Wetland Raised-Field Agriculture and Its Contribution to Sustainability: Ethnoecology of a Present-Day African System and Questions about Pre-Columbian Systems in the American Tropics

Abstract

One adaptation for farming wetlands is constructing raised fields (RF), i.e., elevated earth structures. Studies of RF agriculture have focused mostly on the vestiges of RF that were cultivated by pre-Columbian populations in the Americas. Ironically, whereas RF agriculture is still practiced nowadays in many parts of the world, including the Congo Basin, these actively farmed RF have received scant attention. Yet, studying how RF function today can shed new light on ongoing debates about pre-Columbian RF agriculture. Also, in a context of climate change and widespread degradation of wetlands, the study of RF agriculture can help us evaluate its potential as part of an environmentally sustainable use of wetlands. We carried out an ethnoecological study of RF agriculture combining qualitative and quantitative methods over a total of eight months’ fieldwork in the Congo Basin. We found that RF show great diversity in size and shape and perform several functions. Incorporation of grasses such as green manure, allows RF to produce high yields, and RF agriculture decreases flooding risk. However, it is labor-intensive and is likely always only one component of a multi-activity subsistence system, in which fishing plays a great role, that is both resilient and sustainable.

The Amazonian Savannas of French Guiana: Cultural and Social Importance, Biodiversity, and Conservation Challenges

“…In the Guianan coastal savannas, as elsewhere (McKey et al, 2014), raised-field agriculture was certainly only one component of complex subsistence systems including numerous activities in rich coastal biotopes, making long-term sedentarism possible (Rostain, 2010). This is confirmed by raised-field landscapes in the Congo Basin, where fishing and trading play a great role, and not all the raised-field areas are currently used (Comptour et al, 2018). This may also mean that previous estimates of population density made based on the areal extent of raised-field vestiges may be biased (Comptour et al, 2018).…”

“…The labor-intensive raised-field systems must have faced particular stress, leading to their abandonment (Iriarte et al, 2012;Rostain, 2010). However, it is also possible that, independent of the European conquest, changes in other activities may have diminished the relative efficiency and advantages of raised fields, contributing to the decline of their use and construction (Comptour et al, 2018). The extent to which vestiges of raised fields have survived since their abandonment has depended upon various factors including the actions of soil engineers, erosion driven by centuries of heavy rainfall and favored by burning, modern agricultural activities, and construction of current earthworks, such as roads, that modify the local hydrography and accelerate the process of return to a flat topography (McKey et al, 2010;Rostain, 2008;Rostain & McKey, 2015).…”

Agricultural innovation and environmental change on the floodplains of the Congo River

“…A more detailed and updated account of this farming system is provided by Comptour et al. (). Beyond the reach of the flood waters on the elevated surfaces of raised fields, the tuberous roots (“tubers”) of manioc have time to reach their full size and can be left in the ground for up to three years.…”

“…Although our results should be viewed with caution given the small sample size, they are consistent with farmers’ reports and our observations. Manioc grows slowly in raised fields, but the addition of grasses as green manure in raised fields to increase soil fertility (Comptour et al., ), and the possibility of leaving manioc in the ground for enough time to mature, result in high yields. By contrast, flood‐recession fields allow rapid growth of manioc tubers but are inundated for at least three months of the year and tubers must be harvested before they reach full size.…”

“…The strong interest in mitsaba cultivation is concomitant with flagging interest in raised‐field agriculture, which is not only labour‐demanding but is losing importance because one of its main functions (storage of manioc) today confers a smaller advantage, owing to the ease of access to manioc in markets (Comptour et al., ).…”