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The Amazon basin strongly influences the global carbon cycle, storing billions of tonnes of carbon in a relatively small number of 'hyperdominant' tree species. However, the Amazon carbon stock is threatened by land-use change. In the remaining forest patches, trees close to the forest border bear various physical and biotic edge effects that alter plant growth and survival. To assess how edge effects influence tree mortality and carbon storage, we investigated the occurrence of hyperdominant tree species in the Brazilian Amazon between 1988 and 2021. Evaluating tree records from a network of permanent plots and herbarium collections, we found that 22 % of tree occurrence records were in deforested areas, 35% within 1 km of the forest edge, and 43 % in continuous forest. At the local scale in Central Amazonia, tree monitoring data over 30 years revealed that forest fragments hyperdominant trees had twice the mortality rate of continuous forest ones due to edge effects during the 15 years following edge establishment. Although trees in fragments had higher initial growth, this pattern declined over the years and eventually resulted in significant carbon loss, mainly from tree mortality. Edge effects have led to annual declines in the biomass of forest remnants, suggesting that hyperdominant species are also susceptible to disturbances that lead to degradation and forest losses. Conservation of the Amazon forests requires an approach that considers the effects of local disturbances on carbon stocks in the region. • In recent decades, deforestation has lost 22 % of historical records of hyperdominant tree species in the Brazilian Amazon. • 35 % of occurrence data are on forest edges, susceptible to the negative impacts caused by fragmentation and deforestation. • Hyperdominant populations in Central Amazon edges showed twice the mortality rate in the first 15 years after edge creation. • The unbalanced tree mortality directly affects the Carbon cycle, representing losses, even in forested areas. [ABSTRACT FROM AUTHOR]