Presentation on theme: "Pesticides and Other Environmental Impacts of Agriculture."— Presentation transcript:
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 13-29
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-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 LossSoil Water Air PollutionHuman 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 13-10
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) PreventionRemediation
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?
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 (N 2 O). Ruminants (cows) produce methane as a by- product of digestion.
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