Impact of ozone pollution on agricultural production Gina Mills Head of the Programme Centre for the ICP Vegetation Centre for Ecology and Hydrology, Bangor, UK http://icpvegetation.ceh.ac.uk/
CO 2, Ozone How does ozone damage crops? Cell membranes are damaged, spots appear on leaves Photosynthesis is inhibited Seeds are smaller, fewer in number Roots are smaller Leaves die back early http://icpvegetation.ceh.ac.uk/
ICP Vegetation: Collating field evidence of ozone effects Visible ozone injury on field grown crops Biomonitoring with ozone-sensitive and resistant varieties Greece Reducing ozone concentration by filtration Ozone injury on bean leaves Ozone sensitive Ozone resistant Experiments in Spain http://icpvegetation.ceh.ac.uk/
Based on concentration Ozone concentrationbased methods overestimate effects Based on leaf stomatal uptake, the effects are lower and the distribution is different (e.g. USA) Based on ozone uptake Mills et al., submitted to PNAS Mean % wheat yield loss (2010 2012)
% yield loss (provisional results) Ozone sensitive crops Wheat Moderately sensitive crops Soybean Maize % yield loss Rice 0 2 5 7.5 10 12.5 15 17.5 20 >25
Production losses by DAC category* All crops in Upper Middle Income countries Wheat and Rice in Lower Middle Income countries Rice in Least Developed Countries (LDC) * Provisional data
Sustainability concerns (1) increasing irrigation will worsen O 3 effects Additional % yield loss would occur if irrigation is fully in use as soil moisture would not be limiting ozone uptake Some of yield benefits of added irrigation would be lost Mills et al., submitted to PNAS
Sustainability concerns (2) Reduced fertilizer efficiency 1.2 Global data Swedish experiment relative N fertilizer efficiency 1.0 0.8 0.6 0.4 0.2 y = -0.0045x + 1.0299 R² = 0.6065 0.0 0 50 100 150 [O 3 ] daytime, ppb The fraction of N (P and K) added that ends up in the grain is negatively affected by ozone leading to additional environmental problems Adding more N fertilizer is not a good solution to the ozone problem! Broberg et al. (submitted)
ICP Vegetation: New flux-based critical levels agreed in 2017 Species (group) Effect parameter Potential effect at CL (% reduction) Critical level (mmol m -2 PLA) Potential max. rate of reduction (%) per unit POD Y SPEC Crops (POD 6 SPEC) Wheat Grain yield 5% 1.3 3.85 1000-grain weight 5% 1.5 3.35 Protein yield 5% 2.0 2.54 Potato Tuber yield 5% 3.8 1.34 Tomato Fruit yield 5% 2.0 2.53 Fruit quality 5% 3.8 1.30 Forest trees (POD 1 SPEC) Beech and birch Whole tree biomass 4% 5.2 0.93 Norway spruce Whole tree biomass 2% 9.2 0.22 Med. deciduous oaks Whole tree biomass 4% 14.0 0.32 Root biomass 4% 10.3 0.45 Med. evergreen Above-ground biomass 4% 47.3 0.09 (Semi-)natural vegetation (POD 1 SPEC) Temperate perennial grassland Above- ground biomass 10% 10.2 0.99 Total biomass 10% 16.2 0.62 Flower number 10% 6.6 1.54 Med. annual pasture Above- ground biomass 10% 16.9 0.85 Flower/ seed biomass 10% 10.8 1.61
Summary The ICP Vegetation PCC is collating global evidence of ozone effects on crops in the field Quantifying impacts using ozone flux (Phytotoxic Ozone Dose) indicates areas of the world/europe where the risk is greatest Production losses in Upper Middle Income Countries match those for developed countries when totalled for wheat, soybean, maize and rice Increased use of irrigation will worsen ozone impacts Ozone reduces fertilizer efficiency applying more fertilizer is not a simple solution for compensating for yield losses New critical levels have been established this year for vegetation and Chapter 3 of the Modelling and Mapping manual has been updated http://icpvegetation.ceh.ac.uk/
SPARES
Potential O 3 impacts in Europe: wheat yield 2005 Current legislation, 2020 Current legislation, 2030 10.7% loss 8.8% loss 8.2% loss Percentage yield loss determined using (POD 3 IAM) 1 Yield losses due to ozone still expected in 2030 with current legislation 1 simplistic soil water function used http://icpvegetation.ceh.ac.uk/
Ozone profile effects are explained by flux (POD 6 SPEC) Yield (tonnes ha -1 ) 12 10 8 6 4 2 0 (A) y = -0.76x + 11.6 Adj. R² = 0.70 0 2 4 6 8 10 POD 6 SPEC (mmol m -2 ) O 3 (24h mean) background peaks Low 27.0 30.3 Medium 37.0 39.2 High 48.6 50.2 Very high 56.5 55.4 Key Open symbols represent background O 3 treatments Closed symbols represent peak O 3 episodes. Symbols of the same shape represent pairs of similar 24 h mean O 3 concentrations The yield response of wheat to ozone is determined by the accumulated POD 6 SPEC, regardless of whether the ozone is applied with a peaks profile or as elevated background Policy implication: all ozone flux counts!
Are current cultivars as sensitive? 1.2 1.0 Relative yield 0.8 0.6 0.4 0.2 Older varieties Mulika Skyfall 0.0 0 10 20 30 40 50 Ozone flux (mmol m -2 ) Ozone exposure experiments, CEH, UK Bread-making wheat varieties show a range of sensitivity to ozone E.g. two recently introduced varieties Skyfall and Mulika, released in 2014 and 2011 respectively Could resistant cultivars be exploited in breeding programmes?