think, because they're-they're global treasures and very few people know they exist. and so i think now i feel like it's one of my missions to make sure that people know that they're here and we need to decide again, as a society, not just a few companies, not just one government, how do we all want to see this place a long, long time from now. >> greenberg: alaska is a kind of jewel, with all its facets still sparkling. where 200 million salmon can be caught each and every year, and all the connections are in place from ocean to river to fish to forest, just as they have been for millennia. >> if you treat them correctly, they're going to outlast the oil, they're going to outlast the mines, they're going to outlast everything else, and just keep coming back. we have an amazing abundance of salmon. a lot of people don't

from an old fishing family, keeps watch over canadian proposals for massive gold and copper mines. >> if built as proposed, they'd be some of the largest in north america, if not the world. and tailings dams that have to hold back the waste forever. and so it really is, in our minds, ticking time bombs, and we're sitting ducks. downstream there's ticking time bombs upriver that have to hold back that waste in perpetuity. >> greenberg: this is heather hardcastle's fear-- the mount polley mine dam wasn't even 20 years old when it burst and emptied millions of tons of tailings into canada's fraser river watershed in 2014. >> just over the border in the taku watershed is the best coho salmon-rearing habitat in the world. uh, and i get emotional, i think, because they're-they're global treasures and very few