Karst landform is a distinctive topography resulting from the solution process of acidic water acting on carbonate bedrocks. Globally, karst landscapes occupy 22,000,000 km2, accounting for approximately 15% of the total land area. Among the three largest continuous karst regions in the world, southwest China possesses the largest area of exposed carbonate and the most complete array of karst landscape types. However, karst regions face a serious environmental problem--- rocky desertification.

Rocky desertification (RD) is a process of land degradation that often results in extensive soil erosion, bedrock exposure and considerable decrease of land productivity. The spatio-temporal evolution of RD not only reflects regional ecological environmental changes but also directly impacts regional economic and social development.

In a paper in Environmental Earth Sciences, researchers in the Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA) employ remote sensing, geographic information systems (GIS) and statistical techniques to the evolution, including the identification of driving forces, of karst RD in the Northwestern Guangxi.

The team found RD became most apparent between 1990 and 2005 when areas of various types of RD increased.

“The process of RD in the study area was faster than for the recovery process and the situation of RD had become worse over the 15-year span.” said YANG Qingqing, a doctoral researcher at ISA and first author on the paper. “In karst RD landscape, slight RD was the matrix of the landscape, potential RD had the largest patch sizes, and extremely strong RD was the most influenced by humans. The landscape had evolved from fragmented to agglomerated, which means general RD status had become more serious.”

Land condition changes were categorized as five types: desertified, recovered, unchanged, worsened, and alleviated land. The team also found the largest turnover within the RD land was between slight and moderate RD. The factors impacting RD vary according to the type of RD. Specifically, while potential RD was mainly influenced by natural factors, slight and moderate types were influenced by natural and anthropogenic factors. Strong and extremely strong were significantly related to human activities. Moreover, the dominant impact factors of the RD landscape had shifted from town influence and bare rock land in 1990 to bare rock and grassland in 2005.

Besides, the RD condition around roads and towns had been alleviated from extremely strong to moderate and from strong to slight RD, respectively, which may be attributed to several management projects initiated in 2001. However, there were also large turnovers from non-RD land to various types RD, especially the rapid expansion of strong RD.

This research was supported by funding from the Chinese Academy of Sciences Western Action Program (No.KZCX2-XB2–08), National Natural Science Foundation of China (41071340 41001287), the Western Light Program of Talent Cultivation of the Chinese Academy of Sciences, the National Key Technology R&D Program (No.2009BADC6B008).

The study entitled “Spatio-temporal evolution of rocky desertification and its driving forces in karst areas of Northwestern Guangxi, China” has been published in the September issue of Environmental Earth Sciences, details could be found at http://www.springerlink.com/content/t28222g3n4423857/