The monument is not as large as it could have been; Mr. Obama chose not to extend its boundaries out to the full 200-mile territorial limit for all the islands within it. Still, environmental groups are uniformly praising him for going as big as he did and for defying opposition from Hawaiian fishing interests whose loyalties lie with the producers of canned tuna. That industry has other places to fish; it will not suffer. But, at a time when the world’s oceans are threatened by rampant pollution, overfishing and climate change, the benefits of Mr. Obama’s decision will be profound, particularly if other countries now follow the United States’ excellent example.

Few of us will see these benefits directly. But out there beyond Honolulu, living in splendid isolation, are sharks, rays and jacks; coconut crabs; moosehorn, staghorn and brain corals; humpback and melon-headed whales; green and hawksbill turtles; bottlenose and spinner dolphins; and untold millions of boobies, curlews and plovers. All these, and countless other living things, will be better off.

Republicans will complain, but they should remember that it was President George W. Bush who created the monument. Mr. Obama only expanded it. Building an environmental legacy is an idea with bipartisan appeal.