Ecosystem-level estimates of the effect of lianas on tree growth in mature tropical forests are needed to eval- uate the functional impact of lianas and their potential to af- fect the ability of tropical forests to sequester carbon but these are currently lacking. Using data collected on tree growth rates local growing conditions and liana competi- tion in five permanent sampling plots in Amazonian Peru we present the first ecosystem-level estimates of the effect of lianas on above-ground productivity of trees. By first con- structing a multi-level linear mixed effect model to predict individual-tree diameter growth model using individual-tree growth conditions we were able to then estimate stand-level above-ground biomass (AGB) increment in the absence of lianas. We show that lianas mainly by competing above- ground with trees reduce tree annual above-ground stand- level biomass increment by ∼10% equivalent to 0.51 Mg dry weight ha−1 yr−1 or 0.25 Mg C ha−1 yr−1. AGB incre- ment of lianas themselves was estimated to be 0.15 Mg dry weight ha−1 yr−1 or 0.07 Mg C ha−1 yr−1 thus only com- pensating ∼29% of the liana-induced reduction in ecosys- tem AGB increment. Increasing liana pressure on tropical forests will therefore not only tend to reduce their carbon storage capacity by indirectly promoting tree species with low-density wood but also their rate of carbon uptake with potential consequences for the rate of increase in atmospheric carbon dioxide.