Food and land part 3 lec

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Environmental Science
Environmental Science 1021F/G
Geoff Stewart

Food and land 3 2/27/2013 6:17:00 PM Pests and Pesticides Pest – unwanted organism that interferes with human activities; subjective "A weed is a plant whose virtues have not yet been discovered" – Waldo Emerson for the farmer any plant that is not the crop is a pest pest = very broad general term  pest to western farmers, but in Africa it is a crop (subjective) Pesticide – kills or controls undesirable organisms 100 species (1%) cause 90% of the damage Disturbs predator-prey cycles in natural ecosystems and polyculture Pesticide is disruptive to predator prey cycles – when you disrupt one species it affects whole food chain when you kill the prey, the predator decreases (lost its food source) if pesticide is for predator the prey will increase in numbers Pesticides: Types 1) Insecticides – block reproduction, airways, nervous system to kill insects 2) Herbicides – disrupt plant growth and metabolism meant to harm plants not to kill but to suppress the growth 3) Fungicides attack fungus 4) Rodenticides kill rodents Pesticide History  Before pesticides - Crop rotation, vary planting times, plant diversity, hedgerows  Based on plants natural “instincts”  First generation - Sulphur, lead, arsenic, mercury – problem b/c poisonous to humans - Nicotine sulphate, pyrethrum, rotenone naturals=come from plants  Second generation - Synthetic organic compounds (eg DDT), broad- and narrow-spectrum, persistence reduction, some natural persistence reduction – major problem is they persist in soil for a very long time even after say DDT was banned it still is present in soil - second generation try to create pesticides that breakdown in the soil - reduces that persistence has been the goal broad spectrum = roundup, partnered with GMO crops and will kill any plant that hasn’t been modified to resist narrow spectrum = opposite, would only affect one specific species DDT = banned but not everywhere because used to kill mosquitos with malaria – therefore use of pesticides does help save lives so not completely banned If stopped using pesticides half of global food production would decrease, so there would be famine and a giant increase on price of food The Case For Pesticides Saves human lives – Malaria, bubonic plague, typhus Increase food supplies and profits; lower costs Work faster and better than alternatives Health risk *may* be insignificant compared to benefits 3000-6000 death/yr (EPA) New pesticides are safer and used at lower rates than older pesticides The Case Against Pesticides: What are the true costs? Genetic resistance – insects and plants Kill non-target organisms, incl. natural predators 85-90% sprayed don’t hit target Can increase other pests Harm wildlife Pesticide movement Human health threat; 20,000–40,000 deaths Environmental health threat Still 6% decrease in yield loss to pests Economic threshold of use Use reduced without yield decrease Economic thresh hold use – is it more expensive for farmer to buy it and then lose it to spraying and missing – then affects rest of farm (ie soil) if soil get affected then would have to use fertilizer – its about looking at the big picture. Alternatives to Synthetic Chemical Pesticides Some based on biomimicry, part of Integr
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