The answer to 'why is my shrub erosion' is that shrub erosion is typically caused by soil loss around the base of the shrub. This can happen due to factors like heavy rainfall, poor drainage, or excessive foot traffic. Symptoms include the shrub's roots becoming exposed and the soil around the base washing away.
To fix shrub erosion, you'll want to address the underlying cause. This may involve improving drainage, adding mulch or groundcover around the shrub, or even relocating the shrub to a more stable area. In some cases, you may need to rebuild the soil around the shrub's base. If the erosion is severe, it's best to call in a professional landscaper to assess the situation and recommend the best solution.