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Environmental Science 1021F/G Study Guide - Final Guide: Smog, Shelterwood Cutting, Soil Salinity

Environmental Science
Course Code
Christie Stewart
Study Guide

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Environmental Science Final Exam Notes
Producing More Fish and Shellfish: Problems/Solutions
Problems (most are with fish farming): high waste concentration, food requirement,
eutrophication, habitat destruction, species entanglement, GMO escape
oEutrophication: loss or reduction of oxygen in the water due to high levels of
Solutions: sustainable aquaculture practices, aquaponics
oAquaponics: mimic what happens in natural systems
Environmental Issues Affecting Soil
Land degradation: natural or human processes that decrease future ability of land to
support crops, livestock, wild species
Mostly agricultural causes
30-40% of world’s agricultural land is degraded
examples of land degradation: soil erosion, desertification, soil salinization, waterlogging
degradation: overusing something past its sustainable yield
Soil Erosion
soil erosion: movement of soil (esp. litter and topsoil) from one place to another
oloss of soil fertility and increase in sediment buildup
oloss of soil quantity and quality from one area
the “Big Three” causes: wind, water, people
soil erosion is a problem when it comes to food
Global Soil Erosion
Sustainable yield: rate at which a resource can be used to ensure it is not degraded or
depleted so it does not become unusable for future generations
Soil Loss in Canada
Wind erosion mostly in prairies
Regions with high rainfall experience water erosion (maritimes, BC, ON), effects runoff
and water quality
Water erosion: movement down a slope
What Causes Desertification?
Desertification: results in decrease in production potential
Causes: overgrazing, deforestation, erosion, salinization, soil compaction, climate
Soil Degradation on Irrigated Land
Irrigated croplands supply 40% food production
Salinization: accumulation of salt deposits left on soil surface from evaporating water
Waterlogging: irrigation applied to leach salts, inadequate drainage leads to rising water
All water including freshwater contains salt
Solutions to Environmental Issues Affecting Soil
Prevention and/or cleanup
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oSoil conservation techniques
oSoil restoration
oSustainable agriculture
oSolutions for soil salinization
Soil Conservation
Conservation-tillage vs. conventional-tillage
Tilling (turning the soil over): incorporates O horizon into soil (not natural), disrupts
natural processes of organic material breakdown
Conventional-tillage: used for weed control, creating smooth surface
Moving towards conservation-tillage: reducing amount of tillage or not tilling at all
Land classification: prevents soil from eroding
Conservation Tillage
Advantages: cheaper, reduces soil compaction, allows for more than one crop per
season, does not reduce crop yields, reduces CO2 release from soil
Disadvantages: can pass on pests, increases herbicide and pesticide use
Soil Conservation
Terracing: steps in side of slope that crops are planted along
Contour planting: following the shape of a river in parallel fashion
Strip cropping: each strip is of a different crop (polyculture)
Alley cropping: agroforestry, crops planted between trees
Windbreaks: stop wind from blowing across the field, reducing soil erosion, trees
planted around crops
Soil Restoration (restoring quality of the soil)
Organic fertilizer
oAnimal manure: has nitrogen and phosphorus
oGreen manure: organic material is put in where another crop is going to be
planted without allowing breakdown
oCompost: organic material has already begun process of being broken down
Crop rotation: making a different crop each year, restores soil cause each crop will use
nutrients differently
Commercial inorganic fertilizer: most used, produced by mining, needed to produce
enough food
oAdvantages: easy, cheap
oDisadvantages: does not input organic material into soil, limiting nutrients,
releases greenhouse gas nitrous oxide, can leach into water
Sustainable Agriculture
Low-input agriculture: includes fertilizer, water, pesticides, e.g. organic farming
Includes soil conservation/restoration
Economic incentives: government subsidies, funding for research
Looks at agroecosystem as a whole, idea is low-input
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More polyculture, organics, resorting to chemical pesticides last, using water efficiently,
perennials (continuously grow without replanting), subsidizing farmers for being more
Soil Salinization on Irrigated Land
Soil salinization: when water evaporates it leaves the salt behind making the soil salty
Flushing the salt out with more water can cause waterlogging
Can avoid the land for a while (loss of income)
Underground drainage systems, avoid waterlogging and reduces salt (alters how water
flows, increases water pollution)
Pests and Pesticides
Pest: unwanted organism that interferes with human activities; subjective
“a weed is a plant whose virtues have not yet been discovered”
Pesticide: kills or controls undesirable organisms
oDisturbs predator-prey cycles in natural ecosystems and polyculture
Pesticides: Types
Insecticides (kill or damage insect): block reproduction, airways, nervous system
Herbicides (plants): disrupt plant growth and metabolism
Rodenticides: rodent might be problematic with the plant or the seed
Pesticide History
Before pesticides
oCrop rotation, vary planting times, plant diversity, hedgerows
First generation
oSulphur, lead, arsenic, mercury
oNicotine sulphate, pyrethrum, rotenone; based on plants natural instincts
Second generation
oSynthetic organic compounds (DDT), persistence reduction, some natural
oBroad-spectrum: impact many species
oNarrow-spectrum: ideally only target the pest you want
The Case for Pesticides
Saves human lives – malaria (mosquitos), bubonic plague (fleas on rats, use
rodenticides), typhus
Increase food supplies and profits; lower costs
Work faster and better than alternatives
Health risk may be insignificant compared to benefits
New pesticides are safer and used at lower rates than older pesticides
The Case Against Pesticides
Genetic resistance in insects and plants
Kill non-target organisms, including natural predators (can increase other pests, harm
Pesticide movement
Human and environmental health threat
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