World’s Soil Resources

In Tunisia, decades of open grazing in the Bou Hdma National Park have caused severe loss of perennials and
increased density of annuals (Belgacem, Tarhouni and Louhaichi, 2013). The study reported that grazing has
reduced total plant cover by 38 percent and the contribution of perennials by 72 percent, while annuals were
affected 100 percent. Overgrazing of rangelands generally causes replacement of highly palatable species with
less desirable plants. Along the sea coast of Egypt, overgrazing during the period from 1974 to 1979 decreased
the total density vegetation by more than 15 percent, mainly due to a decrease in some perennial herbs, while
at the same time the total cover increased by about 38 percent, due mainly to perennial shrubs and succulents.
Also in Egypt, vegetation on Mount Elba and the surrounding valleys has been reduced, and the resulting
increased runoff threatens the diversified natural plant communities in the valleys. Some of these plant
species are considered to be of high value as genetic resources as they are adapted to the desert conditions. In
Lebanon biodiversity is threatened by many factors, chief among them are erosion, urban development and
overgrazing resulting in dominance of xerophytes at the expense of other species (Zahreddine et al., 2007).
Rising levels of poverty in the Ramallah area of Palestine have led to most farmers (83 percent) turning to the
collection of medicinal plants for commercial use (Abu Hammad and Tumeizi, 2012).
13.3.7 Waterlogging
Waterlogging is a common constraint in irrigated areas of the region because of inadequate drainage. The
problem is exacerbated by the dominant heavy textured alluvial soils and by seepage from the conveyance
canals. Soil salinity, sodicity and water logging conditions have definite adverse impacts on soil productivity,
estimated to be of the order of 30-35 percent of the potential productivity. In many areas of the old Nile Valley
in Egypt, waterlogging has led to increased soil salinity and in certain areas to increased soil sodicity. In the
Siwa oasis, for instance, the rate of water table rise during the period 1962–1977 was 1.33 cm yr -1 . Subsequently,
the rate increased to 4.6 cm yr -1 and consequently subjected fertile soil to degradation (Misak, Abdel Baki and
El-Hakim, 1997).
Waterlogging has also become a serious problem on many farms in the United Arab Emirates due to poor
drainage caused by the presence of a strong and thick hardpan and by excessive use of irrigation water. In
addition, sea water intrusion in many areas reaches the surface and causes complete vegetation failure
(Abdelfattah, Shahid and Othman, 2008). In Tunisia, of the 410 000 ha of irrigated area, about 87 000 ha (22
percent) are affected in varying degrees by waterlogging. This hydromorphy affects most of the irrigated areas
in the valley of Medjerda, from Ghardimaou up to Kalaat Andalous, and also affects the majority of oases.
Overall, waterlogging affects 29-67 percent of irrigated areas in the north, 35 percent in the oases of Kibili and
Toezure, and to a lesser extent the plains of Dorsal and irrigated areas of Gabes and Cap Bon (14-20 percent).
It also affects some irrigated areas in the far north (Nefza, Sejnane and Mateur) and some irrigated areas of
the centre.
13.3.8 | Nutrient balance change
The problem of nutrient-constrained agriculture is particularly acute in the region. It is associated with land
use pressure and the consequent intensification of cropping systems and related soil degradation. Nutrient
depletion is increasingly affecting land productivity in the region. In Sudan, continuous cultivation over nearly
a century has decreased the base saturation percentage by 25 to 42 percent, indicating leaching with irrigation
water of soluble anions and cations down the soil profile. Soil degradation due to nutrient depletion in Sudan
is largely concentrated in the arid and semi-arid parts, particularly in southern Kordofan and Darfur, and in the
dry sub-humid and moist sub-humid zones of south-western Sudan. This soil degradation is clearly related to
agricultural activities and to deforestation.
Status of the World’s Soil Resources | Main Report Regional Assessment of Soil Changes
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in the Near East and North Africa