2.4 Background layers
Considering the movement characteristics of North China leopard through landscape, we used a total of nine layers to define landscape properties (Fig. S1). The selection of layers is based on the relevant literature, the availability of spatial datasets and the opinions of relevant experts (Cao et al., 2020 ;Petsas et al., 2020 ;Zhu et al., 2021 ).
The first five layers was built upon land use types, namely agricultural areas, forest areas, grassland areas, water bodies and artificial surfaces. In each layer, the percentage cover of land use type within every 1 km range was calculated to form a background layer, and different resistance values were assigned according to the percentage cover of land use type in the later stage. For each background layer, if there was no presence of the respective land use type, the assigned value was zero. If a land use type was full coverage, the assigned value was 1.
The elevation and slope data were selected in the background layers to represent topographic features. Data of land use, elevation, and slope were obtained from the National Earth System Science Data Center (http://www.geodata.cn), with the spatial resolution of 30m.
As for the impact of linear transportation infrastructure, we developed a background layer by combining information from expressways, national highways, provincial highways and railways, which were known for posing barriers for the movement of North China leopard. The spatial distribution of linear traffic infrastructure datasets was derived from Earth Data Sciences and Sharing Research laboratory, Institute of Geographic Sciences and Natural Resources Research, CAS. Each cell was assigned a value, representing the shortest distance from the cell’s center to any linear transportation feature, and the spatial resolution was 30 m.
The last layer represented human population density (http://www.geodata.cn), with a spatial resolution of 1 km.