland plateau has become virtually totally barren (about ten percent of the country) as a result of slash-and-burn deforestation, an element of shifting cultivation practiced by many natives. See also Development easement Land use statistics by country List of environment topics Soil fertility References External links Article from Technorati on Shrinking Arable Farmland in the world Surface area of the Earth Agricultural land