Environmental science Final 1021G exams notes.pdf

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Western University
Environmental Science
Environmental Science 1021F/G
Geoff Stewart

Pest – unwanted organism that interferes with human activities; subjective "Aweed is a plant whose virtues have not yet been discovered" - Waldo Emerson Pesticide – kills or controls undesirable organisms 100 species (1%) cause 90% of the damage Disturbs predator-prey cycles in natural ecosystems and polyculture Insecticides – block reproduction, airways, nervous system Herbicides – disrupt plant growth and metabolism Fungicides Rodenticides Pesticide History Before pesticides Crop rotation, vary planting times, plant diversity, hedgerows Based on plants natural “instincts” First generation Sulphur, lead, arsenic, mercury Nicotine sulphate, pyrethrum, rotenone Second generation Synthetic organic compounds (eg DDT), broad- and narrow-spectrum, persistence reduction, some natural 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) The CaseAgainst Pesticides: What are the true costs? • Genetic resistance – insects and plants • Kill non-target organisms, incl. natural predators • 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 Alternatives To Synthetic Pesticides • Some based on biomimicry (mimicing nature), part of Integrated Pest Management (IPM)= making sure that the use of chemical synthetic pesticides is the last resort • pic top right, solar trees look like trees, give shade like trees, use solar power, also has outlets..cool 1. Change cultivation practices (cultural) 2. Biological pest control – Insect birth control (hormones/pheromones) (capture males radiate them so they are infertile) – Predators 3. Hot water 4. Genetically-resistant plants – Recall: associated problems Energy and waste of agriculture: Plant, irrigate, fertilize, apply pest control, harvest Transport for processing Store, clean, cook, mix, preserve, package Transport to the grocery store Keep food chilled/frozen, displayed Transport and preparation at home/restaurants Disposal transport • Most energy is from non-renewable fossil fuels • Release GHG’s (green house gas and other pollutants Energy efficient food is…. …food that requires less energy before it gets to your plate than most traditional NorthAmerican food choices. Which uses more energy? •Raising a cow for its lifetime (1-2yrs) =Driving an SUV half-way from New York to LA •Steak dinner for four = Driving an SUV around for 3 hours while leaving all lights on at home How can you decrease the energy cost of your food? •Choose •locally/native/organically grown food •foods in season •less processed, whole foods •foods with less packaging •to eat less meat, especially red meat (lower trophic level = less energy waste) – see next slide •to compost Conserve water Store it - dams and reservoirs Transport it Groundwater withdrawal Desalination – convert salt water to fresh water Reduce water waste A. Selective cutting – High grading – more damage in tropical forests than boreal – most stainable – however after 3-10 those forests are then clear cut B. Shelterwood cutting, only purpose is to
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