Unit 4 Test

malnutrition

Many of the world's poor can afford only to live on a low-protein, high-carbohydrate, vegetarian diet consisting mainly of grains such as wheat, rice, or corn. They often suffer from chronic malnutrition—deficiencies of protein and other key nutrients—which weakens them, makes them more susceptible to disease, and hinders the normal physical and mental development of children. According to the U.N. Food and Agriculture Organization (FAO), the estimated number of chronically undernourished or malnourished people fell from 918 million in 1970 to 862 million in 2006. This is a good start, but it is still high—nearly three times the population of the United States. A 2007 study by University of Minnesota economists Ford Runge and Benjamin Senauer estimated that increased food prices from the massive diversion of corn to produce ethanol for fueling cars could increase the number of hungry and malnourished people to 1.2 billion by 2025 instead of decreasing it to 625 million as projected by the FAO. Despite some progress, one of every six people in developing countries (including about one of every three children younger than age 5) is chronically undernourished or malnourished. About 75% of these people live in rural areas of developing countries. In 2005, the FAO estimated that each year, nearly 6 million children die prematurely from chronic undernutrition and malnutrition and increased susceptibility to normally nonfatal infectious diseases (such as measles and diarrhea) because of their weakened condition. This means that each day, an average of 16,400 children die prematurely from these mostly poverty-related causes. How many people died from such causes during your lunch hour?

Be able to use a soil triangle (ternary diagram) to determine soil texture

Soil scientists caun use a soil triangle to classify soils into groups.

How does carbon get stored into soil? How can it be released?

Some of the carbon fixed through photosynthesis moves from plant roots into the soil. Once there, it is very stable and can remain in the soil for 1,000s of years. There is a ton of carbon in the soil - even more than vegetation. Carbon can be released through producers, consumers, and decomposers adding CO2 through respiration. Therefore, soil is an important carbon reservoir in addition to forests, the atmosphere and fossil fuels.

Review Units 1-3 Study Guides

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Know the names and basic characteristics of the six possible soil horizons

*Up to 6 in soil profile *Soil profile is cross section of soil layers present O horizon: O stands for organic. This layer is sometimes called humus and consists of decaying organic material. It is most pronounced in forest ecosystems. A horizon: The A horizon is a zone where minerals and organic material have been mixed together. Another name for it is topsoil. In some ecosystems, there will be no O, so the A horizon will be at the top. B horizon: Also called subsoil. This layer contains mostly inorganic material and is where nutrients will accumulate. The B horizon is present in all soils. C horizon: The C horizon is below the B horizon and is the least weathered layer of soil. It consists of pieces of the parent material. R horizon: The R horizon is below the C horizon and is bedrock. R stands for Rock. E horizon: There are some soils that have extra horizons because of particular properties of the soil. The E horizon is a zone of leaching that can sometimes be found above the B horizon in acidic soils. (E stands for eluviation) This is a zone of leaching. Due to soil's acidity, material is more likely to dissolve and be transported down to the B horizon - taiga.

Famine

A famine occurs when there is a severe shortage of food in an area accompanied by mass starvation, many deaths, economic chaos, and social disruption. Faced with starvation, desperate people eat the seed grain they have stored to grow crops in future years and slaughter their breeding livestock. Famines often result in mass migrations of starving people to other areas or to refugee camps in a search for food, water, and medical help. Many die during these journeys or in these camps. Famines are usually caused by crop failures from drought, flooding, war, and other catastrophic events.

What is a CAFO/ feedlot?

A CAFO, or Concentrated Animal Feeding Operation , is an industrial-sized livestock operation. CAFO animals are confined at least 45 days or more per year in an area without vegetation. CAFOs include open feedlots, as well as massive, windowless buildings where livestock are confined in boxes or stalls.

What are perennial plants? How can they be beneficial in agriculture?

A way farmers could reduce soil erosion in the future is through these. Do not need to be planted each year. Currently most food crops are annuals, but there are several universities and institutions that are working to develop perennial food crops that could be used in the future. Perennial crops would be advantageous because their root systems would be much more developed than those of annual crops, allowing them to hold the soul in place more effectively. Annual crops have to re-grow their root systems each year, so they are not able to grow as deep into the soil. Photo shows the roots of an annual wheat plant on the left and a perennial grass plant on the right.

Know the advantages & disadvantages of modern pesticides

Advantages:-They save human lives. Since 1945, DDT and other insecticides probably have prevented the premature deaths of at least 7 million people (some say as many as 500 million) from insect-transmitted diseases such as malaria (carried by the Anopheles mosquito), bubonic plague (carried by rat fleas), and typhus (carried by body lice and fleas).-They increase food supplies. According to the FAO, 55% of the world's potential human food supply is lost to pests. Without pesticides, these losses would be worse and food prices would rise.-They increase profits for farmers. Officials of pesticide companies estimate that every $1 spent on pesticides leads to an increase in U.S. crop yields worth approximately $4. (However, studies have shown that this benefit drops to about $2 if the harmful effects of pesticides are included.)-They work fast. Pesticides control most pests quickly, have a long shelf life, and are easily shipped and applied. When genetic resistance occurs, farmers can use stronger doses or switch to other pesticides.-When used properly, their health risks are very low relative to their benefits. Pesticide industry scientists argue that when pesticides are used in the approved regulatory manner, they pose no major risk to farm workers and consumers.-Newer pest control methods are safer and more effective than many older ones. Greater use is being made of chemicals derived originally from plants. They are safer to use and less damaging to the environment than are many older pesticides. Genetic engineering is also being used to develop pest-resistant crop strains and genetically altered crops that produce natural pesticides.Disadvantages:-They accelerate the development of genetic resistance to pesticides by pest organisms. Insects breed rapidly, and within 5 to 10 years (much sooner in tropical areas) they can develop immunity to widely used pesticides through natural selection and then come back stronger than before. Since 1945, about 1,000 species of insects and rodents (mostly rats) and 550 types of weeds and plant diseases have developed genetic resistance to one or more pesticides.-They can put farmers on a financial treadmill. Because of genetic resistance, farmers can pay more and more for a pest control program that often becomes less and less effective.-Some insecticides kill natural predators and parasites that help control the pest populations. Wiping out natural predators, such as spiders, can unleash new pests whose populations their predators had previously held in check and can cause other unexpected effects. Of the 300 most destructive insect pests in the United States, 100 were once minor pests that became major pests after widespread use of insecticides.-Pesticides do not stay put and can pollute the environment. According to the U.S. Department of Agriculture (USDA), only 0.1-2% of the insecticides applied to crops by aerial spraying or ground spraying reaches the target pests, and less than 5% of herbicides applied to crops reaches the target weeds.-Some pesticides harm wildlife. According to the USDA and the U.S. Fish and Wildlife Service, each year, pesticides applied to cropland in the United States wipe out about 20% of U.S. honeybee colonies and damage another 15%. Pesticides also kill more than 67 million birds and 6-14 million fish. According to a 2004 study by the Center for Biological Diversity, pesticides also menace one of every three endangered and threatened species in the United States.-Some pesticides threaten human health. The WHO and UNEP estimate that, each year, pesticides seriously poison at least 3 million agricultural workers in developing countries and at least 300,000 people in the United States. They also cause 20,000-40,000 deaths per year, worldwide. Each year, more than 250,000 people in the United States become ill because of household pesticide use. Such pesticides are a major source of accidental poisonings and deaths of young children.-According to studies by the National Academy of Sciences, exposure to legally allowed pesticide residues in food causes 4,000-20,000 cases of cancer per year in the United States. Some scientists are concerned about possible genetic mutations, birth defects, nervous system and behavioral disorders, and effects on the immune and endocrine systems from long-term exposure to low levels of various pesticides. The pesticide industry disputes these claims, arguing that the exposures are not high enough to cause serious harm. Children are much more susceptible to low levels of pesticides and other toxic chemicals, because on an amount-per-weight basis, they eat more food, drink more water, and breathe more air. They also put their fingers in their mouths more often and spend more time playing on grass, carpeting, and soil where pesticides can accumulate.

Know the main ways that food can be grown to promote soil conservation: Alley cropping/windbreaks

Alley cropping is when one or more crops are planted in between rows of trees. The trees also provide shade which retains soil moisture and reduces the need for irrigation. The trees can provide habitats for birds or other organisms that eats pests (depending on the species of tree) and the trimmings of the trees can be used as compost. Windbreaks are similar to alley cropping except that the trees are planted around crops, instead of between them. The trees hold soil in place and block the wind to prevent wind erosion. They also retain soil moisture and provide habitats for pest-eating birds and insects.

Know the main ways that food can be grown to promote soil conservation: No-till farming

Also called reduced-till farming. Normally when farmers prepare to plant, they will till and plow their fields. This means they basically turn over the soil, killing any weeds that are growing and releasing carbon and moisture stored in the soil. This also loosens the soil, making it more susceptible to erosion. No-till farming, in contrast, skips this step. Farmers only dig a small hole in which to plant the seed. This reduces the water lost to evaporation and the fuel required to run tractors and other machinery required for tilling. It usually raises crop yields as well. However, it does require more herbicides since weeds are no longer being killed during the tilling process. It many also require more fertilizers since the weeds are no longer decomposing the soil. No-till or reduced-till farming is becoming more common worldwide. (Approximately 41% of US crop land was farmed using reduced-tilling methods in 2007).

Know the specific definition and be able to explain the consequences of: Waterlogging

Another problem with irrigation is waterlogging, in which water accumulates underground and gradually raises the water table. Farmers often apply large amounts of irrigation water to leach salts deeper into the soil. Without adequate drainage, waterlogging occurs and saline water then envelops the deep roots of plants, lowering their productivity and killing them after prolonged exposure. At least one-tenth of the world's irrigated land suffers from waterlogging, and the problem is getting worse.

Be able to explain how overgrazing affects the soils of grasslands

Because grass grows from the base, grazing is actually good for rangeland ecosystems. When an animal eats the top of the blade of grass it stimulates growth at the base of the plant. On the right side of the photo, you can see an area that has been moderately grazed and is healthy. Because these ecosystems have evolved with grazing herbivores, it is possible to have rangeland that is under grazed, which reduces its overall productivity. However, the bigger problem is when there are too many animals grazing in the same area because they will eat the whole plant and not leave enough of the blade of grass for it to regrow quickly. When the number of animals exceeds the land's carrying capacity itis called overgrazing and is shown to the left of the fence in the photo above. Some consequences of this overgrazing are that grass cover is reduced & more soil is exposed to erosion. Soil is also exposed to the trampling of animals which can compact the soil and reduce pore space. This would reduce the moisture content because there would be less pore space to hold water and it would ultimately limit the rangeland's resilience.

Know the specific definition and be able to explain the consequences of: Salinization

Between 1950 and 2007, the world's area of irrigated cropland tripled, with most of the growth occurring from 1950 to 1978, and little growth occurring since 1990. The 20% of the world's cropland that is irrigated produces almost 40% of the world's food. But irrigation has a downside. Most irrigation water is a dilute solution of various salts, picked up as the water flows over or through soil and rocks. Irrigation water that has not been absorbed into the soil evaporates, leaving behind a thin crust of dissolved salts in the topsoil. Repeated annual applications of irrigation water in dry climates lead to the gradual accumulation of salts in the upper soil layers—a soil degradation process called salinization. It stunts crop growth, lowers crop yields, and can eventually kill plants and ruin the land. The United Nations estimates that severe salinization has reduced yields on at least one-tenth of the world's irrigated cropland, and the problem is getting worse. The most severe salinization occurs in Asia, especially in China, India, Egypt, Pakistan, and Iraq. Salinization affects almost one-fourth of irrigated cropland in the United States, especially in the western states.

Understand why meat production & consumption has increased since 1960

Between 1961 and 2007 world meat production— mostly pork, poultry, and beef—increased fourfold, and is likely to more than double again by 2050 as affluence rises and middle-income people begin consuming more meat and meat products in developing countries. During this same period, average meat consumption per person more than doubled. Industrialized meat production may face certain limits in the future. For example, if we include land used to grow grain fed to livestock, the FAO estimates that 30% of the earth's ice-free land is already directly or indirectly involved in livestock production. And this percentage is likely to increase.

Understand how industrialized agriculture threatens biodiversity

Biodiversity and some ecological services are threatened when forests are cleared and grasslands are plowed up and replaced with croplands. For example, one of the fastest growing threats to the world's biodiversity is the clearing or burning of large areas of tropical forest in Brazil's Amazon basin and in its cerrado, a huge savanna-like region south of the Amazon basin. This land is being burned or cleared for large plantations of soybeans, grown for use as cattle feed, and sugarcane used for making ethanol fuel for cars. Other tropical forests are burned to make way for plantations of oil palm trees increasingly used to produce biodiesel fuel. These activities threaten biodiversity and contribute to climate change by releasing carbon dioxide into the atmosphere. A closely related problem is the increasing loss of agrobiodiversity—the world's genetic variety of animals and plants used to provide food. But we are replacing nature's resilient genetic diversity developed through millions of years of natural selection with human-engineered monocultures. Scientists estimate that since 1900, we have lost three-fourths of the genetic diversity of agricultural crops. For example, India once planted 30,000 varieties of rice. Now more than 75% of its rice production comes from only 10 varieties and soon, almost all of its production may come from just one variety. Rice varieties around the world may drop even more if there is a shift toward genetically engineered golden rice and other genetically engineered crops. In the United States, about 97% of the food plant varieties available to farmers in the 1940s no longer exist, except perhaps in small amounts in seed banks and in the backyards of a few gardeners. In other words, we are rapidly shrinking the world's genetic "library," which is critical for increasing food yields. In fact, we might need it more than ever to develop new plant and livestock varieties that can adapt to climate change. This failure to preserve agrobiodiversity is a violation of the biodiversity principle of sustainability. Wild and endangered varieties of crops important to the world's food supply are stored in about 1,400 refrigerated gene or seed banks, agricultural research centers, and botanical gardens scattered around the world. But increasingly, power failures, fires, storms, and war are causing irreversible losses of these stored plants and seeds. However, a new ice vault built underground in the Norwegian Arctic will eventually contain duplicates of much of the world's stock of seeds and will not be vulnerable to such hazards. Shortages of storage space and money severely limit the number of species that can be preserved, and the seeds of many plants (such as potatoes) cannot be stored successfully in gene banks. Because stored seeds do not remain alive indefinitely, periodically they must be planted (germinated) and new seeds collected for storage. Unless this is done, seed banks become seed morgues. Because of such limitations on seed banks, ecologists and plant scientists warn that the only effective way to preserve the genetic diversity of most plant and animal species is to protect representative ecosystems throughout the world from agriculture and other forms of development.

What are porosity and permeability? How are they related to each other and to soil texture?

Both porosity and permeability are properties that are directly determined by the texture of the soil. Porosity is the amount of space in between the grains of sand, silt and clay that make up the soil. Porosity is important because it determines the ease with which water, oxygen, and nitrogen can work their way down between soil particles to the root zones of plants. It also determined how quickly and easily water can soak in and become groundwater in an aquifer. Permeability (measures rate in cm/s) describes how easily water passes through soils. It is influenced by the porosity and can be measured with a percolation test. If the permeability is too low, the soil can become water-logged, but if it is too high, the soil can't retain enough water for plant growth. As a result the best soils for plant growth have medium-sized pores or a mixture of pore sizes - loam

Know the three major macronutrients that humans need

Carbohydrates, proteins, and fat

Know the advantages & disadvantages to the methods of harvesting trees (clear-cutting, stripcutting and selective cutting) & the disadvantages of building logging roads

Clear-cutting makes good economic sense because it allows the logger to get the most money out of the land at that time, but there are some ecological problems with clear-cutting such as extreme soil erosion, loss of soil nutrients, water pollution in downhill streams, and loss of habitat and biodiversity in the ecosystem. Selective cutting is good because only intermediate or older trees are cut so that some trees remain to the soil and it can serve to avert much of the environmental damage caused by clear cutting, but it is not effective in every forest ecosystem because the logging machinery damages trees surrounding each tree that is cut. Strip cutting is good because you only clear-cut a strip of the forest at a time, allowing it to regenerate and then cutting a nearby stop. It prevents water pollution because trees remain in the watershed downhill of the cut strip, so they can capture and hold any soil or nutrients that run off from the cut strip. Roads expose soil to erosion, fragments habitats, make it easier for invasive species to get into the forest (by hitching a ride with humans) and cause damage to the ecosystem. Also, roads provide a point of access for more and more people (miners, hunters, farmers, etc.) to get into this forested area and potentially cause damage.

Know what the different types of pesticides are designed to kill (insecticides, herbicides, rodenticides etc)

Common types of pesticides include insecticides (insect killers), herbicides (weed killers), fungicides (fungus killers), and rodenticides (rat and mouse killers).

Know what a CSA is and why eating locally/ seasonally is environmentally advantageous

Eating crops that are produced locally and seasonally can help reduce energy inputs from industrial agriculture. Crops produced out of season can take more energy to produce and are often transported long distances. Eating locally also reduces the amount of energy needed for transporting food. CSA stands for Community-supported agriculture. When consumers join, they pay farmers in advance for a share of their yield. Consumers get fresh local produce in season and farmers get a guaranteed income.

Know the advantages and disadvantages of genetically modified food

Despite its promise, controversy has arisen over the use of genetically modified (GM) food and other forms of genetic engineering. Its producers and investors see this kind of food as a potentially sustainable way to solve world hunger problems and improve human health. Some critics consider it potentially dangerous "Frankenfood." Critics recognize the potential benefits of GM crops. But they warn that we know too little about the longterm potential harm to human health and ecosystems from the widespread use of such crops. They point out that genetic engineering mixes genes from widely differing species, which has never occurred in nature or even in selective breeding. They warn that if GM organisms released into the environment cause some unintended harmful genetic and ecological effects, as some scientists expect, they cannot be recalled. For example, there is the potential for GM plant pollen to spread among nonengineered species, threatening crop biodiversity. In a 2006 study by the Union of Concerned Scientists, half of the nonengineered corn and soybean varieties tested by one laboratory contained DNA from GM varieties. Once experimental GM pollens are in the environment, they are impossible to retrieve. Most scientists and economists who have studied the genetic engineering of crops believe that its potential benefits outweigh its risks. They also contend that some of the potential problems associated with GM crops can be eliminated by genetically engineering plants without inserting a gene from another species. This new technique, called chimeraplasty, involves inserting instead a chemical instruction that attaches to a gene, altering it to give desired genetic traits. Critics call for more controlled field experiments, long-term testing to better understand the risks, and stricter regulation of this rapidly growing technology. A 2004 study by the Ecological Society of America recommended more caution in releasing genetically engineered organisms into the environment without adequate testing.

What is leaching?

Drain away from soil, ash, or similar material by the action of percolating liquid, especially rainwater. Examples: A soil with heavy rainfall may be less fertile due to the leaching of nutrients from the soil; The E horizon is a zone of leaching that can sometimes be found above the B horizon in acidic soils; Highly acidic soils can exhibit leaching of minerals from the O and A horizons so they will not be available to plants.

Know what problems are caused by deficiencies in the following micronutrients: Iodine

Elemental iodine is essential for proper functioning of the thyroid gland, which produces hormones that control the body's rate of metabolism. Iodine is found in seafood and in crops grown in iodine-rich soils. Chronic lack of iodine can cause stunted growth, mental retardation, and goiter—a swollen thyroid gland that can lead to deafness. According to the United Nations, some 600 million people—mostly in rural areas of south and southeast Asia—suffer from goiter, and 26 million children suffer brain damage each year from lack of iodine.

How is fire helpful in a forest ecosystem? What is the best way to prevent enormous forest fires?

Fire is a natural part of many forests and other biomes. In biomes where fires naturally occur frequently, organisms are adapted to withstand moderate fires and recover quickly. For example in most forests, fires will burn small trees and grasses but won't damage large fire‐resistant trees. In forests, some seeds/cones will not open to germinate without fire. Fires also restore nutrients to the soil very rapidly. Therefore, these biomes need regular fires. If regular fires don't happen, underbrush will build up and when there is finally a fire, there will be more fuel, so it will burn hotter and longer. If that happens, it can even cause the fires to reach the tops of the large fire‐resistant trees, causing much more damage and making it harder for the forest to regenerate. Therefore, the best way to prevent enormous forest fires is to have small, frequent, and regular fires.

What is artificial selection? What is genetic engineering? How are they similar and different?

For centuries, farmers and scientists have used crossbreeding through artificial selection to develop genetically improved varieties of crops and livestock animals. Such selective breeding in this first gene revolution has yielded amazing results. Ancient ears of corn were about the size of your little finger and wild tomatoes were once the size of grapes. Traditional crossbreeding is a slow process, typically taking 15 years or more to produce a commercially valuable new crop variety, and it can combine traits only from species that are genetically similar. Resulting varieties remain useful for only 5-10 years before pests and diseases reduce their effectiveness. But important advances are still being made with this method. Today, scientists are creating a second gene revolution by using genetic engineering to develop genetically improved strains of crops and livestock animals. It involves altering an organism's genetic material through adding, deleting, or changing segments of its DNA, to produce desirable traits or to eliminate undesirable ones. It enables scientists to transfer genes between different species that would not interbreed in nature. The resulting organisms are called genetically modified organisms (GMOs) or transgenic organisms. For example, genetic engineers used genes from ordinary daffodils and a soil bacterium to produce golden rice. Compared to traditional crossbreeding, gene splicing takes about half as long to develop a new crop variety, usually costs less, and allows for the insertion of genes from almost any other organism into crop cells. Ready or not, much of the world is entering the age of genetic engineering. Bioengineers are developing, or planning to develop, new varieties of crops that are resistant to heat, cold, herbicides, insect pests, parasites, viral diseases, drought, and salty or acidic soil. They also hope to develop crop plants that can grow faster and survive with little or no irrigation and with less fertilizer and pesticides. Bioengineers have altered citrus trees, which normally take 6 years to produce fruit, to yield fruit in only 1 year. They also hope to use advanced tissue culture techniques to mass-produce only orange juice sacs, which would eliminate the need for citrus orchards. Many scientists believe that such innovations hold great promise for helping to improve global food security. Others warn that genetic engineering is not free of drawbacks. Artificial selection selects for traits already present in a species, whereas genetic engineering creates new traits.

Know the main ways that food can be grown to promote soil conservation: Strip cropping

Form of polyculture. In strip cropping, a farmer alternates row crops (cotton, corn) with cover crops (completely cover the soil and trap any eroding soil). Both crops are not harvested at the same times so the cover crop will continue to trap soil after the row crop is harvested.

Food security

Having food security means that every person in a given area has daily access to enough nutritious food to have an active and healthy life. Today we produce more than enough food to meet the basic nutritional needs of every person on the earth. But even with this surplus of food, one of every six people in developing countries is not getting enough to eat. These people face food insecurity, living with chronic hunger and poor nutrition, which threatens their ability to lead healthy and productive lives. Most agricultural experts agree that the root cause of food insecurity is poverty, which prevents poor people from growing or buying enough food. For example, since 1990, India has produced enough grain to feed its entire population. But more than 200 million Indians—about one-fifth of the country's population—are hungry because they cannot afford to buy or grow enough food. Other obstacles to food security are political upheaval, corruption, and war. These problems interfere with food distribution and transportation systems and can result in people going hungry while stored foods spoil or are distributed unevenly in a country or region. Achieving food security on regional and global levels for both poor and affluent people also depends on greatly reducing the harmful environmental effects of agriculture, which we explore further in this chapter.

Know what problems are caused by deficiencies in the following micronutrients: IRON

Having too little iron—a component of the hemoglobin that transports oxygen in the blood—causes anemia, which results in a general lack of vitality. According to the WHO, one of every five people in the world—mostly women and children in tropical developing countries— suffers from iron deficiency. It causes fatigue, makes infection more likely, and increases a woman's chances of dying from hemorrhage in childbirth. New strains of golden rice contain more iron than conventional strains and could help to reduce the severity of iron and vitamin A deficiencies. However, some critics view these claims as mostly a public relations ploy financed by the seed industry to soften up widespread consumer opposition to genetically engineered crops. They contend that golden rice is drawing funding and attention away from a possibly quicker and cheaper option of giving two vitamin A capsules per year to each of the millions of children suffering from vitamin A deficiency. In addition, scientists want more evidence on how much of the beta-carotene in the golden rice will actually be converted to vitamin A in the body. And they want evidence that golden rice strains that perform well in the laboratory will perform as well in nature where many more factors come into play. Current field trials of golden rice in the Philippines may provide such information.

Know the specific definition and be able to explain the consequences of: Desertification

In arid and semiarid parts of the world, the contribution to the world's food supply from livestock and crops is being threatened by desertification. It occurs when the productive potential of soil, especially on arid or semiarid land, falls by 10% or more because of a combination of prolonged drought and human activities that reduce or degrade topsoil. The process can be moderate (a 10-25% drop in productivity), severe (a 25-50% drop), or very severe (a drop of more than 50%, usually creating huge gullies and sand dunes). Only in extreme cases does desertification lead to what we call desert. But when severe desertification occurs, it can expand existing desert area or create new desert in areas that once were fertile land. Over thousands of years, the earth's deserts have expanded and contracted, mostly because of natural climate change. However, human activities have accelerated desertification in some parts of the world. In its 2007 report on the Status of the World's Forests, the FAO estimated that some 70% of world's drylands used for agriculture are degraded and threatened by desertification. Most of these lands are in Africa and Asia, with countries including Nigeria, Iran, Afghanistan, and China suffering from serious desertification. Increasing desertification is also a threat in dryland areas of Brazil and Mexico. According to a 2007 study by the Intergovernmental Panel on Climate Change (IPCC), projected climate change from global warming during this century (mostly the result of human activities) is expected to greatly increase severe and prolonged drought and, consequently, desertification in many arid and semiarid parts of the world. This could result in sharp drops in food production, water shortages for 1 billion-3 billion people, and huge numbers of environmental refugees.

Know what happened in the Dust Bowl in the 1930's in the Midwest and how this relates to soil erosion

In the United States, a third of the country's original topsoil is gone and much of the rest is degraded. In the state of Iowa, which has the world's highest concentration of prime farmland, half of the topsoil is gone after a century of farming. According to the Natural Resources Conservation Service, 90% of American farmland is, on average, losing topsoil 17 times faster than new topsoil is being formed. In the 1930s, Americans learned a harsh environmental lesson when much of the topsoil in several dry and windy midwestern states was lost because of a combination of poor cultivation practices and prolonged drought. This threatened to turn much of the U.S. Great Plains into a vast desert. Before settlers began grazing livestock and planting crops there in the 1870s, the deep and tangled root systems of native prairie grasses anchored the fertile topsoil firmly in place. But plowing the prairie tore up these roots, and the crops that settlers planted annually in their place had less extensive root systems. After each harvest, the land was plowed and left bare for several months, exposing it to high winds. Overgrazing by livestock in some areas also destroyed large expanses of grass, denuding the ground. The stage was set for severe wind erosion and crop failures; all that was needed was a long drought. It came between 1926 and 1937 when the annual precipitation dropped by almost two-thirds. In the 1930s, dust clouds created by hot, dry windstorms blowing across the barren exposed soil darkened the sky at midday in some areas. Rabbits and birds choked to death on the dust. During May 1934, a cloud of topsoil blown off the Great Plains traveled some 2,400 kilometers (1,500 miles) and blanketed most of the eastern United States with dust. Laundry hung out to dry by women in the state of Georgia quickly became covered with dust blown in from the Midwest. Journalists gave the most eroded part of the Great Plains a new name: the Dust Bowl. This calamity triggered one of the largest internal migrations in U.S. history. Thousands of farm families from the states of Oklahoma, Texas, Kansas, and Colorado abandoned their dust-choked farms and dead livestock and migrated to California or to the industrial cities of the Midwest and East. Most found no jobs because the country was in the midst of the Great Depression. In May 1934, Hugh Bennett of the USDA went before a congressional hearing in Washington, D.C., to plead for new programs to protect the country's topsoil. Lawmakers took action when Great Plains dust began seeping into the hearing room. As Bennett put it, "This nation and civilization is founded upon nine inches of topsoil. And when that is gone there will no longer be any nation or any civilization." In 1935, the United States passed the Soil Erosion Act, which established the Soil Conservation Service (SCS) as part of the USDA. Soil conservation districts were formed throughout the country, and farmers and ranchers were given technical assistance to set up soil conservation programs. (The SCS is now called the Natural Resources Conservation Service.) Of the world's major food-producing nations, only the United States is sharply reducing some of its soil losses through a combination of conservation-tillage farming and government-sponsored soil conservation programs. Under the 1985 Food Security Act (Farm Act), farmers participating in the Conservation Reserve Program receive a subsidy for taking highly erodible land out of production and replanting it with topsoil-saving grass or trees for 10-15 years. Since 1985, these efforts have cut soil losses on U.S. cropland by 40%. However, effective soil conservation is practiced today on only half of all U.S. agricultural land. Also, in recent years, some farmers have been taking erodible land out of the conservation reserve in order to receive government subsidies for planting corn to make ethanol for use as a motor vehicle fuel.

Industrialized agriculture

Industrialized agriculture, or high-input agriculture, uses heavy equipment and large amounts of financial capital, fossil fuel, water, commercial fertilizers, and pesticides to produce single crops, or monocultures. The major goal of industrialized agriculture for any crop has been to steadily increase its yield—the amount of food produced per unit of land. Industrialized agriculture is practiced on one-fourth of all cropland, mostly in developed countries, but has spread since the mid-1960s to some developing countries and now produces about 80% of the world's food. Plantation agriculture is a form of industrialized agriculture used primarily in tropical developing countries. It involves growing cash crops, such as bananas, soybeans (mostly to feed livestock), sugarcane (to produce sugar and ethanol fuel), coffee, palm oil (used as a cooking oil and to produce biodiesel fuel), and vegetables on large monoculture plantations, mostly for export to developed countries. Producing such monoculture crops in the tropics increases yields but decreases biodiversity when tropical forests are cleared or burned for crop plantations. A new form of industrialized agriculture involves widespread use of greenhouses to raise crops. But it requires large inputs of water and energy to move water from one part of the country to another. On a small scale, however, greenhouse production of crops can be water-efficient. Hydroponics is a method whereby plants are grown with their roots in troughs of water inside a greenhouse. Water is pumped from the troughs and sprayed on the plants as artificial rain.

Know how industrial agriculture and traditional farming compare in terms of the amount of energy required to get 1 unit of food energy to the table (& why these values are different)

Industrialized food production takes 10 units of fossil fuel energy to make 1 unit of food energy. By comparison, every unit of energy from human labor in traditional farming provides 1 to 10 units of food energy. Values are different because, with industrial agriculture, energy is required to grow, store, process, package, transport, refrigerate, and cook all plant and animal food.

Know what IPM is

Integrated Pest Management. Has a goal of reducing crop damage by viewing crops and pests as part of an ecosystem. It used all the different methods we discussed to prevent damage from pests, but requires expert knowledge about each crop, its pests and their interactions. Rather than just applying pesticides in case of pests, the farmer constantly evaluates the crop-pest interaction and applies new solution as they are needed. Chemicals can be used, but only as a last resort and only those that are derived from plants. Many countries are experimenting. Indonesia is a success story. Santa Clara County working on it.

Why is eating lower on the food chain a more sustainable way to support the human population?

It allows us to feed more people if more people are eating a plant based diet because 90% of energy is lost at each trophic level.

What are some major harmful effects of soil erosion?

Leads to a loss of soil fertility and leads to an increase of sentiments in surface waters which pollute the water, kills fish, and clogs the water supply.

What is the most desirable texture for agriculture?

Loam

Know what problems are caused by deficiencies in the following micronutrients: Vitamin A

New strains of golden rice contain more iron than conventional strains and could help to reduce the severity of iron and vitamin A deficiencies. However, some critics view these claims as mostly a public relations ploy financed by the seed industry to soften up widespread consumer opposition to genetically engineered crops. They contend that golden rice is drawing funding and attention away from a possibly quicker and cheaper option of giving two vitamin A capsules per year to each of the millions of children suffering from vitamin A deficiency. In addition, scientists want more evidence on how much of the beta-carotene in the golden rice will actually be converted to vitamin A in the body. And they want evidence that golden rice strains that perform well in the laboratory will perform as well in nature where many more factors come into play. Current field trials of golden rice in the Philippines may provide such information. Without vitamin A, one is more susceptible to common infectious diseases - can go blind and die.

Nitrogen Cycle

Nitrogen is a major limiting factor for plant growth, because it is a necessary component of amino acids.Nitrogen is required by all organisms. It's most important role is as a component in amino acids, which make up proteins. Most organisms CANNOT use atmospheric nitrogen (N2), although we are surrounded by it. This is due to the fact that in a molecule of N2, the atoms are connected with a triple bond. This bond takes a large amount of energy to break, so most organisms cannot do it.1. Nitrogen fixation: This is one of the most important processes in nature and another example of a natural service. In this process, nitrogen fixing bacteria take atmospheric nitrogen and use energy to turn it into ammonium, a more usable form of nitrogen. In terrestrial ecosystems these bacteria occur in the soil or in root nodules of certain plants called legumes. Beans and alfalfa are examples of legumes.Nitrogen fixation can also happen abiotically- lightning can fix nitrogen, though this is rare and only a small component of all naturally fixed nitrogen.2. Nitrification: While some plants can take up ammonium directly, many cannot. Most plants need nitrogen in the form of Nitrates. Nitrification is the process that converts ammonium into the more usable nitrates. This is a two step process. First, ammonium is converted to Nitrite. Then a different type of bacteria convert the nitrites into nitrates. There are some bacteria that can do both nitrogen fixation and nitrification, but this is rare.3. Assimilation: Now that nitrogen is available in a useful form, plants absorb it and incorporate it into their tissues. It is then passed up the food chain to consumers. From here, a nitrogen molecule has two possible fates. It can re-enter the nitrogen cycle through the ammonification process (step4a) or it can return to the atmosphere (step 4b).4a. Ammonification: This step is similar to nitrogen fixation in that it creates ammonia- don't get these two steps confused! Animals & plants release organic nitrogen into the environment as excretions and upon death. Bacteria break down organic nitrogen molecules to ammonia. That ammonia can do through nitrification again and the cycle will continue.4b. Denitrification: Instead of going through the proceess of ammonification, an atom of nitrogen can also go through denitrification. This can only occur in anaerobic environments if there is an excess of nitrates. This step produces more N2 and releases it into the atmosphere. This step happens instead of ammonification NOT in addition to and prevents accumulation of nitrates in the environment.

What are the three main nutrients that must be in soil for plant growth?

Nitrogen, potassium, and phosphorus.

Know the main differences between old growth forest, second growth forests and tree plantations

Old growth forests are forests that have not been seriously disturbed by humans or natural disasters for at least 200 years. They are important reservoirs of biodiversity and have been seriously depleted by human population growth. Approximately 40% of the existing forests on earth are old growth forests. These maps are just showing coverage of old growth forests. If we looked at total forest coverage, it has actually increased since 1920 in the form of 2nd growth forests and tree plantations. Currently the US is growing more wood each year than it uses. Second growth forests are forests that have been significantly disturbed by humans or natural disasters.They have regenerated through secondary succession and are still important ecosystems in harboring biodiversity. They make up roughly 60% of forests on earth. Tree Plantations are like man‐made forests. They are also called tree farms. On these plantations, growers plant trees of one or two species and then they harvest them all at the same time, then plant more. These trees are sold and turned into wood products. There are several problems with this. There is also a lack of biodiversity since it is a monoculture, so the plantations can be very susceptible to pests. Soil can also be eroded easily when all trees are cut and habitat is destroyed when all the trees are cut. A benefit of these plantations is that they provide wood products without requiring the logging of old growth or second growth forests. Many biologists suggest only establishing tree plantations on area that has already been cleared and rather than clearing forests to plant tree plantations.

Slash-and-burn agriculture

One type of polyculture is known as slash-and-burn agriculture. This type of subsistence agriculture involves burning and clearing small plots in tropical forests, growing a variety of crops for a few years until the soil is depleted of nutrients, and then shifting to other plots. Early users of this method learned that each abandoned patch normally had to be left fallow (unplanted) for 10-30 years before the soil became fertile enough to grow crops again. While patches were regenerating, growers used them for tree crops, medicines, fuelwood, and other purposes. In this manner, most early growers practiced sustainable cultivation. However, when too many people use this approach or don't understand its limitations, it can become unsustainable and lead to depletion and degradation of tropical forests, as is now taking place in parts of Africa. In parts of South America and Africa, some traditional slash-and-burn farmers grow as many as 20 different crops together on small cleared plots in tropical forests. The crops mature at different times, provide food throughout the year, and keep the soil covered to reduce erosion from wind and water. This lessens the need for fertilizer and water, because root systems at different depths in the soil capture nutrients and moisture efficiently, and ashes from the burning provide some fertilization. Insecticides and herbicides are rarely needed because multiple habitats are created for natural predators of crop-eating insects, and weeds have trouble competing with the multitude of crop plants.

What activities can lead to the destruction of topsoil?

Overgrazing, deforestation, cropland agriculture, other overexploitation, and industrialization. Humans are the primary cause.

overnutrition

Overnutrition occurs when food energy intake exceeds energy use and causes excess body fat. Too many calories, too little exercise, or both can cause overnutrition. People who are underfed and underweight and those who are overfed and overweight face similar health problems: lower life expectancy, greater susceptibility to disease and illness, and lower productivity and life quality. We live in a world where 1 billion people have health problems because they do not get enough to eat and another 1.6 billion face health problems from eating too much. According to 2004 study by the International Obesity Task Force, one of every four people in the world is overweight (with a body mass index of 25 or more) and one of every 20 is obese (with a body mass index of 30 or more). In the United States, a 2005 study at Boston University found that about 66% of American adults are overweight and 33% are obese (up from 15% in 1980), the highest overnutrition rate in any developed country. The more than $50 billion that Americans spend each year trying to lose weight (according to the MarketData research firm) is more than two times the $24 billion per year that the United Nations estimates is needed to eliminate undernutrition and malnutrition in the world.

undernutrition

People who cannot grow or buy enough food to meet their basic energy needs suffer from chronic undernutrition, or hunger. Most of the world's chronically undernourished children live in developing countries. They face the possibilities of suffering from mental retardation and stunted growth and dying from infectious diseases such as measles and diarrhea, which rarely kill children in developed countries. According to the U.N. Food and Agriculture Organization (FAO), the estimated number of chronically undernourished or malnourished people fell from 918 million in 1970 to 862 million in 2006. This is a good start, but it is still high—nearly three times the population of the United States. A 2007 study by University of Minnesota economists Ford Runge and Benjamin Senauer estimated that increased food prices from the massive diversion of corn to produce ethanol for fueling cars could increase the number of hungry and malnourished people to 1.2 billion by 2025 instead of decreasing it to 625 million as projected by the FAO. Despite some progress, one of every six people in developing countries (including about one of every three children younger than age 5) is chronically undernourished or malnourished. About 75% of these people live in rural areas of developing countries. In 2005, the FAO estimated that each year, nearly 6 million children die prematurely from chronic undernutrition and malnutrition and increased susceptibility to normally nonfatal infectious diseases (such as measles and diarrhea) because of their weakened condition. This means that each day, an average of 16,400 children die prematurely from these mostly poverty-related causes. How many people died from such causes during your lunch hour?

Know some alternative ways of controlling pests

Pests can be tricked by methods like rotating crops each year will keep specialist pests searching for food. Farmers can also grow crops in a different field each year; again specialist pests will spend more time searching. By changing planting times, even by just a week, farmers can avoid a certain life phase of pest because pest life cycles are very short. Farmers can also provide nearby habitats for the natural enemies of pests. When farmers practice polyculture, they can plant multiple types of plants together so that if one plant attracts a pest, another might be undesirable to the same pest. Farmers can deliberately introduce these natural enemies but this can lead to the enemies becoming pests too. Hormones and pheromones are less common but can be used to repel pests or attract natural predators. Hormones can also be used to disrupt the life cycle of insects to prevent reproduction. These can be expensive to develop and also need to be applied with very specific timing for these reasons they are not all that widely used. On some crops, farmers will spray hot water to kill the pests. This only works on specific corps and if there is an abundant supply of freshwater.

How do plants prevent soil erosion?

Plants slow down water as it flows over the land and this allows much of the rain to soak into the ground. Plant roots hold the soil in position and prevent it from being blown or washed away.

What are the disadvantages of chemical fertilizers?

Pollute local water and air. Nitrates from fertilizers can volatilize (evaporate) into the air which can then form smog in the atmosphere. Excess nitrates runoff into surface water (lakes and rivers) and cause cultural eutrophication. This is when the excess nutrients cause an algae bloom that depletes oxygen in the water as the algae die. Excess nitrates can also leach through soil and contaminate groundwater. If humans pump drinking water from groundwater, these nitrates will then contaminate drinking water. When nitrates enter the human body they are converted to nirities which can bind to hemoglobin. When nitrate binds with hemoglobin molecules, it inhibits their ability to bind with oxygen and thus inhibits hemoglobin's ability to transport oxygen to body tissues. In adults, a small amount of nitrates will not cause a problem, but in babies the same amount can kill them because of their small size. This condition is called blue baby syndrome - the baby will develop blue lips and extremities as those tissues are deprives of oxygen. Eventually this can lead to death. The current EPA standards for nitrates in drinking water is set low specifically to protect infants.

Be able to name some of the ecosystem services provided by soil

Provides habitats for many organism, both macroscopic and microscopic. Allows for the cycling of nutrients through terrestrial ecosystems: nitrogen, phosphorus, sulfur. Provides a substrate for plant growth. Filters water as rainwater passes through it on its way to rivers and groundwater.

Know who Rachel Carson was & what her contribution to environmental science was

Rachel Carson began her professional career as a biologist for the Bureau of U.S. Fisheries (now called the U.S. Fish and Wildlife Service). In that capacity, she carried out research in oceanography and marine biology and wrote articles and books about the oceans and topics related to the environment. Throughout the 1950s, DDT use was increasing, and in 1958, DDT was sprayed to control mosquitoes near the home and private bird sanctuary of one of Carson's friends. After the spraying, her friend witnessed the agonizing deaths of several birds. She begged Carson to find someone to investigate the effects of pesticides on birds and other wildlife. Carson decided to look into the issue herself and found that independent research on the environmental effects of pesticides was almost nonexistent. As a well-trained scientist, she surveyed the scientific literature, became convinced that pesticides could harm wildlife and humans, and methodically gathered information about the harmful effects of widespread use of pesticides. In 1962, she published her findings in popular form in Silent Spring, a book whose title alluded to the silencing of "robins, catbirds, doves, jays, wrens, and scores of other bird voices" because of their exposure to pesticides. Many scientists, politicians, and policy makers read Silent Spring, and the public embraced it. Chemical manufacturers viewed the book as a serious threat to their booming pesticide business and mounted a campaign to discredit Carson. A parade of critical reviewers and industry scientists claimed her book was full of inaccuracies, made selective use of research findings, and failed to give a balanced account of the benefits of pesticides. Some critics even claimed that, as a woman, Carson was incapable of understanding such a highly scientific and technical subject. Others charged that she was an hysterical woman and a radical nature lover trying to scare the public in an effort to sell books. During these intense attacks, Carson was a single mother, the sole caretaker of an aged parent, and was suffering from terminal breast cancer. Yet she strongly defended her research and countered her critics. She died in 1964—about 18 months after the publication of Silent Spring—without knowing that many historians consider her work an important contribution to the modern environmental movement then emerging in the United States. It has been correctly noted that Carson made some errors in writing Silent Spring. But critics concede that the threat to birds and ecosystems—one of Carson's main messages—was real and that her errors can be attributed to the primitive state of research on the topics she covered in her day. And her critics cannot dispute the fact that her wake-up call got the public and the scientific community focused on the potential threats from uncontrolled use of pesticides, which led to many of them being banned for use in the United States and many other countries.

What is rangeland?

Rangelands are grassland biomes (including chapparal) where animals can roam and graze on grasses and brush. Sometimes rangelands will be fenced in to form pastures where animals are more contained. If these lands are not good for farming, grazing animals on these rangelands is a great way to produce food from them. You are taking plant energy that our bodies cannot process and turning it into meat, a form that we CAN process, just by having cows or sheep eat the grass.

Climatographs

Refer to unit 2 quizlet and ecosystem diversity practice quiz for specific climatographs of each biome.

How can nutrients be returned to/ maintained in soil without using chemical fertilizers

Rotate crops or plant many types of crops on the same area of land (polyculture). This way, some crops will deplete nutrients and other crops will add nutrients to the soil. Manure can also be added as well as green manure (freshly cut or still growing vegetation that is plowed into the soil to restore nutrients by increasing the O-horizon of the soils). Compost is another option. This is when organic waste material is aerobically decomposed and turned into nutrient rich soil. Composting is easy to do at home as well as on farms and it has the added benefit of reducing your trash production.

Know the relative sizes of silt, sand and clay particles

Sand is the largest particle, followed by silt and then clay.

What was the green revolution?

Since 1950, about 88% of the increase in global food production has come from using high-input industrialized agriculture to increase yields in a process called the green revolution. The green revolution involves three steps. First, develop and plant monocultures of selectively bred or genetically engineered high-yield varieties of key crops such as rice, wheat, and corn. Second, produce high yields by using large inputs of fertilizers, pesticides, and water. Third, increase the number of crops grown per year on a plot of land through multiple cropping, or multicropping. Between 1950 and 1970, this high-input approach dramatically increased crop yields in most developed countries, especially the United States in what was called the first green revolution. A second green revolution has been taking place since 1967. Fast-growing dwarf varieties of rice and wheat, specially bred for tropical and subtropical climates, have been introduced into India and China and several developing countries in Central and South America. Producing more food on less land has the benefit of protecting biodiversity by saving large areas of forests, grasslands, wetlands, and easily eroded mountain terrain from being used to grow food crops. Between 1950 and 1996, mostly because of the two green revolutions, world grain production tripled. Per capita food production increased by 31% between 1961 and 1985, but since then it has generally declined.

Understand the difference between polyculture and monoculture and why polyculture is more sustainable

Some traditional farmers focus on cultivating a single crop, but many grow several crops on the same plot simultaneously, a practice known as polyculture. Such crop diversity—an example of implementing the biodiversity principle of sustainability—reduces the chance of losing most or all of the year's food supply to pests, bad weather, and other misfortunes. The crops mature at different times, provide food throughout the year, and keep the soil covered to reduce erosion from wind and water. This lessens the need for fertilizer and water, because root systems at different depths in the soil capture nutrients and moisture efficiently. Insecticides and herbicides are rarely needed because multiple habitats are created for natural predators of crop-eating insects, and weeds have trouble competing with the multitude of crop plants. Recent research shows that, on average, low input polyculture produces higher yields than does high-input monoculture. For example, a 2001 study by ecologists Peter Reich and David Tilman found that carefully controlled polyculture plots with 16 different species of plants consistently outproduced plots with 9, 4, or only 1 type of plant species. Therefore, some analysts argue for increasing use of polyculture, along with monocultures, to produce food more sustainably in the future. Both industrialized and conventional production of crops depend on having fertile soil.

Forest and rangeland biomes

Temperate deciduous forest: grow in areas with moderate average temperatures that change significantly with the season. These areas have long, warm summers, cold but not too severe winters, and abundant precipitation often spread fairly evenly throughout the year. Because of a slow rate of decomposition, these forests accumulate a thick layer of slowly decaying leaf litter, which is a storehouse of nutrients. Taiga: Cold forests. In this subarctic climate, winters are long, dry, and extremely cold; in the northernmost taigas, winter sunlight is available only 6-8 hours per day. Summers are short, with cool to warm temperatures, and the sun shines up to19 hours a day. Beneath the stands of these trees is a deep layer of partially decomposed conifer needles. Decomposition is slow because of the low temperatures, waxy coating on conifer needles, and high soil acidity. The decomposing needles make the thin, nutrient-poor soil acidic, which prevents most other plants (except certain shrubs) from growing on the forest floor. Chaparral: Closeness to the sea provides a slightly longer winter rainy season than nearby temperate deserts have, and fogs during the spring and fall reduce evaporation. The soil is thin and not very fertile. Long, warm, and dry summers. Temperate grassland: Winters are bitterly cold, summers are hot and dry, and annual precipitation is fairly sparse and falls unevenly throughout the year. Because the above-ground parts of most of the grasses die and decompose each year, organic matter accumulates to produce a deep, fertile soil. This soil is held in place by a thick network of intertwined roots of drought-tolerant grasses (unless the topsoil is plowed up, which exposes it to be blown away by high winds found in these biomes). The natural grasses are also adapted to fires, which burn the plant parts above the ground but do not harm the roots, from which new grass can grow.

Know the disadvantages of raising animals in feedlots & how raising cows on grass (instead of grain) helps solve some of these problems (think back to Food, Inc)

The digestive system of a cow is not designed to constantly consume grain or corn products, which leaves most producers giving cattle a constant dose of antibiotics. Cattle stand in small, crowded areas in their own feces and urine all the time. Products from pasture-raised animals are healthier for you to eat than those from grain-fed animals for many reasons. Animals get more readily available nutrients from fresh pasture plants than from grains, so their products contain more vitamin E, beta carotene, conjugated linoleic acid (CLA) and omega-3 fatty acids.

Know some ecological/ economic services that are provided by forests

There are a number of ecological services provided by forests: Support nutrient cycling, reduce soil erosion, provide habitats and promote biodiversity. As you read about in The Omnivore's Dilemma, forest soils can absorb and retain water. Forests also serve to purify air and water as they take it in and then release it. Trees absorb carbon and store it while producing oxygen. Finally, trees can influence local climates through transpiration. As they release water into the atmosphere from their leaves, this increases the humidity of the air. In tropical rainforests, this is part of a positive feedback loop that maintains enough moisture in the air for rainforests to exist where they do. Forests also provide a variety of economic services. They provide fuelwood for heating and cooking, lumber and pulp for paper making. Forests can also be used for grazing some livestock (like the farmer does with the pigs in the Omnivore's Dilemma). Finally forests provide jobs for the people who harvest.

Know some strategies for using rangeland more sustainably

There are techniques that ranchers can use to continue utilizing rangelands for grazing their animals without degrading them. The best way to do this is to make sure the carrying capacity of a particular area is not exceeded. The most widely used method is rotational grazing. Ranchers use portable fencing to confine their animals to one area for 1 or 2 days. They allow them to graze and then move them to a new area to repeat the process. They are not returned to the first area until it has a chance to regenerate. Ranchers can also preserve particularly vulnerable areas, like riparian zones, by fencing them off entirely. Animals naturally head towards water, so ranchers can also protect vulnerable areas by placing watering holes, salt blocks and supplemental feed at different locations to draw the animals away from natural water sources.Finally, environmentalists, ranchers and the government can work together to make sure that rangelands are sustained for the future. In the Southwest, where there is a lot of rangeland, there has been a lot of pressure to develop these lands as the population has increased. Environmental groups have paid ranchers to put restrictions on the deeds to their lands (conservation easements). These would prevent any future owner of the land from developing it further into houses or shopping centers etc. Local governments can also zone fragile rangeland so that it cannot be developed.

Carbon cycle

There are two basic steps to the carbon cycle. First, producers remove CO2 from atmosphere through photosynthesis. Producers, consumers, and decomposers add CO2 through respiration. Some of the carbon fixed through photosynthesis moves from plant roots into the soil. Once there, it is very stable and can remain in the soil for 1,000s of years. Therefore, soil is an important carbon reservoir in addition to forests, the atmosphere and fossil fuels.

Understand how genetic resistance to pesticides works and the consequences of it for agriculture

They accelerate the development of genetic resistance to pesticides by pest organisms. Insects breed rapidly, and within 5 to 10 years (much sooner in tropical areas) they can develop immunity to widely used pesticides through natural selection and then come back stronger than before. Since 1945, about 1,000 species of insects and rodents (mostly rats) and 550 types of weeds and plant diseases have developed genetic resistance to one or more pesticides. Pesticide use has not reduced U.S. crop losses to pests, mostly because of genetic resistance.

subsistence agriculture

Traditional subsistence agriculture uses mostly human labor and draft animals to produce only enough crops for a farm family's survival, with little left over to sell or store as a reserve in hard times.

Know the main ways that food can be grown to promote soil conservation: Terracing

Used to retain soil on steep terrain. Creates steps on a steep slope. Crops are planted on the horizontal part of each of these steps. This retains water by controlling runoff and therefore erosion. Terracing is a method that has been done around the world for hundreds of years.

Know the main ways that food can be grown to promote soil conservation: Contour planting

Used to retain soil on steep terrain. This is where a farmer plants with the contours of the land rather than in straight rows. Each row acts like a dam to stop soil from eroding from uphill.

Know how soil moisture content relates to its texture

Water-holding capacity is controlled primarily by soil texture and organic matter. Soils with smaller particles (silt and clay) have a larger surface area than those with larger sand particles, and a large surface area allows a soil to hold more water.

How does soil form? What influences the speed of soil formation?

Weathering is the primary process that forms soil. Weathering breaks down the parent material, which is rock, into smaller particles. These small particles of mineral or rock combine with decomposing organic material to form soil. As a result, soil is neither completely biotic nor completely abiotic. There are three types of weathering that can contribute to soil formation. Physical weathering consists of water or wind separating piece of the rock. It can also occur when water in a crack in the rock freezes, wedging the rock apart. Chemical weathering occurs when the rock reacts with surrounding materials, such as when a weak acid dissolves part of a rock. Biological weathering is weathering caused by organisms such as tree roots wedging a rock apart or lichens secreting acids to dissolve a rock. Weathered material can be transported by wind or water or it can remain in situ. There are a number of factors that can influence the quality of soil that forms in a particular location and how quickly that soil forms. Climate: Temperature and humidity will influence the speed of weathering. For example in very cold climates, there will be little water movement, so physical and chemical weathering will proceed slowly. As a result you will have underdeveloped soils that do not contain a lot of minerals or rocks. They will mostly contain poorly decomposed organic material since biological activity is also slow at these temperatures. Organisms: Burrowing animals can help to mix soils and distribute organic and inorganic components. Plants can secrete acids that can help to speed chemical weathering. Topography: (how quickly they accumulate) Steeper slopes will loose soils due to erosion, so will not have very developed soils, whereas valleys will accumulate large amounts of soils. Wind exposure or heavy rains on one side of a hill/mountain could speed weathering as well. Parent material: The chemical composition of the parent material (ei. basalt, limestone, granite) determines how quickly it will weather and will determine the mineral content and many other properties of the soil. Time: (how quickly they accumulate) The more time has passed, the more developed soil will become. Old soils with productive ecosystems and moderate rainfall can become very deep and fertile (such as grasslands). However, a soil with heavy rainfall may be less fertile due to leaching of nutrients from the soil.

Know the three main grains that provide most of the world's food

Wheat, rice, and corn.

Understand the difference between weathering & erosion

When the smaller rock pieces (now pebbles, sand or soil) are moved by these natural forces, it is called erosion. So, if a rock is changed or broken but stays where it is, it is called weathering. If the pieces of weathered rock are moved away, it is called erosion.

Understand what organic agriculture is and specific reasons why it is more sustainable

When we put all these practices together, they make up organic agriculture. Part of the main tenets of sustainable/ organic agriculture is seeing food production systems as ecosystems and treating them as such, as you read in The Omnivore's Dilemma chapter, the word "organic" has a legal meaning in the United States due to the Organic Food Production Act which established national standards for organic products. The USDA strengthened these criteria in 2000 by indicating what stipulations food producers had to meet to have their food labeled organic. Some states, like California, have gone beyond this and passed even stricter guidelines for labeling food as organic.