Current and lost diversity of cultivated varieties, especially cassava, under swidden cultivation systems in the Brazilian Atlantic Forest

Tropical agricultural systems characterized by swidden-fallow practices have been studied in many tropical areas of the world. One feature of these systems is the high diversity of cultivated species and varieties. The objective of this paper was to analyze the inter and intraspecific diversity of cultivated crops under swidden cultivation systems adopted by caicaras in the Brazilian Atlantic Forest, and the genetic erosion of this diversity in the last decades. To analyze the inter and intraspecific diversity of cultivated crops under swidden cultivation systems in the Brazilian Atlantic Forest, interviews were performed in 33 swidden agriculturists' households concerning the species and varieties under cultivation and others that have been lost. The plots were visited to check the crops cited in the interviews. The agriculturists cited 261 varieties from 53 crop species, with 30.6% of lost varieties. Each agriculturist cited an average of 25 varieties. The main crop was cassava (Manihot esculenta Crantz), followed by yams (Dioscorea spp.), sweet potato (Ipomoea batatas Poir.), squash (Cucurbita pepo L.), sugarcane (Saccharum officinarum L.), and beans (Phaseolus vulgaris L.). Among the interviewed agriculturists, 87% of them have sons and/or daughters not involved in agricultural activity, reflecting a trend toward the loss of the local agricultural skills. A model was proposed to explain the dynamics of the system focusing on the crop diversity and considering the resource resilience. The exchange of crop varieties among agriculturists builds a network which buffers against the loss of the managed diversity in the regional scale. Features such as the itinerancy cycles of fallow/swidden, and the traditional ecological knowledge contribute to the increasing of the managed diversity. However, the agriculturists also pointed out several factors contributing to the depletion of the managed diversity, related to restrictive environmental laws, rural exodus, increasing tourism, and changing of livelihood activities. The loss of crop diversity indicates the urgency for strategies towards the maintenance of the diversity and knowledge tied to the agricultural systems of caicara communities, calling for specific strategies and policies to avoid the loss of their agricultural legacy.