Soil Renewal and Sustainability - Principles of Sustainable Soil Management in Agroecosystems - page 478

the growing world demand for food (Cassman et al. 2011). This demand will con-
tinue to grow, with projections that food production must increase 50% by 2030 to
meet human dietary needs (United Nations Secretary-General's High-Level Panel
on Global Sustainability 2012), meaning that yields will have to increase as the per
capita land area available for food production is steadily decreasing. Yields must
increase on already-degraded soil, soil that will experience increasing production
pressure, and with this pressure comes a high probability of continued and even
increased degradation.
Soil erosion is arguably the most important land degradation process associated
with farming. Pimentel (2006) and Lal (1995) estimated independently that globally,
10 million and 3 million ha, respectively, of cropland are lost annually due to soil
erosion. The total area of productive land destroyed by erosion since the beginning
of settlement agriculture may be as high as 130 × 10 6 ha (Lal 1995) or approximately
9% of today's arable land area. Continued erosion based on current estimated soil
degradation, and potential future accelerated erosion rates, have dangerous conse-
quences. The goal of this chapter is to address the role and implications of soil ero-
sion in light of estimated soil regeneration rates on sustained production such that
agriculture's ability to meet the future demand for agricultural products might be
sustained.
17.2 SOIL RESOURCES AND AGRICULTURE PRODUCTION
The implication of lost production due to soil degradation looms large. This is espe-
cially disconcerting because degradation often results from human choices regard-
ing land care and soil management. Humans also make choices regarding use of land
capable of producing agricultural commodities. Land use choice is often determined
by the market value associated with various potential uses of the property, especially
in more developed countries. Often, agriculture and crop production do not offer the
greatest financial return, at least in the short term, and therefore, agricultural land
is converted to uses such as urban development, housing, or roads/infrastructure.
Essentially, none of the converted agricultural land will be, or can be, recovered for
agricultural uses. The Food and Agriculture Organization (2002) estimates that 7%
of the world's agricultural land of 2002 will be lost to other uses by 2030.
The world's soil resource base suitable for food, feed, fiber, and fuel production is
fixed. That is, land area suitable for agricultural production, both farmed and poten-
tially farmable, is finite. Expansion of agriculture into unfarmed areas that have
acceptable production potential remains a possibility and a distinct probability con-
sidering growing global demand for agricultural commodities. Fischer et al. (2002)
indicated that about 57% of the world's rain-fed agricultural land with production
potential (considering existing technology) was being farmed in the mid-1990s. The
potential for expansion of rain-fed agricultural land to meet growing food demand
and to replace degraded/lost agricultural land seems reassuring; however, one must
look a bit deeper to gain a calculated understanding of what expansion of rain-fed
agriculture realistically means for potential increases in agricultural production.
This estimate of potentially farmable area is the gross expansion potential. From
this area, roads, communities, and other legally protected areas must be reserved,