## 4 Results and Analysis
### Analysis of Vegetation Area Changes  
The changes in the area and percentages of typical vegetation in the study area from 2020 to 2022 are shown in Figure 6. Notably, except for _Sparting alterniflora_, the area of the other four vegetation species increased. Among these, _Phragmites_ exhibited the most rapid growth, followed by _Suueda glauc_, _Tumarisk_, and _Typha orientalis Presl_, which increased by 5.27 km\({}^{2}\), 5.09 km\({}^{2}\), 0.75 km\({}^{2}\), and 0.25 km\({}^{2}\), respectively. The _Suueda glauc_ community covers the largest percentage of the mapped area in the study area, which is related to the growth characteristics of the _Suueda glauc_ community, which is sparsely dispersed. In 2022, the percentage of the area increased by 1.38% compared with that of 2020. The _Tumarisk_ community and _Typha orientalis Presl_ community accounted for a relatively small area, and the overall change trend was not significant. The area of the _Sparting alterniflora_ community decreased by 4.45 km\({}^{2}\), reducing its share from 30.28% to 26.83%. Figure 5: Vegetation classification of the Yellow River Delta in 2020 and 2022. (**a**) 2020 RF, (**b**) 2022 RF, (**c**) 2020 SVM, (**d**) 2022 SVM, (**e**) 2020 MLE, (**f**) 2022 MLE. Table 7 presents the before-and-after comparisons of the four regions with significant vegetation changes between 2020 and 2022 in the study area (Figure 7). Notably, regions a, b, and c saw changes in _Spartina alterniflora_ vegetation. Through a review of relevant information, Shandong Province officially launched the Implementing Measures for Prevention and Control of _Spartina Alterniflora_ in Shandong Province in 2020. Based on the images and the documented measures for the management of huperzia, it can be concluded that areas a, b, and c have adopted the \"moving + flooding\" and moving management measures, respectively, which also confirms the view that the area of _Spartina alterniflora_ has been reduced, as mentioned above. Area d comprises an ecological restoration pool within the study area. The vegetation that has experienced more noticeable changes is _Phragmites_. As this region is primarily characterized by a water body, it is greatly influenced by precipitation and seasonal variations. When the water level drops, revealing bare land, there is rapid vegetation growth, which leads to a change in the cover type. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Classification**} & \multicolumn{5}{c}{**2020**} & \multicolumn{5}{c}{**2022**} \\  & **RF** & \multicolumn{2}{c}{**SVM**} & \multicolumn{2}{c}{**MLE**} & \multicolumn{2}{c}{**RF**} & \multicolumn{2}{c}{**SVM**} & \multicolumn{2}{c}{**MLE**} \\ \hline  & PA/\% & UA/\% & PA/\% & UA/\% & PA/\% & UA/\% & PA/\% & UA/\% & PA/\% & UA/\% & PA/\% & UA/\% \\ Phragmites & 82.00 & 79.35 & 81.33 & 78.21 & 76.00 & 73.08 & 83.33 & 89.29 & 78.67 & 83.10 & 76.00 & 73.08 \\ Suaeda glauc & 78.67 & 83.10 & 80.00 & 82.19 & 74.67 & 76.71 & 80.67 & 80.13 & 76.00 & 78.62 & 74.67 & 76.71 \\ Typha orientalis & 83.33 & 73.53 & 73.33 & 66.67 & 67.33 & 61.21 & 78.00 & 83.57 & 73.33 & 72.85 & 67.33 & 61.21 \\ Presl & 79.33 & 79.33 & 78.00 & 78.52 & 78.00 & 78.52 & 82.67 & 77.02 & 80.00 & 78.43 & 72.67 & 73.15 \\ Tamarix & 85.33 & 85.91 & 84.67 & 83.01 & 70.00 & 68.63 & 86.67 & 82.28 & 84.67 & 84.11 & 70.00 & 68.63 \\ Indand mudflat & 90.00 & 90.00 & 80.00 & 83.92 & 80.00 & 83.92 & 85.33 & 80.00 & 82.00 & 72.35 & 73.33 & 76.92 \\ Clear water & 94.00 & 100.00 & 96.67 & 100.00 & 96.67 & 100.00 & 99.33 & 100.00 & 97.33 & 100.00 & 96.67 & 100.00 \\ Turbid water & 95.33 & 100.00 & 95.33 & 100.00 & 95.33 & 100.00 & 94.00 & 100.00 & 94.67 & 100.00 & 95.33 & 100.00 \\ Overall accuracy & 85.92 & 83.67 & 79.75 & 86.25 & 83.33 & 78.25 & 87.25 & 87.25 & 87.25 \\ Kappa coefficient & 0.84 & 0.81 & 0.76 & 0.84 & 0.809 & 0.75 & \\ \hline \hline \end{tabular} PA: producer’s accuracy, UA: user’s accuracy.  
\end{table} 
Table 6: Classification accuracy statistics.