Deadly Divide: How Insects, Pathogens, and People Defied the US-Mexico Border
by Mary E. Mendoza
The first environmental history to chronicle the construction of race, fencing, and policing at the US-Mexico border
When most people picture the US-Mexico border, they think of walls, fences, concrete, and wire. But in this first history of how the environment influenced physical boundary-making between the two nations, Mary E. Mendoza focuses on how the natural world shaped ideas about race, gender, and security. In so doing, she unearths surprising origins of the modern-day immigration debate.
Mexican migrants have historically been seen by some in the US as invasive and less than human. But actual invasive pests are part of this story. Deadly Divide shows how cattle ticks, the body louse, foot-and-mouth disease, and the female Mexican fruit fly contributed to the to the ever-increasing racialization of Mexican migrants, which in turn led to increased policing, criminalization, and fears about immigrants infiltrating the US. As Mendoza follows the stories of migrants in relation to various species, Indigenous peoples, and officials on both sides of the border, she argues that the need for mobility overpowered both governments’ laws, fences, and agents. At the same time, the border’s symbolic power became a source of terror not only for migrants who try to cross into the US but for those who feel they cannot cross back, making the US a nation that suspends immigrants between two worlds.
Click Here to Purchase
by Mary E. Mendoza
The first environmental history to chronicle the construction of race, fencing, and policing at the US-Mexico border
When most people picture the US-Mexico border, they think of walls, fences, concrete, and wire. But in this first history of how the environment influenced physical boundary-making between the two nations, Mary E. Mendoza focuses on how the natural world shaped ideas about race, gender, and security. In so doing, she unearths surprising origins of the modern-day immigration debate.
Mexican migrants have historically been seen by some in the US as invasive and less than human. But actual invasive pests are part of this story. Deadly Divide shows how cattle ticks, the body louse, foot-and-mouth disease, and the female Mexican fruit fly contributed to the to the ever-increasing racialization of Mexican migrants, which in turn led to increased policing, criminalization, and fears about immigrants infiltrating the US. As Mendoza follows the stories of migrants in relation to various species, Indigenous peoples, and officials on both sides of the border, she argues that the need for mobility overpowered both governments’ laws, fences, and agents. At the same time, the border’s symbolic power became a source of terror not only for migrants who try to cross into the US but for those who feel they cannot cross back, making the US a nation that suspends immigrants between two worlds.
Click Here to Purchase
Reviews
“A triumph of intellect and compassion. Mendoza tells a century-long tale of the entire US-Mexico border that no one else has.” —Susan Lee Johnson, Harry Reid Endowed Chair for the History of the Intermountain West, University of Nevada, Las Vegas
“Equally compelling and disturbing, Mendoza’s study illuminates the extensive roots of today’s border control apparatus and crises.” —Julian Lim, author of Porous Borders: Multiracial Migrations and the Law in the U.S.-Mexico Borderlands
“Many historians have written about the Mexican border, but they have not seen what Mary E. Mendoza reveals in this remarkable and original environmental history.” —Richard White, Margaret Byrne Professor of American History at Stanford University
“Accessible history of the highest order, Deadly Divide is distinguished by its humility and, even more, its humaneness.” —Thomas G. Andrews, author of Killing for Coal: America’s Deadliest Labor War
“In adding nonhuman life to the history of the border, Mendoza makes one of the most important contributions that I have read in a while.”
—María E. Montoya, associate professor of history, New York University
“Brilliantly researched and clearly written. Mendoza shows, in exquisite detail, the environmental, geopolitical, and social dimensions of the history of border-making.” —Virginia Scharff, University of New Mexico
“A triumph of intellect and compassion. Mendoza tells a century-long tale of the entire US-Mexico border that no one else has.” —Susan Lee Johnson, Harry Reid Endowed Chair for the History of the Intermountain West, University of Nevada, Las Vegas
“Equally compelling and disturbing, Mendoza’s study illuminates the extensive roots of today’s border control apparatus and crises.” —Julian Lim, author of Porous Borders: Multiracial Migrations and the Law in the U.S.-Mexico Borderlands
“Many historians have written about the Mexican border, but they have not seen what Mary E. Mendoza reveals in this remarkable and original environmental history.” —Richard White, Margaret Byrne Professor of American History at Stanford University
“Accessible history of the highest order, Deadly Divide is distinguished by its humility and, even more, its humaneness.” —Thomas G. Andrews, author of Killing for Coal: America’s Deadliest Labor War
“In adding nonhuman life to the history of the border, Mendoza makes one of the most important contributions that I have read in a while.”
—María E. Montoya, associate professor of history, New York University
“Brilliantly researched and clearly written. Mendoza shows, in exquisite detail, the environmental, geopolitical, and social dimensions of the history of border-making.” —Virginia Scharff, University of New Mexico
Author Bio
Mary E. Mendoza is a historian of the U.S.-Mexico Borderlands, the environment, and the history of race relations across the United States and Latin America.
Her book, Deadly Divide: How Insects, Pathogens and People Defied the U.S.-Mexico Border (UNC, 2026), examines how the natural world shaped ideas about race, gender, and security. Mendoza also co-edited Not Just Green, Not Just White: Race, Justice, and Environmental History, which brings together a group of diverse contributors to explore the rich intersections between race and environment. Together these contributors demonstrate that the field of environmental history, with its core questions and critical engagement with the nonhuman world, provides a fertile context for understanding racism and ongoing colonialism as power structures in the United States.
Mendoza has also written about migration, public health, race and racism, disability history and ableism, the carceral state, and U.S.-Mexico relations. She has published op-eds for the Washington Post and TIME Magazine, been interviewed for major news outlets, joined podcasts, and seen elements of her research featured in the New York Times and on The Daily Show. Her research has been funded by the National Science Foundation, the National Endowment for the Humanities, the Smithsonian Institution, the Woodrow Wilson Foundation, the Huntington Library, and the Clements Center for Southwest Studies, among other institutions.
Mary E. Mendoza is a historian of the U.S.-Mexico Borderlands, the environment, and the history of race relations across the United States and Latin America.
Her book, Deadly Divide: How Insects, Pathogens and People Defied the U.S.-Mexico Border (UNC, 2026), examines how the natural world shaped ideas about race, gender, and security. Mendoza also co-edited Not Just Green, Not Just White: Race, Justice, and Environmental History, which brings together a group of diverse contributors to explore the rich intersections between race and environment. Together these contributors demonstrate that the field of environmental history, with its core questions and critical engagement with the nonhuman world, provides a fertile context for understanding racism and ongoing colonialism as power structures in the United States.
Mendoza has also written about migration, public health, race and racism, disability history and ableism, the carceral state, and U.S.-Mexico relations. She has published op-eds for the Washington Post and TIME Magazine, been interviewed for major news outlets, joined podcasts, and seen elements of her research featured in the New York Times and on The Daily Show. Her research has been funded by the National Science Foundation, the National Endowment for the Humanities, the Smithsonian Institution, the Woodrow Wilson Foundation, the Huntington Library, and the Clements Center for Southwest Studies, among other institutions.
Additional Resources:
- Podcast interview with Dr. Geraldo Cadava on PublicBooks.org
- Book talk: The Greenhouse Center for Environmental Humanities
- Review: "Migrants or Animals?" in the Latin American Review of Books
