The Floating Forest: Traditional Knowledge and Use of Matupa Vegetation Islands by Riverine Peoples of the Central Amazon

Matupas are floating vegetation islands found in floodplain lakes of the central Brazilian Amazon. They form initially from the agglomeration of aquatic vegetation, and through time can accumulate a substrate of organic matter sufficient to grow forest patches of several hectares in area and up to 12 m in height. There is little published information on matupas despite their singular characteristics and importance to local fauna and people. In this study we document the traditional ecological knowledge of riverine populations who live near and interact with matupas. We expected that their knowledge, acquired through long term observations and use in different stages of the matupa life cycle, could help clarify various aspects about the ecology and natural history of these islands that field biologists may not have had the opportunity to observe. Research was carried out in five riverine communities of the Amana Sustainable Development Reserve (Brazil). Semistructured interviews were conducted with 45 inhabitants in order to register local understandings of how matupas are formed, biotic/abiotic factors related to their occurrence, the plants and animals that occur on them, their ecological relevance, and local uses. Local people elucidated several little-known aspects about matupa ecology, especially regarding the importance of seasonal dynamics of high/low water for matupas formation and the relevance of these islands for fish populations. Soil from matupas is especially fertile and is frequently gathered for use in vegetable gardens. In some cases, crops are planted directly onto matupas, representing an incipient agricultural experiment that was previously undocumented in the Amazon. Matupas are also considered a strategic habitat for fishing, mainly for arapaima (Arapaima gigas). The systematic study of traditional ecological knowledge proved to be an important tool for understanding this little-known Amazonian landscape.