Pesticides and Other Environmental Impacts of

Agriculture

We use chemicals to repel or kill pest organisms as plants have done for millions of years.

Chemists have developed hundreds of chemicals (pesticides) that can kill or repel pests.

The ideal pest-killing chemical has these qualities:• Kill only target pest.• Not cause genetic resistance in the target organism.

• Disappear or break down into harmless chemicals after doing its job.

• Be more cost-effective than doing nothing.

Reality: most pesticides are persistent and wide-ranging

After an application, not all pests will be killed.

The resistant ones will multiply.

The farmer will have to apply a greater quantity or a chemical that is stronger.

Then (again) some will survive and reproduce to yield an even more resistant generation.

Use of pesticides has increased by 33% since 1942•Today 37% of crops are lost to pests•In 1940s 31% of crops were lost to pests

Superpests are resistant to pesticides.

Superpests like the silver whitefly (left) challenge farmers as they cause > $200 million per year in U.S. crop losses.

Figure 13-29Figure 13-29

Pesticide widely used starting in WWII

Used in agriculture and private sector

Banned in the US in 1972 after publication of "Silent Spring" and awareness of the impacts on wildlife

Still used to combat malaria Health impacts:

• Since it is hydrophobic, DDT is fat soluble and tends to build up in fatty tissues in animals

• Endocrine disrupter• In humans, reduced fertility• Lower mental acuity in infants born to exposed women

• Neurological damage• Carcinogenic

Wrote Silent Spring which introduced the U.S. to the dangers of the pesticide DDT and related compounds to the environment.

Figure 13-AFigure 13-A

Most widely used herbicide in the US

Health effects:• Endocrine disrupter• Suspected carcinogen• Interferes with menstrual cycles

• Linked to birth defects• Lowers sperm count in men

Ecological effects:• Feminization of male frogs

Hayes et al. 2002

American leopard frogs

Government regulation has banned a number of harmful pesticides, like DDT, but some scientists call for strengthening pesticide laws.• The Environmental Protection Agency (EPA), the Department of Agriculture (USDA), and the Food and Drug Administration (FDA) regulate the sales of pesticides under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA).

• The EPA has only evaluated the health effects of 10% of the active ingredients of all pesticides.

Circle of poison• Pesticides that have been banned in the US are shipped to developing countries

• The crops grown with those pesticides are then sold to the US

The world’s worst industrial accident occurred in 1984 at a pesticide plant in Bhopal, India.• An explosion at Union Carbide pesticide plant in an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas.

• Nearly 4,000 people died immediately.

• A number of safety and faulty equipment oversights led to the accident.

Modern agriculture has a greater harmful environmental impact than any human activity.

Loss of a variety of genetically different crop and livestock strains might limit raw material needed for future green and gene revolutions.

Loss of topsoil has limited productivity and led to desertification.

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 depletion

Pesticide 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

Waterlogging

Sediment 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 sprays

Soil erosion is the movement of soil components, especially surface litter and topsoil, by wind or water.

Soil erosion lowers soil fertility and can overload nearby bodies of water with eroded sediment.

When crops are harvested or recently planted, fields are vulnerable to erosion.

Soil is eroding faster than it is forming on more than one-third of the world’s cropland.

Figure 13-10Figure 13-10

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.

Fig. 13-11, p. 280

Very severeSevereModerate

Levels of desertification globally

Repeated irrigation can reduce crop yields by causing salt buildup in the soil and water-logging of crop plants.

Salinization prevention and remediation

Avoid planting crops that need lots of water in arid and semi-arid areas

Irrigate with water that has few dissolved salts

Use drip irrigation Incorporate humus into soil

Use salt-free fertilizers

Flush out soil with lots of water

Plant crops that can remove salt from the soil (eg barley, oats)

Prevention Remediation

Run-off of animal waste and inorganic fertilizers

Water pollution from agricultural lands

Imagine that the farm above raises cattle. How would expect the water quality to be different from Point A to Point B?

What tests would you do? How would the biotic community change from Point A to Point B? How about further downstream?

Water quality Nitrates Phosphates Fecal coliform Biological oxygen demand Turbidity/Total suspended solids

Agriculture is responsible for approx. 35% of global greenhouse emissions.• Lots of energy needed to make fertilizers and pesticides.

• Energy needed to run farm equipment for planting, irrigation systems, and harvesting.

• Transportation of products to distribution or processing centers uses a lot of fuel.

The decomposition of animal waste produces nitrous oxide (N2O).

Ruminants (cows) produce methane as a by-product of digestion.