Chemistry Reference
In-Depth Information
appears to be a small effect of the recent sugar maple decline on the change in
nitrate export.
4
Food Security Implications of Forest and Soil
Responses to Global Change
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4.1 Anthropogenic Soil Degradation
Forest degradation and the resulting soil degradation are closely tied to the
major issues facing world food production in the face of global environmental
change. Because soil degradation is affecting crop productivity and contribut-
ing to malnourishment around the world,
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improving soil quality is essential
to maintaining life on earth.
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Soil health is a high priority listed by the
United Nations' Millennium Project hunger task force and the United States
Department of Agriculture reports that decreasing degraded soils and
increasing crop yields by 0.1% could reduce the number of starving people
by 5% in a decade. Global hotspots of degradation include central and
southern Asia, China, the Andes, the Caribbean, and the savannas of South
America.
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In 1991-1992, the International Soil Reference and Information Center
(ISRIC) developed a global database of human-induced soil degradation. Soil
degradation derives from increasing pressure on land to improve living
conditions, provide higher standards of living, or simply allow human survival.
Five human causes of soil degradation are: (1) deforestation or removal of
natural vegetation for agricultural use, roads, timber harvest or urbanisation,
(2) overgrazing, (3) inefficient agricultural practices, (4) overexploitation of
vegetation for domestic use, such as fuels and fencing (incomplete vegetation
removal is insufficient to prevent topsoil removal), and (5) bio-industrial
activities that lead to soil pollution.
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In a 2004 Science article, J. Kaiser
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gave an overview of global soil
degradation and its impacts on regional food scarcity. Soil degradation is given
as the main obstacle to reducing hunger in Africa and the cause of the current
devastation in Haiti. The previously forested landscape of Haiti has been
severely denuded until only 3% of the original forest cover remains. At least
one-third of the landscape has lost too much topsoil to be able to support
crops. In the 1930s, the USA temporarily experienced a similar plight when a
combination of poor land-management and drought contributed to a massive
loss of topsoil in the midwestern states. In China, the Loess Plateau, the site of
the fastest topsoil loss in the world, loses approximately 1.6 tons of loess each
year, and some lands in the lower Himalayas have totally lost the capacity for
food production. In sub-Saharan Africa, where farmers cannot afford
fertilisers, and crop residues and animal excrement are used for fuel, soil
fertility is quickly declining. In some parts of Africa, farmers traditionally
rested fields, but now land constraints are too tight. In the Middle East and
India, poor irrigation is leading to salinisation of soil, and in Australia the
