Potential impact of global warming on citrus production. L. Gene Albrigo Citrus Research & Education Center University of Florida

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1 Potential impact of global warming on citrus production L. Gene Albrigo Citrus Research & Education Center University of Florida

2 Global warming (GW) More appropriately Industrial Global Warming Typical questions What is it? What will really happen? Will it effect citrus production?

3 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

4 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?

5 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

6 What is the major global warming?

7 Interglacial warming periods

8 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?

9 Ice ages with interglacial periods Today

10 Ice ages - continued Normal interglacial increase is 50 increase % interglacial of 50 %, period, but now now near % % We are now We about are 15, 15, to to 18,000 18,000 years years into into interglacial period period

11 Temperature change CO2 out of previous range CO2 and T have been coincident in previous cycles

12 Medium cycles year cycles These are ground based measurements satellite measurements are almost flat

13 Short cycle climate change

14 Short- short cycle changes ENSO Florida Winters Albrigo 3 to 7 years Pattern less regular past years.

15 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

16 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

17 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

18 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

19 Potential effects of temperature changes on citrus Flower bud induction Fruit set Fruit growth rate Fruit quality

20 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

21 Increased temperature (2( o C) & flower bud induction hours Normal induction hours Decrease New Induction hours 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

22 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

23 Temperature effect on fruit growth hotter colder

24 Temperatures in tropical and subtropical climates Tropics

25 Temperature effect on fruit maturation % Juice Valencia senescent in 9.5 months

26 Temperature effect on fruit maturation Tropical % SS Subtropical

27 Temperature effect on fruit maturation Subtropical Tropical

28 Temperature effect on fruit maturation Tropical Subtropical

29 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

30 Potential effects due to rainfall changes Flower bud induction drought stress Interaction with temperature Additional adverse effects Fruit set Fruit size Fruit quality

31 Flower bud induction & water relations Tropical climates do not have cool temperature flower bud induction Economic levels of flower bud induction require drought stress 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

32 Would Mexico and maybe Florida become more dependant on a mixture of induction factors?

33 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

34 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

35 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

36 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

37 Hurricane effects Fruit losses Tree losses Canopy effects Leaf loss Fall flush Very slow tree recovery Disease and vector spread

38 Hurricanes through Florida in 2004 Charley Frances Jeanne Ivan rain only

39 Fruit losses 25 to 80 %

40 Canopy effects heavy fall flushes

41 Heavy fall flush damaged by second hurricane

42 Canopy losses fall flush age Shoot age and flowering ability Total buds New shoots # Flower shoots # Flowers % 4 weeks weeks weeks weeks

43 Canopy effects long term yield losses unprecedented number of hurricanes over same citrus area (4-5) Area with only 2004 hurricanes (3) had reduced yields through harvest Even flower bud induction required more hours than normal to get a heavy bloom Can citrus be economical if hurricanes become more frequent?

44 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

45 What does the future bring for your citrus production area next year or in the next 2000 years?