Central Asia consists of the five former Soviet Republics of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan,which include a range of landscapes from mountains to steppes and deserts and is isolated by mountain ranges and the Caspian Sea. When Central Asia was part of the Soviet Union, much of the agricultural policies directed by the governments resulted in degradation of the dryland areas. Kazakhstan is the biggest out of these five countries, and its degradation status is relatively well-studied and is chosen here as a representative example to illustrate dryland degradation which occurs throughout the Central Asia region.
Dryland Degradation in Kazakhstan
The problem of dryland degradation is crucial for Kazakhstan (Almaganbetov and Grigoruk, 2008).Kazakhstan's drylands consist of 30 million hectares (~11.24% of total area) of sandy land and 34 million hectares (~12.74% of total area) of saline land. 179.9 million hectares out of 272.5 million hectares (66% of total area) are degrading, which is about the size of Missouri.
31.3% of total irrigated lands are salinized and all degraded arable lands have lost humus (Almaganbetov and Grigorukm, 2008).Humus increases the cation exchange capacity such that it reacts with the anions in the soil and thereby decreases soil salinity.
In a study conducted in central Kazakhstan, where extensive land was used for agricultural production during the Soviet Era, about 2/3 of the cropland was abandoned and the number of livestock dropped dramatically after the collapse of the socialist economic system in 1991. However, some places, particularly those located near large rural settlements, experienced an increase in anthropogenic impacts after the collapse of the Soviet Union through intensification of agricultural and grazing (Propastin and Kappas, 2008).
"About 70% of the agricultural lands of Kazakhstan are used as year-around natural desert and semi-desert pastures" (Karnieli et al, 2008).
Overgrazing and mismanagement of the rangelands in the Soviet era resulted in 60% of the Kazakh rangelands exhibiting some degree of degradation by 1980 and these practices are still having an impact today.However, some studies show that degradation caused by overgrazing has recovered. For example, in the Kyzylkum Desert, most of the grazing activities have decreased leading to recovery of the natural vegetation and rehabilitation of the land (Karnieli et al, 2008).
Exploration and exploitation of gas and oil reserves also contribute to land degradation. The increased use of heavy-duty equipment and vehicles damages the soil surface by compaction (Karnieli et al, 2008). After Kazakhstan became independent, the development of the gas and oil industry accelerated, particularly in the Ust-Urt Plateau where exploration and extraction is leading to land degradation.
The increase in planting water-demanding crops with inefficient water usage in semi-arid regions leads to soil salinization, soil and vegetation degradation, and the encroachment of sand into cultivated land through the activation of fixed or semi-fixed sand dunes. Sand encroachment problems are common in the Aral and Caspian Sea regions and the Hei and Tarim River basins. Large areas are used for cotton monoculture and cultivation of food crops that are water-demanding. This has been fueled by the advance in hydrotechnical infrastructure, along with population migration from rural areas and external economic factors (Geist and Lambin, 2004).
Modification of stream flow has also intensified dryland degradation, resulting in a reduction of pasture productivity.As a result of stream flow modification that has lead to more water use in irrigated farmlands, the Aral Sea is drying up and the surface and underground water quality has deteriorated (Serverskiy, 2004).
Under global climate change, it is predicted that the Central Asia region will be warmer and drier.The decrease in precipitation and increase in surface run-off are likely to exacerbate land degradation in the region (Thomas, 2008).
The region is facing an increasing problem of food security.Land degradation, coupled with a decrease in precipitation, is projected to reduce the food production. Especially for those people living in rural areas, whose livelihoods are dependent on the quality and functioning on the agro-ecosystems to provide them food, construction materials and fuel, land degradation is making them even more vulnerable to poverty (Thomas, 2008).
The decrease in vegetation and accelerated soil erosion cover as a consequence of dryland degradation is reducing the total soil carbon pool and accelerating carbon emissions due to (Lal, 2001). In this way dryland degradation will indirectly contribute to climate change with a potential positive feedback.
Invasive species are replacing the native, more salt-sensitive plants due to soil salinization in the Aral Sea Basin. The frequent occurrence of dust storms in the region is caused by dryland degradation and a rapid decrease in the waters of the Aral Sea. In 1987, the Aral Sea split in two and the salinity in the remaining water bodies increased by as much as 450 percent (Peachey, 2004; Serverskiy, 2004).
Dryland degradation decreases the number of wildlife species.According to Serverskiy (2004), in the Amudarya Delta near the mouth of Aral Sea, there has been an "abrupt reduction in the water-rat population, 6 species and subspecies of fauna disappeared, more than 20 species became rare, and about 30 bird species disappeared". Water leaching from irrigated areas reduces the water quality and exacerbates the degradation of the land. In addition, groundwater is contaminated by pesticides which causes a decrease in number of wildlife species (Serverskiy, 2004).
Changing the practice of water use is going to save water and increase agricultural yield.In Kazakhstan, changing from wasteful irrigation to alternate furrow irrigation has resulted in water savings of up to 30% and crop yield increases of 15-20% (Thomas, 2008).
Crop rotation can conserve soil and prevent degradation.Since independence, farmers in Kazakhstan have begun to practice various cropping systems and adopt new methods of land management aimed to restore degraded soils and ecosystems (Lal, 2001; Thomas, 2008).
The Central Asian region is adopting a range of technological interventions to reduce vulnerability to climate change by simultaneously preventing and reversing land degradation and sequestering carbon in drylands.In addition to using a more efficient irrigation practice, the farmers have been encouraged to replace the water-demanding crops by more drought and heat tolerant plant species to reduce salinization (Lal, 2001; Thomas, 2008).
Almaganbetov, N. and V. Grigorukm. 2008. Degradation of Soil in Kazakhstan: Problems and Challenges. In NATO Science for Peace and Security Series C: Environmental Security-- Soil Chemical Pollution, Risk Assessment, Remediation and Security. ed. L. Simeonov and V. Sargsyan, 309-320. Netherlands: Springer Netherlands.
Geist, H. G., and E. F. Lambin. 2004. Dynamic Causal Patterns of Desertification. BioScience (54-9): 817-829.
Karnieli, A., U. Gilad, M. Ponzet, T. Svoray, R. Mirzadinov and O. Fedorina. 2008. Assessing land-cover change and degradation in the Central Asian deserts using satellite image processing and geostatistical methods. Journal of Arid Environments (72-11): 2093-2105.
Lal, R. 2001. Potential of Desertification Control to Sequester Carbon and Mitigate the Greenhouse Effect. Climate Change (51-1): 35-72.
Peachey, E. J. 2004. The Aral Sea Basin Crisis and Sustainable Water Resource Management in Central Asia. Journal of Public and International Affairs (15): 1-20.
Propastin, P and M. Kappas. 2008. Spatio-temporal drifts in AVHRR/NDVI-precipitation relationships and their linkage to land use change in central Kazakhstan. EARSeL eProceedings, 7(1): 30-45.
Serverskiy, I. V. 2004. Water-related Problems of Central Asia: Some Results of the (GIWA) International Water Assessment Program. Ambio (330: 1-2): 52-62.
Thomas, R. J. 2008. Opportunities to reduce the vulnerability of dryland farmers in Central and West Asia and North Africa to climate change. Agriculture, Ecosystems and Environment (126): 36-45