# The Impact of Spatial Resolutions on Nature-Based Solution Suitability Mapping for Europe
## 4 Results  
The suitability mapping resulted in three different suitability maps (one for each LULC input layer), indicating areas suitable for implementing riparian forest buffer zones. These three suitability maps were further analysed with (1) cell statistics to compare the suggested suitable areas in terms of coherence with another; (2) patch statistics to assess the degree of fragmentation of proposed suitable areas; and (3) satellite image validation to qualitatively assess the accuracy and appropriateness of the suggested areas. The results of these analyses are presented in the following section. Suitable area size comparison.Overall, the three maps differ in the total size of suitable area and their structure (e.g., number of suitable areas; maximum and mean size). The total size of suitable areas (Table 2) for the LUISA- and CLC-based output maps is around 25,000,000 m\({}^{2}\), while the OSM-based suitability map differs greatly by counting only 14,381,000 m\({}^{2}\). According to the results listed in Table 2, the largest and the mean suggested areas (patches) are of a similar size between all output layers. Interestingly, the sizes of the largest patch and of the mean patch area are higher before removing (sieving) small areas. Suitable area coherence.Comparing the actual suggested areas by overlaying these three output layers and using cell statistics (Figure 4), only 56.8% of the suggested areas are found to be coherent between all three layers, 31.6% by two layers, and 10.6% by single layers. Hence, the results show that the output maps greatly differ from one another, while the difference of 11.2% between the outputs of the CLC and LUISA layers is much lower than that of the OSM layer. This result can be explained by the fact that the LUISA layer is based on the CLC layer. _Fragmentation._ The statistical analysis was used to derive an understanding of the degree of fragmentation. As described in Section 3.2, smaller isolated areas were excluded with the sieving function. The patch statistic results (Table 2) show that through the sieving process, the number of patches of the OSM-based suitability map decreased drastically (compared to the other two outputs). The extensive removal of smaller areas can imply a prior greater degree of fragmentation, which was further explored with the landscape division index and may be explained by the fine spatial resolution. The results show that all output layers have a value close to 1, presenting a great fragmentation which can be traced back to the fact that suitable areas are only located along water areas. However, the index numbers show a minor improvement in fragmentation after the removal of smaller areas. Overall, the OSM-based output has a slightly smaller fragmentation rate than the other two layers. _Thematic accuracy and appropriateness._ The satellite image validation method highlighted a few differences and similarities between the suitability maps of each of the three layers. Firstly, the fine resolution input layer OSM could include non-built areas close to urban areas as suitable spots, while these spaces can be classified as urban areas for the CLC and LUISA maps (see Figure 5a). Secondly, some suitable areas highlighted the inaccuracy due to the coarser resolution of the CLC layer. Figure 5b presents one example of this inaccuracy, where suitable areas are suggested on vineyards and a road, which were defined as non-suitable criteria and should, therefore, be excluded. Thirdly, it was found that inaccuracy of input layers (e.g., displaced ditches) is carried along to the output suitability map (Figure 5c). Overall, the three output layers showed greater coherence in agricultural areas (exemplified in Figure 5d). In comparison to non-sieved output layers, the sieved output layers show less suggestions along larger rivers, such as the Rhine. Whilst some suggested areas are located along the Moselle, no suitable areas were detected along the river Ahr, which can be reasoned by the high coverage of already existing riparian vegetation