Abstract
Despite an attempt at intercontinental synthesis by Denevan and Turner almost 50 years ago, studies of agricultural raised fields (RFs) in the Neotropics, on the one hand, and in Africa and New Guinea, on the other, are separate research traditions, with almost no communication between them. Neotropical studies refer to "raised-field agriculture", and almost exclusively concern archaeological systems in wetlands. Studies in Africa and New Guinea refer to "mound" or "ridge" cultivation, and concern mostly present-day systems (in Africa) or both present-day and archaeological systems (in New Guinea), in both uplands and wetlands. Ethnographic studies of present-day systems provide insights into questions about past systems that are inaccessible using archaeological methods alone. Our review suggests that the Neotropical focus on RF agriculture as an exclusively wetland adaptation is misleading. We argue that the most widespread purpose of building RFs, in both wetland and upland environments, is to concentrate topsoil and organic matter, enabling creation of fertile patches in infertile and low-biomass grassland environments. Avoiding flooding is an important function of RFs built in wetlands and wetland margins. We further show that Old-World RFs are often not perennial, but are short-lived structures that rotate over the landscape, being torn down and rebuilt nearby in successive cycles. Short fallow periods are allowed (or even favored) by methods of managing fertility. Finally, we argue that the restriction-in all continents-of archaeological raised fields to wetland and wetland-margin environments is in part a result of their better preservation from erosion in wetland than in upland environments.