However, the county has acted under the belief that where wetlands are destroyed by development, the replacement wetlands, or mitigation wetlands, are keeping the county's wetland acreage at status quo. This is not true if the mitigations don't work, and recent inspections have shown that they don't. For example, streambank vegetation provides shade for fish and other aquatic creatures, roosting and nesting perches for birds, and wildlife forage.
Roots hold the bank together, and protect it from erosion.
Plants improve water quality by trapping sediment and taking up nutrients that would otherwise harm the stream. If streambank vegetation is cleared, an entire world disappears. Mitigation begins the process of healing and replacing that world. We can't replace a mature ecosystem overnight. It is a very complicated and difficult thing to do.