# Study on the Extraction Method for Ecological Corridors under the Cumulative Effect of Road Traffic
## 4 Discussions
### Analysis of Road Traffic Impact  
Because of the effects of noise, dust, and other pollution, various types of organisms generally have the instinct to reside and migrate away from roads, and the ecological corridors extracted by pre- and post-improvement methods differ significantly in this regard. \begin{table}
\begin{tabular}{c c} \hline \hline
**Class** & **Value** \\ \hline Length of corridors extracted by improved method & 799.12 km \\ Length of corridors extracted by pre-improved method & 842.67 km \\ Length of new corridors & 28.59 km \\ Length of disappeared corridors & 3.76 km \\ Length of changed corridors & 186.64 km \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Statistics of ecological corridors extracted by two methods (Wuhan, China, 2020). \begin{table}
\begin{tabular}{c c} \hline \hline
**Class** & **Value** \\ \hline Change percentage of total length & 5.17\% \\ Length percentage of new corridors & 3.58\% \\ Length percentage of disappeared corridors & 0.45\% \\ Length percentage of changed corridors & 22.15\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Change ratio of ecological corridors extracted by two methods (Wuhan, China, 2020). In Figure 8, the blue paths near positions 1-3 are ecological corridors extracted with the pre-improvement method. When extracted using the new method, they are no longer identified as ecological corridors due to the influence of road traffic resistance. The other surrounding corridors do not change significantly but only show the disappearance of individual ecological corridors. Such changes are manifested in the abandonment of some potential ecological corridors due to road traffic pollution, which makes the extraction results more consistent with the natural patterns of biological habitats and migrations. In Figure 9, the blue paths near positions 4-3 are ecological corridors extracted with the pre-improvement method. When extracted with the new method, they are no longer identified as ecological corridors due to the influence of road traffic resistance, but new ecological corridors are found in the vicinity. This change is mainly manifested in the fact that the new ecological corridors are located as far away from the roads as possible, the length of the ecological corridors is shortened, and the areas where the road network is sparser are preferred for crossing as opposed to the correspondingly disappearing ecological corridors. These changes can also effectively reduce the impact of road traffic on species migration along ecological corridors. Specifically, when extracted with the new method, a section of the ecological corridor near 4 that overlapped with the road disappeared. The new ecological corridor was oriented north-south and intersected the road almost perpendicularly, and the road traffic resistance was significantly reduced. The section of ecological corridor near 5, which overlaps with the road and is located in an area with higher road network density, often resulting in more frequent and higher levels of pollution (one of the important influencing factors in population decline, habitat loss, and degradation) due to the presence of pollution superposition effects, disappears when extracted with the new method. A new east-west ecological corridor was added due south, and the density of the road network in the area it traverses was significantly reduced. Relative to the original ecological corridor, the new ecological corridor near 6 exhibits an obvious vertical crossing with the road, a situation that can reduce the accumulated combined resistance to some extent. The new ecological corridor near 7 is significantly shorter, and the number of intersecting roads is reduced. The distance between the new ecological corridor near 6 and the roughly parallel roads increases significantly. The new ecological corridor near 6 is far from the high-road-network-density area. These changes objectively respond to the reality that both habitat and migration of organisms have to be as far away from road traffic pollution as possible.