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Sustainable Development in Tibet Requires Control of Agricultural Nonpoint Pollution Xiuhong Wang* Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China gross output value of crop production has obviously increased and roughly equaled that of livestock production mainly resulting from increasing agrochemical inputs on limited croplands since 1993. The increase in the gross output value of crop production mainly relies on expanding the sown area of crops and increasing agrochemical inputs. National statistical data for the Xizang autonomous region and Qinghai province show that the sown area of crops on the plateau slightly increased from 1993 to 1999, decreased from 2000 to 2003, and increased from 2004 to 2012. However, agrochemical inputs generally increased from 1993 to 2012 (Figure 1). By using the 1993 statistical data as the base standard to compare the relative rate of increase among the agrochemical inputs and the sown area of crops, the order was plastic film > agricultural diesel fuel > chemical fertilizer > pesticide > sown area of crops. Thus, the increase in the gross output value of crop production has mainly depended on increasing agrochemical inputs on limited croplands. The input of chemical fertilizers generally increased from 1993 to 2012, especially after 2003. Inputs reached 143,000 tons in 2012, about 1.8 times that in 1993. More chemical he Tibetan plateau is the headwater region for the Yellow fertilizers were used for cash crops planted in fields near lakes River, the Yangtze River, and the Lancang River and has a and rivers. For example, in 2012, the average input of chemical downstream influence on about 40% of the world’s population.1 fertilizers in the Xizang autonomous region was 214 kg/ha; It is a region of rich species diversity owing to its unique however, it was 485 kg/ha in Lhasa (the capital city of the environmental conditions. Unfortunately, the plateau is also Xizang autonomous region), where most of the rivers and sensitive and fragilenot only prone to soil erosion and land populations are concentrated. Farmers usually input excessive desertification induced by overuse of alpine grassland but also nitrogen and phosphorus fertilizers with less diversity and prone to agricultural nonpoint pollution from increasing rudimentary technology, leading to nutrient imbalances, agrochemical inputs on limited croplands. inefficient use of chemical fertilizers, and the potential risk of To protect the capacity of the plateau to act as an “ecological agricultural nonpoint pollution.3 In addition, low potassium and security barrier” of land and water resources for China, controls zinc status in soils were intensified because of the continuous are urgently needed on total agrochemical inputs, and removal of crop residues for animal feed, and the increasing monitoring is needed to prevent agricultural nonpoint pollution proportion of livestock dung used for fuel rather than fertilizer.4 The input of pesticides had generally displayed a fluctuating in fields near lakes and rivers. An increase in the quality and upward trend, and the increase was especially evident from diversity of agrochemicals could be helpful to reduce 2003 to 2008. It reached 3,141 tons in 2008, about 1.4 times agricultural nonpoint pollution, and biological agricultural that in 1993. Pesticides were mainly used for cash crops. More materials should be widely used to reduce the side effects of pesticides had to be used due to their declining use efficiency agrochemicals. Furthermore, ecological compensation with and efficacy resulting from their low quality, less diversity and grain and cash on the plateau can be replaced with high repeated use over time. Some pesticides were left on crops and quality agrochemicals and biological agricultural materials. in soils, allowing some to seep into the ground or into nearby The potential risk of agricultural nonpoint pollution from lakes and rivers. High concentration levels of atmospheric increasing agrochemical inputs on croplands has been almost organochlorine pesticides were found in Lhasa, which was covered up by the risk of soil erosion and land desertification closely related to the improper use of pesticides.5 induced by overuse of alpine grassland on the plateau. This is Compared with chemical fertilizers and pesticides, the sidebecause that alpine grassland accounts for about 54.6% of the effects of plastic film and agricultural diesel fuel have been total plateau land area, while cropland is only about 0.5% of the total plateau land area, and traditionally, animal husbandry has been the backbone of the plateau economy.2 However, the Published: July 22, 2014
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© 2014 American Chemical Society
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dx.doi.org/10.1021/es503039g | Environ. Sci. Technol. 2014, 48, 8944−8945
Environmental Science & Technology
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Figure 1. Changes in sown area of crops and agrochemical inputs.
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underrated. The input of plastic film slightly increased from 1993 to 2005, but sharply increased from 2008 to 2012. It reached 6,481 tons in 2012, about 21 times that in 1993. The poor quality, low recovery rate, and low degradable rate of plastic film make it harmful to the ecology and environment of both local and downstream areas. In addition, extensive use of plastic film usually intensifies expansion of marginal croplands onto grassland, resulting in serious soil erosion. The consumption of agricultural diesel fuel also increased from 1993 to 2012, especially from 2009 to 2012. It reached 112,000 tons in 2012, about 3.6 times that in 1993. Mechanized farm work can liberate the local labor force and improve cropland productivity; however, the increased consumption of diesel fuel greatly contributes to environmental pollution. It is clear that agricultural nonpoint pollution can be largely reduced by limiting the quantity and increasing the quality and diversity of agrochemicals. Furthermore, the side-effects of agrochemicals can be weakened by using more biological agricultural materials. For example, organic fertilizer can be applied by returning crop residues and livestock dung to fields; the use of biopesticides together with crop rotation can control the occurrence of pests and diseases; straw pulp film can also improve soil hydrothermal conditions for crop growth; and extensive use of biodiesel in energy-saving machinery can largely reduce pollutant emissions. Agricultural nonpoint pollution can also be mitigated by reducing the proportion of livestock dung used for fuel, and avoiding expanding croplands onto grassland near lakes and rivers.
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REFERENCES
(1) Yu, C.; Zhang, Y.; Claus, H.; Zeng, R.; Zhang, X.; Wang, J. Ecological and environmental issues faced by a developing Tibet. Environ. Sci. Technol. 2012, 46, 1979−1980. (2) Wang, X.; Fu, X. Sustainable management of alpine meadows on the Tibetan Plateau: Problems overlooked and suggestions for change. Ambio. 2004, 169−171. (3) Hou, Y.; Dawazhuoma; Chen, G. The situation and countermeasure of using chemical fertilizers in Tibet. Tibet J. Agric. Sci. 2010, 32, 43−46. (4) Nicholas, G. P.; Samantha, P. P. G.; Liu, G.; Jin, T.; Murray, J. U.; Nyima, T.; David, R. C. Soils, crop nutrient status and nutrient dynamics on small-holder farms in central Tibet, China. Plant Soil. 2011, 348, 219−229. (5) Li, J.; Lin, T.; Qi, S.; Zhang, G.; Liu, X.; Li, K. Evidence of local emission of organochlorine pesticides in the Tibetan plateau. Atmos. Environ. 2008, 42, 7397−7404.
AUTHOR INFORMATION
Corresponding Author
*Fax: (+86)10-64851844. E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This study is supported by Natural Science Foundation of China (NSFC 41371531) and Director Fund of Institute of Geographic Sciences and Natural Resources, Chinese Academy of Sciences (2013SJ008). 8945
dx.doi.org/10.1021/es503039g | Environ. Sci. Technol. 2014, 48, 8944−8945
