Environmental and Cultural Factors Limiting Potential Yields Environmental Factors Carbon dioxide ¾Atmospheric Carbon Dioxide ¾Solar Radiation ¾Temperature (Extremes) ¾Water ¾Wind ¾Nutrients (N and K) ¾Others, ozone etc., ¾Growth Regulators (PIX) K. Raja Reddy Krreddy@pss.msstate.edu Why are we concerned with CO2? CO2 • Atmospheric CO2 is essential for life on earth. • Plants grow through photosynthesis, a process that uses the energy from sunlight to combine carbon dioxide (CO2) from the air with water to make carbohydrates plus oxygen. H2 0 Light, Plant, Water, Nutrients 6 CO2 + 6 H2O C6H12O6 + 6 O2 • The carbohydrates formed through photosynthesis feed not only the plants, but also almost all other organisms on earth, including those that eat the plants and those that eat the animals that eat the plants. • Now, as the atmospheric CO2 is rising, we are seeing almost parallel decreases in atmospheric oxygen. • The oxygen concentration is so much higher than that of CO2 that the decrease in oxygen from fossil fuel combustion is not a problem, but it demonstrates the connections between these two critically important atmospheric constituents. A Hierarchy of Plant Responses to CO2 – C3 Plants Atmospheric CO2 ? Stomatal Resistance Photosynthesis Transpiration About 250 per sq mm . Direct effect of CO2 on canopy or Microclimate Soybean Face Experiments Photorespiration Carbon Availability Tissue Temperature Tissue Water Potential Growth and Development Yield Acock, 1990 1 Crop Responses to Atmospheric Carbon Dioxide Atmospheric CO2 and Plant Responses C3 example, cotton response Of the 250,000 higher plant species: C3 photosynthetic model 222,000 (89%) C4 photosynthetic model 8,000 (3.2%) Crassulacean Acid Metabolic (CAM) photosynthetic model 20,000 (8%) Canopy Photosynthesis, mg CO2 m-2 s-1 5 4 3 2 1 0 0 200 400 600 800 1000 Carbon Dioxide Concentration, ppm or µL L-1 Carbon Dioxide and Photosynthesis Species Variability Plant Adaptations to Atmospheric Carbon Dioxide Direct effect of increased CO2 on crop photosynthesis might lead to higher global food production ¾ Weeds: Plants are NOT unique and UNIFORM in stimulation of their photosynthesis by elevated CO2. ¾ Losses to Pests: Several recent studies show that insects eat more high-CO2 grown material, because of decreased protein levels. ¾ Climate: The connection between CO2 and climate is increasingly well understood, with vast majority of evidence indicating that continued build up of these radiative gases causes gradual warming. Plant Adaptations to Atmospheric Carbon Dioxide Natural Ecosystems In natural ecosystems, elevated CO2 has an effect similar to that on crops; but the responses tend to be smaller or even absent. And, features like: ¾ Recreational value: Since responses are NOT uniform; there will be winners and losers. Evidence suggest that trees and may be introduced species are being favored in a high-CO2 world, thus affecting the recreational and grazing value. ¾ Biodiversity: Rare or endemic species may be at a disadvantageous position because of their poorly adapted features. Our Biosphere is Changing. What are the driving factors for this change? 2 Trends, Signs and Signatures from the Earth Global Carbon Emissions- Sources Global Carbon Emissions- Sources Total 60 6000 5000 4000 Million metric tons of carbon Million metric tons of carbon 7000 50 40 30 20 10 0 1750 3000 Annual carbon emissions, metric tons per person Trends, Signs and Signatures from the Earth 1775 1800 Year 1825 Liquids 1850 Solids 2000 Gases 1000 Cement Flaring 0 1750 1800 1850 1900 Year 1950 7 6 USA 5 4 3 Russia Germany Japan 2 Mexico Global China Brazil India Nigeria 1 0 1950 2000 1970 1980 1990 2000 Year Trends, Signs and Signatures from the Earth Mean Carbon Emission Rates Trends - World Population 6 Mean of 1991-2000 10 5 8 4 Population in Billions Mean Carbon Emissions, metric tons per person 1960 3 2 World 6 4 Developing World 2 1 Developed World 0 1900 0 Global Nigeria India Brazil China Mexico Japan Germany Russia 1920 1940 USA 1960 1980 2000 2020 2040 Year Representative Countries Trends, Signs and Signatures from the Earth Trends, Signs and Signatures from the Earth Atmospheric Carbon Dioxide Concentration Atmospheric Carbon Dioxide Concentration 350 375 300 CO2 Concentration, ppm Carbon Dioxide Concentration, ppm 400 250 200 350 325 300 275 250 1700 150 3000 2000 1000 0 1750 1800 1850 1900 1950 2000 Year Years before the industrial Revolution (1850) 3 Trends, Signs and Signatures from the Earth Trends, Signs and Signatures from the Earth Global Carbon Emissions and Carbon Fixation Atmospheric Carbon Dioxide Concentration Trends, Signs and Signatures from the Earth Trends – Atmospheric Carbon Dioxide – Monthly 400 Mauna Loa, HI Barrow, Alaska Cap Matatula Samoa South Pole Alert, Canada Cape Kumukahi Baring Head NZ Christmas Island Kermadec Island Lo Jolla Pier 380 360 360 359 CO2 Concentration, ppm Atmospheric Carbon Dioxide Concentration, µmol mol -1 Atmospheric Carbon Dioxide Concentration – South to North 340 320 1990 at Mauna Loa, HI 358 357 356 Low 355 354 353 High 352 351 350 300 1957 1962 1967 1972 1977 1982 1987 1992 1997 2002 2007 Year Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Month of Year Trends – CO2 Concentration Diurnal – Starkville, 27 July 1999 Global Circulation Models Predictive Capabilities – Data Requirements 440 CO2 Concentration, ppm 23 July 1999 420 400 380 360 340 0 2 4 6 8 10 12 14 16 18 20 22 24 Time of the Day (Central Standard Time) 4 Trends, Signs and Signatures from the Earth Trends, Signs and Signatures from the Earth Greenhouse gases and Climate Change Projected Global Carbon Dioxide Concentrations Trends, Signs and Signatures from the Earth Predicted Annual Temperature Increase in GCMs for Doubled CO2 Scenario Future trends in global carbon dioxide concentration and associated climate change, if no interventions are made (Adams et al., 1990) Region Climate variable 2025 2050 2100 Carbon dioxide concentration 405-460 ppm 445-640 ppm 540-970 ppm Global mean temperature change from the year 1990 0.4-1.1 oC 0.8-2.6 oC 1.4-5.8 oC 5-32 cm 9-88 cm Global mean sea-level 3-14 rise from the year cm 1990 GISS GFDL °C Southeast Delta 3.5 5.3 4.9 4.4 Northern Plains Southern Plains 4.7 4.4 5.9 4.5 Mountain Pacific 4.9 4.7 5.3 4.7 Historical Lint Yield - Causes and Effects Trends That Shape Our Future Relative Responses CO2, NPK Use, Cotton Acreage and Yields 5 900 12000 10000 8000 6000 337% 700 35 30 Yield 600 25 500 20 CO2 400 15 NPK use 300 4000 200 2000 100 1860 10 4 360 340 320 Relative Response 14000 800 Yield 380 [CO2], µmol CO2 mol-1 16000 40 Area US NPK Use, Million tons 18000 Cotton Lint Yield, kg ha-1 Cotton Harvested Area, ha (*1000) 20000 3 2 Genetics 61% 19% 300 1 280 0 1920 CO2 5 1880 1900 1920 1940 Year 1960 1980 0 2000 1930 1940 1950 1960 1970 1980 1990 2000 Year 5 Summary ¾ CO2 is a critical component of the atmosphere. Suggested Reading Material: ¾ Increases in CO2 will have both positive and negative impacts on agriculture and natural ecosystems. 1. Climate Change and the Global Harvest. C. Rosenzweig and D. Hillel. 1998. Oxford University Press, pages 1-69. ¾ The negative impacts expressed through climate change and global warming affect not only agriculture but also other sectors. 2. Climate change and variability by L. O. Mearns. In: Climate Change and Global Crop Productivity, edited by K. R. Reddy and H. F. Hodges. 2000. Pages 7-35. ¾ Overall, increasing CO2 is likely to cause serious problems. 3. Agricultural contribution to Greenhouse gas emissions by D. C. Reicosky, J. L. Hatfield and R. L. Sass. In: Climate Change and Global Crop Productivity, edited by K. R. Reddy and H. F. Hodges. 2000. Pages 37-55. 4. Reddy, K. R. 2005. Climate change and global productivity of goods and services. Souvenir, Sri Venkateswara University College Golden Jubilee Celebrations, Sri Venkateswara University, Tirupati. India, 163-168. ¾ It is extremely unlikely that terrestrial uptake of CO2 will be sufficient to prevent these climate problems. ¾ A major adaptive response will be breeding or designing new cultivars: heat-and-cold and drought resistance crop varieties that may be better adapted to new climate (short-term fixes). ¾ Additional steps to limit CO2 emission by world’s nations is another possibility (long-term strategies). 6