Evidence of degradation and disappearance of Ramsar Wetland No. 1148 (Chinese Relict Gull Nature Reserve) due to anthropogenic disturbance and climate change on the ORDOS Plateau for nearly half a century

Abstract

Ramsar Site No. 1148 (ORDOS National Nature Reserve, ONNR) serves as a habitat for the rare bird Larus Relictus globally. The gulls disappeared in 2006 and returned in 2019. Why did this happen, and how did it respond to changes in the wetland ecosystem? We developed a remote sensing technology-enabled comprehensive wetland ecological assessment framework for typical inland saline marshes (ONNR) on the Mongolia-Xinjiang Plateau. That is, by integrating natural indicators (Normalized Vegetation Index, NDVI; Temperature and precipitation), anthropogenic indicators (land use and land cover change, LUCC) were used to identify the change characteristics of wetland water indicators (normalized difference water index, NDWI), and verified by statistical analysis and field survey data. It has the advantages of (1) observing water dynamic in wetlands over nearly half a century, (2) observing changes in atmospheric precipitation and surface recharge, and (3) calculating most indices from remote sensing data from 1973 to 2021. Study results showed that: (i) the climate in the inflow area is a strong response to regional climate change, with an evident warming trend. (ii) The area of the lake basin reduced from 14.545 km2 in 1998 to just 0.134 km2 in 2015, causing a decline of 99.08 % in its total area. (iii) During 1973–1999, changes in the water area of the wetland were predominantly driven by climate change, whereas both climate change and anthropological factors influenced the area from 2000 to 2021 (Sig. = 0.007). This study reveals the typical water environment issues of lakes and wetlands confronted in the arid regions of northern China. It helps to provide dataset and decision support for the management and conservation of wetland resources and biodiversity.