OFFQ - Impact of tropospheric ozone on food and feed quality of brassica species: Final report

Human activifies are having an unprecedented impact on the global environment and major climatic changes have been predicted (and are already being observed) as a consequence of this. Ozone (O3) is a naturally occurring Chemical present in both the stratosphere (the 'ozone layer’, 10 - 40 km above the earth) and in the troposphere (0 - 10 km above the earth). Whereas stratospheric O3 protects the Earlh’s surface from solar UV radiation, tropospheric O3 is (after CO2 and CH4) the third most important greenhouse gas (Denman et al, 2007; Solomon et al, 2007). Besides its role as a direct greenhouse gas, O3 has been identified as the most important rural air pollutant, affecting human heaith and materials, as well as vegetation (WGE, 2004).
Increased emissions associated with fossil fuel and biomass buming (Gauss et al, 2006; Denman et al, 2007), long-distance and even intercontinental transport of O3 precursors have resulted in a steady increase in O3 concentration in rural areas hundreds and thousands of kilometres from the original sources of pollution (Prather et al, 2003). Nearly one-quarter of the Earth’s surface is currently at risk from mean tropospheric O3 in excess of 60 ppb during midsummer with even higher local concentrations occurring (Fowler et al, 1999 a,b). This is well above the mean concentration of 40 ppb that has been determined for damage to sensitive plant species (Fuhrer et al, 1997; Mills et al, 2000; LRTAP Convention, 2007). Several scenarios indicate that concentrations of tropospheric O3 might further increase throughout the 21st century (Gauss et al, 2003); simulations for the period 2015 through 2050 project increases in tropospheric O3 of 20 to 25% (Meehl et al, 2007). The global pattems of exposure of vegetation to O3 are also changing. A prediction of the differences in annual global mean surface O3 concentrations from 1990 to 2020 has recently been medelied by Dentener et al (2005), showing increases in all major agricultural areas of the northem hemisphere with large spatial variation. In North America and Western Europe reductions in peak O3 concentrations are expected (e.g. Gardner & Doding, 2000) but these changes are offset by the predicted increases in global background tropospheric concentrations (NEGTAP, 2001). Furlhermore, in parts of Asia, Latin America and Africa, these increases in background concentrations are combined with trends of increased emissions of O3
precursors, suggesting that current and future impacts of O3 on crops and forests in these areas will be very significant (Emberson et al, 2001). Other important interactions may arise from the fact that O3 as such alters the performance of herbivorous insect pests and of plant pathogens, which will themselves be influenced by climate change, e.g. as a result of greater survival under milder winter conditions.