Spatial and Temporal Changes of Wetlands on the Tibetan Plateau Between 1990 and 2020

Highly sensitive to climate change and glacier melt, alpine wetlands on the Tibetan Plateau have important implications for carbon storage and animal habitat. However, long-term accurate mapping and changes of wetlands on the Tibetan Plateau remain knowledge gaps. Here, we qualify wetlands' spatial and temporal changes between 1990 and 2020 using Landsat imagery with an optimized random forest model. We find that the total area of marsh, floodplain, and swamp wetlands was approximately 8.25 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> (2.68% of the plateau area), 6.99 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> (2.27%), and 8.47 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> km<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (2.75%) in 1990, 2000, and 2020, respectively. The total area of wetlands decreased by about 1.29 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> km<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (−15.7%) between 1990 and 2000 but increased by about 1.52 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> km<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (21.7%) between 2000 and 2020. Marsh and floodplain wetlands show a decrease followed by an increase, while swamps continue to increase. The high-density wetlands are mainly distributed in the Yangtze and Yellow River basins, especially with marsh and floodplain wetlands >40%, and Brahmaputra high-density swamps ∼40%. Conversion of wetland types occurred in a relatively high proportion of all periods, but there was a gradual downward trend. The proportion of conversions from wetlands to nonwetlands decreased and the proportion of conversions within wetlands increased. This study elucidates the distribution characteristics, area change, and type conversion of wetlands on the Tibetan Plateau, which provides scientific support for the development and use of alpine wetlands and governmental risk decision making.