Soil Ch 13 and CIE

sources

The changing face of agriculture• 10,000 years ago, people in different cultures

began to raise plants for food and to domesticate animals

• Agriculture: practice of raising crops and livestock for human use and consumption

• Cropland: land used to raise plants for human use • Rangeland: land used for grazing livestock • Land devoted to agriculture now covers 38% of

Earth’s land

The changing face of agriculture

• Traditional agriculture: uses human and animal power– Hand tools, simple machines– Polyculture: different crops are planted in one field

• Industrial agriculture: uses large-scale machines and fossil fuels to boost yields– Also uses irrigation, fertilizers, and pesticides

• Monoculture: planting a single, genetically similar crop – More efficient but reduces diversity, is disease prone– Narrows the human diet– Used in industrial agriculture

Industrialized Crop Production Causes Soil Erosion

• Industrialized agriculture, high-input agriculture (intensive) produces 80% of world’s food supply

• Uses heavy equipment and large amounts of fossil fuels, water, commercial fertilizers, pesticides, and financial capital.

• Primarily monocultures – single crop in one area.– Goal is to steadily increase crop yield, Ex Corn

The effects of industrialized agriculture

• Industrial agriculture has allowed food production to keep pace with population growth– But it has many bad environmental and social effects

• Benefits: increases crop yields while reducing pressure to develop natural areas for new farms

• Drawbacks: water, fossil fuels, fertilizers, pesticides worsen pollution, erosion, and desertification– Requires far more energy than traditional methods– Displaces low-income farmers who can’t afford the

technology, forcing them to move to cities

Sustainable agriculture• Suitable farmland is disappearing– We must improve the efficiency of production

• It is better to raise animals and crops that pollute less, require less fuels, and have less impact on natural systems

• Sustainable agriculture: maintains healthy soil, clean water, and genetic diversity– Treats agricultural systems as ecosystems

• Low-input agriculture: uses smaller amounts of– Pesticide, fertilizers, growth hormones, antibiotics,

water, and fossil fuels than industrial agriculture

Regional differences in soils affect agriculture

• In rainforests, rain leaches minerals and nutrients, reducing their accessibility to roots– Rapid decomposition of leaf litter results in a thin

topsoil layer with little humus– Farming quickly depletes the soil’s fertility

• Swidden agriculture: traditionally used in tropical areas– After cultivation, a plot is left to regrow into forest

• Temperate prairies have lower rainfall and less nutrient leaching, resulting in higher fertility

Differences in regional agriculture

Swidden agriculture is not sustainable at high

population densities

Fertile prairies can be farmed repeatedly if

protected

The Dust Bowl

• In late 1800 and early 1900, farmers and ranchers:– Grew wheat, grazed cattle– Removed native grasses

• Dust Bowl: 1930s drought and erosion caused “black blizzards” of sand

• Thousands of farmers left their land – Relied on governmental help

to survive

The Soil Conservation Service (SCS)

• Started in 1935 by the Congress, the SCS works with farmers to develop conservation plans for farms– The SCS is now named the Natural Resources Conservation

Service

• Other countries started their own conservation agencies– No-till farming in Argentina, Brazil, and Paraguay– Grassroots organizations helped by agronomists and

government extension agents

Agricultural subsidies affect soil degradation

• Theoretically, the market should discourage farmers and ranchers from degrading the land– But degradation is slow, and farmers can’t afford to lose

money

• Many governments spend billions to subsidize agriculture– 20% of a U.S. farmer’s income comes from subsidies

• Pros of subsidies: protect farmers from uncertain weather

• Cons of subsidies: encourage farming of vulnerable land– Producing more food than needed, driving prices down– Farmers should buy insurance against losses

Seed banks conserve wild genes• Industrial agriculture’s use of genetically similar

crops has led to efforts to conserve wild relatives of crops– Wild crops contain genes will will need in the future

• Seed banks: institutions that store seed types– Seeds are collected, stored, and periodically planted

• Wild crops must not be allowed to interbreed with genetically modified crops– To prevent introduction of GM crops into wild

populations

The Green Revolution increased yields• Green revolution: drastically increased food through new

• Technology• Crop varieties• Farming practices

• Spread to the developing world in the 1940s • Wheat, rice, corn

Norman Borlaug won the Nobel Peace Prize for his work

U.S. programs promote soil conservation

• Conservation Reserve Program (1985): farmers are paid to put highly erodible land in conservation reserves– Trees and grasses are planted instead of crops– Each dollar spent saves 1 ton of topsoil– Generates income for farmers – Improves water quality and provides habitat– $1.8 billion/yr protects 30–40 million acres

• The 2008 Farm Bill limits protection to 32 million acres– But funds 14 other programs

• International agencies also promote sustainable agriculture

Sustainable approaches to irrigation

• Match crops and climate– Don’t plant water-guzzling

crops in dry areas – Plant beans or wheat, not

rice

• Subsidies make irrigation water artificially cheap

• Drip irrigation delivers water directly to plants Drip irrigation works best

on smaller plots with perennial plants (fruit trees)

Fertilizers boost yields• Fertilizers: substances containing essential nutrients to

enhance crop production• Inorganic fertilizers: mined or synthetically

manufactured mineral supplements• Organic fertilizers: the remains or wastes of organisms– Manure, crop residues, fresh vegetation (green manure)– Compost: produced when decomposers break down organic

matter

Inorganic fertilizers cause problems

• Inorganic fertilizers have boosted production– But also severely pollute

• Leaching and runoff of inorganic fertilizers causes:– Groundwater

contamination– Dead zones in water

systems– Air pollution from

evaporated nitrates

Inorganic fertilizer use has skyrocketed worldwide

Sustainable fertilizers

• Sustainable approaches to fertilizing delivers nutrients directly to plant roots and avoids overapplication– Add fertilizers to drip irrigation water– No-till or low-till systems inject fertilizers with seeds– Monitor soil nutrients and add only when they are low– Strips of vegetation along field edges and streams capture

nutrient runoff

• Organic fertilizers add nutrients and organic matter– Improving soil structure, nutrient and water retention

• Integrate inorganic and organic fertilizer systems

Pesticides control pests• Pest: any organism that damages valuable crops • Weed: any plant that competes with crops• Pests and weeds especially threaten monocultures• Pesticides: poisons that target pest organisms– Insecticides kill insects, herbicides kill plants, and

fungicides kill fungi

• 75% of pesticides are applied to agricultural land• Exposure to synthetic pesticides can cause health

problems for humans and other organisms• Pesticides also kill many nontarget organisms

Pests evolve resistance to pesticides

• Pesticides lose effectiveness as pests evolve resistance• Individuals that can metabolize and detoxify a pesticide

survive and pass these genes to their offspring– As the population increases, pesticides lose their

effectiveness

• Pesticide treadmill: chemists increase the toxicity of pesticides to compete with resistant pests

• Many species (green peach aphid, diamondback moth) have evolved resistance to multiple chemicals

Evolution of pesticide resistance

• Over 586 species are resistant to 330 insecticides• Hundreds of weeds and plant diseases have evolved

resistance to herbicides and pesticides

Biological control (biocontrol)• Biological control: uses a

pest’s predators or diseases to control the pest– But organisms can’t be

easily controlled• Organisms can harm

nontargets– Example: introduced cactus

moths eat rare Florida cacti • Biocontrol must be carefully

planned and regulated

Integrated pest management (IPM)• Techniques to suppress pests include:

* Biocontrol * Habitat alteration* Chemicals, if necessary * Crop rotation * Population monitoring * Transgenic crops* Alternative tillage methods* Mechanical pest removal

IPM in Indonesia increased rice yields 13% and saved $179 million/yr in phased-out subsidies

Pollinators are beneficial “bugs”

• Not all insects are pests; some are absolutely vital– Over 800 cultivated plants rely on pollinators

• Pollination: male plant sex cells fertilize female sex cells• Flowers are evolutionary adaptations to attract

pollinators– Nectar, pollen, sweet smells, bright colors

• U.S. bees provide $3 billion/year in pollination services, but parasitic mites decimated populations– Beekeepers were driven to financial ruin

Conservation of pollinators is vital

• Colony collapse disorder: entire beehives have died– One-third of all U.S. honeybees die/year– Unknown causes—Insecticides? Parasites? Stress?

Populations of bees further plummeted in 2006

Genetically modified food• Despite the Green Revolution, relentless

population growth demands more innovation to feed us

• Scientists alter genes of organisms– Crop plants and livestock

• Genetically modified organisms enhance nutrition and agricultural efficiency

• But the risks are not well understood, leading to anxiety and protest from:– Consumer advocates, small farmers,

environmentalists, critics of big business

Genetically modified organisms• Genetic engineering:

laboratory manipulation of genetic material– Add, delete, modify DNA

• Genetically modified (GM) organisms: organisms that have been genetically engineered using …

• Recombinant DNA: DNA created from multiple organisms

Biotechnology is impacting our lives

• The goal of genetic engineering: put genes that code for desirable traits (rapid growth, nutrition, etc.)– Into organisms lacking those traits

• Transgenic organism: an organism that contains DNA from another species – Transgenes: the genes that have moved between organisms

• Biotechnology: the application of biological science to create products derived from organisms – It has created medicines, cleaned up pollution, dissolved blood

clots, and made better food

Some genetically modified foods

Selective breeding vs. genetic engineering

• Selective breeding: changes organisms through selective breeding of the same or similar species– Works with organisms in the field– Genes come together on their own– Uses the process of selection to change organisms

• Genetic engineering: mixes genes of different species (e.g., spiders and goats)– Works with genetic material in the lab– Directly creates novel combinations of genes– Resembles the process of mutation

Biotechnology is changing our world

• GM foods are a big business• Most GM crops are herbicide

and pesticide resistant– Large-scale farmers grow crops

more efficiently– Most U.S. corn, soybeans, and

cotton are genetically modified

What are the impacts of GM crops?• As GM crops expanded, citizens, scientists, and

policymakers became concerned that:– GM crops could have adverse impacts on human

health– Pests could evolve resistance and become

“superpests” and “superweeds”– GM crops could harm nontarget organisms– GM crops could interbreed with closely related wild

plants• Millions of Americans eat GM foods without

obvious harm– But it is too early to dismiss concerns

Some impacts of GM crops• Mixed results on pesticide use– Insecticide use declined, but herbicide use

increased• GM foods can advance sustainable agriculture– Grown with no-till farming– Drought resistant and high-yielding

• Problems with GM foods: – Expensive– Little incentive to develop crops for small-scale

farmers

Genetic engineering is profit driven• This “gene revolution” is driven by financial interests of

corporations• A few large agribiotech corporations dominate the world’s

food supply

• Europeans want GM foods labeled• U.S. consumers have mostly accepted GM crops• Brazil, India, and China are aggressively pursuing

GM crops• We should follow the precautionary principle

and proceed with caution on GM foods

Consumption of animal products is growing

• As wealth and commerce increase, so does consumption of meat, milk, and eggs

• Since 1950, global meat production has increased fivefold, and per capita meat consumption has doubled

As developing nations become wealthier, meat consumption will double by 2050

Our food choices are also energy choices

• Eating meat is far less energy efficient than eating crops

• 90% of energy is lost from one trophic level to the next

• Some animals convert grain into meat more efficiently than others

Resources needed for livestock production

When we choose what to eat, we choose how we use resources

• Land and water are needed to raise food for livestock– Eggs and chicken meat

require the least – Producing beef requires

the most

Feedlot agriculture• Feedlots (factory farms): also called concentrated animal

feeding operations (CAFOs)• Huge warehouses or pens deliver food to animals living at

extremely high densities– House over half of the world’s pork and most of its poultry

Most U.S. meat is raised in feedlots, which use liberal amounts of antibiotics to control disease

Pros and cons of feedlot agriculture• It allows greater production of affordable meat

• It reduces grazing impacts on the land• 45% of the world’s grain is fed to livestock– Endangering food security for the world’s poor

• Feedlots produce huge amounts of manure and urine– Can pollute surface water and groundwater

• Crowded housing causes outbreaks in disease– Heavy use of antibiotics

• More greenhouse gases (CO2, methane, nitrous oxides) than automobile emissions

We raise seafood with aquaculture• World wild fish populations are plummeting– Increased demand and technology

• Aquaculture: raising aquatic organisms in a controlled environment – Open-water pens or land-

based ponds• The fastest-growing type

of food production– Most widespread in Asia

Aquaculture’s benefits and drawbacks• Benefits:– Reduces pressure on overharvested wild fish– Uses fewer fossil fuels, is safer, and produces more

fish than commercial fishing• Drawbacks:– Lots of waste produced– Uses grain, which affects food supplies for people– Fish meal is made from wild ocean fish– Escaped fish introduce disease or outcompete wild

fish

Organic agriculture• Sustainable agriculture keeps high crop yields,

minimizes resource use, and decreases environmental impacts

• Organic agriculture: uses no synthetic fertilizers, insecticides, fungicides, or herbicides

• Organic Food Production Act (1990) establishes national standards for organic products– The USDA issued criteria in 2000 by which food could

be labeled organic– California, Washington, Texas passed stricter

guidelines for labeling

Benefits and costs of organic farming

• Farmers have lower input costs, enhanced income, reduced chemical pollution and soil degradation– Obstacles include the risks and costs of switching to

new methods• The main obstacle to consumers is the higher

price– But many are willing to pay the price– Worldwide, sales surpassed $54 billion

Organic agriculture is booming

U.S. land devoted to organic agriculture has quadrupled since the mid-1990s

U.S. consumers spent $24.8 billion on organic food in 2009

Governments can support organic farming

• The U.S. 2008 Farm Bill gives $112 million over 5 years for organic agriculture– It helps defray certification costs

• In 1993, the European Union started supporting farmers financially during conversion to organic farming– Reduced inputs and higher market prices will make it

as profitable as conventional methods

Locally supported agriculture is growing• Sustainable agriculture reduces fossil fuel use

from long-distance transport of products– The average U.S. food product travels 1,400 miles

• Farmers’ markets: provide fresh, locally grown food– Provide organic items and unique local varieties

• Community-supported agriculture (CSA) – Consumers pay farmers in advance for produce– Consumers get fresh food– Farmers get a guaranteed income

Sustainable agriculture: a roadmap for the future

• Sustainable agriculture mimics natural ecosystems– They operate in cycles and are internally stabilized by

negative feedback loops• Agricultural systems can be integrated with the

surrounding ecosystems– Reducing environmental impacts from food

production• Making agriculture sustainable is crucial for all of

us

Biofuels can affect food supplies• Biofuels: fuels derived from organic materials– Replace petroleum in engines

• Ethanol: a biofuel derived from corn– The main biofuel in the U.S. – 2007 subsidies doubled U.S. production

• Use of corn for biofuel reduced corn supplies– Food prices increased – Farmers sold corn for ethanol, not food– Farmers planted biofuels, not food crops– Riots erupted in many nations

Conclusion• Industrialized agriculture has had substantial

negative environmental consequences• To support 9 billion humans, we must shift to

sustainable agriculture to prevent further land degradation– Biological pest control, organic agriculture– Pollinator protection, preservation of native crops– Aquaculture– Careful, responsible genetic modification of food

Case StudiesMEDC- (Dustbowl 1930s)LEDC- India see article