Perhaps the greatest challenge I faced in writing this book was presenting a balanced depiction of the celebrated conservationist and nature writer Aldo Leopold. Few people have thought more deeply about the human relationship to nature, and he presented his ideas in beautiful, flowing prose. He played a key role in an early-twentieth-century wilderness movement that set aside vast swaths of federal land in a somewhat pristine state (at least if we disregard historical ecological transformations propelled by Native Americans). For species requiring large ranges, like the grizzly bear, this may have played a key role in their preservation.Yet Leopold’s love for wilderness had a troubling upshot. His pursuit of unpeopled spaces engendered a disdain for human population growth that sometimes involved callous disregard for the worth of a life. Fearful of producing “more strain on an overcrowded range,” he questioned the wisdom of providing medical aid or agricultural assistance to vulnerable people in the developing world. Leopold exchanged these ideas with the ecologist William Vogt, who made similar arguments in his bestselling book, Road to Survival. Lacking Leopold’s subtlety and using more overtly misanthropic language, Vogt encountered criticism for rekindling fears of “yellow peril”—the prospect of the nonwhite races of the world (especially Asians) swamping white nations through greater reproduction.Interestingly, Leopold’s opposition to human crowding appears to have informed and been informed by his investigations of animal populations. Leopold’s most famous game management study centered on the deer of the Kaibab Forest in Arizona. He believed that their population had irrupted due to state-sponsored predator extermination before the deer overgrazed the landscape, propelling their own annihilation. Leopold and Vogt likened the extermination of wolves and cougars in the Kaibab to the eradication of disease and hunger among people of the developing world. In both instances, human interference threw the balance of nature off kilter, setting the stage for future environmental exhaustion. Such assertions failed to recognize that, in many instances, increasing affluence and security actually brought about a leveling of human population growth.By drawing associations between white American vigor and the nation’s wild lands, these conservationists set the stage for an enduring divide between the U.S. environmental movement and the country’s poor and nonwhite people. This is unfortunate because most environmental activists today almost certainly do not share the racial views of their predecessors. Indeed, many environmental organizations are now seeking ways to diversify their membership and broaden their support base.These historical legacies are difficult to overcome, though. When the Sierra Club toyed with adding immigration restriction to its agenda in the late 1990s and early 2000s, it faced accusations of racism and xenophobia. Most of the advocates of this policy were likely acting on a perceived correlation between human population growth and increased environmental impact. According to this perspective, the backlash they encountered would have seemed perplexing and surprising. When these proposals were placed in the context of the history described above, though, the reaction made perfect sense.With Vanishing America, I do not seek to devalue the immense accomplishments of the historical actors under scrutiny. These conservationists foresaw the danger facing many of the nation’s birds, fish, game, and plants, and articulated sophisticated arguments for their preservation. They helped achieve important and necessary reforms that likely prevented the extinction of the American bison, California condor, and other iconic species. I do, however, hope that by revealing American conservation’s often exclusionary and racist past, this book will help set the stage for a more inclusive and effective environmental dialogue moving forward. It’s time for a new environmental movement, one involving a wider range of voices, and devoted to preserving a broader vision of nature.