As these histories emerged, another wave of publications began to place animals in a particular time and place, explore the consequences for nations and empire, and also describe animals as actors in their histories and ours. Students of environmental history long had recognized these transformations, including Alfred Crosby in The Columbian Exchange: Biological and Cultural Consequences of 1492 and William Cronon in Changes in the Land: Indians, Colonists, and the Ecology of New England. A subsequent generation of environmental histories cast the extension of agriculture and domesticates as part of a larger project of colonialism, a perspective pioneered in Frieda Knobloch’s The Culture of Wilderness: Agriculture and Colonization in the American West. More recently, Diana L. Ahmad’s Success Depends on the Animals: Emigrants, Livestock, and Wild Animals on the Overland Trails, 1840–1869 explores the different or even contradictory relationships of empathy, animosity, and brutal pragmatism that animated relationships with animals in westering. One of the most detailed and sophisticated accounts of encounter with diverse species is Virginia DeJohn Anderson’s Creatures of Empire: How Domestic Animals Transformed Early America. Anderson’s work explores the English and their livestock, and how domestic animals in the Atlantic colonies were agents of an ideological challenge and environmental change, and causes of conflict and death in the clash between Natives and newcomers.
The Columbian exchange : biological and cultural consequences of 1492 by 
Changes in the land : Indians, colonists, and the ecology of New England by 
The culture of wilderness : agriculture as colonization in the American West by 
Success depends on the animals : emigrants, livestock, and wild animals on the Overland Trails, 1840-1869 by 
Creatures of empire : how domestic animals transformed early America by