Transformation of aquatic vegetation in Chinese lakes from 1988 to 2023

Aquatic vegetation (AV) is crucial for maintaining lake ecosystem's stability. Transformation of certain types of AV (e.g., submerged aquatic vegetation (SAV)) into other lake features (e.g., algal bloom) may cause a shift in lake's stable state. However, such transformations in Chinese lakes remain largely unknown. Using 0.23 million Landsat images from 1988 to 2023, a comprehensive investigation was conducted to reveal the long-term conversions between SAV, floating and emergent AV (FEAV), and non-AV (e.g., water or algal bloom) across 4375 Chinese lakes (with area > 1 km²). Results show that from 1988–1993 to 2018–2023, the total lake AV area experienced a reduction of 0.7 × 10³ km²_. Despite a countrywide net increase in FEAV (+0.9 × 10³ km²), it could not offset the sharp decline in SAV (−1.6 × 10³ km²). The SAV decline was mainly observed in Eastern Plain lake region. Nationwide, 3.6 × 10³ km² of SAV have transitioned into non-AV, with 78.3% of this area transformation occurring in Eastern Plain. In contrast, many non-AV areas on the Tibetan Plateau saw an emergence of SAV, expanding at +17.9 km² per year. However, mutual conversions between SAV and FEAV were minimal. National FEAV gains were primarily from non-AV conversions (+1.3 × 10³ km²), occurring mainly in Eastern Plain, while SAV-to-FEAV transitions accounted for only 23.8% of total FEAV gains. Driving forces analysis shows that lake eutrophication dominated SAV reduction, whereas FEAV variations were primarily influenced by eutrophication, temperature, and lake water area changes. These findings could provide important insights for lake restoration management in China.