Evaluating ecological effects of roadside slope restoration techniques: A global meta-analysis

Given the increase in infrastructure construction, ecological restoration techniques need to be scientifically assessed so that appropriate measures can be taken. However, the specific effects of these techniques are often confounded by multiple ecological stressors, and robust evaluations of their effects are rare. Here, we conducted a global meta-analysis of 68 peer-reviewed publications to quantitatively evaluate the ecological impacts of roadside slope restoration techniques and explored potential mechanisms using linear regression and random-forest models. We found that roadside slope restoration techniques generally enhanced restoration effectiveness, but the recovery rate differed over space and time. Relative to the degraded reference group, the synthetic technique (63.10%) and species selection (62.09%) had more positive impacts on restoring slopes than erosion control (44.82%), seed spraying (43.55%), and substrate amelioration (12.96%). Additionally, we found that vegetation condition, soil quality, and species diversity were negatively correlated with restoration time, implying that recovery might not be stable during early restoration periods. Our findings highlighted the importance of biodiversity for restoration success, but the negative relationship between species diversity, precipitation, and age highlighted the potential risks of losing biodiversity during restoration. Finally, the importance of soil substrate but difficulty in restoring it suggested that restoration actions should stress soil substrate amelioration. Generally, this study provides evidence-based references to support decision making and ensure the effectiveness and sustainability of future slope restoration efforts.