The Columbian exchange of crops affected both the Old World and the New. Amerindian crops that have crossed oceans—for example, maize to China and the white potato to Ireland—have been stimulants to population growth in the Old World. The latter’s crops and livestock have had much the same effect in the Americas—for example, wheat in Kansas and the Pampa, and beef cattle in Texas and Brazil. –Alfred W. Crosby "The Columbian Exchange” What was overall impact of the Columbian Exchange on the continents of North America, South America, Europe, Africa, and Asia? A - The exchange caused widespread famine and food shortages. B - The exchange cut off interactions between cultures. C - The exchange permanently changed the natural and human environments. D - The exchange ensured that native populations retained control of their lands.