Despite eco-migration, rapid urbanization and growth still cause soil erosion — Mongolia proves

5. Discussion Soil erosion is a surface process that is often accelerated by human activity. Between 2000 and 2010, the level of urbanization in Inner Mongolia had increased significantly, along with an increase in urban population, a decrease in rural population, an increase in GDP-2, and an expansion of the overall urban area. Soil erosion problems clearly declined in the ten-year period examined. A similar trend—of rapid urbanization and reduced soil erosion—obtained here was reported in Inner Mongolia [30]. Indeed, urbanization is known to have a positive influence on sensitive arid and sub-arid regions [51,52]. The growth of the total human population, especially of its rural population, put more pressure on agricultural land. About 679.65 km2 of grassland and 568.77 km2 of wetland were converted to farmland in Inner Mongolia from 2000 to 2010. The phenomenon has led to the acceleration of land desertification resulting in the increased risk of soil erosion [30,53–55]. It has been reported that with the development of croplands, the potential soil erosion increases by an estimated 17% [56]. Similarly, a potential overall increase in global soil erosion is driven by farmland expansion [57]. Without the targeted management of farming activities and well-planned conservation measures, an increase in the rural population could indirectly accelerate soil erosion [55,57]. By contrast, with an increase in the urbanization rate, more and more people leave rural life for the cities, where they become concentrated and engaged in non-agricultural work instead of prior agricultural activities (e.g., planting and grazing). This process could be called “eco-migration”, carried out from 1998, to reduce disturbance to soil and thus provide a favorable environment for natural ecosystem restoration to proceed [58,59]. Approximately 1427.93 km2 , 659.94 km2 area of grassland and farmland, respectively, were restored to forest and wetland (Table 1). From the perspective of demand, the economy’s development has placed enormous pressures on the scarce natural resources of Inner Mongolia, and this extensive economic development has led to greater demands for energy and resources, which is characterized by high energy consumption, large amounts of waste, and serious levels of pollution. From 2000 to 2010, about 2469.73 km2 area of other land was converted to urban land, the GDP-2 rate had improved by 29.66% and the GDP-1 rate had fallen by 64.87%; together, this indicates that the economic structure has been transformed, shifting in emphasis from agriculture to industry. The production of energy and the mining of mineral resources have been accompanied by the destruction of vegetation and the accumulation of waste materials [60]. Large areas of grassland, approximately 1754.03 km2 had been converted to urban land via transportation and excavation that have markedly disturbed local natural ecosystems. The soil erosion generated in just one year due to this activity would be the equivalent of the amount of natural, and even agricultural, erosion occurring over dozens of years [61]. The results of this study suggested that increasing the GDP-2 proportion of total GDP could worsen soil erosion. A study of the WuLanMuLun River, in the Shenfu mining area, indicated that sediment discharge had doubled after mining commenced, the erosion modulus of the mining area had increased by 15,000 t/km2 ·a, with a 14.965-million ton increase in the annual soil erosion loss [62]. In addition, heavy industry, mining, and construction not only directly influence the land surface through excavation and waste accumulation, but they indirectly further aggravate soil erosion through road transport and the consumption of resources and energy [63]. In general, the urbanization process is complicated. It may promote soil conservation by reducing the soil disturbance driven agricultural activity, as more people migrate to urban areas [32]. However, in contrast to that, secondary industries, especially those in mining, transportation, and construction, which all benefit from rapid urbanization, would have a side effect on soil erosion. Therefore, in the urbanization process in Inner Mongolia, the principles of urban planning should be determined before future construction, with the layout and form of the city optimized to make full use of the urban space. By making full and better use of the opportunities for the human population transfer created by urbanization and industrialization, adjusting the policy for registering urban households, reducing the economic dependence of farmers and herdsmen on ecosystems, and helping people to transfer successfully into urban centers, we could achieve enhanced ecological protection and restoration of land. To minimize the harm to soil that is generated from the development of secondary industries, and to reduce soil erosion while exploiting regional resources, it is necessary to adjust and upgrade the industrial structure, strengthen the management of resources, and improve the efficiency of resource utilization, while adopting a strategy of alternative resource use and environmental protection. Collectively, such action should work to enhance the sustainability of industry, maintain the quality of resources and the environment, and optimize the process of urbanization.