Tropical forests store vast quantities of carbon account for one-third of the carbon fixed by photosynthesis and are a major sink in the global carbon cycle. Recent evidence suggests that competition between lianas (woody vines) and trees may reduce forest-wide carbon uptake; however estimates of the impact of lianas on carbon dynamics of tropical forests are crucially lacking. Here we used a large-scale liana removal experiment and found that at 3 y after liana removal lianas reduced net above-ground carbon uptake (growth and recruitment minus mortality) by