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The creation of farmland by gully filling on the Loess Plateau: a double-edged sword Zhao Jin* State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, 710075, China to create farmland on the Loess Plateau” in 2010. The project aims to create 4.0 million ha of farmland in gully channels between 2011 and 2020, and the total investment has reached 30 billion Renminbi. Currently, the project is performing experiments in Yan’an city, the so-called Red Capital of China. Briefly, the approach of filling gullies to create farmland involves removing soil from the surrounding hills and using this material to fill gully channels. The flat fields created in the channels are used for cultivation and ultimately increase the farmland area within the Loess Plateau. Although the gully filling project has received support from the Chinese central government and recently Liu et al. analyzed its benefits,5 the project is controversial among Chinese geological, ecological, and environmental scientists. The focus of this controversy includes four aspects. First, the feasibility of the gully filling project has been questioned. The gullies of the Loess Plateau are generally deep, with depths of 100−300 m; filling soils in the deep channels and building dams to retain the sediments require huge amount of work, and therefore many geo-engineering scientists doubt the feasibility of the project construction. Second, it is possible that gully filling will lead to more significant disasters. The Loess Plateau is formed by he “Grain for Green Program” (GGP) is the largest and Quaternary loessial dust deposits that are poorly structured and most acclaimed ecological program since the founding of highly susceptible to erosion by water; thus, gully filling can the People’s Republic of China in 1949. The program is increase the frequency of significant disasters, such as dam intended to increase vegetation cover, combat land desertificabreaks and landslides. Third, gully filling projects require tion, and improve the eco-environment. The Loess Plateau is significant investments, and it is unclear whether the investexperiencing the most extensive soil erosion in China and is the ment for filling gullies can be balanced by the income from top-priority area for implementation of the GGP. Based on farming the cropland created by the project. Fourth, it has been rigorous scientific research, Loess Plateau croplands that have a questioned whether gully filling will damage the environment slope greater than 15° are the target areas for the GGP and 1 and result in more extensive soil erosion; the filling of gullies include an area of 2.52 million ha. Based on a per capita arable requires the excavation of soil from the surrounding hills and land demand of 1.5 mu (0.1 ha), the potential area for GGP 2 will likely damage the vegetation and stability of hill slopes. implementation is limited to 2.36 million ha. However, 4.83 I believe that gully filling to create farmland on the Loess million ha of cropland have been converted to forest and Plateau is a double-edged sword. The Loess Plateau is now grassland on the Loess Plateau between 2000 and 2008, which facing the dilemma of GGP expansion and grain shortage. The is double the limitation area for GGP.3 Although the GGP on filling of gullies to create farmland might serve as an important the Loess Plateau has been met with a chorus of praise for its measure to solve certain problems. However, gully filling is successes, which include increased vegetation cover, decreased likely to create many types of environmental problems, such as soil erosion, and an improved eco-environment, the program geological disasters, ecosystem disruption, and soil erosion. At has also resulted in socioeconomic problems, such as a present, we must find a balance between the positive and substantial decrease in farmland and a critical grain shortage.4 negative impacts, eliminate the negative effects as much as Currently, balancing the population’s needs, grain supply needs, possible, and evaluate case studies to improve the gully filling and environmental needs requires greater consideration. project. In recent years, Chinese scientists and government officials have noticed problems induced by the large-scale implementation of the GGP on the Loess Plateau. Shaanxi province, a Received: December 3, 2013 province in northern China that includes 12.68% of the Loess Accepted: December 17, 2013 Plateau area, developed a program titled “Plan for filling gullies Published: December 26, 2013
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dx.doi.org/10.1021/es405392c | Environ. Sci. Technol. 2014, 48, 883−884
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Figure 1. The excavation of soils from the surrounding hill slopes has damaged the slope environment and exacerbated landslides.
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In June and July of 2013, Yan’an city of Shaanxi province, the main area in which gully filling has been implemented, suffered heavy rainfall. The resulting flood disaster provided an opportunity to test the feasibility of the project and evaluate existing problems. Through field investigation, we found the following: (1) a well-designed drainage system is the primary factor that guarantees the safety of the project; otherwise, water logging and dam breaks will seriously affect the engineering; (2) the filling soils are generally excavated from the surrounding hill slopes, which has damaged the slope environment and exacerbated soil erosion and landslides (Figure 1); and (3) the collapsibility of the loess soils has directly led to dam instability, and existing trial dams are at a high risk for failure. To address the aforementioned problems, I suggest the following: (1) scientific design of drainage systems to improve flood discharge; moreover, reservoirs, which can retard floods and conserve water resources, should be considered in the upper gully channels; (2) scientific design of soil excavation sites and reduction of damage to the hill slopes; (3) improvement of standards for the construction of dams and the reduction of dam break risk; and (4) a decrease in the engineering scale and an increase in the quality of the farmland that is created when investments are lacking. Shortsighted increases in the scale of engineering and decreases in the quality of created farmland should be forbidden.
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REFERENCES
(1) Tang, K. L.; Zhang, K. L.; Lei, A. L. Critical slope gradient for compulsory abandonment of farmland on the hilly Loess Plateau. Chin. Sci. Bull. 1998, 43 (2), 200−203. (2) Yang, Y. Z.; Feng, Z. M.; Zhang, P. T. The scale of land conversion and its effect on the grain production in Loess Plateau Area. J. Beijing Forest. Univ. (social sciences) 2005, 4 (1), 58−63. (3) Lü, Y.; Fu, B.; Feng, X.; Zeng, Y.; Liu, Y.; Chang, R.; Sun, G.; Wu, B. A policy-driven large scale ecological restoration: quantifying ecosystem services changes in the Loess Plateau of China. PLoS ONE 2012, 7 (2), e31782. (4) Feng, Z. M.; Yang, Y. Z.; Zhang, Y. Q.; Zhang, P. T.; Li, Y. Q. Grain-for-green policy and its impacts on grain supply in West China. Land Use Policy 2005, 22, 301−312. (5) Liu, Q.; Wang, Y. Q.; Zhang, J.; Chen, Y. P. Filling gullies to create farmland on the Loess Plateau. Environ. Sci. Technol. 2013, 47, 7589−7590.
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The authors declare no competing financial interest. 884
dx.doi.org/10.1021/es405392c | Environ. Sci. Technol. 2014, 48, 883−884
