Seeding the divide: John Tanton, the Sierra Club and the struggle over US environmentalism

At the turn of the twenty-first century, the Sierra Club, one of the most prominent environmental organisations in the United States, faced a polarising internal battle over whether to endorse immigration restrictions. Two dominant explanations have emerged to account for why immigration became such a flashpoint in an environmental organisation. One, advanced by watchdog groups like the Southern Poverty Law Center, cast the controversy as a far-right infiltration, a cynical effort to greenwash xenophobia. The other, grounded in critical race and decolonial theory, argued that exclusionary politics have always been an intrinsic part of environmentalism, given its settler-colonial and eugenicist foundations. I offer a third explanation by turning to the 1970s, a pivotal moment when mainstream environmentalism briefly embraced population control as an ecological imperative. Drawing on archival records, I show how this institutional flirtation with population control − though short-lived − created an infrastructure and ideological opening that activists like John Tanton would later exploit. As population control lost mainstream legitimacy due to political backlash and the rise of laissez-faire demographic thinking, Tanton repurposed its ecological language and organisational networks to build an immigration restrictionist movement. I show how he strategically reworked liberal environmentalism to cast racial exclusion as ecological necessity. At the same time, however, the archival record reveals paths not taken, reminding us that environmentalism, like any political project, has always been a terrain of struggle.