Contact with the Europeans caused a population shortage when the Native Americans contracted deseases that they were not immune to. This population decrease indirectly caused a drastic labor shortage throughout America, which eventually resulted in African slavery on a vast scale in the Americas. The landscape was also drastically effected, by replacing the New World plants with Old World plants. The Columbian Exchange marked the beginning of an era of global trade. Oceans no longer represented barriers to people, goods, animals, plants and microbes. Contact catalyzed progress, but it also produced suffering and exploitation.