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Forests are an important resource, both for the environment and for human use.
Clear-cutting is a method of harvesting trees in the forest for human use
Clear-cutting has many environmental consequences even though from an economic standpoint it is a benefit since it is cheaper than other methods.
Since trees have roots that hold the soil, when we clear cut large areas of land we expose this soil, leaving it vulnerable to erosion and/or flooding.
This soil may end up in a river, lake, or stream leading to problems there.
Trees also provide shade, so when we cut them down, the temperature in these areas is increased because the sun hits the ground directly.
Drip irrigation—This method saves water because only about 5 percent of the water is lost to evaporation, but it is pretty expensive.
Flood irrigation—In flood irrigation the farmer floods an entire field with water (Figure 9.3).
Furrow irrigation—This method is similar to flood irrigation except that trenches are dug between rows of crops and that area is flooded with water.
Spray irrigation—This method is the one you are probably most familiar with. You see this on lawns all the time with sprinklers, but on a large scale this is done on crops (Figure 9.5). This method loses less water than either flood or furrow but is more expensive.
Waterlogging happens when so much water is left on the soil it is saturated.
Aquifers are underground layers of water that can be tapped for irrigation and other uses.
There are many minerals found on Earth’s surface and underground that we need for human purposes
For example: coal. When the mineral resource is found on the surface of the Earth and we extract this mineral resource, it is called surface mining (Figure 9.6).
When the resource is found deep underground, it is called subsurface mining, which is more expensive (Figure 9.7).
There are many methods of surface mining, such as strip mining, open-pit mining, and mountaintop removal.
Each of these has its own set of environmental impacts. In order to get to these resources, miners must first remove the soil, plants, and rock known as overburden.
After mining, the wastes from mining, called slag and tailings, are left behind to be dealt with.
Mining removes plant life, opens the soil up to erosion and runoff, harms habitats, can contaminate aquifers, releases methane from the soil, and causes fine particles of dust to be released.
As we discussed earlier in this chapter, as we pave surfaces, build buildings, and put in roads, we stop allowing water to infiltrate into the soil and we increase the amount of water that runs off.
Impervious surfaces like concrete or asphalt don’t allow for water to infiltrate into the ground.
Our agricultural practices have environmental impacts.
Many farmers and ranchers are looking at ways to reduce this and still produce food for humans.
Ranchers can make sure to not overgraze by rotating their animals to different pastures, allowing the grass to regrow and recover.
This is called rotational grazing. We can prevent soil from losing valuable nutrients by rotating the places we plant these crops or by adding manure to increase nutrient values and limestone to balance acidity to protect soil health.
Contour plowing: Planting crops along the contours of the land as shown in Figure 9.9.
Windbreaks—Planting trees or shrubs to limit erosion as shown in Figure 9.10.
Perennial crops—Planting crops that don’t need to be replanted each year and can be harvested multiple times during the year. After harvest, they automatically grow back. By eliminating replanting each year, perennial cropping can reduce soil erosion.
Terracing—Similar to contour plowing but when an area is very hilly or mountainous. The farmer will make step-like rows and plant the crops on these rows. This helps to reduce soil erosion. Figure 9.11 shows how the steep mountain was made into steps and crops were planted on the top of each step.
No-till agriculture—This method is what it sounds like, planting crops but without tilling the soil before planting. This reduces soil erosion because when we turn the soil over (tilling), it is vulnerable to wind and water erosion.
Strip cropping—Planting a strip of one crop, then a strip of another, alternating throughout the field. This prevents soil erosion because one row might have crops with deep roots, while the next one doesn’t. The deep roots will hold in the soil for the plants that don’t have deep roots. You can see an example of this in Figure 9.12.
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