Potential impact of global warming on citrus production L. Gene Albrigo Citrus Research & Education Center University of Florida
Global warming (GW) More appropriately Industrial Global Warming Typical questions What is it? What will really happen? Will it effect citrus production?
Characteristics of global warming Common concept As fossil fuels are consumed, CO 2 and other gases increase in the atmosphere These causes more of the sun s s heat to be trapped in the near-surface atmosphere of the earth, thus a Greenhouse Effect Expected climatic results are higher air, soil and water (ocean) temperatures Many areas expected to have less rain But maybe more storms & rain in our area
Why is it controversial Will it happen? Already has, temp +0.2 o C How fast will it happen? Some believe significant change in 10 years What will be the magnitude? Some predict 2 o C in ten years, others believe that will be total effect Why is all of the above uncertain How much effort will people make to stop elevation of greenhouse gases? How will these effects play out with normal climatic cycles?
Sources Will we stop production of greenhouse gases Automobile emissions Emissions from energy production Fossil fuel burning Question - Is C pool finite and therefore maximum CO 2 is regulated? Will we control our use and find alternatives fast enough? Important long time lag to reduce effects
What is the major global warming?
Interglacial warming periods
Climatic cycles and GW interaction Four (or more) climate cycles Ice ages 100,000 to 120,000 years (Sun s magnetic field changes), 15, -20,000 years between Little ice ages 1000 years Medium cycles 50 to 150 years (solar changes?) Short cycles 10 years (sun spots) Short-short cycles 3 to 5 years (ENSO) Where are we in these cycles as GW occurs?
Ice ages with interglacial periods Today
Ice ages - continued Normal interglacial increase is 50 increase % interglacial of 50 %, period, but now now near 100 100 % % We are now We about are 15, 15, to to 18,000 18,000 years years into into interglacial period period
Temperature change CO2 out of previous range CO2 and T have been coincident in previous cycles
Medium cycles 50-60 year cycles These are ground based measurements satellite measurements are almost flat
Short cycle climate change
Short- short cycle changes ENSO Florida Winters Albrigo 3 to 7 years Pattern less regular past 15-20 years.
The long and the short of it Several normal climate cycles exist Where are we in each cycle Then we can assess the likely impact of global warming Is GW affecting us this year? GW should be a trend, not a 1 year change This is not an easy assessment and of course it is controversial
Climate Summary 15, -18,000 into interglacial warm period Another 2, to 5,000 years to go? Temperature has risen 4.1 o C, increase another 1 degree? Sea elevations have risen 90 meters CO 2 would have risen 50 % anyway High CO 2 effect might be very useful in another 2, to 5,000 years Water vapor more important than CO 2
Possible CW changes Higher temperature, but in an Interglacial, high temperature, period Some areas expected to have lower rainfall Some areas of more rainfall tropical storm & hurricane pattern areas
CO 2 is out of range and if we assume GW will enhance the natural global warming to some Result magnitude Even higher temperatures Lower or (higher) rainfall
Potential effects of temperature changes on citrus Flower bud induction Fruit set Fruit growth rate Fruit quality
Flower bud induction Cool temperatures <20 o C are primary means of induction in all Mediterranean countries, Florida & Northern Mexico Good flowering requires 700 to 1200 hours Current crop load and tree condition important For Florida a 2 o C increase in temperature would decrease total induction hours 150 to 300 hours
Increased temperature (2( o C) & flower bud induction hours Normal induction hours Decrease New Induction hours 1300-1500 300 1000-1200 850 220 630 720 160 560 Calculations by Dr. Juan Valiente, Assistant Professor, Monterrey Tech Clearly this much climate warming would cause many years, especially in Mexico, to be marginal for cool temperature flower bud induction Two recent years in Mexico identified as too low for cool T induction
Temperature effects on fruit set Higher early spring temp gives faster drop This leaves less fruit for second drop High T during this drop decreases yield
Temperature effect on fruit growth hotter colder
Temperatures in tropical and subtropical climates Tropics
Temperature effect on fruit maturation % Juice Valencia senescent in 9.5 months
Temperature effect on fruit maturation Tropical % SS Subtropical
Temperature effect on fruit maturation Subtropical Tropical
Temperature effect on fruit maturation Tropical Subtropical
Increased temperature effects Less flower bud induction Higher fruit drop Faster volume growth of fruit Earlier maturation Earlier loss of juice Faster decline in acidity Usually less total soluble solids, but may accumulate faster initially Fruit reaches insipid and dry states earlier
Potential effects due to rainfall changes Flower bud induction drought stress Interaction with temperature Additional adverse effects Fruit set Fruit size Fruit quality
Flower bud induction & water relations Tropical climates do not have cool temperature flower bud induction Economic levels of flower bud induction require drought stress - 60-70 days Most tropical climates have 2 drought and 2 rainy periods Therefore 2 flowerings/year occur Citrus yields have always been less in these conditions
Would Mexico and maybe Florida become more dependant on a mixture of induction factors?
Some water related adverse impacts from global warming If GW becomes more severe and leads to extended drought periods Excessive amounts of drought stress cause leaf drop and suppressed photosynthesis Extended drought reduces available water for irrigation but trees need more water if hotter climate Less river and underground water If ocean warming leads to more tropical storms More water, more tropical storms & hurricanes
Fruit set and fruit size Fruit set Available water essential for good fruit set Interacts with temperature high temperature requires more water - stress more likely with inadequate irrigation Fruit growth Water essential for cell expansion Faster growth at higher temperatures (tropics) but only with adequate irrigation or rainfall
Summary Change in rainfall effects Less water We become warmer & dryer In winter = more drought induction In spring = less fruit set and fruit growth In summer & fall = higher soluble solids concentration, less total SS/area More water We become warmer but wetter In winter = less chance for flower bud induction by drought particularly if temperatures higher In spring = more fruit set and fruit growth In summer & fall = diluted soluble solids
Why would Florida become wetter? Higher temperatures from GW Temperature increases in Atlantic and Caribbean oceans More tropical storms and hurricanes are formed and impact Caribbean basin Florida gets more rainfall and hurricanes but possibly more seasonal
Hurricane effects Fruit losses Tree losses Canopy effects Leaf loss Fall flush Very slow tree recovery Disease and vector spread
Hurricanes through Florida in 2004 Charley Frances Jeanne Ivan rain only
Fruit losses 25 to 80 %
Canopy effects heavy fall flushes
Heavy fall flush damaged by second hurricane
Canopy losses fall flush age Shoot age and flowering ability Total buds New shoots # Flower shoots # Flowers % 4 weeks 722 155 2 1.2 6 weeks 583 167 32 19.2 8 weeks 537 139 83 59.7 10 weeks 390 166 113 68.1
Canopy effects long term yield losses 2004 2005 unprecedented number of hurricanes over same citrus area (4-5) Area with only 2004 hurricanes (3) had reduced yields through 2007-8 8 harvest Even 2007-08 08 flower bud induction required more hours than normal to get a heavy bloom Can citrus be economical if hurricanes become more frequent?
Summary Global warming is happening due to natural interglacial period, but intensity of human effect is speculative only It would make flower bud induction more difficult and require dryer winters to compensate for reduced cool temperatures Depending on dryer or wetter scenario, fruit set and development could be significantly benefited or hindered
What does the future bring for your citrus production area next year or in the next 2000 years?