Page 24 - Soil Degradation, Conservation and Remediation

1.5 Global Arable Land 9

from the assessment. (2) Crop performance and response to management are empha-
sized. They depend on soil and climatic conditions. (3) Irrigation is not considered in
this analysis. (4) Crops other than food crops are not considered. (5) Productivity is
a function of management. For purposes of evaluating the response to management of

the inherent land quality classes, the levels of input as defined in FAO ( 1976 ) are used.
(6) Assessment of resilience is empirical, as there are few measurements of resilience
available (Greenland and Szabolcs 1994 ). (7) The integrity of the environment and a
rational balance between agricultural use and environmental management (Tinker
1998 ) are important considerations. (8) A general notion of risk is included. Though
some values are given, these are to indicate magnitudes rather than absolute numbers.
Class I lands or prime lands occur in the USA, Argentina, Uruguay, southern

Brazil, Europe, northern China, and South Africa. Such lands are not found in the
tropics. Tropical soils are generally of low productivity. Class II and III lands are
extensive in the tropics and in the temperate areas. Most of these lands are under
some form of agriculture and irrigated, when possible, in the semiarid parts. Only
about 3.1 % of the global land surface can be considered as prime or Class I land.
Along with Class II and III lands, the 12.6 % of land represent the total land area that
is generally free of constraints for most agricultural uses. They are not equally spread
around the globe. A larger portion of these soils are in the temperate countries of the
world. Class I and II lands generally have good resilience and are highly productive.
They are benefitted from conservation technologies that are directed to preserving

the favorable attributes. Many countries have very few, none of either Class I or II
lands, or have utilized all available I, II, and, III lands and consequently have to use
more inferior lands. A major part of Class IV, V, and VI lands, particularly the Class
V lands, are in the tropics. In the Amazon basin, Central Africa, and Southeast Asia,
these form large tracts of forests. Class IV, V, and VI lands occupy a signifi cant part
2
of the earth’s surface (36.8 million km ) and also support more than 50 % of the
world’s population. Class IV or poorer quality lands may be managed with high
inputs and can be made productive (Buol and Eswaran 1994 ). From a sustainability
point of view, Classes VII, VIII, and IX are not suitable for agriculture.
Eswaran et al. ( 1999 ) estimated that the total global land area suitable for cultiva-
2
2
tion is 60.2 million km . WRI ( 1997 ) estimated that about 49.77 million km were
under cultivation in 1995. This suggests that the amount of globally available land
2
is only about 10 million km for future cropping, forestry, and for other uses. The
percentage of cropland in Asia, Africa, South America, North America, and Europe
are 15.2, 6.3, 6.0, 13.0, and 6.0, respectively. The proportions of pasture in the cor-
responding regions are 20, 22, 14, 08, and 23 % (WRI 1997 ). Figure 1.2 shows area
of land under different quality classes.

1.5 Global Arable Land

The world population up to July 2009 became 6.79 billion, and the global arable land
area is estimated as 1.351 billion hectares (Anonymous 2009 ). Arable land per capita
on a global basis stands at only 0.20 ha, and according to Eswaran et al. ( 1999 ), per