Certainly true in the Amazon rain forest, but too late in the PNW.  We should plant fast growing trees wherever we can, they are great carbon sinks.  Far more water quality damage comes from runoff.  Phosphates and other fertilizers, along with runoff from animal agriculture are one of the main contributors to algae growth.  It is the main reason there is a dead zone in the Gulf of Mexico from the inflow of the Mississippi River.