Paleoecology and Archaeology provide the tools to reconstruct past ecosystems. Via these techniques we can obtain a long-term vision of disturbance and land use that may have left a legacy on modern ecology and ecosystem services. This leads us to ask “What is natural in the Americas?” and “What was the ecological legacy of as many as 11 million inhabitant of the New World prior to 1492?”. The implication that we do not know the natural state of ecosystems resonates in applied ecology, i.e. how can we conserve if we do not know what it is we are trying to conserve? Concerns over past impacts are also applicable to theoretical studies: i.e. are our classic forest plots for tree distribution analysis just one generation away from being a field? For years archaeologists have discussed the possibility that the Americas were far more influenced by pre-Columbian (i.e. before the appearance of significant European influences) human activity than previously supposed. A paradigm shift in our view of native American cultures has taken place from the old perception of hunter-gatherers whose presence on the ecosystem was barely felt, to one of complex societies capable of landscape transformation. Evidence for such large changes includes the terracing of much of the tropical Andes, the construction of habitation islands and fishweirs in Bolivia, the modification of Amazonian soils to increase fertility, and large organized settlements along the Amazon channel. In North America, the city of Cahokia provides evidence of the development of complex societies. Paleoecological and archaeological records provide the most direct means of knowing how humans used and shaped ecosystems prior to European settlement. The goal of this symposium is to bring together paleoecologists, ethnobotanists, historical ecologists, and archaeologists who will present data and case studies from a variety of ecosystems and time periods to enhance our understanding of pre-Columbian impacts in the Americas. Our first speaker will provide an overview of the influence of humans on fire regimes in the Americas over the past 10,000 years. The next four speakers will address the influences that humans had on pre-Columbian landscapes in North America. One speaker will focus on human modification of the landscape in Central America and four speakers will provide evidence for cultural landscapes in South America. The last talk will discuss the conservation implications of pre-historic and historic human modification of landscapes.