The answer to 'why is my shrub erosion' is that shrub erosion is a common problem caused by a variety of factors, including heavy rainfall, poor soil drainage, and excessive foot traffic around the plant. Symptoms of shrub erosion include exposed roots, soil loss around the base of the plant, and stunted growth.
To address shrub erosion, you can try adding mulch around the base of the plant to help retain moisture and prevent further soil loss. If the erosion is severe, you may need to transplant the shrub to a better-draining location or amend the soil with compost or other organic matter. In some cases, you may need to install erosion control measures, such as retaining walls or terraces, to stabilize the soil. If the problem persists or you're unsure of the best course of action, it's best to consult a professional landscaper for guidance.