The answer to 'why is my mulch erosion' is that mulch can easily erode due to factors like heavy rain, wind, or sloping terrain. Mulch is designed to provide a protective layer on top of the soil, but it can get washed or blown away if not properly maintained.
Some common causes of mulch erosion include heavy downpours that dislodge the mulch, strong winds that blow it away, and sloping or uneven ground that allows the mulch to slide downhill. Over time, the exposed soil can then lead to weed growth, soil compaction, and other landscaping issues.