Earlier eras of logging in addition to allowing large sediment run offs allowed cutting down to tributary creeks and main streams them selves leaving the water exposed to direct sunlight for large portions of surface area. Increased water temperatures hurt the runs in the hotter months, sediment run offs in the winter, and less habitat in the spawning areas, IE wood debris/ logs etc.
Theres a ton of regulations now that go into logging around streams, IE buffer zones along streams where you must leave a barrier of trees X distance from the water/ riparian zone. Replanting is a lot more strict now, in the time frame it must be done after cutting accrued. In addition to regulations on the volume of land that can be harvested at one time. Its really a lot healthier than what it used to be.
Im 100% for harvesting timber.