On a Thursday in October, dozens of Alaskans piled into a cavernous airplane hangar in the remote village of Iliamna to discuss — yet again — the fate of the proposed Pebble Mine. Seventeen miles to the northwest, underneath snaking rivers and spongy bogs, lies one of the largest undeveloped deposits of copper and gold in North America. Mining companies have been exploring it for decades. But many fear that an open pit mine here, at the headwaters of two of the last great salmon rivers on Earth, will harm fish — and the people who depend on them.

In 2014, the Environmental Protection Agency moved to impose restrictions that would have blocked plans for a large mine, citing