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Scale Measurement and Threshold Optimization for Implementation of the “Returning Farmland to Forests or Grass” Policy: Based on the Dual Perspectives of Human and Nature
  • Jing Wang,
  • Jun Liu,
  • Na Yang
Jing Wang
Northwest A&F University
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Jun Liu

Corresponding Author:[email protected]

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Na Yang
Northwest A&F University
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Abstract

Land degradation is the most serious environmental issue globally, which is associated with human activities and climate change. Quantified information on land degradation and restoration is required to support the development of policies for sustainable ecosystem management and socioeconomic development. The arid and semiarid zones of China (ASZC) have experienced significant land degradation, and multiple ecological projects have implemented to address the issue. Among them, The Returning Farmland to Forests or Grass (RFFG) is a major ecological project in China. It is intended to protect and improve the ecological environment and achieve sustainable development. Since 2002, the country has incorporated the county economies, which are key components of the national economy, into the reform system. This paper uses 342 counties (districts) of the Loess Plateau as the basic research unit to more comprehensively evaluate the effect of the RFFG. Based on meteorological and socioeconomic data from 2000 to 2019, fractional vegetation cover (FVC) was derived from the MODIS normal difference vegetation index using threshold regression models in two dimensions, namely the population level of urbanization (PLU) and the standardized precipitation evapotranspiration index (SPEI). Using the FVC, we demonstrate the ecological restoration effects of implementing the “RFFG” on the Loess Plateau. We performed scale measurement and studied methods to optimize the implementation of this policy on the Loess Plateau, via empirical analysis of threshold effects and optimal thresholds of the PLU and SPEI. The findings are as follows: In terms of PLU, the rapid development of the population level of urbanization in 55 of the 342 counties (districts) in the Loess Plateau (PLU more than 76.41%) seriously hinders the implementation of the RFFG. The 12 counties (districts) are further effective in ecological projects in the Loess Plateau. The priority development area applied (PLU does not exceed 18.12%). Only 27 counties (districts) in the region have achieved the FVC optimal value, and the growth space of FVC in Qinghai and Ningxia is close to 100%, followed by Gansu and Shanxi. The optimized area of the Loess Plateau is as high as 64.748 million hm2, covering the whole region (98.51% of the area). In terms of SPEI, the ecological project in the Loess Plateau is expected to be further effectively implemented in 29 counties (districts) that tend to turn mild drought to extreme drought, and the implementation of the RFFG has been strongly inhibited by 37 counties (districts) (which tends to the evolution of moderate flooding to extreme flooding). The 202 counties (districts) in the region achieved the FVC optimal value, and the FVC growth areas in Gansu, Ningxia, and Shanxi were relatively large. The optimized area can reach 31.235 million hm2, accounting for 47.52% of the total area of the Loess Plateau. The empirical results of the two threshold regression models show that the effect of SPEI on the FVC is weaker than that of PLU, and the effect of flooding on the FVC is more significant than that of drought, which is concentrated in the central Loess Plateau. Furthermore, the implementation of the “RFFG” has promoted the coordinated development of PLU and FVC, and SPEI and FVC.