The biophysical interactions between soil and vegetation are discussed from a mechanical and hydrological perspective. How these interactions impact the stability of soil on slopes and protect against shallow landslides is presented, along with a brief outline of models used to calculate the reinforcing effects of roots on soil, and how these models have been derived in the last half-century. Methods are discussed for measuring root-permeated soil shear strength in the field and laboratory. Future challenges for research are outlined, and include the difficulties encountered when integrating large roots and the architecture of complex root system into mechanical models, as well as scaling up to the landscape level