## 3 Results and Findings  
According to UNESCO and the heritage community [29], a core zone has strict protection status, where human intervention must be kept to a minimum. A buffer zone may set limits to protect views, settings, land uses, and other aspects but may also positively encourage developments that would be beneficial to the site and community. Therefore, a high interference degree in the core zone usually implies a high risk to the heritage site. A high value in the buffer zone indicates the heritage site needs to be further evaluated to assess whether these changes have strengthened or weakened the relationship between humans and heritage. By applying the proposed workflow to our three study sites, the interference degree of these CHS is listed in Table 2. As can be seen, the interference degrees in the core zone were all lower than those in the buffer zone, suggesting a better protection in the core zone. The Yungang Grottoes had the highest interference degree in the buffer zone (4.93%) among three study areas and a median value in the core zone (0.64%). The Wooden Pagoda of Yingxian had nothing changed in the core zone and only some minor changes in the buffer zone (0.51%). The interference degree of the Chengcun Ancient City Ruins also remained at a high level in the core zone (1.11%) and the buffer zone (3.54%). Five classes can basically cover land-cover types in the study areas, including built-up land, farmland, barren land, vegetation, and water. Built-up land includes buildings, roads, and some under-developed areas. Farmland includes planted and unplanted farmland, without paddy fields in these study areas. Barren lands are mostly bare soil and rocks, with a few tidal-flat areas. Vegetation includes woodland, bush, and grass. Water includes rivers and reservoirs. Among the five classes, built-up land and farmland were closely related to human activities, and the other three classes (i.e., barren land, vegetation, and water) contribute to environmental factors. Some research assigned different weights to different land-cover classes for risk assessment [39]. In these three study areas, the changes of these five land-cover classes were interactive. Especially, the changes of barren land and vegetation were mostly caused by human intervention rather than natural changes. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Interference Degree (\%)** & **Interference Degree (\%)** \\  & **in Core Zone** & **in Buffer Zone** \\ \hline Yungang Grottoes & 0.64 & 4.93 \\ Wooden Pagoda of Yingxian & 0 & 0.51 \\ Chengcun Ancient City Ruins & 1.11 & 3.54 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Interference degree of three cultural-heritage properties. Therefore, without distinguishing different impacts of land-cover classes on the interference degree, these five classes were used for classification to refine the change-detection result and to obtain the change information (some study sites may not include all the five classes). The from-to land cover-change information is shown in Figures 4-6, and heat maps of the transition matrix indicating change quantities and directions [40] are displayed in Figure 7 for all three study sites. The greatest change in the Yungang Grottoes was from vegetation to built-up land (Figure 7a), appearing in the southwest of the buffer zone (Figure 4). This change was due to a large increase in solar panels, which can be seen clearly from VHR images. The second greatest change was from built-up land to barren land in a village (called Wuguantun village) in the northern part of the buffer zone. The Yungang Grottoes are surrounded by some coal mining areas, and people in the Wuguantun village used to mine for a living. Due to a serious threat to the grottoes, the mining activities stopped in nearby villages. People moved away from the Wuguantun village after the coal mining stopped; therefore, many low flat-roofed buildings in the village were demolished.