Topsoil is the uppermost layer of the soil. This layer contains partially decomposed organic material called humus; broken up leaves, flowers, and other organic material, called litter; and weathered bits of sand, silt, and clay. Besides organic matter, topsoil is full of living things.
One kilogram 2. The ph of a substance is a measure of its acidity or alkalinity. The H in pH refers to the free positively charged hydrogen ions. The acidity of a substance is measured on the pH scale. The numbers of the pH scale range from 0 to 14, where 7 is neutral, meaning it is neither acid nor alkaline. Numbers higher than 7 are alkaline also called basic ; numbers lower than 7 are acidic. The lowest numbers are the strongest acids; the highest numbers are the strongest bases. The pH scale is logarithmic: A change of one unit equals a tenfold increase or decrease in acidity.
Thus, even small changes in pH mean large changes in acidity. If clean rain has a pH of 5. Natural rainfall is slightly acidic, with a pH of about 5. The acidity of natural rain is due to the small amount of CO2 that dissolves in rainwater and forms mild carbonic acid. Strong acids can be harmful enough to burn skin. Strong bases are also harmful. The pH scale. A neutral solution has a pH of 7. Hydrogen ion concentration is shown on the upper axis of the scale.
Forests and thousands of insects, worms, nematodes, and mites. Water readily passes through topsoil, taking soluble or dissolvable elements to the soil layers below. Climate is extremely important to soil formation. Soils form faster in warm, wet climates. In humid regions, such as the northeastern United States, where plants are prolific, the topsoil is rich with organic matter. Soils in arid climates, such as the southwestern United States, are thin and contain little organic matter. Several other factors are important for soil formation. Abundant organic activity increases the amount and rate of soil formation.
For example, burrowing animals and plant roots break up soil, add gases, make humus, and form acids that contribute to weathering. Also, the steepness of a slope plays a role in soil formation. On steep slopes, weathered material erodes quickly, resulting in less soil development than on shallower slopes. The direction a slope faces is also important. Time is another factor in soil development. In general, soils mature over time: On average, a soil deepens about one inch 2.
Soils erode about as rapidly as they form. The high density of trees found in old-growth forests supports many other plants, animals, and 19 20 geosphere microbes. Old-growth forests are very rich ecosystems because they include young trees, old trees, standing dead trees, and decaying logs, all of which provide a myriad of habitats for wildlife.
Climate determines which of the many types of forests will be found in a region. Boreal forests stretch across enormous areas of Canada and northern Eurasia. Compared to the other forest types, the trees here are short and stand far apart. Boreal forests have relatively low species diversity but are home to some beautiful and important animals such as bighorn sheep, Siberian tigers Panthera tigris altaica , Canadian lynx, and moose.
Temperate forests extend across the more temperate regions of North America and Eurasia, where the climate is cool, and annual rainfall is high. The two distinct climate types of this region result in two different types of temperate forests. Deciduous forests are found where summers are hot and winters are cold. Deciduous trees lose their leaves in the winter so that the leaves do not freeze in the frigid temperatures. Black bears, deer, wolves, foxes, eagles, and small mammals such as squirrels, pine martens Marten sp. Evergreen forests are found where both summers and winters are mild; thus, evergreen trees do not lose their leaves seasonally.
Spectacular forests of coastal redwoods Sequoia sempevirens and Douglas fir Pseudotsuga menziesii , both of which can grow to more than feet 90 meters tall, are found in western Canada and the United States. Tropical rain forests are more hospitable to life than other forest types: Temperatures are mild and fairly constant year round, and rain is Forests profuse.
Plants are at the heart of rain forest biodiversity. Each hectare 2. Biodiversity is so high that only one or two representatives of each tree species are found in each hectare. Rain forest trees include teak Tektona sp. Monkeys, apes, jaguars Panthera onca , leopards Panthera pardus , and many other creatures can be found in rain forests. Tropical and subtropical dry forests receive a lot of moisture but have up to eight months of drought each year.
Compared with rain forests, dry forests have a smaller variety of species, but dry forests also are important locations for biodiversity. Trees in broadleaf dry forests include teak and mountain ebony Bauhinia variegata , which are often logged. These services keep biological systems—including systems that people rely on—operating.
Organisms make living spaces for other species. Soils contain minerals, microbes, and plant materials that cleanse the water that trickles through. Although nitrogen is the most abundant gas in the atmosphere, it is not in a chemical form plants can use. Plants are an important part of the water cycle, which is the movement of water between the oceans, atmosphere, lakes, streams, and organisms. Plants are extremely important for regulating global climate.
Plants absorb CO2, which is an important greenhouse gas. Forests Forests contain an enormous plant biomass. Biomass is the mass of all the living matter in a given area. Forests help recharge groundwater aquifers, the layers of underground rock or soil that contain usable water. As with other ecosystems, early humans used the forests for food, shelter, and other resources. There is evidence that some Native American groups burned forests to create grasslands so that they could hunt more easily.
This chapter discusses deforestation. More importantly, rising populations require more food and living space, so more forests are converted to agricultural or urban land. Many forests are now managed for the crops they produce, such as timber and wood products. These tree farms hardly resemble natural forest ecosystems.
However, sustainable forestry practices and reforestation are increasing in popularity in some areas.
The trees that 24 Using Forests Logging truck piled high with freshly cut logs heads to the mill for processing. When loggers practice selective logging, they take only the valuable trees from the forest. Selective logging is more common in tropical and subtropical forests, where species diversity is high, and only some of the trees are valuable. Besides being logged for timber and wood products, forests are also being cleared for agriculture, grazing, and other human activities.
Cattle ranching: Ranchers clear tropical rain forests to create cattle pastures. Agriculture: Forests worldwide are cleared for farmland. The underlying causes of deforestation are economic growth and population growth. Developed nations consume more timber and wood products, while developing nations depend on the income that timber sales from their forests generate.
Many of these farms are subsistence farms where a family can only grow enough food to feed itself and little more. Forests also serve as an outlet for excess human population. Britain chopped down nearly all of its virgin forest by about years ago. Deforestation in the United States began with the arrival of the Europeans and continued well into the twentieth century. With the temperate forests largely logged out, developed nations have increasingly turned to tropical and subtropical forests for wood products.
About , square miles , sq. Other tropical rain forests are faring just as badly or worse. The areas most at risk from deforestation are shown in red. Roads that allow loggers to enter the area are cut through formerly intact forest. Decomposers break down dead plant and animal tissue and waste products into nutrients, which can be used by plants to make food. Selective logging also degrades forests. Heavy equipment moved into the forest to cut down and remove trees damages untargeted plants and churns up the soil, making erosion more likely.
When they are cut, falling trees knock down other nearby trees. Selective logging may also cause the valued species to completely disappear locally. The most obvious effect of deforestation is the loss of biodiversity. Species may vanish locally or, if they are found only in that location or have been wiped out in the rest of their range, they may become extinct. When a species is lost, so are its potential benefits for humans. Some plants and animals contain compounds that provide medical benefits for people.
Scientists can isolate these compounds and make them into the active ingredients in pharmaceuticals. One such drug is the important anticancer agent Taxol, which is derived from the Pacific yew tree Taxus brevifolia. Wild organisms are also used by agriculturalists to improve a characteristic of a domesticated species. To do this, scientists look to wild populations for organisms with the desired trait, find the gene that controls it, and breed in or genetically engineer that gene into the domestic population.
A gene is the unit of inheritance that passes a trait from one generation to the next. Removing plant biomass lessens photosynthesis, which limits the number of animals the region can support. Eradicating a forest also alters the water cycle in the region. Evapotranspiration is greatly 29 30 geosphere reduced, which can lower the amount of precipitation that falls both in the deforested region and in regions downwind in the direction the wind is blowing from that area.
Deforestation has widespread impact on the health of the planet. Using Forests Deforestation increases flooding and erosion. Without forest cover, rainwater runs off the land quickly and causes rivers to swell. The eroded sediments carried by rainwater into the waterways silt up lakes, ponds, man made reservoirs, and even seas and oceans.
The sediment clouds the water and hinders photosynthesis in aquatic plants. Entire ecosystems, such as coral reefs, may be buried by sediments. When the soil that is exposed after logging becomes laden with water during a heavy rain, gravity may pull the soil downhill. In February , a massive landslide killed more than 1, people and buried portions of the town of Guinsaugon in the Philippines.
The region is heavily deforested, and illegal logging was common, even though a logging ban had been initiated more than a decade earlier. Some threatened villages were evacuated in late , but many of the people returned to their homes and livelihoods because they had nowhere to go and no other way to provide for themselves. Cutting down trees means that they are no longer available to absorb carbon dioxide. The general term for material moving downhill is landslide. Although gravity continually pulls rock and soil downslope, hillsides ordinarily remain stable.
This is because cohesion and friction with other nearby materials keeps them in place. Some slopes are more prone to landslides than others. Steeper slopes, or those that are made of loose material, are more likely to experience landslides. The removal of the base of a steep or loose slope by stream erosion, wave erosion, or human excavation may cause slope failure. Because plant roots bind soil together, loss of vegetation by fire or logging also contributes to slope failure. And while small amounts of water bind sediment grains together and inhibit landslides, too much water acts as a lubricant and increases the likelihood of slope failure.
Water also adds weight to a slope, further increasing its instability. Finally, certain events—an earthquake, a volcanic eruption, or even a loud noise—may trigger a landslide on an already unstable slope. There are several types of mass wasting. For example, the material may flow, slide, or fall down a slope. In flow, loose sediment moves as a viscous gooey fluid. Another type, called creep, occurs when shallow layers of a soil flow slowly downhill, a phenomenon that is common in humid climates.
Although creep is not life threatening—a creeping slope moves at only about one-half inch 1 cm per year—it can damage hillside property, breaking streets and sidewalks and cracking retaining walls and foundations. Indications of creeping slopes are tree trunks that are curved in the downslope direction and tilted fences, gravestones, or telephone poles. Rapid flows, called mudflows, can move at up to 50 miles 80 km per hour. Mudflows are ordinarily slurries of mud and rocks.
During slides, a large slab of rock or soil moves downhill along fractures. In one type of slide, known as a slump, a block of soil slips downhill and rotates backwards into the hill. In the other type of slide, a rock slide, chunks of bedrock break up as they slide downhill. Sometimes air becomes compressed beneath the rocks, creating a kind of river that carries them at speeds of up to miles km per hour.
When a rapidly moving rock slide hits the bottom of the slope in a valley, it sometimes travels up the other side. Avalanches of snow and ice are similar to rock slides. A fall is exactly what it sounds like— a rapid free fall of material that occurs when chunks of rocks break away from cliffs. Falls are generally vertical. Using Forests Even where forests are not logged directly, forest ecosystems are damaged by nearby logging. Dividing large ecosystems into these smaller islands of habitat separated by agriculture or urban land is known as habitat fragmentation. The additional sunlight increases the growth of low plants such as shrubs.
Drier conditions and more small plants increase the intensity of forest fires, which often start during deforestation or in areas of human activity. Forest loss also means a loss of aesthetic beauty. In economic terms, beautiful lands may attract tourists, who bring money into the area. Historically, foresters have been charged with harvesting timber and planting new trees, but modern forests may be managed for ecosystem services as well as for their aesthetic value.
Geosphere: The Land and Its Uses (Our Fragile Planet)
The most extreme type of managed forest is a tree farm, which is also called a plantation. Tree farms are monocultures, where only one species of tree is grown. Little attempt is made to grow native trees, and the species chosen for planting is usually resilient and fast growing. Pine Pinus sp. They grow the trees as they might any crop, planting them all at the same time and in rows, for example.
Rather than being allowed to mature, the trees are harvested after 10 to 60 years. Decaying dead wood, which is very important to natural forest ecosystems, is absent. A tree farm does not much resemble a natural forest ecosystem. In Finland, for example, forests are completely managed as plantations by the wood products industries.
Forest managers may plant trees in a tree farm, or they may create a natural forest where one no longer exists. Reforestation supplies trees to the timber industry and increases the amount of forest ecosystem. If the soil is healthy, and other conditions are favorable, reforestation can take place with no human effort. If the soil has been degraded, more active reforestation efforts are necessary. In these instances, people may break up the soil or add soil, plant seedlings, add water, or build protection from erosion. Companies in some Central American countries, such as Costa Rica and Panama, are planting trees for future lumber harvests on old cattle pastures.
Faster-growing trees, such as pine and eucalyptus, are also planted. Forest management has long meant fire suppression. Forest fires were thought to damage trees and forest ecosystems. Yet, in the types of forests in which fire is a natural part of the ecosystem, such as boreal and temperate forests but not tropical rain forests or dry forests , fire suppression usually means the forest ecosystem is unhealthy. Fire suppression causes too much brush to accumulate, so that the delayed and inevitable fire will burn hotter. The excess fuel allows the fire to travel up the tree trunks, damaging leaves and wood.
An intense fire may even burn the organic portion of the topsoil, making recovery of the ecosystem difficult. Sustainable forestry practices are meant to mimic natural processes as much as possible because these are the conditions in which the trees evolved. Forests that contain all stages of tree growth and the right amount of woody underbrush more closely resemble natural ecosystems and make better homes for forest animals. Selective logging, for example, mimics a tree falling down. Trees to be logged are carefully chosen with regard to the space between them and the amount of underbrush that grows in their vicinity.
In sustainable forestry practices, old-growth forests also serve as a source of seeds. Old trees are more resilient and better adapted to their environment and likely produce better offspring than trees that were killed off by disease or fire. An adaptation is a structure or behavior alteration that is able to be passed from one generation to the next. Other common practices for managing sustainable forests include controlled burning, a common and important practice in boreal and temperate forests.
Certification programs inform customers whether a wood product comes from a sustainably managed forest. As of December , the FSC had certified more than million acres , sq. A forest may also be managed for reasons other than timber and wood products. AGC scientists are also restoring tropical dry forest, one of the most threatened forest ecosystems, by buying and converting ranchland. In the United States, little remains of the once vast expanses of virgin forests.
Increasingly, though, people are gaining awareness that forests are valuable ecosystems, which is leading to sustainable forest management. Lands that are suitable for farming are called arable. In the developed countries, most of the arable lands are already being farmed. Among these are most of the lands once covered by the deciduous 41 42 geosphere forests of Europe and the eastern United States.
Wetlands have been drained to create highly productive farmlands. Peasant farmers prepare the land by slashing down trees at the forest edge, then burning the unusable scrub and other material. However, former rain forests make terrible farmland because of their nutrientpoor laterite soils. In a few years, the soil is exhausted of nutrients, and peasants graze cattle on it.
The cattle then tramp down the soil, leaving behind a bricklike surface layer. Carrying capacity is the number of organisms that can be sustained indefinitely by an environment. Farmers came together to form settlements in places where soil was rich, such as on floodplains, former wetlands, or cleared temperate forests. Settling in one place allowed people to build houses and develop more advanced farming tools, such as simple plows. In some locations, animals such A subsistence farmer at Gyeongju in South Korea plowing the land by hand. To keep the soil healthy, farmers used crop rotation, crop mixing, and organic fertilizers.
Toxic compounds made from tobacco or chrysanthemum leaves were sometimes used as natural pesticides to kill or deter unwanted insects. In developed nations, mechanization, such as the use of the steel plow designed by John Deere, became widespread after New fertilizers, which included the nutrients nitrates and phosphates, were discovered and gained widespread use.
Mechanization and artificial fertilizers increased the amount of arable land and decreased the number of farmers who were needed for agriculture. In many locations, small family farms were replaced by larger farms or plantations. At the same time, chemical pesticides and herbicides entered widespread use to keep unwanted pests and plants away from the new industrialized farms.
Oklahoma Farm Bureau advanced mechanization to feed the maximum number of people as inexpensively as possible. He did this by selective breeding: breeding generation after generation of only the wheat plants that exhibited the traits he desired. There, the importation of his hybrid wheat increased the yields many times.
These plants have been bred for these traits for so long that they no longer resemble their wild ancestors. In some developed countries, such as the United States, crops developed by selective breeding techniques are now being replaced by genetically modified crops, where scientists take a gene from one organism and put it into the DNA of another.
Water for farming can come from surface or groundwater sources. One side effect of dams is that they keep rivers from flooding except in extreme instances. Tractors are large and efficient. These fertilizers are essential because modern agricultural practices such as monocultures that are planted year after year and flood control deplete the soil of nutrients or prevent the addition of nutrients to the soil by flooding. Nearly all chemical fertilizers are produced from mineral deposits. Phosphates are mined from phosphate beds in sedimentary rocks and are chemically altered to forms that are more concentrated and soluble such as superphosphate, triple superphosphate, or ammonium phosphate.
Nitrogen fertilizer is made from atmospheric nitrogen in a process that uses methane derived from fossil fuels. Methane, a hydrocarbon gas composed of hydrogen and carbon, is also a greenhouse gas. Chemical fertilizers are extremely effective. The best of them selectively kill weeds and leave the crop plant unharmed. Insecticides kill unwanted insects. Chemical insecticides were first used in the early s and became increasingly common in the years after World War II.
The Green Revolution has allowed food production to keep pace with population growth. The Green Revolution has come at enormous costs to the social structure of many societies and to the environment in such forms as soil degradation, pollution, and loss of natural ecosystems. The consequences arising from the Green Revolution are the subject of this chapter. Without the ability to buy grain strains, machines, and chemicals—and unable to compete with the corporations and plantation owners who can—these farmers can no longer support themselves.
As a result, they have flooded into the cities looking for work; but when they get there, they find that there are few jobs. Most of these people wind up living in abject poverty. It is easier to grow a single strain of wheat in a field, for example, because planting, growing, and harvesting it use the same techniques and equipment. Monocultures also result in a loss of pollinators, especially bees, because there is no food for them.
Journey through the Northwest Passage – in pictures
The loss of pollinators has deadly consequences for the natural world and could be a problem for agriculture if a particular pollinator is needed for future crops. Yet some of the weeds are food plants that local people have eaten for centuries. The Costs of Modern Agriculture The environmental costs of modern agriculture include massive soil erosion, deforestation, pollution, and the loss of plant and animal genetic diversity.
Of those 7,, only are widely cultivated today. The Costs of Modern Agriculture Irrigation The dependence of modern farming on irrigation requires massive engineering projects, such as dams, to trap and move the water. Ecology is the study of the distribution and abundance of species and their relationship to their environments. Dams block the upstream migration of fish so that many of them die without reproducing. To compensate, farmers were forced to add artificial fertilizers.
Overuse causes many desert rivers to run dry during part of the year, bringing about ecological changes, including the loss of native species. In semiarid and arid regions, enormous quantities of water evaporate from reservoirs and canals, leaving behind salts. The brackish water used to irrigate crops either evaporates or is absorbed by the plants while the salts collect in the soil. Worldwide, salinization has damaged , square miles , sq. Approximately 5, square miles 15, sq. The Costs of Modern Agriculture Salinization can be treated by flooding and draining the fields, but only if there is enough water, which may not always be the case.
Farmers can drill a well into the ground to tap into this underground water supply. In some places, of course, the cost of drilling a well is prohibitive. Overuse of an aquifer causes the water table to fall and wells to run dry. The solution to the problem is to drill deeper, an expensive and sometimes difficult task.
Groundwater use in most places far exceeds the rate the water in the acquifer is replenished. The Ogallala aquifer, which provides much of the water for the midwestern United States breadbasket, is being pumped at eight times the rate that it is being recharged. The machines it depends on are built and powered by the use of natural resources, such as metals and fossil fuels. Fossil fuels have many uses in modern agriculture: One acre 4, sq. Since , rates of energy use have increased, but the increase in food production has been minimal.
Phosphate mining, from sedimentary rocks or bird guano excrement , can be ecologically damaging. Most chemical fertilizers are produced from petroleum products. As Richard Manning stated in Harpers Magazine, Oil is annual primary productivity stored as hydrocarbons, a trust fund of sorts, built up over many thousands of years.
On average, it takes 5. The use of inorganic fertilizer can cause extreme damage to aquatic ecosystems. When more fertilizer is placed on a field than the plants can use, the excess runs off into the water supply, where it becomes fertilizer for algae and other aquatic plants. Without oxygen, fish and other animals cannot survive. The Costs of Modern Agriculture There are dead zones in nearly all coastal areas where rivers bring excess nutrients into the sea.
One of the largest and most persistent in United States coastal waters is in the Gulf of Mexico, off the coast of Louisiana. Spring rains wash these excess fertilizers from the fields into the river. In the summer of , the Gulf dead zone grew to its largest area to date, totaling 9, square miles 25, sq. Although the dead zone varies in size and duration from year to year, over the past two decades it has continued to appear earlier and become larger. This growth is not surprising because three times more fertilizer runs downstream now than during the period from the s to the s.
Before the construction of the elaborate system of levees along the Mississippi, floodwaters ran over riverbanks and dumped excess nutrients onto the floodplain. Nutrient runoff into the Gulf of Mexico can be reduced by requiring farmers to decrease fertilizer use. But, so far, the government requires only voluntary reductions. Researchers also suggest that nutrient levels entering the Gulf can be reduced by reducing runoff.
Crops that cover the ground year round rather than only part of the year reduce runoff, as does controlling drainage. Excess nitrogen can also become part of a chemical reaction that produces acids, a process known as acidification. If a new insect species enters an area that is covered by a single crop, the organisms will have unlimited amounts of food available to them.
This means that pests can get out of control. Getting rid of them often requires the use of chemical pesticides. Chemical pesticides are members of a class of chemicals known as persistent organic pollutants POPs. POPs do not break down or dissipate in the environment, and most of them bioaccumulate. Large predators at the top of the food chain accumulate the most. Some POPs may cause neurological or other physiological disorders. Hormones are released into the bloodstream in carefully measured amounts by the endocrine glands, including the pituitary gland, the thyroid, the adrenal gland, the thymus, the pancreas, the ovaries, and the testes.
Each type of hormone travels until it reaches a cell with a receptor that it fits as a key fits a lock. An endocrine disruptor might block a hormone from doing its job in a receptor, or it might give a signal that is too strong, causing the cell to malfunction. An endocrine disruptor might cause a cell to perform its correct function, but at the wrong time. Because endocrine disruptors eventually make their way into the water system, aquatic animals bear the brunt of the damage.
Some of them have been found to have misshapen and undersized sex organs. Male fish and amphibians, for example, may develop smaller testes, suffer from reduced sperm production, develop ovaries and produce eggs, or develop as females. Female organisms may develop male traits, such as penises. The offspring may develop poorly or have reproductive-system problems, or the population may be reduced due to limited reproductive success. Terns are born with birth defects. Frogs are born with three legs, and fish grow 59 60 geosphere large tumors. Some of the worst POPs have been taken off the market in the developed nations.
As a result, the birds laid eggs with extremely thin shells that broke when the mother sat on them, causing the populations of the susceptible species to plummet. Other pesticides have also been banned. In many developing countries, the situation with POPs is even worse. Also, the farmers spraying these chemicals do not have the money to buy protective suits or may live in climates where it is too hot to wear them, resulting in direct exposure.
Without protection, the ground is vulnerable to rain, wind, and gravity. When erosion is extreme, deep gullies cut into and remove the soil. The gullies increase in size as more soil is lost. Fine soil may be blown away by wind, leaving coarser and less fertile sand behind. China has the highest rate of soil loss, with a national annual average loss of about 18 tons per acre 40 metric tons per hectare.
In some locations, soil is lost at 25 tons per acre 48 metric tons per hectare per year. The rate of soil loss is 8 tons per acre 7. The midwestern breadbasket has lost one third of its topsoil in just years, with soil eroding 30 times faster than it is forming. In the early s, the nation was losing 3 billion tons 2. This amount of soil could produce 7 million tons 6. Erosion can be prevented by covering the soil to reduce the force of the wind and rain. Soil can be protected by adding mulch organic material to hold it in place while plants grow.
Strip cropping alternates a row of a crop that leaves the ground exposed with a row of a crop that grows close to the ground so it can catch blowing soil. To prevent water erosion, steep hillsides can be terraced, and gentler slopes can 61 62 geosphere be contoured. The CRP pays farmers to plant highly erodable cropland with grass or trees instead of food crops. In addition to energy costs, modern agriculture takes an enormous toll on the soil. This chapter discusses how grazing animals compact the soil and carry seeds into regions where the plants are not native, among other impacts.
In arid and semiarid regions, overgrazed lands may turn into desert. Factory farms produce meat cheaply, but they use great amounts of fossil fuels and create an enormous amount of pollution. The best grazing land is grassland, although forests are sometimes logged to make way for ranching, or the ranching begins after an area has been logged for its trees. Before the arrival of widespread irrigation, the western United States was too arid for agriculture, so the region was used as rangeland.
Cow herders moved cattle from place to place, wherever the grass was good. By the end of the nineteenth century, more lands were privately owned, and barbed-wire fences were put up to divide the open prairies. Railroad companies supported fence construction to keep cattle from wandering onto their tracks. Although the open range is gone, huge ranches still exist. Ranching is a common activity in former tropical rain forest land and is responsible for a great deal of deforestation. Even if the land is not altered to accommodate the cattle, the cattle still impact the land.
People also have intentionally introduced nonnative grasses, called invasive or alien species, to regions to provide forage for the animals.
Invasive or alien species are organisms that have been introduced by human activities into a location where they are not native. Buffelgrass Cenchrus ciliaris or Pennisetum ciliare , a native of Africa, was introduced to the Arizona desert for this reason. The grasses grow well after a rain and provide fuel for fires, which, in turn, help the buffelgrass to sprout, so after each fire there is more of the nonnative grass. This cycle has been a disaster for portions of the Sonoran desert, where cacti and other plants are not adapted to fire.
Deforestation and overgrazing decrease plant cover, which increases erosion and makes the land less hospitable for new plants. In developing countries, the soil nutrients that were taken up by trees or animals are burned as firewood or as animal dung for heat and to cook food. Burning destroys the nutrients and also the chance that the region will recover its fertility. A significant example of desertification can be seen in the semiarid Sahal region south of the Sahara Desert of Africa.
Traditionally, the Sahal was populated by nomadic tribes, who kept their populations low, migrated frequently by following the rains, and were careful not to overgraze an area. This proved disastrous when the worst drought of the century hit from to During that time, nearly , people and 3. The end result is soil exhausted of value for agricultural use, which negatively impacts economies around the globe. Meat Production These confined animal feeding operations CAFO , or factory farms, are enormous production facilities that, in some cases, may house up to hundreds of thousands of animals, including pigs, cattle, dairy cows, and chickens.
On a typical North Carolina hog farm, for example, between and 1, animals live together in a barn with slatted floors for the waste to pass through. CAFOs are designed to grow animals for slaughter or to produce milk or eggs as quickly and cheaply as possible. In a factory poultry farm, machines deliver feed and water and remove wastes automatically. When a chicken reaches the desired weight, it is processed in an assembly line. Because the capital outlay to start a mechanized farm is high, factory farms are often owned by large corporations. Farmers are contracted to grow the animals for these corporations.
One reason that CAFOs are major polluters is the sheer numbers of animals they process. For example, feedlots in the United States produce nearly billion pounds million metric tons of manure daily. Because they are packed so close together, the animals can easily become sick, and antibiotics are given to prevent the spread of disease. However, excess use of antibiotics poses a threat to animals and humans as bacteria 67 68 geosphere develop resistance to the antibiotics.
The animals burn the rest of the calories for warmth, for movement, and for reproduction. On ranches, grazing animals convert grass, which is not digestible by humans, into useful food, but the health of the land may be compromised by overgrazing. Sustainable agriculture strives to promote environmental stewardship and stable, prosperous farm communities by making small individual farms profitable. To avoid the risks of agricultural monocultures, which are vulnerable to pests and disease and deplete the soil of nutrients, farmers plant a diverse assortment of crops that grow in different seasons.
Crop rotation also counteracts the problems of monocultures; although farmers may grow only one type of crop at a time, they plant different crops in different years. Some crops, such as legumes, even replenish some nutrients. Sustainable farming also follows the principles of organic farming.
A product labeled organic must meet standards set by the federal government. This means that crops and animals are not exposed to synthetic chemicals or pharmaceuticals. Organic farming takes a more flexible approach to dealing with unwanted insects and weeds than conventional farming. Organic farmers tolerate some loss of crops to pests. They also carefully select crops to minimize the chance that they will be harmed by insects.
Using integrated pest management, growers design a plan to attract species that will eat the pests. In sustainable agriculture, only fertilizers from natural sources such as manure, rock phosphate, and recycled crop waste are used. Often these nutrients are produced elsewhere on the farm.
Animals grown sustainably are fed only organic feed, are allowed outdoors, and are not raised in crowded conditions. Sustainable farming is best done in communities where farmers can share machinery, manure, and expertise. A CSA is a group made up of growers and consumers. Having the capital up sustainable Agriculture front gives the farmers money to grow the crops and also spreads the financial risk associated with sustainable farming.
No matter how bad the weather is, or how much produce is consumed by insect pests, each farmer receives the same amount of money from the CSA members. Theresa Mauer: Applying Ecological Principles to Agricultural Practices Teresa Maurer has found the perfect way to meld her interests in biology and in growing, cooking, and eating food that is healthy and good for the environment. Using her biology background, Maurer helps farmers understand and use sustainable agriculture practices. Maurer began her career investigating the ecology of insect-plant relationships in the grasslands of Eastern Oregon.
Her field site was located on a nature preserve in the middle of a working ranch. The rancher told the scientist about cattle grazing and grassland management while she shared with him what she learned about the plant and insect species she was studying. A few years later, at a presentation on using principles of grasslands ecology to design ways to produce food and fiber that are less harmful to soil, water, air, and people, Maurer saw the way to combine her interests in biology and food production.
Since that time, Maurer has used ecological principles to design better agricultural practices and has helped farmers convert to using these sustainable practices. She and her staff help farmers convert to organic farming by advising them on how to meet the complex organic standards. They encourage using sheep and goats, instead of herbicides, for vegetation management.
During the past 25 years, Maurer has seen consumers develop a greater awareness of how and where their food is produced and has seen the number of groups working in sustainable and organic agriculture grow from about 30 to more than She says that, while at the federal level there is more recognition of sustainable practices, promoting them is still a tiny portion of the federal agriculture budget.
Not long ago, a product labeled organic was also likely to have been raised sustainably. Although the plants and animals are raised according to federal standards for organic food, the effort is not necessarily made to grow the food in a sustainable manner. One of the tenets of sustainable farming is that the food should be priced responsibly. If growing crops without using artificial fertilizers, pesticides, and fossil fuels costs more, then the food should cost more.
Food produced by big agribusiness is not priced responsibly: Many of its costs are not paid by either the growers or the consumers.
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For example, the cost of the excess nutrients used on crops is borne by the fishers who can no longer harvest in the eutrophic lakes or marine dead zones created by the runoff of those nutrients. In a year study of crop yield, researchers at Cornell University discovered that organically farmed soybeans and corn had the same yield as crops farmed by conventional methods. As a bonus, it took less energy to grow the organic crops, and they had no pesticide residues. On the positive side, the Swiss study found that much less money was spent on fertilizers and energy. Sustainable agriculture is growing as consumers seek to have more of a connection with the food they eat and with the environment it comes from.
Organizations such as CSAs make it easier for people to connect with farmers and the land. However, food consumption is one area in which people collectively can make a big difference in how land is used and how agriculture is practiced. Useful minerals can be categorized as gems, metals, or nonmetals. When they find a deposit, the scientists work to determine its size and the quality of its mineral content.
Economic factors help to decide whether the deposit is worth mining. If the answer is yes, the valuable rock is extracted from the ground surface or below ground. Many types of mining require the movement of tremendous amounts of rock material, and extracting the useful minerals from the rock may involve the addition of heat or chemicals.
A few of them are used for industry. For example, diamond, an extremely hard mineral, is used for the precision cutting of other materials. Metals—shiny elements that can conduct heat and electricity—include copper, tin, iron, lead, gold, silver, platinum, and mercury. Rock that contains sufficient amounts of one or more valuable minerals for profitable mining is called ore. Note, then, that the definition of ore is economic, rather than geologic. Mining Other important metals include lead, silver, gold, vanadium, titanium, and tellurium.
Important nonmetals are salt, gypsum, and phosphates. Metallic minerals are heavy and sink to the floor of the magma chamber as a pluton forms. There are many types of hydrothermal deposits. The valuable material in these deposits may be so dispersed that ore concentrations may be less than one ounce 28 grams per ton. Marble, a popular building stone, is metamorphosed limestone. Many gemstones, such as garnet, are metamorphic minerals.
As peat sinks deeper into the ground, it is compressed and transformed into coal. Because the ore minerals are heavy, when the stream slows down, the dense, heavy particles fall to the bottom and are concentrated. Gold placers were very important to the development of the western United States.
Minerals such as halite, gypsum, carbonates, and potassium salts precipitate out of a solution as the water evaporates. Iron comes from Mining banded iron formations, which are very rich bodies of iron ore that formed primarily between 2. First, the plants produced oxygen as a byproduct of photosynthesis. In warm, tropical, or subtropical regions, rainwater percolates through the soil, picking up soluble ions but leaving behind insoluble ones.
Weathering can also increase the concentration of ore minerals around ore bodies. This process may concentrate tens to hundreds of times more ore than was found in the original ore body. Common building stones come from each of the three major rock types. Granite, marble, slate, limestone, and sandstone are among the most popular. Sand and gravel are used for building roads and stabilizing beaches.
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These materials are mined from deposits left by streams, glaciers, wind, and ocean waves. Phosphorus is a major constituent of the mineral apatite, which is found in bones, teeth, and shells. Most economically viable deposits of apatite are the result of the collection of plankton shells in productive regions of the ocean.
The largest phosphate deposits in the United States are found Ore Types and Their Uses Commodity Uses Aluminum engineering, transportation, aerospace Coal energy Copper wire, pipes, electrical uses, home products Diamonds jewelry, industry Gold jewelry, dentistry, electronics, ornamentation Halite salt food preservation and flavor Iron structures, steel Lead batteries, bullets, radiation shields Limestone building stone, neutralizing acids Nickel industry, home products Phosphate fertilizer, water softener in detergents Platinum jewelry, industry, medications Tin corrosion resistance, food preservation, electrical uses, chemical uses Uranium shielding, nuclear power Mining in sedimentary rocks in Florida.
Some ores and their uses are shown in the table on page On flat terrain, strip mining disturbs large areas. On hillsides, terraces are created to allow access to the ore. Gold, copper, and other metals are taken from open pit mines. In hydraulic mining, a strong jet of water breaks heavy minerals away from sediments. The sediments are then run through a rippled wooden trough known as a sluice box. Underground mining requires miners to blast and then tunnel into overlying rock to gain access to ores that lie farther below the surface. Underground mining is done only when surface methods would be too costly or unsafe.
The type of underground method chosen depends on the size, shape, and orientation of the ore body; the depth of the ore body; the grade of the ore; and the strength of the surrounding rock. The process that is chosen depends on the type of ore, the minerals it is bound up with, and its grade. Extraction processes may be used in combination until the desired mineral is nearly pure. The added compound, along with the valuable mineral, attaches to the air bubbles. Smelting: In this process, rock is roasted in a furnace with the appropriate compounds, which causes the material to segregate into layers.
Chemical reduction: A chemical reducing agent which adds electrons , such as carbon coke , is mixed with the ore and heated. The oxygen from the ore moves into the carbon to produce carbon dioxide and carbon monoxide. Sulfide extraction: To extract metal from sulfide, the rock is heated until two liquids form. Copper ore is most commonly found bound up in copper sulfide and copper oxide minerals in porphyry copper deposits. Once the copper is nearly pure, it is made into wires, logs, slabs, and bricks. Whether a mineral deposit will be mined is an economic decision based on the amount of money it will cost to remove the rock from the ground, extract the ore from the rock, and transport the ore to where it will be used.
A mineral deposit that is regarded as valuable one day may not be valuable the next if the price of the commodity drops or the cost of extracting it goes up. This chapter explores these problems. Disturbed rock and soil erode more easily. Water and sediments from a mine site are often contaminated with pollutants, particularly heavy metals such as lead and mercury, which actually are of heavy weight, or cyanide from gold mines.
Heated ore releases particles including metal oxides , oils, and other pollutants. In modern mining operations, emission control devices capture these materials; some of these emissions are even mined for metals and other valuable materials. For example, sulfur dioxide can be captured and converted to sulfuric acid that can be used in heap leaching. The mining process also creates acid pollutants.
Water that comes into contact with rock becomes slightly acidic. Rock that has been disturbed and exposed by mining has a greater surface area for water to access, causing the water to become even more acidic. The acidity can rise to alarming levels if the disturbed rock is made up of sulfides, which are broken down by colonies of bacteria into metal ions and sulfuric acid. The flow of acids from a mine site is called acid mine drainage.
The process that forms acid mine drainage also generates heat. This high acidity occurs when water evaporates from an acidic pool, leaving behind the hydrogen ions. If an acid mine system has a pH near 3, the iron ions form iron hydroxide. Wetlands are naturally good at cleaning up the pollution from mines. Bacteria change sulfur into a form that can create a chemical bond with heavy metals, causing metal sulfides to precipitate out of the solution. Once a wetland is constructed, it can be largely left alone, although mine effluent from it may need additional treatment.
On the other hand, a treatment plant must be constructed and maintained and needs money to keep operating. It is also unique because gold has limited practical use for society. Gold mining is a big business, and about 2, tons 80 million troy ounces, or 2. If the gold is bound into a mineral, the rock must first be roasted, chemically altered, or ground until it is ultrafine.
Depending on the type of rock and the form of the gold, the preferred method for extracting gold from the rock is heap leaching, using a dilute about 0. The solution flows out the base of the heap and is next run through activated carbon.
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The sodium cyanoaurite adsorbs onto the carbon, and the mixture is separated by a screen. A hot, strong solution of sodium cyanide and sodium hydroxide is then used to leach the gold from the carbon. The gold is electrically or chemically removed from this new solution. Cyanide is a notorious poison: A teaspoonful 4. Cyanide blocks the absorption of oxygen by cells and damages the central nervous system, respiratory system, and cardiovascular system.
Low doses of cyanide are known to harm mammals, birds, and—in extremely low doses—fish, in which it inhibits the ability to reproduce. Cyanide does not bioaccumulate. Solar radiation breaks down cyanide, but this process cannot occur underground or in cloudy or rainy conditions. Cyanide gas was used in the gas chambers of Nazi Germany during the Holocaust. If the cyanide solution is alkaline, the cyanide will not break down. Even if cyanide Environmental Effects of Mining does break down, it may decompose into other compounds that are toxic to aquatic organisms, such as cyanate and ammonia.
Following heap leaching, giant quantities of waste rock remain that are badly contaminated with cyanide. This rock is placed in pits that are coated with clay and plastic liners designed to keep the cyanide poison from leaching into the soil and water. The pile is then covered to keep out birds and other animals. Of course, liners sometimes leak, and pits may overflow, which is especially likely to happen after the mine has been abandoned. Contact: Kassie Siegel. Global warming presents the gravest threat to life on Earth in all of human history. Such a catastrophic loss would irreversibly diminish biodiversity, severely disrupt ecosystems, and cause immense hardship for human societies worldwide.
Since the Center was established, our mission has been to help protect species facing extinction, and as the threat of global warming has spread, our focus on the issue has intensified. The first creatures to be dramatically and visibly affected by global warming have been those in the Arctic , where the impacts of rising temperatures have been felt earlier and more intensely than anywhere else. As warmer air melts the vast expanses of sea ice that help define the Far North, all the animals depending on that ice for hunting, resting, reproducing, and other key life activities lose the platform on which their existence depends.
At the other end of the Earth, around the South Pole, the emperor penguin is also facing enormous threats from global warming, which causes profound changes in the Antarctic ecosystem and hurts penguins in diverse ways, from reducing prey species to causing ice shelves to collapse.
Thanks to a petition and lawsuit by the Center, the emperor and nine other penguin species hailing from around the southern hemisphere are on their way to federal protection. The polar regions are by no means the only areas of the planet already affected by global warming. As temperatures rise worldwide, many species are forced to flee the warming by moving up in elevation — like the American pika — or by moving northward or southward, away from warmer equatorial areas. Snow-dependent species like the American wolverine are finding less and less of the snow they need, while forest-dwelling species like the West Virginia northern flying squirrel are threatened right along with their arboreal habitat.
Amphibians and fish are threatened by the drought that accompanies climate change, while reptiles like the loggerhead sea turtle have been found altering their centuries-old nesting habits because of warmer ocean temperatures. Even insects are affected: The beautiful Bay checkerspot butterfly , for example, is threatened as global warming reduces food availability for its larvae.