Unit 4 – Agriculture

Unit 4 – Agriculture

Thomas Robert Malthus: An English political economist, explained in simple terms the connection between population

pressure and misery, which he defined as famine, poverty, disease and war.

(from his 1798 book, An Essay on the Principle of Population.)

Ch.11

•Food is necessary for human existence.

•Human population, if not checked, tends to grow faster than the power in the earth to produce subsistence.

•The effects of these two unequal powers must be kept equal.

•Misery is the mechanism that balances human requirements and available resources.


The Human-Induced Biome: AgroecosystemsCh.11

•11% of the land area in the world is used for agriculture (about the size of North & South America combined)

• A rising % of NPP (Net Primary

Production) is being converted

from natural systems to

support people


Food and Population IncreaseCh.11

• As populations increase, the amount of land under cultivation MUST also increase

• We usually see food shortages when pop’s reach their carrying capacity


How We StarveCh.11

Undernourishment: Malnourishment:

Lack of Calories< 1.2 x BMR Lack of Nutrients

Both seem to be caused by energy-protein deficiency

Can lead to:Marasmus

Can lead to:Kwashiorkor

Deficiency in certain nutrients

micronutrients seem to lead to

Kwashiorkor

Unit 4 – Agriculture Ch.11

Global food production has stayed ahead of population growth. However:• One of six people in developing countries cannot grow or buy

the food they need.• There will need to be a 40% increase in food over the next 20

years

The root cause of hunger and malnutrition is poverty.


A 2005 Boston University study found that about 60% of American adults are overweight and 33% are obese (totaling 93%).

Americans spend $42 billion per year trying to lose weight.$24 billion per year is needed to eliminate world hunger.

Overnutrition:


~150 plants have been used as cropsOnly 14 are significant for world-wide food energy

Wheat Rice Maize Potatoes Sweet Potatoes Sugar CaneSugar Beets Beans SoybeansBarley Sorghum CoconutBanana Manioc (yucca/cassava)

Crops:


Traditional agricultureLow-input polyculture

AgroecosystemsIndustrialized agriculture

High-input monoculture

Plantation agricultureCrops grown for export

RangelandUnplanted grazing land

PasturePlanted grazing land

AquacultureFarming in aquatic

habitats

Can produce higher yields than high-input

monoculture


1. Try to stop ecological succession and keep the agroecosystem in an early successional state

2. Monoculture: Large areas planted with a single species

3. Crops are planted in neat rows

4. Farming greatly simplifies biological diversity

5. Plowing is unlike any natural soil disturbance

6. Genetic modification of crops.

How are Agroecosystems different than natural ecosystems?

Leading to poor soil quality (N, P & K)

Crops have low genetic variability

Easy for pests and disease to spread

Leading to greater soil erosion

Requiring irrigation


After WWII (1950’s – 1980’s) programs were enacted aimed at feeding a booming population

Development of crops with… higher yields (mostly due to better irrigation techniques)better disease resistancebetter ability to grow under poor conditions

The Green Revolution


To increase crop yields, we can mix the genes of similar types of organisms and mix the genes of different organisms

(Genetic Engineering).

The GENE Revolution

Develop hybrids faster than nature

Introduce the “terminator gene”

Transform genes from one major form

of life to another

Used to:

Unit 4 – Agriculture Ch.12Soils

High organic content – very fertile

Humus/leaf-litter

Mineral-rich

Clay

Weathered bedrock

(E)

Undisturbed soils form

layers/horizons

Unit 4 – Agriculture Ch.12Soil TextureParticle size:

Texture (when wet):

Gritty

Sticky

Slippery

Water/nutrient Retention:

Erosion/ Sedimentation

threat:

Unit 4 – Agriculture Ch.12SoilsClearing natural vegetation

+ Tilling Soil

↓Erosion of fertile topsoil

↓Sedimentation of waterways

Annual Crop

Perennial grasses

Unit 4 – Agriculture Ch.12SoilsMethods to help mitigate

soil erosion:• No-till or minimum till

seeding• Contour cropping /

terracing• Leaving fields fallow

• Rotating crops


Pesticides

Only 10% of pesticide ingredients sprayed on American crops have been tested by the FDA


There are cultivation, biological, and ecological alternatives to conventional chemical pesticides.

•Cultivate a more diverse crop•Provide homes for the pest enemies.

•Implant genetic resistance.•Bring in natural enemies.

•Use pheromones to lure pests into traps.•Use hormones to disrupt life cycles.

Integrated Pest Management (IPM)•Uses a combination of alternative strategies and minimal chemical

pesticides•Goal: to reduce crop damage to an economically-tolerable level

Unit 4 – Agriculture Ch.12Animal FarmingOvergrazing occurs when the carrying capacity is

exceeded. It can cause severe damage to lands.

Livestock production in developed countries is industrialized:Feedlots are used to fatten up cattle before slaughter.Most livestock are fed grain grown on cropland. (40% of

grain grown worldwide)Systems use a lot of energy and water and produce huge

amounts of animal waste and methane gas.


Desertification

About one-third of the world’s land has lost some of its productivity because of drought and human activities that

reduce or degrade topsoil.


Biodiversity Loss Soil Water Air Pollution Human Health Loss and degradation of grasslands, forests, and wetlands

Erosion Water waste Greenhouse gas emissions from fossil fuel use

Nitrates in drinking water

Loss of fertility Aquifer depletionPesticide residues in drinking water, food, and air

Salinization Increased runoff and flooding from cleared land

Other air pollutants from fossil fuel use

Fish kills from pesticide runoff

WaterloggingSediment pollution from erosion Greenhouse gas

emissions of nitrous oxide from use of inorganic fertilizers

Contamination of drinking and swimming water with disease organisms from livestock wastes

Desertification

Killing wild predators to protect livestock

Fish kills from pesticide runoff

Surface and groundwater pollution from pesticides and fertilizers Belching of the

greenhouse gas methane by cattle

Loss of genetic diversity of wild crop strains replaced by monoculture strains

Bacterial contamination of meat

Overfertilization of lakes and rivers from runoff of fertilizers, livestock wastes, and food processing wastes Pollution from

pesticide spraysReturn to

question # 4

1. What is the predicted percent decrease in grain consumption from 1984 to 2015?

2. Using data from the graph explain why that decrease from # 1 is expected.3. Why was there a huge increase in grain consumption from 1950 – 1984? Explain fully.

4. What are the environmental consequences of that massive increase in grain production?5. What needs to be done in order to increase grain production in the future?

1. What is the predicted percent decrease in grain consumption from 1984 to 2015?

350 kg/yr - 250 kg/yr =100 kg/yr

100 kg/yr ÷ 350 kg/yr x 100 = 28.5%

28.5%

2. Using data from the graph explain why that decrease from # 1 is expected.

Gross grain production is expected to increase by about 14% during this time, while population is expected to increase by 30%. This gap will cause the grain that is available to each person to decrease

3. Why was there a huge increase in grain consumption from 1950 – 1984? Explain fully.

Green Revolution!!• Programs initiated to

increase crop yields• A switch to industrialized,

high-input, monoculture• Advances in machinery,

irrigation, chemical fertilizer, and pesticide technology

4. What are the environmental consequences of that massive increase in grain production?

Mention and explain degradation of• Biodiversity• Soil• Water • Air

Consequences Chart

5. What needs to be done in order to increase grain production in the future?

• Convert land used for livestock to grains for human consumption

• Increase crop yield• Genetically

modified crops• Soil conservation

techniques• Cultivation

techniques

Documents

Unit 4 – Agriculture