The incoming Trump administration is likely to see the greatest revival of environmentalism as a confrontational, grassroots, sometimes radical movement since at least 1970, when more than a million people took part in the first Earth Day.

The vigil at Standing Rock, which surprised nearly everyone by blocking the proposed route of the Dakota Access Pipeline through traditional Sioux lands, was a far cry from the litigation and high-level lobbying that are so much of the environmental movement’s work these days. As courts and lawmakers continue to falter in addressing climate change, with professional climate-change denier Myron Ebell heading the Environmental Protection Agency’s transition team, and Scott Pruitt tapped to lead it (Pruitt is an ally of the fossil fuel industry and key architect of the legal strategy against President Obama's climate policy) and the prospect of public lands opening to expanded mining and drilling, ever more people who believe that environmental responsibility has become a life-or-death issue are going to start acting like it.

A more confrontational environmentalism will find new allies, like the Native American activists of Standing Rock and the military veterans who showed up there just before the Army Corps of Engineers announced it would not approve the controversial pipeline route. It may also strain some of the relationships with wealthy funders and corporate partners that have become central to mainstream environmentalism. Activists will have to decide whether to cultivate alliances with other movements that have sprung up in recent years: the Movement for Black Lives, which has called for divestment from fossil fuels and pointed out that incinerators, waste facilities, and other pollution sources are often concentrated in poor and heavily non-white neighborhoods, or whatever comes after Bernie Sanders’s campaign, which blamed the fossil-fuel industry for blocking climate progress and promised to “keep it in the ground” in a rapid transition to renewable energy.

Joining environmentalism to movements for economic and racial justice wouldn’t be new. It would shift the movement toward what you might think of as its left wing, often called the environmental-justice movement, which emerged in the 1980s as an internal criticism of “mainstream environmentalism” for being too elite, too white, and too focused on beautiful scenery and charismatic species. But it would also point toward a longer history, now mostly forgotten. For decades, environmentalism and what we now call environmental justice were deeply intertwined. Care for the earth and for vulnerable human communities belonged together. Empowering workers, protecting public health, and preserving landscapes were part of a single effort. Maybe it’s time to reclaim that older environmental movement, and see that it was an environmental-justice movement all along.

Modern environmental law is defined by a set of statutes that were adopted in a burst of legislation in the 1970s: the NEPA on New Year’s Day, 1970; the Clean Air Act later in 1970; the Clean Water Act in 1972; the Endangered Species Act in 1973; laws governing waste disposal and reworking the management of federal public lands in 1976.

Environmentalism is also defined by a set of advocacy organizations that grew up in the same years: the Natural Resources Defense Council, the Environmental Defense Fund, the Sierra Club Legal Defense Club (which later became Earthjustice, the major environmental litigation group), and the Environmental Law Institute either appeared or took their current form in these years. The advocacy groups are an important part of the story because they help to define the field.