Lake shrinkage-induced terrestrial ecological environmental quality degradation in a semiarid lake basin

Lake water environmental problems caused by lake shrinkage in semiarid zones have attracted widespread attention, but few studies have quantified the impact of lake shrinkage on the terrestrial ecological environmental quality of watersheds. In this study, remote sensing image inversion, digital elevation modeling, and statistical analysis were applied to explore the impact of Lake Daihai shrinkage on the terrestrial ecological environmental quality of its receding water areas from 1986 to 2019. The results showed that the area of Lake Daihai shrank from 170.7 km² in 1961 to 50.67 km² in 2019, a shrinkage of 70.32%. The average annual shrinkage was 2.07 km² during the period of 1986-2019 (r = -0.99, p < 0.01). The main conclusions of this study are as follows: The mean remote sensing ecological index values decreased significantly from 0.628 in 1986 to 0.441 in 2019 (r = -0.78, p < 0.05), which means that the terrestrial ecological environmental quality of the water receding area degraded from a good grade to a moderate grade. The increase in water use by residents in the basin was an important reason for the shrinkage of Lake Dahai. Approximately 90% of the wetlands in the receding water areas formed after the shrinkage of Lake Daihai were converted to farmland by local residents, which significantly degraded the terrestrial ecological environmental quality of these areas from good to moderate grade over the 34-year period (r = -0.83, p < 0.05). Correlation analysis indicated that the remote sensing ecological index was positively correlated with lake area (r = 0.85, p < 0.01). The results indicate that steps should be taken to decrease the impact of human activities on the terrestrial ecological environmental quality of lake basins in semiarid zones.