Announcements – Oct.13, 2006

Exam # 2 next Wednesday(on October 18th)

Public Lecture:Dr. Jack Williams, University of Wisconsin at Madison

"How will species respond to future novel climate regimes? Lessons from the late Quaternary"

4:00 PM, Wednesday, October 18, 2006B102 CLSL, Auditorium

Agricultural Approaches

“Slash-and-burn”

Labor-intensive

Mechanized

“Slash-and-Burn” Agriculture

Usually conducted in areas with nutrient poor soils (e.g., tropical forests)

Cut & burn existing vegetation to provide nutrients, use land for brief period, then move to new patch

land can be slow to recover

Usually plant polycultures (more than 1 species) advantages: species benefit one another, avoid insect/fungal

pests

Only sustainable in low population densities

Labor-Intensive Agriculture Intense form of agriculture using human

and animal labor to grow crops Typical farming practice until Industrial

Revolution Still practiced today when:

1. Growing site won’t allow machinesMountain regions, small, oddly-shaped plots

2. Type of crop requires careful handlingRice planting, harvesting fruits

3. Economic conditions poor, human labor cheap

Mechanized Agriculture

Requires large areas of land

Found in areas with good soils, and necessary money and land US, Europe, USSR, South America

Usually monocultures (one crop)

Labor reduction in the United States: 1913: Required average of 135 hours of labor to

produce 2,500 kg of corn. 1980: Required average of 15 hours.

Mechanized Agriculture

Benefits Reduced labor Increased yields (per area)

Mechanized Agriculture

Biological ProblemsFields left bare, leads to erosionOrganic matter often removedPlanting only 1 or 2 crops

Depleted nutrients Insect/Fungal problems

Genetic similarity in crops Insect/Fungal problems

Increased energy usage Increased reliance on fertilizers &

pesticides

Energy

Farming in industrialized countries is highly energy-intensive. Between 1920-1980, energy use rose directly with

mechanization of agriculture

US food system consumes 16% of our total energy use. Buy locally!

Most foods require more energy to produce, process, and transport than we yield from them!!!

Fossil Fuel Use

Takes 5.5 tons of fossil fuel to produce 1.1 tons of fertilizer.

Developed world is dependent on oil to produce energy to manufacture pesticides.

Points to Know 1. What is the most common dietary problem in wealthy

countries? In poor countries?

2. What is a famine? What conditions can lead to famines?

3. What three crops provide most of the world’s nutrition?

4. How is meat consumption related to the Earth’s carrying capacity?

5. What are the characteristics of the three agricultural approaches?

6. What are the benefits and problems of mechanized agriculture?

Agriculture II

Lecture Objectives:

1) Learn the pros & cons of fertilizer use

2) Learn types of pesticides and their pros & cons

3) Explore the controversy over DDT

Are these increased yields solely due to mechanization?

NO!

Other factors increasing production:

Chemical fertilizers

Chemical pesticides

Intensive plant breeding & genetically modified crops (Monday)

Impact of Chemical Fertilizer 25% of crop yield because of fertilizers Price tied to price of oil

raw material source of energy for industrial processing

Impact of Fertilizers Why fertilize?

Replace nutrients in soil used by plants

Macronutrients Nutrients plants need most of Nitrogen (N), Phosphorous (P), Potassium (K)

Micronutrients Nutrients plants need in trace amounts boron, zinc, manganese

Impacts of Fertilizers

Problems and limitations of fertilizers They do not replace organic matter

Organic material needed for soil structure, helps maintain soil chemistry, food for soil bacteria

RunoffDecreases efficiency of useProblems for aquatic systems

Next problem:

Humans raise crops for ourselves and livestock to eat, but other organisms like to eat them as well…

tomato fruitworm (also called corn earworm and cotton bollworm)

Aphids

Sugarbeet wireworm larvae

Pesticide Sales

Why Are Pesticides So Widely Used?

Food Production Worldwide, pests destroy 35% of crops.

Economic Concerns Pesticides increase yields and profits.

Health Reasons Insecticides curtail many diseases.

Types of Pesticides

Pesticide: any chemical used to kill or control unwanted organisms Insecticides: control insects Herbicides: control plants Fungicides: control fungal pests Rodenticides: control mice/rats

Other attributes to keep in mind…

Which species does the pesticide affect? Target organism: the one you’re trying to kill Non-target organism: anything else affected

How long does the pesticide last? Persistent pesticides: stable compounds that

remain active for long periods of time Nonpersistent pesticides: break down quickly

Insecticides Insect pests can cause serious economic

problems (e.g., corn rootworm)

Many insects also spread human diseases

Insecticides

DDT was first synthetic organic insecticide

Long lasting, deadly to insects

DDT is a Chlorinated hydrocarbon

Banned in US in 1972

Three main types of organic insecticides

Chlorinated hydrocarbons

Organophosphates

Carbamates

Chlorinated hydrocarbons

DDT, toxaphene, aldrin, dieldrin, heptachlor

Thought to affect insect nervous system

Cons:•Extremely persistent•Bioaccumulation•Non-target species

Pros:•Extremely persistent•Helps prevent disease

Banned in many parts of the world

Organophosphates and Carbamates

Malathion, Parathion, Diazinon (used in gardens) interferes with nervous system

results in continuous nerve impulse, leads to uncontrolled spasms

Organophosphates more toxic than carbamates

Pros:

Less persistent than chlorinated hydrocarbons

Cons:

Are not insect specific

Usually much more toxic to humans

Herbicides

Herbicides

60% of pesticides used in US are herbicides Used to control “weeds” - unwanted plants

rights-of-way, lawns, crops Why control weeds?

Compete with desirable species Need to separate from crop at harvest

Traditionally controlled manually

Herbicides

Some kill seeds, other plants Most act by disrupting physiological

processes growth regulators interfere with plant

compounds others interfere with photosynthesis, stop cell

division, etc. Some toxic to all plants, some selective

Can depend on concentration

Fungicides and Rodenticides

Fungicides some fungi decompose

organic matter some fungi act as parasites

RodenticidesMice/rats can destroy food supplies, carry disease, damage crops in fieldwarfarin - causes internal bleeding in all mammalsin many cases, safer to build rodent proof storage buildings

Problems with Pesticide Use

Perfect Pesticide: Inexpensive Always 100% effective Only affect target organism Short half-life Break down into harmless materials

But it doesn’t exist!! Newer pesticides have fewer drawbacks

than early pesticides, but all have problems.

Problems With Pesticide Use

Pesticide Resistance — Insecticides only kill susceptible individuals. Most surviving individuals have characteristics

that allowed them to tolerate the pesticide. Survivors pass on genetic characteristics for

tolerance. Subsequent pesticide applications become less

effective.

Problems With Pesticide Use

Effects on Non-Target Organisms Most pesticides are not species specific, and

kill beneficial species as well as pest species.

Many kill predator and parasitic insects that normally control pest insects.

Problems With Pesticide Use

Human Health Concerns Acute poisoning during application. Inadvertent exposure to small quantities.

Chronic minute exposure.

Migrant workers

Pesticides in People

•Recent study led by Mount Sinai School of Medicine (NY)

•Blood and urine work on nine volunteers

•Found 167 chemicals76 cause cancer in humans or animals 94 are toxic to the brain and nervous system79 cause birth defects or abnormal development

Problems With Pesticide Use

Persistence — Persistent pesticides become attached to small soil particles and are easily moved by wind or water. May be distributed throughout world from local applications.

DDT is still one of the most commonly detected pesticides in breast milk

DDT can stay in the environment for as long as 90 years

Problems With Pesticide Use Bioaccumulation and Biomagnification

Bioaccumulation — Accumulating material within an organism’s body. Many persistent pesticides are fat soluble and build

up in fat tissues.

Biomagnification — Acquiring increasing levels of a substance in bodies of higher trophic-level organisms. DDT, Mercury, PCBs

The controversy over DDT

•1930s, DDT was considered a miracle chemical

•Inexpensive, seemed harmless

•Came into wide agricultural and commercial usage in US in the late 1940s

•First used in WWII as a delousing agent

DDT (Dichloro-Diphenyl-Trichloroethane)

Environmental Impacts

In the 1960s, noticeable decline in populations of peregrine falcons, bald eagles, brown pelicans and other predatory birds

In humans, large doses result in tremors and seizures In small doses:

Increased chance of having a premature baby Reduction in the duration of lactation Possible ties to cancerPossible ties to falling sperm counts

Rachel Carson

CBS Reports 1963

Published Silent Spring in 1962

DDT banned in the US in 1972

Many have pushed for a world-wide ban, but it is still used in some countries

Why?

DDT Kills Mosquitoes

Mosquitoes carry disease

Diseases carried by Mosquitoes

At least 30 known human diseases are carried by mosquitoes

West Nile Virus Encephalitis Yellow Fever Malaria

Mosquito bites infected person, gets the disease, then transfers it to the next person

Mosquito Life Cycle

Mosquitoes require water

Can try to control both the adult stage and the larval stage

Should DDT be banned Worldwide?

Negative environmental impacts

Possible effects on human health

40% of the world’s population at risk of contracting malaria

300 to 500 Million cases a year1 to 3 million deaths per year

Points to Know

1) What 4 factors are responsible for the increases in food production over the last 50 years?

2) Why are chemical fertilizers tied to the price of oil? What 6 nutrients do fertilizers provide (3 macro, 3 micro)? What are the problems and limitations of chemical fertilizers?

3) Know the 4 categories of pesticides and their target species.

4) What is the perfect pesticide? Besides cost, how do the attributes of a perfect pesticide relate to the problems with pesticide use?

5) What is the controversy over DDT use?