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Sustainable Agriculture: The Food Chain Chapter j 24 509

chemical and biological contamination of underground pure water). In addi-
tion, the creation of such negative externalities is not internalized in current
irrigation cost (often set on the simple need to cover the service and delivery
costs).
Moreover, evidence of the negative consequences of high intensive irri-
gation is the increase of marshlands and soil salinization. It is estimated that
about 30% of irrigated land is affected by these two problems in a more or less
extensive way; progressive salinization of irrigated areas is provoking the
reduction of usable land with an increase of 1%e2% per year (FAO, 2002).
The effect of water on the soil is strictly influenced by water management
actions. Increasing erosion effects are evident in many areas, and erosion is
one of the major factor causing loss of both organic matter and fertile soil.
Estimates indicate a yearly loss of 12 million hectares of agricultural land due
to soil degradation, which equals a loss of 20 million tons of grain (UNCCD,
2011).
Erosion is still one of the most critical concern with respect to climate
change due to the intensification of heavy rain phenomena. Some of the
world’s most important agricultural districts are located in megadeltas where
salt water intrusion and rising level of seas will become a severe threat for food
production (Beddington et al., 2011).
Climate change is, moreover, influenced by human agricultural activities,
and among others animal husbandry is the most critical. Agriculture as a whole
generates approximately 20%e35% of greenhouse gas (GHG) emissions
(IPPC, 2001) and 40%e50% of the total anthropogenic emissions of CH 4 and
N 2 O (up to more than 80% according to some authors; Smith et al., 2008).
Leaving aside the solutions that rely on abatement of GHG emissions by
means of a reduction of livestock and those related to research effects in the
field of animal diet and breeding that are yet to give consistent outcomes, the
most effective managing option to be adopted is the concentration of hus-
bandries. This may allow to manage the housing and storage activities in a
closed environment and apply “end-of-pipes strategies” to treat wastes and
mitigate the emissions.
This is the most reliable choice if considering the consequences of a
change in the diet. Given the current genetic value of animals, alteration of
feeding protocols would determine a lower production per capita; accordingly
a larger number of animals would serve to satisfy the market demand, and
eventually the production of GHG would increase.
Different strategies to limit the production of GHG also present strong
implications on other relevant aspects of agriculture. One of the most invoked
solutions with respect to food safety and environment-friendly cultivation
practice is organic agriculture. However, organic agriculture requires a higher
use of manure and slurry, which on the other hand increases the soil emissions
of CH 4 and N 2 O. Extensive agriculture, in contrast to intensive agriculture, can
contribute to lowering the emission of CH 4 (thanks to the grassland diet) but at