An environmental activist friend of mine recently shook her head and marveled at the extraordinary accomplishments of the last several months. “Still lots of work to be done,” she said. “But wow! This has been an epic period for environmentalists!”

From the rejection of the Keystone pipeline to the Paris Agreement on Climate Change (COP21), “epic” may be an apt descriptor for someone who is an environmentalist.

However, nothing galvanizes opposing forces to action better than significant wins by their foes. And 2016 appears to promise that environmental issues—particularly climate change—will be more politicized than ever before.

It wasn’t always this way.

By and large, environmental action since the 1960s proceeded in the U.S. in a bipartisan fashion, emphasizing issues of human health and resource conservation. That’s no longer true: almost by default, the Democratic Party stands largely alone, rather than together with the Republican Party, to uphold the ethic that environmental protection is a united, American common interest.