While I understand your point, it’s not as simple as just restoring salmon habitats. Many salmon rivers have been blocked by dams, with the runs being exterminated decades ago. Even if the dams were tore out, we would need to restock the rivers, with genetics that were killed decades ago. Greenberg does show this is possible, as with salmon river, but it would take a very long time and cost a lot of money. Furthermore, many of these dams are still in use, and with the current rate of climate change, who are we to be tearing down renewable energy sources? There’s many factors involved, that’s not just simply boiled down to convenience.