Unit 5: Land and Water Use
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The tragedy of the commons suggests that
individuals will use shared resources in their own self interest rather than in keeping with the common good, thereby depleting the resource.
Clearcutting can be economically advantageous but leads
to soil erosion, increased soil and water temperatures, and flooding.
Forests contain trees that absorb
pollutants and store carbon dioxide.
The cutting and burning of trees releases
carbon dioxide and contributes to climate change.
The Green Revolution started a shift to new
agricultural strategies and practices in order to produce food production, with both positive and negative results.
Some of these strategies and methods are
mechanization, genetically modified organisms, fertilization, irrigation, and the use of pesticides.
Mechanization of farming can increase
profits and efficiency for farms and reliance on fossil fuels.
Agricultural practices that can cause environmental damage include
tilling, slash and burn farming, and the use of fertilizers.
The largest human use of freshwater is for
irrigation (70%)
Types of irrigation include
drip irrigation, flood irrigation, furrow irrigation, and spray irrigation.
Waterlogging occurs when
too much water is left to sit in the soil, which raises the water table of groundwater and inhibits plants’ ability to absorb oxygen through their roots.
Furrow irrigation involves
cutting furrows between crop rows and filling them with water. This system is inexpensive but about ⅓ of the water is lost to evaporation and runoff.
Flood irrigation involves
flooding an agricultural field with water. This system sees about 20% of the water lost to evaporation and runoff. This can also lead to waterlogging
Spray irrigation involves
pumping groundwater into spray nozzles across an agricultural field. This system is more efficient than flood and furrow, with only ¼ or less of the water lost to evaporation or runoff. However, spray systems are more expensive than flood and furrow irrigation, and also require energy to run.
Drip irrigation uses
perforated hoses to release small amounts of water to plant roots. This system is the most efficient, with only about 5% of the water lost to evaporation and runoff. However, this system is expensive and so is not often used.
Salinization occurs when
the salts in groundwater remain in the soil after the water evaporates. Over time, salinization can make soil toxic to plants.
Aquifers can be severely depleted if
overused for agricultural purposes, as has happened to the Ogallala Aquifer in the central United States.
One consequence of using common pest control methods such as pesticides, herbicides, fungicides, rodenticides, and insecticides is that
organisms can become resistant to them through artificial selection. Pest control decreases crop damage by pests and increases crop yields.
Crops can be genetically engineered to increase their
resistance to pests and disease. However, using genetically modified crops in planting or other ways can lead to loss of genetic diversity of that particular crop.
Methods of meat production include
concentrated animal feeding operations (CAFOs), also called feedlots, and free range grazing.
Meat production is less efficient than
agriculture; it takes approximately 20 times more land to produce the same amount of calories from meat as from plants.
CAFOs are used as a way to
quickly get livestock ready for slaughter. They tend to be crowded, and animals are fed grains or feed that are not as suitable as grass. Additionally, feedlots generate a large amount of organic waste, which can contaminate ground and surface water.The use of feedlots are less expensive than other methods, which can keep costs to consumers down.
Free range grazing allows animals to
graze on grass during their entire lifecycle. Meat from free range animals tends to be free from antibiotics and other chemicals used in feedlots. Organic waste from these animals acts as fertilizer. Free range grazing requires large areas of land and the meat produced is more expensive for consumers.
Overgrazing can cause
desertification. Desertification is the degradation of low precipitation regions toward being increasingly arid until they become deserts.