The document discusses the Columbian Exchange, which was the widespread transfer of animals, plants, and microbes between the Old and New Worlds following contact between Europeans and indigenous peoples in the Americas. Some key impacts included the introduction of new world crops like potatoes and tomatoes to Europe, and old world crops and livestock to the Americas. However, European diseases had a devastating impact on indigenous populations, with estimates of 90% population declines in North America due to smallpox and other diseases against which Native Americans had no immunity. The exchange transformed global agriculture and economies.