Soil cover is subject to the influence of various types of erosion. Erosion is caused by local environmental conditions, such as strong winds, heavy rains, droughts, dissected relief, on the one hand, and anthropogenic factors such as ploughing of steep slopes, inappropriate land use, omission of pasture turnover, unsatisfactory irrigation, on the other.
Water erosion mainly results from heavy rainfall on the areas of dissected relief and bedrock soils that are not resistant to washout. This type of erosion is typical for pastures and rain-fed lands, as well as for lands of low hills and mid mountains, suitable for irrigation. Deforestation considerably contributes to the water erosion processes. According to expert estimates, 40-50% of soils are subject to water erosion.
Wind erosion (deflation) occurs mainly in regions with gray-brown and light-gray soils, where wind velocity is more than 10-15 m/sec. Strong winds destroy soil structure and carry away a humus, that results in the decrease of agricultural productivity. Wind erosion is mostly characteristic for the southern regions of Khatlon region and Syrdarya area of Sogd region.
Irrigation erosion occurs as a result of surface washout of soils and abundant irrigation. Over 80% of all irrigated lands, mainly newly irrigated lands (lands that have been irrigated for less than 30-40 years), as well as rocky and sandy soils, are subject to this type of erosion. As a rule, long-term irrigated lands are weakly eroded. The illustration of the first case could be the lands of Yavan, Dangara, Asht and Obikiik valleys, and other lands mastered after the 1970s. The irrigation of the Vakhsh Valley in Khatlon region and Khodjabakirgan in Sogd region illustrate the second case.
The most dangerous type of erosion is gully formation on newly irrigated lands and landslides. The reasons of gully formation and landslides are both natural and anthropogenic factors, such as irrigation of areas without considering natural properties of local soils. In Karategin Valley, from 200 to 1,800 hectares of lands are exposed to intensive gully formation, this process being intensified by forest cuttings and overgrazing. Gully formation processes actively develop on newly irrigated lands in Dangara, Yavan, Vose and Parhar regions; this type of erosion covers nearly 50 thousand ha.
The development of Yavan valley in the south of Tajikistan can serve as an example. Over 80% of gullies in this valley formed after the irrigation started in 1965. The total length of ravines and gullies here is 56 km, of which 45 km were formed in the recent period. Before the irrigation, the density of gullies had actually not exceeded 1 unit/sq.km, whereas now this indicator has increased to 40-50 unit/sq.km. Many gullies are 25 meters deep, and 100 meters wide. The valley is a center of numerous irrigation landslides and other adverse anthropogenic phenomena. All these processes cause essential economic damage to local irrigated lands and settlements.
As a result of erosion processes, the annual washout of soils all over the republic is estimated at 50 million tonnes of soil, including 1 million tonnes of humus.
The overgrazing in the Eastern Pamirs resulted in the replacement of mountain meadows with ecosystems consisting of thorn herbs and open desert herbal communities. A decline in productivity of droughty high-altitude pastures is observed everywhere.
The pastures of plain and foothill areas are also characterized by digression. The productivity of winter pastures, located in Dangara, Yavan, Shahrituz, Vose and Ura-Tube regions, has reduced from 500-700 kg/ha to 200-300 kg/ha. In the Asht area, summer pastures are choked up with uneatable plants and weeds. Winter pastures have completely degraded in some areas.
The poor state of the collector-drainage network in many agricultural regions resulted in a significant rise of groundwater level and deteriorating lands. The rise of groundwater level, including mineralized water, resulted in the degradation of gardens and vineyards in the Isfara, Asht and Khujand areas of Sogd region. Over 75 thousand hectares of lands are subject to weak salinization and 25 thousand hectares of lands are subject to moderate salinization. The area of lands with heavy salinization is 10 thousand hectares. More than 28 thousand hectares of irrigated lands in Sogd region (Kanibadam, Isfara, and Zafarabad) are subject to bogging.
Due to the large-scale erosion processes on irrigated lands, the agricultural crop productivity has decreased. Thus, the cotton crops productivity has decreased from 3,500 kg/ha to 1,600-1,800 kg/ha in Vose district, from 2,700 kg/ha to 1,200-1,500 kg/ha in Vakhsh district, from 2,500 kg/ha to 1,500-1,700 kg/ha in Sogd region.
All these factors have resulted in the decline of populationís living standards. Poverty and low income of the population have contributed to the negative consequences of land degradation and desertification.
Last update 03/03/2003