An increasingly scented world

We know that, at least in the short term, a rise in temperature exponentially increases the emission rates of most biogenic volatile organic compounds (BVOCs). It does so by enhancing the enzymatic activities of synthesis, by raising the BVOC vapour pressure, and by decreasing the resistance of the diffusion pathway (Tingey et al., 1991). BVOC emissions are thus expected to increase strongly with globally rising temperatures (IPCC, 2007). By applying the most frequently used algorithms of emission response to temperature (Guenther et al., 1995), it is easy to estimate that climate warming over the past 30 yr (IPCC, 2007) could have already increased BVOC global emissions by 10%. A further 2–3°C rise in the mean global temperature, which is predicted to occur early this century (IPCC, 2007), could increase BVOC global emissions by an additional 30–45%. Furthermore, global warming in boreal and temperate environments not only means warmer average and warmer winter temperatures, but also implies an extended plant activity season (Peñuelas & Filella, 2001), further increasing the total annual emissions. The biological and environmental effects of such increases in emissions can be substantial (Peñuelas & Llusià, 2003). However, many investigations are conducted in the laboratory, and we still do not know very much about the emissions of BVOCs in the field in response to warming. We know even less about mediumto long-term responses of BVOC emissions to warming, and about some regions of our planet, such as the Arctic, that are likely to experience the most pronounced effects of climatic warming. Tiiva et al. have started to fill this gap in our knowledge in this issue of New Phytologist (pp. 853–863). They have measured the emissions of isoprene, the most emitted reactive BVOC from vegetation, at a subarctic heath that they have experimentally subjected to a 3–4°C air temperature enhancement for 8 yr. Tiiva et al. have measured increases in emissions ranging between 56 and 83% depending on the year. Their results confirm the percentage increases in emissions expected using the standard algorithms of Guenther et al. (1995).