Unit 5 Review Book Pt. 2 Flashcards
(27 cards)
How to prevent decrease in biodiversity
One way to prevent this phenomenon is to practice crop rotation, in which different crops are planted in the area in each growing season.
Another practice that farmers will use to increase sustainability is polyculture, planting several crops on the same plot of land simultaneously.
This increases biodiversity.
Other problems with modern agriculture
include its reliance on large machinery (which can damage soil through compaction), and the fact that as an industry, agriculture is a huge consumer of energy.
Energy is consumed both in the production of pesticides and fertilizers and in the use of fossil fuels to run farm machinery.
Soil Erosion
The small rock fragments that result from weathering may be moved to new locations in the process of erosion, and bare soil (upon which no plants are growing) is more susceptible to erosion than soil covered by organic materials.
Because of the constant movement of water and wind on the Earth’s surface, the erosion of soil is a continual and normal process.
However, when erosion removes valuable topsoil or deposits soil in undesirable places, it can become a problem for humans.
Eroded topsoil usually ends up in bodies of water, posing a problem for both farmers, who need healthy soil for planting, and people in general, who rely on bodies of water to be uncontaminated with soil runoff.
The most significant portion of erosion caused by humans results from logging and from agriculture—especially slash-and-burn agriculture, which we’ve already discussed.
The removal of plants in an area makes the soil much more susceptible to the agents of erosion.
Unfortunately, human activities—unsustainable agricultural practices, overgrazing, urbanization, and development deforestation—have significantly increased the levels of erosion in the upper layers of soil.
These processes will continue to create problems for farmers searching for arable land until new techniques that preserve the integrity of soil are introduced and utilized.
Soil Degradation
1930s, droughts in the Great Plains reduced the area to a giant Dust Bowl.
Although the drought was the major cause of the Dust Bowl, farming practices used at that time also contributed to the destruction of the land.
Much of what we know about soil conservation was established relatively recently.
The Soil Conservation Act was passed in 1935 and led to the creation of the Soil Conservation Service.
These developments came in response to the Dust Bowl of the 1930s, which was a period of unprecedented dust storms caused by severe drought and ill-advised farming practices.
The Soil Conservation Service was a federal agency founded by Hugh Hammond Bennett.
Its mission was to promote sustainable soil conservation practices among farmers and other landowners and to help restore ecological balance across the nation’s landscape.
The agency is now called the Natural Resources Conservation Service.
Soil Conservation
In order to conserve soil resources, several best management practices have been developed.
These practices return organic matter to the soil, slow down the effects of wind, and reduce the damage to the soil from tillage (plowing). Here are some of the more common methods.
Organic agriculture
Modification of tillage practices
Use of trees and other wind barriers to reduce erosion from wind.
Terracing
Perennial crops
A windbreak
Crop rotation
Intercropping
Another way to prevent soil degradation is to add nutrients to the soil using green manure or limestone.
Organic agriculture
Use of animal waste (manure), compost, and the residue of plants to increase the amount of organic matter in the soil.
The practice of organic agriculture, a method of farming that utilizes compost, manure, crop rotation, and non-chemical methods to enhance soil fertility and control pests.
Organic producers avoid or strictly limit the use of chemical fertilizers and pesticides as well as genetically modified organisms.
Modification of tillage practices
Reduces the breakup of soil and to reduce the amount of erosion.
These include no-till farming, contour plowing, and strip planting.
The practice of contour plowing,
in which rows of crops are plowed across a hillside, prevents the erosion that can occur when rows are cut up and down on a slope.
No-till methods
Additionally, no-till methods are quite beneficial; in no-till agriculture, farmers plant seeds without using a plow to turn the soil.
Soil loses most of its carbon content during plowing.
Plowing accelerates the decomposition of organic matter in the soil, decreasing soil fertility and releasing carbon dioxide gas into the atmosphere. (And as you know, increased levels of CO2 in the atmosphere have been associated with global climate change!)
Terracing
Perennial crops
Terracing
Terracing also aids in preventing soil erosion on steep slopes.
Terraces are flat platforms that are cut into the hillside to provide a level planting surface; this reduces the soil runoff from the slope.
Perennial crops
Crops that grow back without replanting each year—are another way to reduce the need to till (by eliminating replanting) and keep erosion at bay.
A windbreak
Crop rotation
A windbreak
made up of one or more rows of trees or shrubs planted near crops in such a way as to provide shelter from eroding winds.
Crop rotation
Finally, crop rotation can provide soils with nutrients when legumes are part of the cycle of crops in an area.
Intercropping
An alternate to crop rotation is intercropping (also called strip cropping), which is the practice of planting bands of different crops in a field.
This type of planting can also prevent some erosion by creating an extensive network of roots.
As you might be aware, plant roots hold the soil in place and reduce or prevent soil erosion.
Another way to prevent soil degradation is to add nutrients to the soil using green manure or limestone.
Green manure is made by leaving plants (uprooted or simply sown) to wither and then serve as mulch: they are plowed under and incorporated into the soil before they can rot, providing valuable nutrients.
Specific cover crops can be grown for this purpose.
Alternatively, pulverized limestone can be used as a soil conditioner to neutralize soils with too much acidity.
Free-range grazing
simply implies that animals are able to move about outdoors and eat the foods they are adapted to eat, is a new term for the traditional way livestock animals were fed: by grazing on the land.
Free-range animals tend to be free from antibiotics and their waste can be used as fertilizer, but since this method requires large areas of land, the meat produced is more expensive for consumers.
Feedlots and CAFOs
In contrast, new meat production industry techniques include feedlots, or concentrated animal feeding operations (CAFOs), in which animals are confined and concentrated into smaller spaces in order to keep costs down and quickly get livestock ready for slaughter.
They tend to be crowded and are often fed grains or feed rather than grass.
Feedlots often require the use of antibiotics to prevent the spread of disease among animals densely packed together, and create problems in disposing of animal waste, which can contaminate ground and surface water.
Manure is not used as fertilizer due to difficulty with transport.
It has instead become the most widespread source of water pollution in the United States.
Overgazing
As long as the grazing area is sufficient for the number of animals, livestock grazing is a sustainable practice.
If, however, grass is consumed by animals at a faster rate than it can re-grow, land is considered overgrazed.
Overgrazing is harmful to the soil because it leads to erosion and soil compaction.
Overgrazing can cause desertification: the degradation of low-precipitation regions toward being increasingly arid until they become deserts.
Solutions to overgrazing
One solution to the problem of overgrazing is similar to crop rotation.
Rotational grazing is the regular rotation of livestock between different pastures in order to avoid overgrazing in a particular area.
Another solution involves the overall control of herd numbers.
Various tracts of public lands are available for use as rangeland, and cooperation between government agents, environmentalists, and ranchers can help avoid problems of overgrazing on these lands.
The Bureau of Land Management is responsible for managing federal rangelands.
Grazing animals also consume 70 percent of the total grain crop consumed in the United States, making them expensive food stuff.
Meat production is less efficient than agriculture: it takes approximately 20 times more land to produce the same number of calories from meat as from plants.
One possible solution is for people to consume less meat overall: this could reduce emissions such as carbon dioxide, methane, and nitrogen oxides; conserve water and reduce water pollution; reduce the use of antibiotics and growth hormones; and improve topsoil.
There are three major types of forests, which are categorized based on the age and structure of their trees.
An old growth forest
one that has never been cut; these forests have not been seriously disturbed for several hundred years.
Not surprisingly, the controversies that revolve around the issue of deforestation are primarily centered on instances in which deforestation is occurring in old growth forests.
As we mentioned in the last section, old growth forests contain incredible biodiversity, with myriad habitats and highly evolved, intricate niches for a multitude of organisms.
Second growth forests
areas where cutting has occurred and a new, younger forest has arisen naturally.
Plantations or tree farms
About 95 percent of the world’s forests are naturally occurring, and the remaining forests are known as plantations or tree farms.
Plantations are planted and managed tracts of trees of the same age (because they were planted by humans at the same time) that are harvested for commercial use.
Clear-cutting
the removal of all of the trees in an area.
This is typically done in areas that support fast growing trees, such as pines.
Obviously, this is the most efficient way for humans to harvest the trees, but it has major impacts on the habitat, as in our previous example of Vancouver Island.
Selective cutting
the removal of select trees in an area.
This leaves the majority of the habitat in place and has less of an impact on the ecosystem.
When selective cutting is used, it’s quite difficult to remove these trees from the forest, though.
This type of uneven-aged management is more common in areas with trees that take longer to grow or if the forester is only interested in one or more specific types of trees that grow in the area.
Shelter-wood cutting
Another type of uneven-aged management occurs in shelter-wood cutting.
For shelter-wood cutting, mature trees are cut over a period of time (usually 10–20 years); this leaves some mature trees in place to reseed the forest.
agroforestry
In the case of agroforestry, trees and crops are planted together.
This creates a mutualistic symbiotic relationship between the trees and crops—the trees create habitats for animals that prey upon the pests that harm crops, and their roots also stabilize and enrich the soil.
Sustainable forestry field
It makes sense that those in the forestry business would be concerned about finding a way to promote sustainable forestry, because without forests they have no way of perpetuating their income.
From an economic viewpoint, the forest must be managed to continually supply humans’ need for wood.
Silviculture
The management of forest plantations for the purpose of harvesting timber is called silviculture.
This relatively modern field has a basic tenet to create a sustainable yield; to do this, humans must harvest only as many trees as they can replace through planting. There are two basic management plans that attempt to uphold this tenet.
Of course, two options that can also have a great impact in mitigating deforestation are reforestation (planting new forests) and reuse of existing wood.
National Forest Policy
The federal government owns about 28 percent of all land in the United States.
The need to preserve some of the land was recognized by President Lincoln when he set aside a park in Yosemite, California as a land grant (the precursor to the National Park System).
In 1916, the National Park System was created in part to manage and preserve forests and grasslands.
Today, in addition to the National Park System, there are several ways the federal government controls forested land: Wilderness Preservation Areas are open only for recreational activities with no logging permitted.
The National Forest System, Natural Resource Lands, and National Wildlife Refuges are the other groups of federally controlled lands that allow logging with a permit.
One more point about managing treed areas: recent times have seen an increase in the number of greenbelts, nationally.
Greenbelts
open or forested areas built at the outer edges of cities.
Since no one is permitted to build in them, they can increase the quality of life for people living nearby.
They also border cities, putting limits on their growth.
Sometimes, satellite towns are built outside the greenbelts and interconnected with the cities by highways and mass transportation methods; in this way, we can add green spaces in urban areas.
Tree diseases and insect pests
Tree diseases (usually caused by fungal pathogens) and insect pests of trees are two natural problems in forested areas.
These can create problems for humans (in addition to the trees) because, oftentimes, they affect the quality of the food and the number of trees that are available for use.
Some of the most devastating pathogens and diseases are non-native invasive species, introduced—intentionally or not—through human travel and commerce.
Humans manage these natural events in many different ways: by removing infected trees, by removing select trees or planting them sparsely to provide adequate spacing between them, by using chemical and natural pest controls, such as integrated pest management, by carefully inspecting imported trees and tree products, and by developing pest- and disease-resistant species of trees through genetic engineering.
Forest fires types
another natural occurrence.
There are three major types of fires that occur in forests, and you should be familiar with them for the test.
Surface fires
typically burn only the forests’ underbrush and do little damage to mature trees.
These fires actually serve to protect the forest from more harmful fires by removing underbrush and dead materials that would burn quickly and at high temperatures if they accumulate, escalating more severe fires.
Crown fires
may start on the ground or in the canopies of forests that have not experienced recent surface fires.
They spread quickly and are characterized by high temperatures because they consume underbrush and dead material on the forest floor.
These fires are a huge threat to wildlife, human life, and property.
Ground fires
smoldering fires that take place in bogs or swamps and can burn underground for days or weeks.
Originating from surface fires, ground fires are difficult to detect and extinguish.
