Chapter 12Chapter 12

Effects of Agriculture on the Environment

Effects of Agriculture on the Environment

Case Study: Clean-Water Farms

Case Study: Clean-Water Farms

Farmers concerned about erosion, pesticides, fertilizers, and livestock waste (impact on environment). Started clean water project.

Convert some crops to grass to lessen erosion.

Rotate animals in areas of land to reduce concentrated wastes and overgrazing.

Benefits farms and environment.

Farmers concerned about erosion, pesticides, fertilizers, and livestock waste (impact on environment). Started clean water project.

Convert some crops to grass to lessen erosion.

Rotate animals in areas of land to reduce concentrated wastes and overgrazing.

Benefits farms and environment.

Many environmental problems result from agriculture:

Many environmental problems result from agriculture:

Soil erosion

Sediment transport and deposition downstream

On-site pollution from fertilizers and pesticides

Deforestation

Desertification

Degradation of water aquifers

Salinization

Accumulation of toxic metals and organic compounds

Loss of biodiversity

Soil erosion

Sediment transport and deposition downstream

On-site pollution from fertilizers and pesticides

Deforestation

Desertification

Degradation of water aquifers

Salinization

Accumulation of toxic metals and organic compounds

Loss of biodiversity

The Plow PuzzleThe Plow Puzzle

Plowed soil is different than natural soil.

Natural soil has distinct layers and is rich in organic matter.

Plowed soil churns all layers together and is poor in organic matter.

How is it possible that farmers have been growing crops in plowed soil for thousands of years?

Plowed soil is different than natural soil.

Natural soil has distinct layers and is rich in organic matter.

Plowed soil churns all layers together and is poor in organic matter.

How is it possible that farmers have been growing crops in plowed soil for thousands of years?

Layers of SoilLayers of Soil

Our Eroding SoilsOur Eroding Soils

Soil is lost to erosion.

Plowed soils erode more quickly.

Ex: American Midwest circa 1930’s: The Dust Bowl.

Topsoil was blown away when drought occurred.

Soil is lost to erosion.

Plowed soils erode more quickly.

Ex: American Midwest circa 1930’s: The Dust Bowl.

Topsoil was blown away when drought occurred.

FertilizersFertilizers

Fertilizers are used to replace provide nitrates to plants.

Traditional fertilizers were organic such as cow manure.

Artificial fertilizers are converted atmospheric nitrogen into nitrates, mined phosphorus, and other additives.

Erosion has slowed in the US, but not in many other countries.

Fertilizers are used to replace provide nitrates to plants.

Traditional fertilizers were organic such as cow manure.

Artificial fertilizers are converted atmospheric nitrogen into nitrates, mined phosphorus, and other additives.

Erosion has slowed in the US, but not in many other countries.

Where Eroded Soil Goes: Sediments Also Cause Environmental Problems

Where Eroded Soil Goes: Sediments Also Cause Environmental Problems

Ways to slow erosion:

Making Soil Sustainable

Contour Plowing

No-Till Agriculture

Combination of farming practices that include not plowing the land and using herbicides to keep down weeds.

Ways to slow erosion:

Making Soil Sustainable

Contour Plowing

No-Till Agriculture

Combination of farming practices that include not plowing the land and using herbicides to keep down weeds.

Conservation TillingConservation Tilling

Controlling PestsControlling Pests

Pests are any organism that lessens agricultural production.

Controlling pests is the attempt to stop succession.

Pesticides are any chemical used to reduce pests.

Pests are any organism that lessens agricultural production.

Controlling pests is the attempt to stop succession.

Pesticides are any chemical used to reduce pests.

History of PesticidesHistory of Pesticides

Prehistoric farmers planted herbs (to repel insects) near crops.

Early chemical pesticides included arsenic, which is poisonous to most living things.

1930’s farmers used petroleum and plant-based chemicals like nicotine. Safe, but not effective.

Later, scientist began developing chemicals like DDT. Effective, but not safe.

Prehistoric farmers planted herbs (to repel insects) near crops.

Early chemical pesticides included arsenic, which is poisonous to most living things.

1930’s farmers used petroleum and plant-based chemicals like nicotine. Safe, but not effective.

Later, scientist began developing chemicals like DDT. Effective, but not safe.

Pesticides, cont.Pesticides, cont.

Scientists search for a “narrow-spectrum pesticide” to kill pests, but not desired plants.

An alternate to chemical control is to use biological control.

Biological controls are natural predators.

Though safer than chemicals, biological controls may have undesirable side-effects.

Scientists search for a “narrow-spectrum pesticide” to kill pests, but not desired plants.

An alternate to chemical control is to use biological control.

Biological controls are natural predators.

Though safer than chemicals, biological controls may have undesirable side-effects.

Integrated Pest Management

Integrated Pest Management

Control of agricultural pests using several methods together, including biological and chemical agents.

Goals:

To minimize the use of artificial chemicals

To prevent or slow the buildup of resistance by pests to chemical pesticides

Control of agricultural pests using several methods together, including biological and chemical agents.

Goals:

To minimize the use of artificial chemicals

To prevent or slow the buildup of resistance by pests to chemical pesticides

Integrated Pest Integrated Pest ManagementManagement

Genetically Modified OrganismsGenetically Modified Organisms

Gene for desired trait is removed from donor organism and inserted into bacteria plasmid DNA.

Bacteria infects target plant and inserts gene into target plant DNA.

Target plant (GMO) expresses gene for new trait.

Gene for desired trait is removed from donor organism and inserted into bacteria plasmid DNA.

Bacteria infects target plant and inserts gene into target plant DNA.

Target plant (GMO) expresses gene for new trait.

Spread of GMOSpread of GMO

The Terminator GeneThe Terminator Gene

A genetically modified crop which has a gene to cause the plant to become sterile after the first year.

Used to prevent the spread of GMO’s.

Drawback is that farmers must purchase their seeds every year.

A genetically modified crop which has a gene to cause the plant to become sterile after the first year.

Used to prevent the spread of GMO’s.

Drawback is that farmers must purchase their seeds every year.

GMO DownfallsGMO Downfalls

GMO’s can have unexpected effects on the ecosystem.

Ex: Bacteria gene inserted into a potato caused ALL of the potato cells to produce a toxin, thus endangering other organisms.

GMO’s can have unexpected effects on the ecosystem.

Ex: Bacteria gene inserted into a potato caused ALL of the potato cells to produce a toxin, thus endangering other organisms.

Traditional vs. Industrial Grazing

Traditional vs. Industrial Grazing

In traditional grazing, herds of animals are led from one area to another and allowed to graze on existing plants.

In industrialized grazing, plants are grown specifically for grazing, and animals are contained in small, fenced-in areas, thus upsetting the environment.

In traditional grazing, herds of animals are led from one area to another and allowed to graze on existing plants.

In industrialized grazing, plants are grown specifically for grazing, and animals are contained in small, fenced-in areas, thus upsetting the environment.

Grazing on RangelandsGrazing on Rangelands

Overgrazing occurs when the carrying capacity is exceeded. It can cause severe damage to lands

It is important to properly manage livestock, including using appropriate lands for gazing and keeping livestock at a sustainable density

Overgrazing occurs when the carrying capacity is exceeded. It can cause severe damage to lands

It is important to properly manage livestock, including using appropriate lands for gazing and keeping livestock at a sustainable density

Carrying Capacity of Pasture and Rangeland Carrying Capacity of Pasture and Rangeland (Cows per square kilomenter) (Cows per square kilomenter)

DesertificationDesertification

Desertification is the deterioration of land in arid, semi- arid and dry sub humid areas due to changes in climate and human activities

Can be caused by

Poor farming practices

Conversion of marginal grazing lands to croplands

Desertification is the deterioration of land in arid, semi- arid and dry sub humid areas due to changes in climate and human activities

Can be caused by

Poor farming practices

Conversion of marginal grazing lands to croplands

Symptoms of DesertificationSymptoms of Desertification

Lowering of water table

Increased salt content of soil

Reduced surface water

Increased erosion

Loss of native vegetation

Lowering of water table

Increased salt content of soil

Reduced surface water

Increased erosion

Loss of native vegetation

How Agriculture Changes the Biosphere

How Agriculture Changes the Biosphere

Land cover changes result in changes to sunlight reflection, evaporation, and chemical cycles.

Increase in CO2 by use of fossil fuels and clearing of land.

Species diversity reduced.

Land cover changes result in changes to sunlight reflection, evaporation, and chemical cycles.

Increase in CO2 by use of fossil fuels and clearing of land.

Species diversity reduced.

SummarySummaryIndustrial Revolution and rise in agricultural sciences have led to a revolution in agriculture.

Modern fertilizers have led to an increase in crop yields per unit area.

20th Century agriculture has relied on machinery and the use of abundant energy.

Little attention paid to erosion, loss of groundwater, effects of pesticides.

Overgrazing damages land.

Desertification is caused by poor farming practices.

Currently, both ecological and genetic revolutions are happening.

Industrial Revolution and rise in agricultural sciences have led to a revolution in agriculture.

Modern fertilizers have led to an increase in crop yields per unit area.

20th Century agriculture has relied on machinery and the use of abundant energy.

Little attention paid to erosion, loss of groundwater, effects of pesticides.

Overgrazing damages land.

Desertification is caused by poor farming practices.

Currently, both ecological and genetic revolutions are happening.