LWR324 – CLIMATE CHANGE & VARIABILITY

LWR324 CLIMATE CHANGE & VARIABILITY

EFFECTS OF CLIMATE CHANGE ON AGRICULTUREL. De WetLWR324 CLIMATE CHANGE & VARIABILITYINTRODUCTIONWhat is CLIMATE CHANGE?The American Meteorological Society (AMS) defines climatechange as any systematic change in the long-term statistics ofclimate elements (such as temperature, pressure, or winds)sustained over several decades or longer. How does it happen?Climate change may be due to natural external forcings, such aschanges in solar emission or slow changes in the earths orbitalelements; natural internal processes of the climate system; oranthropogenic forcing (Pielke, 2007).

The AMS also defines anthropogenic forcing as Human-induced or resulting from human activities; often used to refer to environmental changes, global or local in scale. The AMS further defines the climate system as the system, consisting of the atmosphere, hydrosphere, lithosphere, and biosphere, determining the earths climate as the result of mutual interactions and responses to external influences (forcing). Physical, chemical and biological processes are involved in the interactions among the components of the climate system (Pielke, 2007).

INTRODUCTIONClimate variability is the cyclic change in the climate, without a change/ shift in the trend in the long term.Global warming (as well as global cooling) refers specifically to any change in the global average surface temperature. Global warming is often misunderstood to imply that the world will warm uniformly. In fact, an increase in average global temperature will also cause the circulation of the atmosphere to change, resulting in some areas of the world warming more and others less. Some areas can even cool.global warming' is still often used by media and others to describe climate change.

INTRODUCTIONGreenhouse gases are important to life here on earth. Without greenhouse gases, Earth's average temperature would be -19C instead of+14C, i.e. 33C colder. It is believed that Carbon Dioxide or CO2 is the most significant greenhouse gas released by human activities, mostly through the burning of fossil fuels and that it is the main contributor to climate change. But is it?Over the past 10,000 years, the amount of greenhouse gases in our atmosphere has been relatively stable, although this cannot be proved, because data measurement only started a few centuries ago in about 1850. Some scientists say their concentrations began to increase due to the increasing demand for energy caused by industrialization and rising populations, and due to changing land use and human settlement patterns. But is this so? For example, if one looks at the climate record, and the CO2 emissions during the Industrialisation period, then a cooling took place, not a warming!

INTRODUCTIONWHAT ARE THE EFFECTS ON AGRICULTURE?Modeling studies with different inputs:CropsTreatments management scenariosto predict yield Study the articles1. An assessment of sustainable maize production underdifferent management and climate scenarios for smallholderagro-ecosystems in KwaZulu-Natal, South Africa (Walker & Schulze 2006).-CERES-Maize crop model was adapted,-different management options (e.g. tillage + fertilizer) and -future climatic scenarios produced the following results:

Walker & Schulze (2006)

Fig. 2. Mean of simulated grain yields over 49 seasons at Potshini under different management options and climate scenarios (Walker & Schulze, 2006 p998)Walker & Schulze (2006)

Mitigation Practices (for impact-reduction)Apply inorganic fertilizer (sustains yields over long-term).No significant differences between tillages (not true for real observations).Sound farming practices & good grazing management.Model results - Tayields, while2 x CO2yields (all treatments).2 x CO2 + 2oC losses of soil organic C & N (all fertilizer and tillage treatments).Conservation tillage + rainwater harvesting (mitigate effects of temporal & spatial variability of rainfall.

Abraha & Savage (2006) 2. Potential impacts of climate change on the grain yield of maize for the midlands of KwaZulu-Natal, South Africa (Abraha & Savage, 2006).Used CropSyst, a cropping systems simulation model Daily weather data was generated for the long-term (using ClimGen) from historical weather data and then used as inputs into the model to assess the potential impact of climate change on the grain yield of maize. The following results were obtained, but should nevertheless be used with caution as the data is generated and not observed:

Fig. 4.Cumulative probability distribution of maize grain yields under (a) baseline climate, (b) equivalent doubling of [CO2]Scenario A, (c) equivalent doubling of [CO2], 2C increment to the mean daily air temperature along with 10 (20%) increment to daily precipitationScenarios B and C, (d) equivalent doubling of [CO2], 4C increment to the mean daily air temperature along with 10 (20%) increment to daily precipitation for early, locally practiced and late planting datesScenarios D and E.

Mitigations: Early planting dates (all yields).4 oCyieldsFor the latter scenario it is suggested that other cultivation adaptation techniques should be sought or

Abraha & Savage (2006) Positive EffectsNegative EffectsUnlimited H20 & 2 x CO2(increase) + Taveyield (Scenario A)Unlimited H20 & 2 x CO2 + Tave(increase)yield

2 x [CO2] + (2 oC + Ta) yield (Scenario B & C)2 x [CO2] + (4 oC + Ta) yield(Scenario D & E)

10% & 20% in precipitation no yield (Scenario B, C, D & E)a shift to other higher TT-requirement crops should be made.The model did not include negative effects of pests, diseases and weeds on yield simulation,but assumed present cultural practices and current varieties.

Abraha & Savage (2006) Van Jaarsveld & Chown (2000)3. Climate change and its impacts in South Africa (Van Jaarsveld and Chown, 2000)Climate change and its impacts on various sectors of South African economy was analyzed & the following came to light:The natural resources sectors stated that climate change would be accompanied by significant impacts on water resources & biodiversityThe production sectors said that the effects were limited or that adaptation could be undertaken to mitigate negative effects.

Van Jaarsveld & Chown (2000)CommercialPredictionsRainfall not consistentTa more consistentArid (dry) & NE (moist) regions likely to have: Evaporation ratesstressfloodSW regions:Winter frontal & orographic rainfallGrasslandsLeast affected = frost

Savanna of 20% in forage productionLivestock unaffectedMaize & Commercial forestryPowerplay between Ta & H2O and[CO2] fertilization effects & new resistant cultivars Forecasts from Natural Resource and Service were more disconcerting:10% in H2O runoff/quartenary catchments likely by 2015 and 2060 in W-SA.

Van Jaarsveld & Chown (2000)Biodiversity impactsSA 7 existing biomes could 40%2 x CO2 could Karoo biome44% of plant &80% of animal speciesalterationChange in communities (structures & functions)

Threats to human healthTwo major parasitic diseases:Malaria (to double)Schizosomiasis (to spread W)HIV/Aids continues

Van Jaarsveld & Chown (2000)SUMMARYSA is likely to experience CC in the next decades and the effects on biodiversity will be dramatic. Even so, much quantitative research still needs to be done as many questions remain unanswered.van Jaarsveld & Chown (2000)Jones & Thornton (2003)4.The potential impacts of climate change on maize production in Africa and Latin America in 2055 (Jones & Thornton, 2003)Main impacts of CC will be on the poorer communities in Africa and Latin America. A third order Markov rainfall model was developed and tested by them for maize. The results varied widely, depending on the present economic situation.Alternative production systems need to be found, although maize is the main crop for many living under the bread linehighly drought-resistant,its production would definitely be decreased, especially where water is limited. Jones & Thornton (2003)

Mitigations:More policies for market developmentfor new and existing cropsand livestock products;Breeding drought-tolerant crops;Modified farm management practicesand improved infrastructure for off-farm employment opportunitiesJones &Thornton (2003)Gbetibouo & Hassan (2005) 5. Measuring the economic impact of climate change on major South African field crops: a Ricardian approach (Gbetibouo & Hassan, 2005)used a Ricardian (empirical) model approach to predict (althoughthey call it measure) the economic impact of climate change onmajor South African field crops (maize, wheat, sunflower, sorghum,soybean and groundnut).Results indicated that:Changes in temperature had a greater influence than changes in precipitation.This implies a breeding for heat tolerance rather than drought tolerance is necessary.Irrigation is an effective adaptation measure for drought.Ta rise positively affected net revenue.

ClimateVariableClimateScenarioWinterSummerBoth seasonsNo adaptation

Withadaptation

No adaptation

With adaptation

No adaptation

With adaptation

Temperature+2 oC-112626631247Rainfall-5%-426-134-227Gbetibouo & Hassan (2005) -Table 3 Impacts of changing only temperature and rainfall on field crops net revenue in percentage (%)Table 3 shows that the impacts on net revenue were favourable in all the seasons when adaptation (e.g. irrigation) was applied. No adaptation resulted in negative revenue %s. The effects were also greater with temperature as opposed to effects with rainfall.Gbetibouo & Hassan (2005)

Fig. 1.Distributional effects of 2 C increase in temperature and 5% reduction in rainfall across South African provincesFigure 1 shows that favourable effects of climate change were experienced by FS, NC, Limpopo, NW & WC. (all cool, dry, except Limpopo). Negative effects were experienced by EC, Gauteng, KZN, Mpumalanga (all warm, wet).Locations and season influenced crop reactions to climate change.Rising Ta was + in summer,but negative in winter months.However, much research and analyses need still to be done.Definite shifts in farming practices and patterns would be required in different regions, e.g.

Gbetibouo & Hassan (2005) Shifts in crop calendars,growing seasons,different crops anddisappearance of some field crop from some regions.Adaptation can be addressed in a number of ways:e.g. educating farmers for awareness of climate changeand through more effective farm planning.Crop Insurance andimproved monitoring and forecasts of weather would also help.

Gbetibouo & Hassan (2005) CONCLUSION

Stick to the factsScience means knowledge, not an (unprovable) theory. Unsure assumptions A scientific fact can be proven by an experiment producing observable results and this experiment should be able to be repeated. Theories speculationphilosophy a science.philosophy = a belief/religion. A belief is a religion, although one should be careful to stay in the truth and not be misled, for example:

Evolution (macro-) is a belief, a theory which cannot be proved. Evolution says that man evolved from apes, but if this is so, then man was not made in Gods image. Furthermore, there are no transitional forms to prove that man evolved from apes or even that any animal evolved from any other animal (not referring to micro-evolution or adaptation). It is therefore a theory which is unproved and can be classified as a belief or religion. It is NOT science.It takes more belief to believe in the Evolution theory than in the Creation as set out according to the Bible.The Bible is reasonable and there are many proofs contained in it for science (e.g. Archeological evidences). The Bible says the creation was made in six days and that each animal was made according to its kind (sort). We can believe this as fact because we have as yet not found any transitional forms from any one animal to another or from any animal to man.

CONCLUSION

So, if we want to know what is true, we need to look at all the evidences and all the facts, and decide what we want to believe, but it must be based on the truth. WHAT IS TRUTH?Truth is true, whether you believe it or not.Truth does not require belief in order to be true,But it deserves to be believed. (Doug Powell)ALSO:Jesus said unto him, I am the way, the truth and the life; No onecomes unto the Father, but by me (John 14:6)

CONCLUSION