A fun read, Mann's 1491 challenges timeworn assumptions about the indigenous people of the Americas and the environments they inhabited. Mann reviews recent scholarship in environmental history, ethnography, and archaeology to make a convincing revisionist case.
Crosby's examination of the exchange of organisms between the Old World and the New following Columbus remains a canonical work in environmental history 35 years after its publication. Jared Diamond (Guns, Germs, and Steel) became a Pulitzer-winning bestseller in part by repackaging Crosby's analysis.
In Ecological Imperialism, Crosby revisited the questions raised by The Columbian Exchange on a larger geographic scale, asking why European people, plants, and animals were so successful in replicating themselves in "Neo-Europes" from Canada to Argentina to South Africa to New Zealand. "What in heaven's name," Crosby asked, "is the reason that the sun never sets on the empire of the dandelion?" You'll have to read the book for the answer.