Extraction and analysis of abandoned farmland: A case study of Qingyun and Wudi counties in Shandong Province

Rapid urbanization and continuous loss of rural labor force has resulted in abandonment of large areas of farmland in some regions of China. Remote sensing technology can indirectly help detect abandoned farmland size and quantity, which is of great significance for farmland protection and food security. This study took Qingyun and Wudi counties in Shandong Province as a study area and used CART decision tree classification to compile land use maps of 1990-2017 based on Landsat and HJ-1A data. We developed rules to identify abandoned farmland, and explored its spatial distribution, duration, and reclamation. CART accuracy exceeded 85% from 1990-2017. The maximum abandoned farmland area was 5503.86 ha during 1992-2017, with the maximum rate being 5.37%. Farmland abandonment rate was the highest during 1996-1998, and abandonment trend decreased year by year after 2006. Maximum abandonment duration was 15 years (1992-2017), mostly within 4 years and only a few exceeded 10 years. From 1993-2017, the maximum reclaimed abandoned farmland was 2022.3 ha, and the minimum 20 ha. The maximum reclamation rate was 67.44%m, with annual average rate being 31.83%. This study will help analyze farmland abandonment driving forces in the study area and also provide references to identify abandoned farmland in other areas.