How do plants reduce erosion? An Eco Evidence assessment

Soil erosion adversely impacts natural and human environments globally. Vegetation is often used as a sustainable approach to mitigate erosion. Although using vegetation to reduce erosion is a widely accepted concept, how different plant traits mitigate different mechanisms of erosion, and the generality of these mechanisms has not been well demonstrated. We developed ten hypotheses on how different plant traits (roots, leaves, and stems) act to reduce erosion through different mechanisms (binding soil particles, promoting suspended sediment deposition and reducing the energy of waves, runoff, and wind). We then conducted a rapid evidence assessment of the scientific literature using the Eco Evidence method. We found strong evidence to support our overarching hypothesis—an increase in plant abundance reduces erosion. We also found support for the specific hypotheses that plant roots bind soil particles and that greater plant stem density and leaf area reduce surface run-off and promote sediment deposition. There was insufficient evidence to support the hypotheses that an increase in stem density or leaf area reduces wave or wind energy. None of our hypotheses were rejected. Species with higher root and stem densities and greater leaf area will be the most effective in mitigating erosion. Our review highlights that there is insufficient evidence regarding some potentially important mechanisms between vegetation and erosion, making these prospective areas for further research. Our results have the potential to aid environmental engineers when designing schemes to reduce erosion and ecologists and managers who are concerned about the conservation and restoration of erosion-prone environments.