## 3 Results  
### Changes in Land Use and Land Cover  
The average overall accuracy of the maps was 90.5%, the producer's accuracy was 93.3%, and the user's accuracy was 90.6%, suggesting that the classification was satisfactory. LUCC experienced a large change since 1988 (Figure 2). The area of forest increased by 618.66 km\({}^{2}\) over the past 30 years, with an average annual increase of 18.07 km\({}^{2}\)/year\({}^{-1}\) (Table 2). The proportion of forests increased from 22.65% (1988) to 25.79% (2019) with a ratio of 0.09% year\({}^{-1}\). The area of shrubland decreased by 45.66 km\({}^{2}\), with an average annual decrease of 1.47 km\({}^{2}\) year\({}^{-1}\) (0.42% year\({}^{-1}\)). The area of grassland decreased overall, showing an obvious decrease from 1988 to 1995 and then increases until 2005. The wetland area first increased and then decreased sharply by 112.26 km\({}^{2}\) from 2011 to 2019. The cropland area increased initially and then decreased, with an overall decrease of 369.14 km\({}^{2}\). The waterbody area showed an obvious phase change. For instance, it increased at a rate of 3.97 km\({}^{2}\) year\({}^{-1}\) from 1988 to 1995, decreased at a rate of 13.75 km\({}^{2}\) year\({}^{-1}\) from 2003 to 2011, and finally increased slowly at a rate of 1.44 km\({}^{2}\) year\({}^{-1}\) after 2011. The area of the impervious surface increased linearly by 5.21 km\({}^{2}\) year\({}^{-1}\), with its proportion increasing from 5.71% (1988) to 6.73% (2019). The area of bare land decreased linearly by 10.70 km\({}^{2}\) year\({}^{-1}\), from 2.77% (1988) to 0.88% (2019). Figure 3 shows the different LUCC types in the recent 30 years. The forest was mainly converted from cropland and bare land (Figure 3a). From 2000 to 2009, most of the increase in the forest came from bare land, and cropland became the largest contributor after 2010. The shrubland was mainly converted from the forest and bare land (Figure 3b). From 1994 to 1996, the shrubland showed rapid transformation into forest. After 2000, shrubland mainly came from bare land, while cropland transferred to the forest. The grassland showed feeble transformation with wetland, cropland, and forest (Figure 3c), but the changes in grassland were highly variable in different periods. There was a main transformation between wetland and waterbody, cropland and forest (Figure 3d). Waterbody areas were \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Year** & **Forest** & **Shrubland** & **Grassland** & **Wetland** & **Cropland** & **Waterbody** & **Imperious** & **Bareland** \\ \hline
1988 & 4518.88 & 351.71 & 2.97 & 1839.46 & 9127.57 & 2431.50 & 1138.22 & 540.11 \\
1995 & 4534.69 & 330.19 & 1.13 & 1836.52 & 9189.68 & 2452.00 & 1142.07 & 464.44 \\
2003 & 4619.41 & 330.59 & 1.22 & 1910.33 & 9803.62 & 2456.85 & 1166.33 & 382.21 \\
2011 & 4754.04 & 326.28 & 2.38 & 1948.63 & 9047.43 & 2352.30 & 1204.63 & 311.89 \\
2019 & 5137.54 & 306.05 & 2.43 & 1836.37 & 8758.43 & 2363.33 & 1341.56 & 176.05 \\
1988–1995 & 15.81 & \(-\)21.52 & \(-\)1.84 & \(-\)2.94 & 62.11 & 20.50 & 3.85 & \(-\)75.67 \\
1995–2003 & 84.72 & 0.40 & 0.09 & 73.81 & 613.94 & 4.85 & 24.26 & \(-\)82.23 \\
2003–2011 & 134.63 & \(-\)4.31 & 1.16 & 38.30 & \(-\)756.19 & \(-\)104.55 & 38.30 & \(-\)70.32 \\
2011–2019 & 383.50 & \(-\)20.23 & 0.05 & \(-\)112.26 & \(-\)289.00 & 11.03 & 136.93 & \(-\)135.84 \\
1988–2019 & 618.66 & \(-\)45.66 & \(-\)0.54 & \(-\)3.09 & \(-\)369.14 & \(-\)68.17 & 203.34 & \(-\)364.06 \\ \hline \end{tabular}
\end{table} 
Table 2: Land use in Dongting Lake Region during 1988–2019 (km\({}^{2}\)). Figure 2: Annual change of land covers in DTLR. (**a**) annual change rate of area (%); (**b**) annual change area (km\({}^{2}\)). mainly converted to wetland before 2006, and then the occurred after 2011. The cropland tended to convert to waterbody and forests (Figure 3e). In the recent ten years, cropland dramatically decreased and was mainly converted to forests, waterbody, and impervious surfaces. Additionally, the forest was the main transformation target from 2016 to 2018.