These forests filter out excess sediment and nutrients from runoff. The leaves and branches that fall from the shoreside trees are a source of food for aquatic organisms. The shoreside trees shade the water. The shading keeps the water cool. Cooler water holds more oxygen.
More oxygen means more and better game fish.
The forests along waterbodies need to be kept healthy, with an intact canopy cover. The best way to do this is to encourage regeneration and multiple canopies. In Maine, there are laws regarding harvesting in shoreland areas. Visit the shoreland web page to learn more. It is this topsoil that absorbs water.