The term "Columbian exchange" was coined by historian Alfred Crosby nearly 500 years after Christopher Columbus' first voyage to the New World. The term refers to the exchange of items and ideas between the Old World and New World following Columbus' journeys. The exchange included animals, plants and cultural diversities that helped to launch an "ecological revolution" beginning in the early 16th century. Virtually every group of people in the world was eventually affected--in mostly positive, but also in negative, ways. New ideas concerning agriculture and the infusion of new crops and plant species helped to feed the people of the globe and increase the population. New items such as corn, potatoes, peanuts and tomatoes became staple crops around the world. Europeans introduced many new species to the New World, including the horse, sugar cane, oranges and coffee. But the diseases brought to the New World by the Europeans drastically reduced the population of many cultures, who had no immunity. The appearance of the disease-carrying brown rats were unknown in the New World until their arrival on European ships, and many forms of unwanted plant life, such as Kudzu and Dutch Elm Disease, found their way to new lands.