Presentation on theme: "Soils, agriculture, and the future of food"— Presentation transcript:
1Soils, agriculture, and the future of food 6Soils, agriculture, and the future of food
2Central Case: No-Till Agriculture in Brazil Southern Brazil’s farmers were suffering falling yields, erosion, and pollution from agrichemicals.They turned to no-till farming, which bypasses plowing.Erosion was reduced, soils were enhanced, and yields rose greatly. No-till methods are spreading worldwide.
3Agriculture todayWe have converted 38% of Earth’s surface for agriculture, the practice of cultivating soil, producing crops, and raising livestock for human use and consumption.Croplands (for growing plant crops) and rangelands (for grazing animal livestock) depend on healthy soil.
4World soil conditions Soils are becoming degraded in many regions. Figure 8.1a
5Soil degradation by continent Europe’s land is most degraded because of its long history of intensive agriculture.But Asia’s and Africa’s soils are fast becoming degraded.Figure 8.1b
6Causes of soil degradation Most soil degradation is caused by:• livestock overgrazing• deforestation• cropland agriculture.Figure 8.2
7Global food production World agricultural production has risen faster than human population.Figure 9.1
8The green revolutionAn intensification of industrialization of agriculture, which has produced large yield increases since 1950Increased yield per unit of land farmedBegun in U.S. and other developed nations; exported to developing nations like India and those in Africaare more productive for plant life.
9Wheat monoculture in Washington MonoculturesIntensified agriculture meant monocultures, vast spreads of a single crop.This is economically efficient, but increases risk of catastrophic failure (“all eggs in one basket”).Wheat monoculture in WashingtonFigure 9.4a
10Crop diversity Monocultures also have reduced crop diversity. 90% of all human food now comes from only 15 crop species and 8 livestock species.
11The green revolutionTechniques to increase crop output per unit area of cultivated land (since world was running out of arable land)Technology transfer to developed world in 1940s-80s: Norman Borlaug began in Mexico, then India.Special crop breeds (drought-tolerant, salt-tolerant, etc.) are a key component.It enabled food production to keep pace with population.
12Green revolution: Environmental impacts Intensification of agriculture causes environmental harm:• Pollution from synthetic fertilizers• Pollution from synthetic pesticides• Water depleted for irrigation• Fossil fuels used for heavy equipmentHowever, without the green revolution, much more land would have been converted for agriculture, destroying forests, wetlands, and other ecosystems.
13Feeding the worldIn 1983, the amount of grain produced per capita leveled off and began to decline.Figure 8.3
14Pest managementTerms pest and weed have no scientific or objective definitions.Any organism that does something we humans don’t like gets called a pest or a weed.The organisms are simply trying to survive and reproduce… and a monoculture is an irresistible smorgasbord of food for them.
15Chemical pesticidesSynthetic poisons that target organisms judged to be pests
16Inorganic Commercial Fertilizers Trade-OffsInorganic Commercial FertilizersAdvantagesDisadvantagesEasy to transportEasy to storeEasy to applyInexpensive to produceHelp feed one of everythree people in theworldWithout commercialinorganic fertilizers,world food output coulddrop by 40%Do not add humus to soilReduce organic matterin soilReduce ability of soil tohold waterLower oxygen content ofsoilRequire large amounts ofenergy to produce,transport, and applyRelease the greenhousegas nitrous oxide (N2O)Runoff can overfertilizenearby lakes and kill fishFigure Page 286
18Pesticide usePesticide use is still rising sharply across the world, although growth has slowed in the U.S.1 billion kg (2 billion lbs.) of pesticides are applied each year in the U.S.Figure 9.5
19Pests evolve resistance to pesticides Pesticides gradually become less effective, because pests evolve resistance to them.Those few pests that survive pesticide applications because they happen to be genetically immune will be the ones that reproduce and pass on their genes to the next generation.This is evolution by natural selection, and it threatens our very food supply.
21Pests evolve resistance to pesticides 3. All pests except a few with innate resistance are killed4. Survivors breed and produce pesticide-resistant populationFigure 9.6
22Pests evolve resistance to pesticides 5. Pesticide applied again6. Has little effect. More-toxic chemicals must be developed.Figure 9.6
23Biological controlSynthetic chemicals can pollute and be health hazards.Biological control (biocontrol) avoids this.Biocontol entails battling pests and weeds with other organisms that are natural enemies of those pests and weeds.(“The enemy of my enemy is my friend.”)
25Biological control Biocontrol has had success stories. Bacillus thuringiensis (Bt) = soil bacterium that kills many insects. In many cases, seemingly safe and effective.Cactus moth, Cactoblastis cactorum (above), was used to wipe out invasive prickly pear cactus in Australia.Figure 9.7
26But biocontrol is risky Most biocontrol agents are introduced from elsewhere.Some may turn invasive and become pests themselves!Cactus moths brought to the Caribbean jumped to Florida, are eating native cacti, and spreading.Wasps and flies brought to Hawaii to control crop pests are parasitizing native caterpillars in wilderness areas.
27Integrated pest management (IPM) Combines biocontrol, chemical, and other methodsMay involve:• Biocontrol• Pesticides• Close population monitoring• Habitat modification• Crop rotation• Transgenic crops• Alternative tillage• Mechanical pest removal
28Genetic modification of food Manipulating and engineering genetic material in the lab may represent the best hope for increasing agricultural production further without destroying more natural lands.But many people remain uneasy about genetically engineering crop plants and other organisms.
29Genetic engineering uses recombinant DNA Genetic engineering (GE) = directly manipulating an organism’s genetic material in the lab by adding, deleting, or changing segments of its DNAGenetically modified (GM) organisms = genetically engineered using recombinant DNA technologyRecombinant DNA = DNA patched together from DNA of multiple organisms (e.g., adding disease-resistance genes from one plant to the genes of another)
30Transgenes and biotechnology Genes moved between organisms are transgenes, and the organisms are transgenic.These efforts are one type of biotechnology, the material application of biological science to create products derived from organisms.
31Genetic engineering vs. traditional breeding They are different:GE can mix genes of very different species.GE is in vitro lab work, not with whole organisms.GE uses novel gene combinations that didn’t come together on their own.They are similar:We have been altering crop genes (by artificial selection) for thousands of years.There is no fundamental difference: both approaches modify organisms genetically.
32Some GM foods Golden rice: Enriched with vitamin A. But too much hype? FlavrSavr tomato: Better taste?But pulled from market.Ice-minus strawberries: Frost-resistant bacteria sprayed on.Images alarmed public.Bt crops: Widely used on U.S. crops.But ecological concerns?Figure 9.12
33Some GM foods Bt sunflowers: Insect resistant. But could hybridize with wild relatives to create “superweeds”?StarLink corn: Bt corn variety.Genes spread to non-GM corn; pulled from market.Roundup-Ready crops: Resistant to Monsanto’s herbicide. But encourages more herbicide use?Terminator seeds: Plants kill their own seeds. Farmers forced to buy seeds each year.Figure 9.12
34Prevalence of GM foodsAlthough many early GM crops ran into bad publicity or other problems, biotechnology is already transforming the U.S. food supply.Two-thirds of U.S. soybeans, corn, and cotton are now genetically modified strains.
35Prevalence of GM foodsNearly 6 million farmers in 16 nations plant GM crops.But most are grown by 4 nations.The U.S. grows 66% of the world’s GM crops.number of plantings havegrown >10%/yearFigure 9.13
36Genetically Modified Food and Crops Trade-OffsGenetically Modified Food and CropsProjectedAdvantagesProjectedDisadvantagesNeed less fertilizerNeed less waterMore resistant to insects,plant disease, frost, anddroughtFaster growthCan grow in slightly saltysoilsLess spoilageBetter flavorLess use of conventionalpesticidesTolerate higher levels ofpesticide useHigher yieldsIrreversible andunpredictable geneticand ecological effectsHarmful toxins in foodFrom possible plant cellMutationsNew allergens in foodLower nutritionIncreased evolution ofPesticide-resistantInsects and plantdiseaseCreation of herbicide-Resistant weedsHarm beneficial insectsLower genetic diversity
37Scientific concerns about GM organisms Are there health risks for people?Can transgenes escape into wild plants, pollute ecosystems, harm organisms?Can pests evolve resistance to GM crops just as they can to pesticides?Can transgenes jump from crops to weeds and make them into “superweeds”?Can transgenes get into traditional native crop races and ruin their integrity?
38Europe vs. AmericaEurope: has followed precautionary principle in approach to GM foods. Governments have listened to popular opposition among their citizens.U.S.: GM foods were introduced and accepted with relatively little public debate.Relations over agricultural trade have been uneasy, and it remains to be seen whether Europe will accept more GM foods from the U.S.
39Viewpoints: Genetically modified foods Indra VasilIgnacio Chapela“Biotech crops are already helping to conserve valuable natural resources, reduce the use of harmful agro-chemicals, produce more nutritious foods, and promote economic development.”“We should expect fundamental alterations in ecosystems with the release of transgenic crops… We are experiencing a global experiment without controls.”From Viewpoints
40Preserving crop diversity Native cultivars of crops are important to preserve, in case we need their genes to overcome future pests or pathogens.Diversity of cultivars has been rapidly disappearing from all crops throughout the world.
41Seed banks preserve seeds, crop varieties Seed banks are living museums of crop diversity, saving collections of seeds and growing them into plants every few years to renew the collection.Careful hand pollination helps ensure plants of one type do not interbreed with plants of another.Figure 9.14
42Sustainable agriculture Agriculture that can practiced the same way far into the futureDoes not deplete soils faster than they formDoes not reduce healthy soil, clean water, and genetic diversity essential for long-term crop and livestock productionLow-input agriculture = small amounts of pesticides, fertilizers, water, growth hormones, fossil fuel energy, etc.Organic agriculture = no synthetic chemicals used. Instead, biocontrol, composting, etc.
43Organic farming Small percent of market, but is growing fast 1% of U.S. market, but growing 20%/yr3–5% of European market, but growing 30%/yrOrganic produce:Advantages for consumers: healthier; environmentally betterDisadvantages for consumers: less uniform and appealing-looking; more expensive
44Conclusions: Solutions Biocontrol and IPM offer alternatives to pesticides.Further research and experience with GM crops may eventually resolve questions about impacts, and allow us to maximize benefits while minimizing harm.More funding for seed banks can rebuild crop diversity.Ways are being developed to make feedlot agriculture and aquaculture safer and cleaner.
45Conclusions: Solutions Organic farming is popular and growing fast.Green revolution advances have kept up with food demand so far. Improved distribution and slowed population growth would help further.Farming strategies like no-till farming, contour farming, terracing, etc., help control erosion.Government laws, and government extension agents working with farmers, have helped improve farming practices and control soil degradation.Better grazing and logging practices exist that have far less impact on soils.
46Industrialized agriculture Modern intensive agriculture on a large scale:• Crop monocultures• Synthetic chemical herbicides, pesticides• Extensive mechanization• Fossil fuel use