Résumé
Floodplain savannas offer unique opportunities for niche construction through soil engineering by plants, animals and humans. In these shallowly, seasonally flooded environments, an elevational increase of even a few cm can make the difference between anaerobic and aerobic conditions in soil. Organisms that can build elevated mounds can thus garner huge benefits. Soil animals create islands of well-drained soil in which they can live, and humans build agricultural raised fields in which to plant flooding-intolerant crops. Our group is conducting a comparative study of the spectacular earth-mound landscapes built by termites, ants, earthworms, and humans in floodplain savannas, in six countries across two continents. We examine the mechanisms driving spatial regularlity, compare the structure and functioning of human-made and natural earth-mound landscapes, and study how the two interact. Ironically, the best-known agricultural raised fields are from South America, where they exist only as vestiges of earthworks made by pre-Columbian farmers. To address the many open questions about how pre-Columbian raised-field agriculture functioned, we seek inspiration by studying present-day floodplain-savanna raised-field farmers in Africa, where this kind of agricultre has been almost entirely neglected by researchers. Some floodplain savannas feature another type of cultural niche construction by humans, fisheries based on earthen fish weirs that cross vast shallow floodplains. Here again, present-day ethnographic analogues from Africa yield insight into pre-Columbian systems in South America.