The idea that Amazonian forests are largely intact has instigated ecologists and conservationists worldwide. Although many ecological studies overlook the influence of pre-Columbian societies in Amazonian forests, archaeological studies are finding mounting evidence of their activities in areas previously considered as pristine. Anthropogenic soils and monumental earthworks are some examples of how these large societies modified their environment. Recently, new ecological evidence has confirmed this view by revealing persistent past human effects on plant communities, and suggesting that Amazonian forests hold legacies of pre-Columbian activities.
However, the relative contribution of pre-Columbian vs. current local human societies in shaping these present-day floristic patterns is still controversial, partly because the distinction between their activities is challenging to quantify. Here we compared the influence of past and recent land use histories in the soils and vegetation of old-growth forests in two Amazonian regions. We studied forests at different distances from pre-Columbian occupation sites and current villages occupied by traditional and indigenous peoples. The study integrated ecological (forest inventories and soil surveys), ethnoecological (free-listing interviews, participatory mappings, guided-tours) and archaeological methods (archaeological surveys).
Results/Conclusions
We found that pre-Columbian villages are more densely distributed than current villages in both regions. Nutrients in the soils of old-growth forests (especially calcium and phosphorus) increased towards pre-Columbian villages, but most nutrients did not change with the distance to current villages. The abundance of species used as food resources increased in nutrient-rich soils, suggesting that past societies provided the environmental conditions required to increase their food security. Today, modern societies preserve these food resources in forests near their villages, whereas species used for construction are over-harvested. Overall, our results reveal that pre-Columbian land use practices enriched Amazonian soils, and that their effects are widespread across old-growth forests. Our results demonstrate how it is important to consider long-term human histories to understand present-day forest ecosystems even in the most remote regions.