copyright © 2005 pearson education, inc., publishing as benjamin cummings powerpoint ® lecture...

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint® Lecture prepared by Jay Withgott

Scott Brennan • Jay Withgott

6 Soils, agriculture, and the future of food

http://www.stumbleupon.com/su/2TaFmD/chipotle.com/en-US/fwi/videos/videos.aspx?v=1/


Central 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.


Agriculture today

We 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.


World soil conditions

Soils are becoming degraded in many regions.

Figure 8.1a


Soil 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


Causes of soil degradation

Most soil degradation is caused by:

• livestock overgrazing

• deforestation

• cropland agriculture.

Figure 8.2


Global food production

World agricultural production has risen faster than human population.

Figure 9.1


The green revolution

An intensification of industrialization of agriculture, which has produced large yield increases since 1950

Increased yield per unit of land farmed

Begun in U.S. and other developed nations; exported to developing nations like India and those in Africa

are more productive for plant life.


Monocultures

Intensified agriculture meant monocultures, vast spreads of a single crop.

This is economically efficient, but increases risk of catastrophic failure (“all eggs in one basket”).

Figure 9.4aWheat monoculture in Washington


Crop diversity

Monocultures also have reduced crop diversity.

90% of all human food now comes from only 15 crop species and 8 livestock species.


The green revolution

Techniques 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.


Green 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 equipment

However, without the green revolution, much more land would have been converted for agriculture, destroying forests, wetlands, and other ecosystems.


Feeding the world

In 1983, the amount of grain produced per capita leveled off and began to decline.

Figure 8.3


Pest management

Terms 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.


Chemical pesticides

Synthetic poisons that target organisms judged to be pests


Trade-Offs

Inorganic Commercial Fertilizers

Advantages Disadvantages

Do not add humus to soil

Reduce organic matter in soil

Reduce ability of soil to hold water

Lower oxygen content of soil

Require large amounts ofenergy to produce,transport, and apply

Release the greenhouse gas nitrous oxide (N2O)

Runoff can overfertilizenearby lakes and kill fish

Easy to transport

Easy to store

Easy to apply

Inexpensive to produce

Help feed one of every three people in theworld

Without commercialinorganic fertilizers,world food output coulddrop by 40% FigurFigur

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Pesticide use

Pesticide 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


Pests 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.



1. Pests attack crop

2. Pesticide applied

Figure 9.6



3. All pests except a few with innate resistance are killed

4. Survivors breed and produce pesticide-resistant population

Figure 9.6



5. Pesticide applied again

6. Has little effect. More-toxic chemicals must be developed.

Figure 9.6


Biological control

Synthetic 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.”)


Figure 23-7Page 528


Biological control

Biocontrol has had success stories.

Bacillus thuringiensis (Bt) = soil bacterium that kills many insects. In many cases, seemingly safe and effective.

Figure 9.7

Cactus moth, Cactoblastis cactorum (above), was used to wipe out invasive prickly pear cactus in Australia.


But 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.


Integrated pest management (IPM)

Combines biocontrol, chemical, and other methods May involve:

• Biocontrol

• Pesticides

• Close population monitoring

• Habitat modification

• Crop rotation

• Transgenic crops

• Alternative tillage

• Mechanical pest removal


Genetic 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.


Genetic 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 DNA

Genetically modified (GM) organisms = genetically engineered using recombinant DNA technology

Recombinant DNA = DNA patched together from DNA of multiple organisms (e.g., adding disease-resistance genes from one plant to the genes of another)


Transgenes 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.


Genetic engineering vs. traditional breeding

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.

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.


Some GM foods

Figure 9.12

Golden rice: Enriched with vitamin A.But too much hype?

Bt crops: Widely used on U.S. crops.But ecological concerns?

Ice-minus strawberries: Frost-resistant bacteria sprayed on.Images alarmed public.

FlavrSavr tomato: Better taste?But pulled from market.


Some GM foods

Figure 9.12

Bt sunflowers: Insect resistant.But could hybridize with wild relatives to create “superweeds”?

Terminator seeds: Plants kill their own seeds. Farmers forced to buy seeds each year.

Roundup-Ready crops: Resistant to Monsanto’s herbicide. But encourages more herbicide use?

StarLink corn: Bt corn variety.Genes spread to non-GM corn; pulled from market.


Prevalence of GM foods

Although 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.


Prevalence of GM foods

Nearly 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 have grown >10%/year

Figure 9.13


ProjectedDisadvantages

Need less fertilizer

Need less water

More resistant to insects,plant disease, frost, anddrought

Faster growth

Can grow in slightly saltysoils

Less spoilage

Better flavor

Less use of conventionalpesticides

Tolerate higher levels ofpesticide use

Higher yields

ProjectedAdvantages

Trade-OffsGenetically Modified Food and Crops

Irreversible andunpredictable genetic and ecological effects

Harmful toxins in foodFrom possible plant cellMutations

New allergens in food

Lower nutrition

Increased evolution ofPesticide-resistantInsects and plant disease

Creation of herbicide-Resistant weeds

Harm beneficial insects

Lower genetic diversity


Scientific 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?


Europe vs. America

Europe: 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.


Viewpoints: Genetically modified foods

Indra Vasil

Ignacio Chapela

“We should expect fundamental alterations in ecosystems with the release of transgenic crops… We are experiencing a global experiment without controls.”

“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.”

From Viewpoints


Preserving 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.


Seed 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


Sustainable agriculture

Agriculture that can practiced the same way far into the future

Does not deplete soils faster than they form

Does not reduce healthy soil, clean water, and genetic diversity essential for long-term crop andlivestock production

Low-input agriculture = small amounts of pesticides, fertilizers, water, growth hormones, fossil fuel energy, etc.

Organic agriculture = no synthetic chemicals used. Instead, biocontrol, composting, etc.


Organic farming

Small percent of market, but is growing fast

1% of U.S. market, but growing 20%/yr

3–5% of European market, but growing 30%/yr

Organic produce:Advantages for consumers: healthier; environmentally better

Disadvantages for consumers: less uniform and appealing-looking; more expensive


Conclusions: 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.


Conclusions: SolutionsOrganic 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.


Industrialized agriculture

Modern intensive agriculture on a large scale:

• Crop monocultures

• Synthetic chemical herbicides, pesticides

• Extensive mechanization

• Fossil fuel use

copyright © 2005 pearson education, inc., publishing as benjamin cummings powerpoint ® lecture...

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