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Desertification in China: 1982-1999
Reference
Piao, S., Fang, J., Liu, H. and Zhu, B.  2005.  NDVI-indicated decline in desertification in China in the past two decades.  Geophysical Research Letters 32: 10.1029/2004GL021764.

What was done
The authors say they used a "time series data set of Normalized Difference Vegetation Index (NDVI) obtained from the Advanced Very High Resolution Radiometer (AVHRR) available from 1982 to 1999 (Tucker et al., 2001; Zhou et al., 2001), and precipitation and temperature data sets, to investigate variations of desert area in China by identifying the climatic boundaries of arid area and semiarid area, and changes in NDVI in these areas."

What was learned
Piao et al. report that "average rainy season NDVI in arid and semiarid regions both increased significantly during the period 1982-1999."  Specifically, they found that the NDVI increased for 72.3% of total arid regions and for 88.2% of total semiarid regions, such that the area of arid regions decreased by 6.9% and the area of semiarid regions decreased by 7.9%.  They also report that by analyzing Thematic Mapper satellite images, "Zhang et al. (2003) documented that the process of desertification in the Yulin area, Shannxi Province showed a decreased trend between 1987 and 1999," and that "according to the national monitoring data on desertification in western China (Shi, 2003), the annual desertification rate decreased from 1.2% in the 1950s to -0.2% at present."

What it means
Noting that "variations in the vegetation coverage of these regions partly affect the frequency of sand-dust storm occurrence (Zou and Zhai, 2004)," Piao et al. conclude that "increased vegetation coverage in these areas will likely fix soil, enhance its anti-wind-erosion ability, reduce the possibility of released dust, and consequently cause a mitigation of sand-dust storms."  Interestingly, in this regard, they report that "recent studies have suggested that the frequencies of strong and extremely strong sand-dust storms in northern China have significantly declined from the early 1980s to the end of the 1990s (Qian et al., 2002; Zhao et al., 2004)."  Hence, it would appear that the dreaded climatic change claimed to have been experienced by the globe over the latter part of the 20th century was either (1) not so dreaded after all or (2) totally dwarfed by opposing phenomena that significantly benefited China, as its lands grew ever greener during this period and its increased vegetative cover helped to stabilize its soils and throw feared desertification into reverse.

References
Qian, Z.A., Song, M.H. and Li, W.Y.  2002.  Analysis on distributive variation and forecast of sand-dust storms in recent 50 years in north China.  Journal of Desert Research 22: 106-111.

Shi, Y.F., Ed.  2003.  An Assessment of the Issues of Climatic Shift from Warm-Dry to Warm-Wet in Northwest China.  China Meteorology, Beijing.

Tucker, C.J., Slayback, D.A., Pinzon, J.E., Los, S.O., Myneni, R.B. and Taylor, M.G.  2001.  Higher northern latitude NDVI and growing season trends from 1982 to 1999.  International Journal of Biometeorology 45: 184-190.

Zhang, L., Yue, L.P. and Xia, B.  2003.  The study of land desertification in transitional zones between the MU US desert and the Loess Plateau using RS and GIS - A case study of the Yulin region.  Environmental Geology 44: 530-534.

Zhao, C., Dabu, X. and Li, Y.  2004.  Relationship between climatic factors and dust storm frequency in Inner Mongolia of China.  Geophysical Research Letters 31: 10.1029/2003GL018351.

Zhou, L.M., Tucker, C.J., Kaufmann, R.K., Slayback, D.A., Shabanov, N.V. and Myneni, R.B.  2001.  Variations in northern vegetation activity inferred from satellite data of vegetation index during 1981 to 1999.  Journal of Geophysical Research 106: 20,069-20,083.

Zou, X.K. and Zhai P.M.  2004.  Relationship between vegetation coverage and spring dust storms over northern China.  Journal of Geophysical Research 109: 10.1029/2003JD003913.

Reviewed 1 June 2005