Drought variability and land degradation in central Asia: Assessment using remote sensing data and drought indices

Abstract

The regional resilience of a landscape to climate change in water-scarce areas is one of the core environmental problems nowadays for Central Asian countries. Responses to increasing temperature and high evapotranspiration (ET0) regimes have contributed to biodiversity loss and altered vegetation dynamics and changed the land use and management in these landscapes. Extremely dry conditions and droughts are recognized as an important factor that triggers land degradation in Central Asia. The aim of this study is to conduct attribution analysis to assess drought trends that are quantified using the Standardized Precipitation-Evapotranspiration Index (SPEI) and effects of other biophysical factors on the region and at a country level. The kriging (geostatistics) method was utilized to predict the status of vegetation change trends and generalize additive smoothed parameters to provide response factors for changes of land cover status. Specific objectives of the study were (a) to assess drought trends and their effects on climate-vegetation trends at the regional and local level; (b) identify the main affected regions among five countries (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan) and characterize their patterns for monitoring land tenures; and (c) define appropriate ecological risk zones, especially trends of spatial changes over time with drought trends. The simulated and predicted maps with kriging dependence terms indicated that the climate-vegetation-driven dataset will suffer substantial losses of vegetation health [normalized difference vegetation index (NDVI)] in precipitation-driven regions of Turkmenistan, Uzbekistan, and Tajikistan, and that these areas, especially, Ahal and Lebap Provinces in Turkmenistan, Kyzylorda in Kazakhstan, Karakalpakstan Autonomous Republic in Uzbekistan, and Gorno-Badakhsan Autonomous Region (GBAR) in Tajikistan, are very sensitive to droughts, which might alert us to the fragility of this ecosystem.