Floristic impoverishment of Amazonian floodplain forests managed for açaí fruit production

• Euterpe oleracea Mart. palms are managed in várzea forests of the Amazon estuary.
• We investigated the tree community structure in managed and unmanaged estuary plots.
• Managed forests have a lower basal area, richness and diversity of tree species.
• Strategic conservation planning is needed to prevent regional biodiversity loss.

Enrichment planting of açaí palms (Euterpe oleracea Mart.) has intensified in Amazonian floodplain forests following increases in both domestic and international demand for the açaí palm fruit, now marketed as a ‘superfood’. The consequences of this expansion for regional biodiversity are poorly understood and herein we aim to evaluate how variation in açaí management intensity in várzea forests influences forest floristic composition and structure. We established 24 (10 × 100 m) sampling plots in eastern Amazonian forests managed for açaí production and 12 sample plots in unmanaged floodplain forests. We explored variation in community structure (richness, diversity and dominance) mediated by açaí density and habitat characteristics. We measured and identified 3168 trees belonging to 43 families, 119 genera, and 169 species. The current exploitation model practiced by Amazonian riverine communities, maintaining a mean density of 200 stem/ha, led to a loss of over 50% of tree species diversity and a 63% reduction in the number of pioneer species. This translated into a homogenization of the floristic community favoring species of economic interest. We underscore the need for multi-taxon studies to support management plans for economic–ecological zoning in Amazonian várzea forests managed for açaí to prevent broad-scale cryptic biodiversity loss.