We simulate the potential changes in natural emissions of volatile gases from the land surface in the UK following afforestation from present-day woodland cover of 13 % to 19 % by 2050. We estimate present-day annual UK emissions of isoprene at 39 kt yr⁻¹ and total monoterpenes at 46 kt yr⁻¹, but emissions from afforested experiments show between a 3 % decrease and 123 % increase in emissions, explained by the variation in emissions activity between and within needleleaf and broadleaf trees.