Overview
- The finding comes from a Science Advances study published on Thursday, August 20, 2026, that used direct air measurements from a 102 m platform at the Beijing Meteorological Tower to track volatile organic compounds in real time.
- Researchers measured that vegetation produced about 10 percent of total VOC emissions but accounted for roughly 52 percent of the chemical reactivity that leads to ground-level ozone, with isoprene from trees the dominant source.
- Isoprene-emitting species such as willow and poplar make up about 35 percent of Beijing’s trees and roughly 65 percent of Sydney’s, and the team found species mix explains much of the differences in urban isoprene emissions between cities.
- Heat sharply amplifies the problem because tree VOC reactivity rises seven- to eight-fold between 20°C and 35°C, raising vegetation’s share of total VOC reactivity from about 21 percent to 74 percent on hotter days.
- Authors recommend adding BVOC emission potential to urban tree-selection rules and targeted replacement of high-emitting trees during routine renewal as a complement to continued NOx controls and other heat-mitigation measures to protect public health.