Depletion and Conservation of Natural Resources

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Human activity on Earth has always altered the land. When populations were small enough, and productive and accessible land was abundant, people could abandon land that had been damaged by overuse and move on. While some countries still have excess land available, if population growth continues at the expected rate, virtually all arable (fit for cultivation) land will be in use.


Nature performs valuable, practical, measurable functions, without which the human economy could not exist. Many experts contend that, as human activity gradually consumes or destroys this natural capital, the monetary value of the ecosystem to the economy must be calculated and considered. Thirteen economists, ecologists, and geographers studied 16 different biomes (ecological areas such as lakes, urban areas, and grasslands) to estimate the economic value of 17 ecosystem services. To do this they assigned dollar values to services performed by nature that are considered necessary to the human economy. Their report, published in the journal Nature (May 1997), estimated that ecosystems perform at least $33 trillion worth of services annually. Marine systems contribute about 63 percent of the value, mainly from coastal systems ($10.6 trillion). Terrestrial systems account for 37 percent of the value, mainly from forests ($4.7 trillion) and wetlands ($4.9 trillion). This total was 1.8 times the 1997 global gross national product of approximately $18 trillion. In other words the services performed by nature were 180 percent as valuable as all of humankind's economic activities.

Most experts, including the authors of the study, recognize the figure is a crude, conservative, "starting point" for an estimate of what the environment does for humans. Others contend nature's value is incalculable. Virtually everyone agrees that without nature's ecological contribution, human life could not exist. Furthermore, as ecosystems become more stressed and scarce in the future, their value will increase. If significant, irreversible thresholds are passed, the valuable services of these ecosystems may become irreplaceable.


For millennia humans have left their mark on the world's forests, although it was difficult to see. By the twenty-first century, however, forests that humans once thought were endless are shrinking before their eyes. Forests are not only a source of timber; they perform a wide range of social and ecological functions. They provide a livelihood for forest dwellers, protect and enrich soils, regulate the hydrologic cycle, affect local and regional climate through evaporation, and help stabilize the global climate. Through the process of photosynthesis they absorb carbon dioxide (CO2) and release the oxygen humans and animals breathe. They provide habitat for half of all known plant and animal species, are the main source of wood for industrial and domestic heating, and are widely used for recreation.

Forests are attractive and accessible sources of natural wealth. They are not, however, unlimited. Deforestation is caused by farmers, ranchers, logging and mining companies, and fuel wood collectors. Governments have often encouraged the settlement of land through cheap credit, land grants, and the building of roads and infrastructure. Much of these activities led to the destruction of forests, causing some governments to reverse their policies.

Forests play a particularly crucial role in the global cycling of carbon. The Earth's vegetation contains two trillion tons of carbon, roughly triple the amount stored in the atmosphere. When trees are cleared, the carbon they contain is oxidized and released into the air, adding to the atmospheric store of carbon dioxide. Many scientists believe that carbon dioxide contributes to global warming. This release happens slowly if the trees are used to manufacture lumber or are allowed to decay naturally. If they are burned as fuel, however, or in order to clear forestland for farming, almost all of their carbon is released rapidly. The clearing for agriculture in North America and Europe has largely stopped, but the burning of tropical forests has taken over the role of producing the bulk of carbon dioxide added to the atmosphere by land use changes.

A 1995 National Oceanic and Atmospheric Administration (NOAA) study found that about half the carbon dioxide emitted by burning fossil fuels is absorbed by plants in the Northern Hemisphere. The finding showed that plants play a role about equal to that of oceans, to which most of the absorption had previously been attributed. The study showed that plants absorb carbon dioxide that is rich in the carbon isotope 12, or C12, while ocean water absorbs C12 and C13 equally. By determining the ratios of the isotopes, scientists can determine the relative effects of oceans and plants on the atmosphere's carbon dioxide concentration.

Rising Pressures on Forests

According to Janet N. Abramovitz in Taking a Stand: Cultivating a New Relationship with the World's Forests (Washington, DC: Worldwatch Institute, 1998), the Worldwatch Institute, an independent, nonprofit environmental research organization, reported that between 1980 and 1995 alone at least 494 million acres of forests vanished—an area larger than Mexico.

According to the United Nations Food and Agriculture Organization (FAO), approximately half the wood cut worldwide is used for fuel and charcoal. Most fuel wood is used in developing countries. In dry countries such as India, the majority of trees cut are for fuel; in moist tropical areas such as Malaysia, most trees are cut for industrial timber.

Tropical Rain Forests

Tropical forests are the most "alive" places on Earth. Although they cover less than 2 percent of the Earth's surface, they are home to as many as 30 million species of plants and animals—more than half of all life forms on the planet. A single acre of tropical rain forest supports 60 to 80 tree species and an enormous number of vines and mosses.

Rain forests also play an essential role in the weather. They absorb solar energy, which affects wind and rainfall worldwide. Regionally, they reduce erosion and act as buffers against flooding. Tropical trees contain huge amounts of carbon which, when they are destroyed, is released into the atmosphere as carbon dioxide.

Of roughly 3,000 plants identified as having cancer-fighting properties, 70 percent grow in the rain forests. One of every three species of birds in the world nest there. In addition to wildlife, more than 1,000 indigenous tribes still survive in tropical forests, just as they have for thousands of years.

The Natural Resources Defense Council (NRDC), a private organization that supports environmental health, reports that nearly half of the forests on the planet have been decimated and every year more than 30 million acres of tropical forests and woodlands are destroyed for agriculture or logging. Exacerbating this problem, global wood consumption is set to double over the next 30 years, according to the NRDC, further stressing the survival of global forests..

In Combined Summaries: Technologies to Sustain Tropical Forest Resources and Biological Diversity (Washington, DC: U.S. Government Printing Office, 1992) the now-defunct U.S. Office of Technology Assessment concluded that the major underlying cause of deforestation and species extinction is the lack of alternative employment for the growing populations of tropical countries. Logging and the conversion of forestland to short-term, usually unsustainable, agricultural use results in destruction of the land, declining fisheries, erosion, and flooding.

Species in tropical rain forests possess a high degree of mutuality, in which two species are completely dependent on one another for survival; for example, a species of wasp and a species of fig tree. Such relationships are believed to evolve as a result of the relatively constant conditions in the tropics. Any species dependent on trees therefore becomes imperiled when a tree is cut down.


The Amazon rain forests, located in South America, are the most famous of the Earth's tropical forests. They serve as a good example of the controversies surrounding rain forests worldwide. This controversy generally centers on the interest of environmentalists (often from developed countries) in stabilizing the environment and the developing world's basic need to cut down its forests for fuel and livelihood. Most developing nations claim that these needs are too great to be set aside for the sake of the environment. They also resent the industrialized world's disdain of practices the developed countries once followed themselves in building their own nations. These poorer, developing countries also wonder why they are expected to pay for the cleanup of a world that they did not contaminate.

There are also international incentives for continuing to cut down the rain forests. Foreign countries, especially Asian nations, are increasingly eyeing the Amazon forests as a source of ancient trees to make plywood, ornamental moldings, and furniture. Granting logging rights to these nations may seem an appealing option for those South American countries desperate for money.

Based on studies of satellite photographs taken over the Amazon, researchers believe that as much as 10 percent of the original Amazon forest has been destroyed, mainly through "slash and burn" methods of clearing land that are used to convert the land to farming use. The cleared land's productivity usually decreases within a few years, and farmers often have to abandon the fields and move on—slashing and burning a new area.


The United States has 747 million acres of forested lands; they comprise roughly one-third of the nation's total land area. (See Figure 9.1.) Forests are valued for a variety of ecological and economical reasons. In their natural state they provide vital habitat for wildlife and play an important role in the carbon cycle. (See Figure 2.10 in Chapter 2.) Forests are also a source of recreation for humans and provide wood for fuel and lumber. Human uses combined with natural environmental stresses (such as disease and drought) pose a constant threat to the health and vitality of the nation's forests.

As shown in Figure 9.2 almost half of America's forested lands are in the hands of private owners with no ties to industry. Another 20 percent are part of the National Forest System overseen by the U.S. Forest Service, an agency of the U.S. Department of Agriculture. Other federal agencies control 13 percent of the country's forest lands. Industrial entities (such as timber companies) own 10 percent of America's forests, while the remaining 8 percent are under state control.

Forest Health—The Latest Government Assessment

In May 2003 the U.S. Forest Service published its latest assessment on the health and well-being of the nation's forests. According to America's Forests: 2003 Health Update, there are five key areas of concern:

  • Wildfires
  • Outbreaks of native insects
  • Nonnative invasive insects and pathogens (diseases)
  • Invasive plant species
  • Ecologically damaging changes in forest type


The Forest Service manages about 155 national forests across the country. (See Figure 9.3.) About 70 percent of these lands are located in the dry, interior areas of the western United States. Management practices in the past called for the Forest Service to put out all wildfires in the national forests. Scientists have recently put forward the idea that wildfires are necessary for forest health. They point out that wildfires are natural occurrences that serve to remove flammable undergrowth without greatly damaging larger trees.

Before pioneers settled the West, fires occurred about every five to 30 years. Those frequent fires kept the forest clear of undergrowth, fuels seldom accumulated, and the fires were generally of low intensity, consuming undergrowth but not igniting the tops of large trees. Disrupting this normal cycle of fire has produced an accumulation of vegetation capable of feeding an increasing number of large, uncontrollable, and catastrophic wildfires. Thus, the number of large wildfires has increased over the past decade, as have the costs of attempting to put them out.

Because the national forests are attractive for recreation and enjoyment, human population has grown rapidly in recent years along the boundaries scientists refer to as the "wildland/urban interface." According to a 1999 U.S. General Accounting Office (GAO) study, Western National ForestsA Cohesive Strategy Is Needed to Address Catastrophic Wildfire Threats, this combination of rising population and increased fire risk poses a catastrophic threat to human health and life along the wildland/urban interface areas. In addition to the risk fires pose to nearby inhabitants, smoke from such fires contains substantial amounts of particulate matter that contaminates the air for many hundreds of miles. In addition, forest soils become subject to erosion and mud slides after fires, further threatening the ecosystem and those who live near the forests.

In 1997 the Forest Service began an attempt to improve forest health by reducing, through "controlled burns," the amount of accumulated vegetation, a program to be completed by 2015. The GAO found that lack of funding and inadequate preparedness may render the program "too little, too late." The National Commission on Wildfire Disasters concluded: "Uncontrollable wildfire should be seen as a failure of land management and public policy, not as an unpredictable act of nature. The size, intensity, destructiveness and cost of … wildfires … is no accident. It is an outcome of our attitudes and priorities.… The fire situation will become worse rather than better unless there are changes in land management priority at all levels."

The summer of 2000 was considered the worst fire season in 50 years in the United States. Nearly 123,000 fires burned more than 8.4 million acres. Ironically, one of these fires resulted when a "controlled burn" near Los Alamos, New Mexico, raged out of control, sweeping across hundreds of acres of land and destroying homes and businesses for miles. In June 2002 a massive fire swept through Arizona destroying hundreds of homes and businesses and causing 30,000 people to flee. The fire burned 375,000 acres in only a week and was called a "tidal wave" by fire fighters trying to contain it. Numerous other fires roared through the American West during the summer of 2002.

According to America's Forests: 2003 Health Update, catastrophic fires are due to decades of fire suppression that have allowed forests to become overcrowded with highly combustible undergrowth. The situation is aggravated by a lingering drought in the West and trees stressed by pests and disease. The report warns that "the fire risk in many forested areas remains high."

Figure 9.4 shows the number of acres burned by wildland fires between 1960 and 2002. In 2002 federal agencies spent $1.66 billion putting out destructive wildfires.

Following the disastrous 2000 fire season the Forest Service collaborated with other agencies to develop The National Fire Plan, a long-term strategy for more effectively dealing with fire threats and preventing future wildfires. In August 2002 the Bush administration presented its plan for wildfire management in Healthy Forests: An Initiative for Wildfire Prevention and Stronger Communities. The so-called Healthy Forests Initiative implements core strategies of the National Fire Plan.


Native insects of concern in American forests include bark beetles and southern pine beetles. Under certain conditions these insects can infest huge areas of forests and kill thousands of trees. This is damaging by itself and exaggerates other threats to forests, such as wildfires. Wildfires are more likely to spread quickly and burn hotter when forests contain large amounts of trees that have been weakened or killed by insect damage.

The Forest Service estimates that southern pine beetles pose a moderate to high risk to more than 90 million forested acres across the Southeast. In 2001 beetle outbreaks affected tens of thousands of acres in the South resulting in $200 million of damages. The Forest Service spent $10 million that year alone fighting the beetle outbreak. In the western United States the bark beetle known as the Mountain Pine Beetle is a major killer of pine trees. Thousands of acres of pine forest across the West are considered at risk. The Forest Service focuses its resources on tracking, suppressing, and preventing beetle outbreaks and on replanting forests decimated by the pests.


Another major threat to America's forests is the spread of nonnative invasive insects and pathogens. Non-native (or exotic) species can be very harmful, because they do not have natural predators in their new environment. This allows them to "invade" their new territory and spread very quickly.

Species of major concern to forest health are as follows:

  • Gypsy Moths—An insect that arrived in the United States during the 1800s from Europe and Asia. In the springtime they devour newly emerged leaves on hundreds of tree species (primarily oaks). They are concentrated in eastern forests where they are blamed for defoliating more than 80 million acres of trees.
  • Hemlock Woolly Adelgid—An insect that arrived in the United States during the 1920s from China and Japan. The pest eats the leaves off of eastern hemlock trees. It has infested hemlock forests across the Northeast and South Central states from Maine to northern Georgia. Trees die within only a few years of being infested.
  • White Pine Blister Rust—A fungus native to Europe introduced to western Canada around 1910. It migrated quickly southward across the mountainous states where it is particularly lethal to high-altitude pine forests. Once firmly entrenched in an area the fungus can kill more than 95 percent of the trees it infects.
  • Sudden Oak Death—A disease caused by the pathogen Phytophthora ramorum. Its origin is unknown, but it was introduced to the United States within the past few decades. So far, it has been found in forests in California and southern Oregon where it has killed thousands of trees (primarily oak) and ornamental and wild shrubs. Scientists fear that it could spread eastward and cause enormous damage to the country's massive oak forests.
  • Emerald Ash Borer—An exotic wood-boring beetle from Asia that targets ash trees. Believed to have entered the United States in cargo packing materials, the beetle was discovered in Southeastern Michigan in the summer of 2002 and has so far killed millions of trees. Ashes are killed when the beetles' larvae bore tunnels within the wood, cutting off the tree's water and nutrients. Infested ash trees, which are predominantly in the Northeastern United States and Canada, die within two to three years of infestation.

The Forest Service employs a variety of measures to combat nonnative invasive pests, including application of insecticides and release of biological control agents. These agents include insects and pathogens found to prey upon the nonnative invasive pests. For example, since 1999 the Forest Service has raised and released more than 500,000 ladybird beetles into forests infested with Hemlock Woolly Adelgids. The beetles, which are native to the United States, feed on the Adelgids and their eggs. Experts hope this measure will wipe out nearly all of the Adelgid population in the forests treated.


Insects and pathogens are not the only invaders causing damage to America's forests. Certain plants (native and nonnative) become a threat when they grow out of control and overpower regular forest vegetation. Invasive plants of major concern include leafy spurge in northern states (particularly in the West), kudzu in the South, and mile-a-minute weed in the Northeast and mid-Atlantic states.

Although these plants are most often a problem in rangelands they are increasingly affecting forests. Invasive plants strangle and smother young seedlings and gobble up resources, such as water and nutrients needed by other plants. They also contribute to buildup of highly combustible undergrowth, making forests more susceptible to hot-burning wildfires. This is one of the reasons that the National Fire Plan targets invasive plants for reduction. In addition, there is the Federal Interagency Committee for the Management of Noxious and Exotic Weeds. This is a collaboration of 17 agencies working to develop control techniques for invasive plants across the country. The Forest Service is working on a variety of measures, primarily biological agents (such as insects or fungi known to attack invasive plants).


America's forests have been changed over the years by many human and natural factors. This has led to ecological changes in entire forest types. For example, prior to the 1900s the forests of the Appalachian Mountains were dominated by the American Chestnut. A fungus introduced from Europe virtually wiped out the chestnut population by the 1950s. Other species of trees soon became predominant. Today scientists consider this type of forest change to be harmful from an ecological standpoint. Major changes in forest type have profound effects on the overall health of a forest, wildlife habitat, and even soil conditions. The Forest Service worries that a combination of stressors, including fire, drought, destructive pests, and human activities, pose major dangers to forests. Human activities that can negatively affect forests include agriculture and residential development.

Forest Health—Other Problems

Environmentalists fear that the forests of the northwest United States are being depleted by "clear-cutting" practices—the method of logging in which all trees in an area are cut—as opposed to "selective management" techniques, in which only certain trees are removed from an area. The lumber industry continually battles with environmentalists and the U.S. Forest Service over the right to clear-cut ancient forests. Experts believe that North American "old growth" forests (stands of old, large trees) may store more carbon than any of the world's other sinks (repositories).

National Aeronautics and Space Administration (NASA) scientists report that satellite pictures show a high level of damage to the evergreen forests of the Pacific Northwest. They attribute the damage to clear-cutting and claim the region has been so fragmented by clear-cutting that the overall health of the forest is at risk. Many observers believe that the biggest threat from this logging technique is the loss of diversity of species in the area. The logging industry contends that restrictions on logging devastate rural communities by causing the loss of thousands of jobs and leading to an increase in retail prices for lumber nationwide.

Logging roads are increasingly blamed for contributing to landslides, floods, and changes in rivers and streams. The Roadless Area Conservation Rule was adopted in January 2001 to protect nearly 60 million acres of national forests from further road building and logging, while keeping them open for recreational uses. The rule had both environmental and economic goals. The Forest Service oversees approximately 386,000 miles of roads, and their upkeep costs billions of dollars. The high cost of building and maintaining these roads is often cited as a reason many national forests lose money on timber sales. The rule was immediately challenged in court by a variety of groups, but a federal appeals court upheld the rule in December 2002.


In an effort to counteract tree loss, forests are often "replanted" or replaced. Most experts contend that, when a natural forest (that has been replanted after clear-cutting) is replanted with commercially valuable trees, the plot becomes a tree farm, not a forest, and the biological interaction is damaged. Primary forests represent centuries, perhaps a millennium, of undisturbed growth. Trees will rebound after clear-cutting within 70 to 150 years but, researchers have found, the plants and herbs of the understory (growth under the canopy of the trees) never regain the richness of species diversity and complexity of their predecessors.

The Effects of Pollution

Many biologists believe that regional air pollution is a serious anthropogenic (made by humans) threat to temperate forest ecosystems. The most dangerous impact on forests comes from ozone, heavy metals, and acid deposition. Ozone exposure reduces forest yields by stunting the growth of seedlings and increasing stresses on trees. Such damage can take years to become evident. Numerous studies suggest that both photosynthesis and growth decline significantly after one or two weeks of ozone at levels of 50 to 70 parts per billion (ppb), more than twice the normal background level of 20 to 30 ppb. During growing seasons average ozone levels are highest in the West (California, Nevada, Utah, and Arizona) and on the East Coast south of Pennsylvania.

In 1995, in a four-year study of a widespread timber species called loblolly pine, researchers at the Oak Ridge National Laboratory in Tennessee determined that ground-level ozone levels that frequently occur in the eastern United States caused growth to slow, especially under drier soil conditions. The loblolly pine, covering approximately 60 million acres, contributes billions of dollars to the economy of the South.

In 2001 the Hubbard Brook Research Foundation reported that more than half of large-canopy red spruce trees in the Adirondack Mountains and the Green Mountains had died since the 1960s. Acid rain was considered the primary cause. Along with acid rain, the Environmental Protection Agency (EPA) also blames other pollutants and natural stress factors for the increased death and decline of northeastern red spruce at high altitudes (in the Adirondacks, for example) as well as the decreased growth of red spruce in the southern Appalachians. Acid rain is also closely linked to the decline of sugar maple trees in Pennsylvania.

In the March 1999 report Soil Calcium Depletion Linked to Acid Rain and Forest Growth in the Eastern United States, the U.S. Geological Survey (USGS) stated that calcium levels in forest soils had declined at locations in ten states in the eastern United States. Calcium is necessary to neutralize acid rain and is an essential nutrient for tree growth.


The GAO reported in 2001 that the federal government managed just over 680 million acres or about 29 percent of the nation's total land surface. Of these lands, 96 percent are managed by four agencies—the National Park Service, the Fish and Wildlife Service, the Bureau of Land Management, and the Forest Service. Most public lands are located in western states.

In much of the West ranchers have petitioned Congress to loosen restrictions on grazing on thousands of acres of federally owned ranch land. Environmental groups strongly oppose the proposal, claiming that grazing imperils land conservation, wildlife, and recreation. Grazing, they charge, is especially destructive to stream banks and sensitive wildlife habitat. Such concern for the soil and wildlife also lies at the heart of the dispute between oil companies and environmentalists over control of public lands such as the Arctic National Wildlife Refuge in Alaska.

A Land Grab

Unfortunately, love of the land has led Americans and developers into isolated, undeveloped areas in record numbers, threatening to destroy the very beauty they enjoy. Increasingly, developers are trying to build in choice, remote locations, such as the Sonoran Desert in Arizona.

In Phoenix and Scottsdale, some government leaders are concerned that developers will transform the desert into a sea of asphalt. Residents have indicated a willingness to invest tax money to protect mountain preserves from encroaching development and have declared several mountain areas off limits to developers. The state of Arizona and those cities involved have undertaken to purchase as many as 700,000 acres of land with tax revenues with the purpose of doing nothing with it and simply allowing it to remain in a natural state.

In 1995 South Carolina's Office of Ocean and Coastal Resource Management denied permission to the owners of 7,000 acres of Sandy Island to build a bridge connecting the island to the mainland. Although the owners claimed the bridge would be used to transport harvested timber from there to the mainland, opponents believed the bridge would, in fact, lead to the construction of homes, condominiums, and golf courses on the island.

In Texas, in an effort to balance development with wildlife preservation, the city of Austin invited the Nature Conservancy, a nonprofit environmental group, to develop a plan to protect the environment while enabling building. The Endangered Species Act of 1973 (ESA; PL 93-205) allows such regional arrangements. The result is the Balcones Canyonlands Conservation Plan, a 70,000- to 75,000-acre preserve in the Texas Hill Country, home to a number of endangered species.

In 1997 the Nature Conservancy finalized one of its many negotiations to keep family ranches in environmentally sensitive areas of the country—especially the West—from being broken up. The organization purchased the Dugout Ranch in Utah, which consists of 5,167 acres of privately owned pastureland and 250,000 acres of grassland leased from the government for grazing, with $4.6 million donated by individuals, foundations, and corporations. The ranch was a favored setting for movies and commercials. The Nature Conservancy will maintain it as a working ranch, ecological preserve, and model for how cattle grazing and conservation—at odds throughout the West—can work hand in hand. As of 2003 the Nature Conservancy owned and managed about 15 million acres in the United States, in addition to assisting with conservation efforts around the world.

In May 2002 the North Carolina chapter of the Nature Conservancy purchased 38,000 acres of isolated woodlands and wetlands from a paper company for $24 million. The purchase is part of a massive 100,000-acre area owned by the organization that will supply protected habitat for black bears and other wildlife.


Marshes, swamps, bogs, estuaries, and bottomlands comprise about 5 to 9 percent of the 48 contiguous states and about 40 percent of Alaska. Although these terms refer to specific biosystems with sometimes very distinctive characteristics, they are commonly grouped together under the name "wetlands." Wetlands provide a vivid example of the dynamic, yet fragile interactions that create, maintain, and repair the world's ecological system. Unfortunately, the fate of many wetlands can also offer concrete evidence of the harmful consequences of human activities that are carried out without regard for, and often without knowledge of, the relationship of each part of the ecosystem to the whole.

Once regarded as useless swamps, good only for breeding mosquitoes and taking up otherwise valuable space, wetlands have become the subject of increasingly heated debate. Many people want to use them for commercial purposes such as agricultural and residential development. Others want them left in their natural state because they believe that wetlands and their inhabitants are indispensable parts of the natural cycle of life on Earth.

What Are Wetlands?

"Wetlands" is a general term used to describe areas that are always or often saturated by enough surface or groundwater to sustain vegetation that is typically adapted to saturated soil conditions, such as cattails, bulrushes, red maples, wild rice, blackberries, cranberries, and peat moss. The Florida Everglades and the coastal Alaskan salt marshes are examples of wetlands, as are the sphagnum-heath bogs of Maine. Because some varieties of wetlands are rich in minerals and nutrients and provide many of the advantages of both land and water environments, they are often dynamic systems that teem with a diversity of species, including many insects—a basic link in the food chain.

Wetlands are generally located along sloping areas between uplands and deep-water basins such as rivers, although they may also form in basins far from large bodies of water. Of the 90 million acres of wetlands in the lower 48 states, almost all (95 percent) are inland, freshwater areas; the remaining 5 percent are coastal saltwater wetlands. Alaska is estimated to have more than 200 million acres of wetlands.

There are several distinct forms of wetlands, each with its own unique characteristics. The main factors that distinguish each type of wetland are location (coastal or inland), source of water (precipitation, rivers and streams, groundwater), salinity (freshwater or saltwater), and the dominant type of vegetation (peat mosses, soft-stemmed, or woody plants). Wetlands are a continuum in which plant life changes gradually from predominantly aquatic to predominantly upland species. The difficulty in defining the exact point at which a wetland ends and upland begins results in much of the confusion as to how wetlands should be regulated.

The Many Roles of Wetlands

Experts have understood some of the functions of wetlands for many years. Other purposes have come to light more recently.


Wetlands are a source of food and habitat for numerous game and nongame animals. For some species of waterfowl and freshwater and saltwater fish, wetlands are essential for nesting and breeding. About one in five plant and animal species listed as endangered by the U.S. government depend on wetlands for their survival. Two-thirds of the species of Atlantic fish and shellfish that humans consume depend on wetlands for some part of their life cycle, as do nearly half of all species listed as endangered or threatened.

Coastal marshes and some inland freshwater wetlands boast some of the highest rates of plant productivity of any natural ecosystem, thus supporting abundant animal populations within the food chain. After a plant dies nearly 70 percent of it breaks down and is flushed into adjacent waters where it can be consumed by fish and shellfish.

Inland wetlands also serve as way stations for migrating birds. The 30,000-acre region in the north central United States and south central Canada, for example, provides a resting place and nourishment for nearly half of the more than 800 species of protected migratory birds (which individually number in the millions) during the migration season. Without this stopover the flight to their Arctic breeding grounds would be impossible.


Wetlands can temporarily or permanently trap pollutants such as excess nutrients, toxic chemicals, suspended materials, and disease-causing microorganisms—thus cleansing the water that flows over and through them. Some pollutants that become trapped in wetlands are biochemically converted to less harmful forms; other pollutants remain buried there; still others are absorbed by wetland plants and either recycled through the wetland or carried away from it. (See Figure 9.5.)


Between 60 and 90 percent of the United States' commercial fish species spawn in coastal wetlands. More than one-half of the country's seafood catch depends on wetlands during some part of their life cycle.


Isolated and floodplain wetlands can reduce the frequency of flooding in downstream areas by temporarily storing runoff water. For example, the Cache River watershed in southern Illinois retains about 8.4 percent of the watershed's total runoff during flooding.


Because of their density of plant life, wetlands can dramatically lessen shoreline erosion caused by large waves and major flooding along rivers and coasts.


Many popular recreational activities, including fishing, hunting, and canoeing, occur in wetlands. In addition wetland areas provide open space, an important but increasingly scarce commodity.

History of Wetlands Use

Early Americans considered wetlands nature's failure, a waste in nature's economy. They sought not to preserve nature in its original form but to increase the efficiency of natural processes. In an agricultural economy, land unable to produce crops or timber was considered worthless. Many Americans began to think of draining these lands, an undertaking requiring government funds and resources.

In the nineteenth century state after state passed laws to drain (reclaim) wetlands by the formation of drainage districts and statutes. Coupled with an agricultural boom and technological improvements, reclamation projects multiplied in the late nineteenth and early twentieth centuries. The farmland under drainage doubled between 1905 and 1910 and again between 1910 and 1920. By 1920 state drainage districts in the United States encompassed an area larger than Missouri.

After the Great Depression of the 1920s and 1930s, programs such as the Works Progress Administration and the Reconstruction Finance Corporation encouraged wetland conversion to form land for urban development. In 1945, at the end of World War II, the total area of drained farmland increased sharply.

In the final few decades of the twentieth century, however, conservationists and the courts have challenged reclamation. Where drainage was once thought to improve the look of the land, today it is more likely to be seen as degrading it. Wetlands turned out not to be wastelands but the conservationist's ideal—systems efficient in harnessing the Sun's rays to feed the food chain. Studies have shown that wetlands have far greater value for flood protection than for their potential agricultural use.


When the first Europeans arrived in America, there were an estimated 215 million acres of wetlands. By the beginning of the twenty-first century only about 90 million or so acres remained. In the 200 years since the birth of the United States, more than 50 percent of the wetlands in the 48 contiguous states have been taken over for agriculture, mining, forestry, oil and gas extraction, and urbanization. Some loss resulted from natural causes such as erosion, sedimentation (the buildup of soil by the settling of fine particles over a long period of time), subsidence (the sinking of land because of diminishing underground water supplies), and a rise in the sea level. However, 95 percent of the losses since the 1970s have been caused by humans, especially by the conversion of wetlands to agricultural land. (See Figure 9.6.)

Eighty percent of the wetland conversions were for agricultural purposes; 8 percent for the construction of impoundments (water confined within an enclosure) and large reservoirs; 6 percent for urbanization; and 6 percent for other purposes such as mining, forestry, and road construction.

More than half (56 percent) the losses of coastal wetlands resulted from dredging for marinas, canals, port development, and, to some extent, from natural shoreline erosion. Urbanization accounted for 22 percent, 14 percent was from creating beaches, 6 percent from natural or human-made transitions of saltwater wetlands to freshwater wetlands, and only 2 percent from agriculture.

California, Ohio, Iowa, Indiana, and Missouri have lost almost all their wetlands. The Fish and Wildlife Service estimates that the United States is losing more than 250,000 acres each year—about 30 acres every hour. Developers have discovered that many of the most tempting sites for new housing or shopping centers are wetlands.

The conversion of wetlands causes the loss of natural pollutant sinks (repositories). As water floods into wetlands from rivers and streams, the loss in velocity causes sediments and their absorbed pollutants to settle out in the wetland before they can enter other water bodies. In the United States artificial wetlands have been proposed as a means of controlling pollution from nonpoint sources. The dramatic decline in wetlands globally suggests not only loss of habitat but also diminished water quality.

One of the largest wetlands in the United States is the Everglades of south Florida. The fresh water that used to flow naturally into this ecosystem has been diverted by decades of canal building. According to Nicole Duplaix in "South Florida Water: Paying the Price" (National Geographic, July 1990), drainage changes implemented since 1920 to create farmland or housing had dried out half of the Everglades National Park, and left the rest heavily polluted. Scientists are studying the complex water flow problems in this area and are working to restore some natural drainage characteristics to the Everglades. According to the Comprehensive Everglades Restoration Plan (CERP) Web site (, as of 2002 some limited progress had been made and environmental improvements were expected by 2010.

Concern over Property Rights

The dispute over wetlands regulation reflects Americans' ambivalence when private property and public rights intersect, especially since three-fourths of the nation's wetlands are owned by private citizens. In recent years many landowners have complained that wetland regulation devalued their property by blocking its development. They argue that efforts to preserve the wetlands have gone too far, citing instances where a small wetland precludes the use of much larger surrounding areas. Some large landowners have long opposed any federal (and state and local) powers to protect resources such as wetlands that might limit their land use options.

Another policy question of concern to the public is the right of the federal government to take property without compensation. The "takings" clause of the Constitution (the Fifth Amendment) provides that, when private property is taken for public use, just compensation must be paid to the owner. Owners claim that when the government—through its laws—eliminates some uses for their land, the value is decreased and they should, therefore, be paid for the loss.


Mountains are one of Earth's most important features. They span one-fifth of the landscape and house one-tenth of Earth's population. Roughly two billion people live downstream from mountains and depend on the water, hydropower, grassland, timber, and mineral resources generated by those mountains.

What Is a Mountain?

A mountain is a landmass that projects conspicuously above its surroundings and is higher than a hill, generally at least 985 feet (300 meters) in height. An additional criterion is that a mountain's rise creates climates, soils, and vegetation distinct from those in surrounding lowlands. Mountains share common physical attributes of steepness, instability, and ecology that create natural hazards, micro-climates, niches of biodiversity, and inaccessibility. The collision of tectonic plates produces mountain uplift and numerous physical hazards, such as earthquakes, volcanic eruptions, landslides, avalanches, and floods. The slope and altitude of mountains create variations in climate—temperature, radiation, wind, and moisture—over very short distances.

Mountains function as the Earth's water towers by attracting much of its precipitation—they are the predominant and most dependable source of fresh water for humankind. A diversity of wild plants makes mountain ecosystems vital sources of food and pharmacological benefits for humans.

A Naturally Vulnerable Resource

A distinguishing feature of mountains is vulnerability to disturbance, largely due to the vertical dimension (height and slope). Because a doubling in water speed magnifies the size of materials that water can transport, the erosive power of rapid runoff from mountains is immense. Unlike lowland environments, mountain ecosystems are typically less able to recuperate from disruptions such as soil erosion or loss of vegetation; soils are usually thin and poorly anchored, and gravity-powered erosion speeds silt and sediment movement. Also, many mountains are still growing and are less geographically stable than flatter landmasses. Seven of the world's 14 tropical "hotspots" for plants threatened by destruction have at least half their area in mountains, and 131 of the world's 247 bird habitats are in tropical mountains.

As studies seem to confirm the warming of Earth's environment, experts predict that such warming will proceed too fast for many ecosystems to adapt. Austrian researchers have found that nine plant species typical of the nival zone (above alpine grasslands) are migrating to higher altitudes at one meter per decade, but will have to move eight to ten meters per decade to keep up with the current rate of warming.

Impacts on Mountain Ecology

Mountains face threats from poor land use patterns, resource extraction, and mass tourism and recreation. Half of U.S. rangeland, most of it in the mountainous West, is now considered severely degraded, with its livestock-supporting ability reduced by 50 percent. The FAO reports that hill and mountain forests are more susceptible to ecological damage from excessive population densities than are lowland forests. Because their slopes permit gravity to increase the power of flowing waters, mountains attract most of the Earth's hydroelectric projects and irrigation reservoirs.

Of all the economic activities in the world's mountains, nothing rivals the destructive power of mining. Environmental impacts include habitat destruction, erosion, air pollution, acid drainage, and metal contamination of water bodies. The result is often denuded forests, eroded hillsides, and dammed or polluted rivers.


Many lowlanders feel that mountains are a refuge from modern life, but problems—environmental ones—are following them up the slopes. In slick ads and commercials, images of pristine mountain wilderness lure multitudes for respite and sport. In industrial countries mass tourism and recreation are fast becoming the largest threats to mountain environments.

Since 1945 visits to the ten most popular mountainous national parks in the United States have increased 12-fold. Infrastructure for leisure and recreation in the mountains can be exorbitant. In 1990 there were 100 Alpine golf courses; by the end of 1996, 500 existed. Thundering helicopters bring skiers to untracked slopes not only in the American Rockies but worldwide. The populations of many small ski towns, like Vail, Colorado, have more than doubled since 1980, causing new home construction and retail sales to grow at double or triple the national average. White-water rafters and mountain climbers prowl the slopes in numbers some consider dangerous. A generation ago conquering Mount Everest was considered an unimaginable feat; today, dozens of climbers reach the peak every month, leaving behind trash—even the bodies of climbers that die on the dangerous climb are sometimes left behind. The interference of trash and excess traffic has become a serious problem on the mountain.


Erosion is the process in which the materials of the Earth's crust are worn and carried away by wind, water, and other natural forces. The destruction of forests and native grasses has allowed water and wind greater opportunity to erode the soil. Changes in river flow and seepage from human technology have shifted the runoff patterns of water and the sediment load of rivers that, in turn, deposit into lakes and oceans. Erosion has become a problem in much of the world in areas that are overfarmed or where topsoil cannot be protected, such as on coasts, which are often overdeveloped.

Coastal Erosion

In Evaluation of Erosion Hazards, a study prepared for the Federal Emergency Management Agency in April 2000, the H. John Heinz III Center for Science, Economics, and the Environment, a nonprofit research organization, found that approximately 25 percent of structures within 500 feet of the U.S. coastline will suffer the effects of coastal erosion within 60 years. Especially hard hit will be areas along the Atlantic and Gulf of Mexico coasts, which are expected to suffer 60 percent of nationwide losses.

The nation's highest average erosion rates—up to six feet or more per year—occur along the Gulf of Mexico. The average erosion rate on the Atlantic coast is two to three feet per year. A major storm can erode 100 feet of coastline in a day. The Heinz Center estimates that roughly 10,000 structures are within the estimated ten-year erosion zone closest to the shore. This does not include structures in the densest areas of large coastal cities, such as New York, Chicago, Los Angeles, and Miami, which are heavily protected against erosion.

The powerful effects of erosion were dramatized by the predicament of the Cape Hatteras lighthouse in North Carolina. When it was constructed in 1870 the lighthouse was 1,500 feet from the shore. By 1987 the lighthouse stood only 160 feet from the sea and was in danger of collapsing. In 1999 the National Park Service, at a cost of $9.8 million, successfully moved the lighthouse back 2,900 feet.

Erosion of beaches on the East Coast is becoming a more serious problem as development inches closer to the ocean. The Army Corps of Engineers has been rebuilding eroded beaches since the 1950s. The federal government pays 65 percent of the cost of beach rebuilding, with states and local governments paying the remaining 35 percent. Many experts, however, believe that beach replenishment is a futile effort and that funds could be better spent elsewhere.

Soil Erosion and Agriculture

Agricultural lands are the principal source of eroded soil. According to the U.S. Department of Agriculture (USDA), approximately 20 percent of the nation's land is set aside for cropland. Three-quarters of this land is actively used to grow crops for harvesting. The remainder is used for pasture or is idled for various reasons. This would include cropland enrolled in the Federal Conservation Reserve Program (CRP). (See Figure 9.7.)

Demands on the Earth to feed growing populations and changes in the Earth's landscape caused by human activities have speeded up soil erosion. Soil erosion has increased to the point where it far exceeds the natural formation of new soil, and experts consider the problem to be of epidemic proportions. According to Excessive Erosion on Cropland, 1997 (2000) the USDA's Natural Resources Conservation Service found that 108 million acres were eroding excessively.


Agriculture depends primarily on the top six to eight inches of topsoil. Fields planted in rows, such as corn, are most susceptible to soil runoff. In 2002 corn comprised 22 percent of total acres used for crops in the United States. Cover crops, such as hay, provide more soil cover to hold the land. Hay crops accounted for 17 percent of total acres used for crops in 2002. (See Figure 8.3 in Chapter 8.)

Historically, when most of the topsoil was lost farmers would abandon the land. Now, however, farmers continue to plow the soil, even when it consists of as much subsoil as topsoil. It costs more money to produce food on such land than on land where topsoil is present. Farmers often use more fertilizer to make up for the decreasing productivity of the soil, and that, in turn, adds to environmental pollution.

The GAO estimates that about 28 percent of the nation's cropland is highly erodible. The states with the highest percentage of highly erodible cropland are New Mexico (90 percent), Arizona (81 percent), and Colorado (77 percent). In absolute terms Texas and Montana have the most erodible land. The amount of erosion has declined in past decades. The USDA attributes the decline to the CRP, which pays farmers to take land out of production for ten years, and to the Conservation Compliance Program. As part of the 1985 Farm Act (PL 99-198), the Conservation Compliance Program was initiated as a major policy tool. To be eligible for agricultural program benefits, farmers must meet minimum levels of conservation on highly erodible land.


Congress, under the 1996 Farm Bill (PL 104-127), authorized the Environmental Quality Incentives Program (EQIP) to address agriculture's natural resource and environmental problems. It is a flexible, voluntary, and effective conservation program that allocates millions of dollars each year to farmers' conservation efforts. EQIP was reauthorized in the Farm Security and Rural Investment Act of 2002 (Farm Bill).

Under EQIP the USDA provides assistance to family-sized farms and ranches for up to 75 percent of the cost of certain environmental protection practices, such as grassed waterways, filter strips, manure management facilities, capping abandoned wells, and wildlife habitat enhancement. The USDA may also offer incentive payments to encourage producers to apply such land management practices to the use of nutrients, manure, irrigation water, wildlife, and integrated pest management.


Human beings have survived in deserts or arid areas only because they have been able to increase the quantity of water available to meet their needs. An elaborate system of dams, reservoirs, irrigation pipelines, aqueducts, and canals allows residents of the American West, for example—especially California—to ignore the fact that they live in a naturally dry climate. That fact has made California's Central Valley the most productive agricultural region in the world on only 3 percent of U.S. farmland.

Constant irrigation, however, is not a miracle solution as once was thought. According to the United Nations Environment Program (UNEP), 90 percent of the land in Egypt, 68 percent in Pakistan, 50 percent in Iraq, 38 percent in Peru, 30 percent in the United States, and 20 percent each in India, Russia, and Australia is suffering salinization (saltiness) caused by irrigation. Sodium in the soil or irrigation water accumulates at the root level of soils or turns into a sterile, rock-hard crust. An estimated 5 million acres of irrigated land are pulled from production each year because of waterlogging and salinization, the result of poor land management. In addition, irrigated land is often paved over for housing, factories, and roads, especially in the United States and Asia, further reducing the productive use of land for agriculture.


Biological diversity, or biodiversity, refers to the full range of plant, animal, and microbial life and the ecosystems that house them. Environmentalists began using the term during the 1980s when biologists increasingly warned that human activities were causing a loss of plant and animal species.

Studies of deforestation have supported the concerns about declining biodiversity, showing that tropical rain forests have dwindled from 3.5 billion acres before the industrial era to fewer than two billion acres. Deforestation has meant extinction for hundreds of species of plants and animals each year. The exact number of species in the remote forests is unknown, although it is generally accepted that they house the greatest number of species on the planet.

Extinction Rates

No one knows how many species of plants and animals exist in the world. By the beginning of the twenty-first century scientists had named and documented 1.4 million species. Educated guesses of the total number of different species range from five million to 100 million. Just as the health of a nation is promoted by a diverse economy, so the health of the biosphere is promoted by a diverse ecology.

Widespread extinctions have occurred infrequently in Earth's history and are generally believed to have been due to major geological and astronomical events. Scientists call the disappearance of only a few species over the period of a million years a "background rate." When that background rate doubles for many different groups of plants and animals at the same time, a mass extinction is taking place.


At least five times in the last 600 million years planet-wide cataclysms, such as drastic climate change or colliding asteroids, have wiped out whole families of organisms. Because of these losses scientists believe that more than 95 percent of all species that have ever existed are extinct. Researchers predict that, as tropical ecosystems are converted to farms and pasture, the extinction rate will approach several hundred extinctions per day before the mid-twenty-first century—millions of times higher than the background rate. The Worldwatch Institute believes that more species of flora and fauna may disappear in our lifetime than were lost in the mass extinction that included the disappearance of the dinosaur 65 million years ago.

The loss of diversity leads to problems beyond the simple loss of animal and plant variety. When local populations of species are wiped out, the genetic diversity within that species that enables it to adapt to environmental change is diminished, resulting in a situation of "biotic impoverishment." Those organisms that do survive are likely to be hardy, "opportunistic" organisms tolerating a wide variety of conditions—characteristics often associated with pests. Experts suggest that, as some species dwindle, their places may be taken by a disproportionate number of pest or weed species that, while a natural part of life, will be less beneficial to human beings.

Most living species have never been identified. Mammals, including humans, make up barely three-tenths of 1 percent of all known organisms. There were 1,263 species in the United States listed as endangered or threatened as of April 2004. Another 558 species are listed for foreign countries. (See Table 9.1.) The number of endangered or threatened species listed in the Unites States has increased dramatically since 1980 when less than 300 species were listed.

Scientists participating in the "Global Biodiversity Strategy," an international team of 500 researchers, believe that the extinction of species will deprive future generations of new medicines and new strains of food crops. With as many as 50 plant species disappearing daily, the researchers calculate that the planet's diversity

GroupU.S.ForeignU.S.ForeignTotal species
Animal subtotal391516128391074
Flowering plants56911440714
Conifers and cycads20125
Ferns and allies2402026
Plant subtotal59711472747
Grand total988517275411821
source: "Summary of Listed Species—Species and Recovery Plans as of 4/1/2004," in Threatened and Endangered Species System (TESS)—Listed Species Summary (Boxscore), U.S. Department of the Interior, U.S. Fish and Wildlife Service, Washington, DC, April 12, 2004 [Online] =4/01/2004 [accessed April 12, 2004]

could be reduced by 10 percent by 2015. One-fourth of all medical prescriptions in the United States contain active ingredients from plants. Among the medically useful species are some used in the treatment of cancer, Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS), circulatory disorders, bacterial infections, anxiety, inflammatory diseases, and for the prevention of organ rejection in transplants.

Species Loss—Crisis or False Alarm?

As with most environmental questions, not all experts agree about the threat to species diversity. Some observers believe that extensive damage to species diversity has not been proven and claim that, while wild habitats are disappearing because of human expansion, the seriousness of the extinction has been exaggerated and is unsupported by scientific evidence. They point to the fact that the total number of species and their geographic distribution are unknown. How, they ask, can forecasts be made based on such sketchy data?

Other observers contend that extinctions, even mass ones, are inevitable and occur as a result of great geological and astronomical events that humans cannot affect. They do not believe that disruptions caused by human activity are enough to create the mega-extinction prophesied by people they consider "alarmists."

Furthermore, some critics of the environmental movement believe that the needs of humans are being made secondary to those of wildlife. They contend that the Endangered Species Act protects wildlife regardless of the economic cost to human beings. Sometimes, as in the case of the spotted owl of the Pacific Northwest forests, that cost is the loss of jobs for people. The owl's presence halted logging there—following protests by environmental groups—at considerable economic loss to communities and families in the area. Furthermore, critics contend that halting development because it threatens a species whose whole population occupies only a few acres and numbers only in the hundreds is simply nonsense.

According to a 1998 poll conducted for the American Museum of Natural History by Louis Harris and Associates, biologists overwhelmingly view the loss of biodiversity as a serious problem. According to the survey, most scientists agreed that, if trends continue, the loss of species will have a very negative effect on the Earth's ability to recover from both natural and human-made disasters.

Earth Summit Biodiversity Treaty

At the 1992 Earth Summit in Rio de Janeiro, 156 nations signed a pact to conserve species, habitats, and ecosystems. This Biodiversity Treaty is regarded as one of two main achievements of the United Nations Conference on Environment and Development, the other being a treaty on global warming. The Biodiversity Treaty makes nations responsible for any environmental harm in other countries produced by companies headquartered in their country.

One provision of the treaty concerns "biotechnology," a term referring to the ownership of genetic material. Plants, seeds, and germ plasm have historically been in the public domain (belonging to the general public), rather than belonging to any particular government. Therefore, anyone could exploit or use them without compensation to the country of origin. For example, the rosy or Madagascar periwinkle, a plant found only in the tropical rain forests of Madagascar, is used as a base for medication to treat Hodgkin's disease and childhood leukemia. Madagascar receives no compensation for use of the plant. The biotechnology treaty drafted in Rio called for compensation to be paid for the use of those genetic materials.

The United States did not sign the treaty at the time. The administration of George H. W. Bush, while agreeing with many provisions of the pact, believed the economic requirements for accomplishing those goals were unacceptable to American businesses because they would be forced to compensate for the use of these species. President Bill Clinton signed the treaty in 1994. However, as of April 2004 the treaty had not been ratified by the U.S. Senate.

Endangered Species Act

The 1973 Endangered Species Act (ESA), passed into law during the administration of President Richard Nixon, was originally intended to protect creatures like grizzly bears and whales with whose plight Americans found it easy to identify. In the words of its critics, however, it has become the "pit bull of environmental laws," policing the behavior of entire industries. In three decades the ESA has gone from being one of the least controversial laws passed by Congress, to one of the most contentious.

The ESA regulates industries that can cause fish and wildlife populations to decline. It also determines the criteria to decide which species are endangered. Since the act was first passed, the pendulum has periodically swung between increased protection and the need to soften the law's economic impact.

The U.S. Supreme Court, in Manuel Lujan, Jr., Secretary of the Interior v. Defenders of Wildlife et al. (504 US 55 1992), determined that groups and individuals cannot sue the government solely on behalf of the public interest or on behalf of the flora and fauna they seek to protect. Instead, they must demonstrate harm to themselves. The ruling has been generally regarded as a victory for business interests and a defeat for environmentalists in their efforts to protect endangered species, since immediate harm is often difficult to show in environmental issues.


The loss of habitats, the contamination of water and food supplies, poaching, and indiscriminate hunting and fishing have depleted the population of many species. Most scientists agree that prospects for the survival of many species of wildlife, and hence biodiversity, are worsening. The expansion of human development into wildlife habitats has resulted in some animals being squeezed into cities and suburbs where encounters between humans and wildlife have become increasingly common.

Species loss and habitat loss are related. Scientists have recognized for some 150 years the connection between the size of an area and the number of species it contains—as large tracts of land are lost, so are some species that make their homes there. Other major causes of animal extinction are hunting and invasive (nonnative) species.

Invasive Species

An invasive species is one that is not native to a particular ecosystem and whose presence there causes environmental or economic harm or harm to human health. This includes species purposely introduced (such as the plant saltcedar, which was brought to the United States to control erosion) and unintentionally introduced (such as zebra mussels, which are thought to have arrived in the ballast water of ships). Invasive species often have high reproductive rates and lack predators in their new environments. They can choke out or "out-compete" native species.

Many scientists consider invasive species to be one of the most serious issues threatening the environment. In response to this threat, the National Invasive Species Council was established by the U.S. government in 1997. The council includes members from a variety of agencies including the EPA, the USDA, and the U.S. Department of the Interior. In 2001 the council issued its management plan for dealing with the invasive species problem in Meeting the Invasive Species Challenge.

The report states that invasive plants infest approximately 100 million acres in the United States and cost around $137 billion annually for prevention and control. Zebra mussels, which are believed to have arrived in the ballast of ships in the Great Lakes, are one invasive species that has spread rapidly. By 1999 zebra mussel populations extended all the way to the Gulf Coast. The zebra mussel is considered so permanently entrenched that wholesale eradication would be virtually impossible. Instead, authorities are concentrating on limiting further spread of the pests, which clog water intake pipes.

In addition, authorities are increasingly concerned about the West Nile virus, an invasive pathogen that is thought to have originated in Africa. The virus was first detected in the United States in 1999 in New York. It infected animals and birds throughout the East and spread west quickly, carried by migratory birds. The virus can be transmitted to humans by mosquitoes that have bitten infected animals and birds. In 1999 there were 62 human cases reported to the Centers for Disease Control and Prevention (CDC), and 7 people died from the virus. The number of human cases and deaths grew steadily each following year. In 2003 there were 9,858 cases reported to the CDC and 262 deaths. Figure 9.8 shows the counties as of March 24, 2004 that have experienced positive test results for West Nile virus in humans.

Sharing the Planet

In the nineteenth century, miners took parakeets with them into the mines. If a bird died, they knew they were in danger from noxious gases. While more scientific and humane procedures now exist to determine how dangerous the situation is, some scientists believe that plants and animals may still serve as indicators of the safety of the world. When biologists discover toxic amounts of poisons in wildlife, they ask whether human beings are also ingesting these poisons.

Some observers believe that animals should be protected out of an intrinsic respect for life, aside from any market value or use to humans. Others contend that humankind must manage wildlife correctly because biodiversity makes good economic and survival sense. Still others believe that there is no species-loss "problem," that species loss is a natural part of evolution. All of these issues are being deliberated as the people of the world struggle to decide how best to live with the other animals and plants that populate the Earth.

A 1996 study by the Nature Conservancy on more than 20,000 American plant and animal species found that about one-third of species were rare or imperiled, a larger fraction than some scientists had expected. The study, the most comprehensive assessment to date of the state of American plants and animal species, found that mammals and birds were doing relatively well compared to other groups, but that a high proportion of flowering plants and freshwater marine species, like mussels, crayfish, and fish, were in trouble. Of the 20,481 species examined, about two-thirds were secure, 1.3 percent were extinct or possibly extinct, 6.5 percent were critically imperiled, 8.9 percent were imperiled, and 15 percent were considered vulnerable. The destruction or degradation of habitat was considered to be the main threat.

City Life Collides with Wilderness

The growth of urban areas has resulted in a collision between city life and wildlife. Increasingly, humans are encountering wild animals in their communities. The 600,000-acre Angeles National Park in the Los Angeles out-back of the San Gabriel Mountains has been the site of numerous attacks on visitors by snakes and wild animals. In addition humans are using some areas designed for wildlife for undesirable purposes; poachers and some hunters shoot deer out of season and prey on the endangered Nelson bighorn sheep. During Christmas season trees are cut down. Crowds of picnickers and hikers often swell to music-festival size and clog roads. Toxic-waste outlaws heave garbage and poisons into creeks and abandoned mine shafts. Criminals sell drugs in the forest and even have small marijuana plantations located there. The Angeles National Park has also become a well-known dumping ground for homicide victims—eight bodies were found in the forest in 1995.

Some Cases of Threatened Species

Almost daily the decline or threat to some plant or animal is reported. Scientists attribute the decline of salmon on the West Coast to spoiled habitat and disruption of river flow. Erosion of the coastline in Florida has left no place for sea turtles to dig their nests, and they are dying off.

Peregrine falcons, one of the first species to be listed on the Endangered Species List, were dying because they were consuming DDT in the food chain. Following their listing under the ESA, and the banning of DDT in 1972, the falcon population has rebounded. In 1999 they were officially removed from the Endangered Species List.

The ivory tusks of African elephants are very valuable as they can be fashioned into jewelry and artwork. In the mid-twentieth century African elephants were so extensively hunted for their ivory that their population dropped to dangerous levels. The international community responded in 1990 by banning trade in African elephant ivory under the Convention on the International Trade in Endangered Species. Poaching of elephants continued but their population began to rebound. By 1999 there were so many elephants in Zimbabwe, Namibia, and Botswana that those countries (unsuccessfully) requested permission to resume limited trade in ivory.

Dolphins tend to swim with schools of tuna in the Pacific Ocean and nets used by commercial fisheries to catch tuna also entrap dolphins. Since netting began in 1958 an estimated seven million dolphins have been killed. In 1972 Congress passed the Marine Mammal Protection Act (PL 92-522) to reduce the deaths of the dolphins. The law was amended in 1985 and 1988 to regulate tuna imported from other countries. Trade groups have challenged these regulations by pointing to the economic losses of companies and nations that abide by the law. Some companies ignore the law, while other companies have printed a "Dolphin Safe" label on their tuna products to show that they obey the law.

Environmentalists have long argued with government and industry over the question of logging in the Pacific Northwest forests. Environmentalists claim that the biological health of the ecosystem is in decline and more than 100 species of plants and animals are threatened with extinction, while the timber industry responds that the forest provides jobs for thousands of Americans and lumber for millions of people.

The argument came to a head in 1990 when the spotted owl—which lived only in this particular region—was added to the list of endangered species. Logging was halted and a succession of lawsuits was filed against the Forest Service and the Department of the Interior. In 1992 President Bush grudgingly restricted logging in that area but, at the same time, moved to amend the law to allow economic considerations to be taken into account. In 1994 President Clinton worked out what was claimed to be a compromise between environmentalists and business interests, allowing logging to resume with restrictions on the size, number, and distribution of trees to be cut.

Scientists investigating a worldwide decline in frogs and other amphibians have found evidence identifying a number of factors that have contributed to the decline: ultraviolet radiation caused by the thinning of the ozone layer, chemical pollution, and a human taste for frog meat. These species are considered indicator species because their sensitivity makes them early indicators of environmental damage. Butterflies, another creature considered an indicator species, are also disappearing in many areas.

Roads and Wildlife

Almost four million miles of public roads cross the 48 contiguous states. As roadways reach further and further into undeveloped areas, encounters with wildlife are inevitable. In Critter Crossing: Linking Habitats and Reducing Roadkill (2000) the U.S. Department of Transportation reported that roads impact wildlife in several ways:

  • Roadkill—Vehicles traveling U.S. roads kill millions of birds, mammals, reptiles, and amphibians every year. The ocelot, an already endangered cat, is in further jeopardy due to highway kills. In addition humans are sometimes killed or injured in animal-vehicle collisions. The insurance industry estimates the cost of these fatalities and injuries is about $200 million; motorists pay at least $2,000 in vehicle repair when they hit a large animal.
  • Habitat loss—When humans build highways and develop areas, they destroy habitat. This forces animals into smaller and smaller areas and into areas inhabited by humans. Some species cannot migrate, and therefore die; others are forced to compete for fewer resources to live and breed.
  • Habitat fragmentation—When roads cut through wild areas, they divide wildlife populations into smaller, more isolated, and less stable groups. These animals become more vulnerable to predators and are given to inbreeding with its resulting genetic defects.

Under the 1998 Transportation Equity Act for the Twenty-First Century (PL 105-178), the Federal Highway Administration can provide wildlife crossings—"habitat connectivity measures"—for new and existing roads. Among the strategies used to counteract habitat loss and roadkill are overpasses and underpasses, tunnels, and culverts.

Deep-Sea Harvesting

Worldwide, after centuries of steady growth, the total catch of wild fish peaked in the early 1990s and has declined ever since. In State of World Fisheries and Aquaculture, 2002, the FAO reported that approximately 47 percent of all commercial fish stocks have been fully exploited. A further 18 percent of stocks were reported to be overexploited.

A result of the declining catches of fish in shallow fisheries is the recent scouring of the deep seas for other varieties of fish such as the nine-inch-long royal red shrimp, rattails, skates, squid, red crabs, orange roughy, oreos, hoki, blue ling, southern blue whiting, and spiny dogfish. Although limited commercial fishing of the deep has been practiced for decades, new sciences and technologies are making it more practical and efficient. As stocks of better-known fish shrink and international quotas tighten, experts say the deep ocean waters will increasingly be targeted as a source of seafood. Scientists worry that the rush for deep-sea food will upset the ecology of the ocean.

A Blue Revolution?

The decline in the availability of fish has produced the growth of aquaculture, or farmed fish. Worldwide, one in every five fish eaten is raised on a farm, a share that is expected to rise in the years ahead. Aquaculture is one of the fastest growing sectors in world food production.

As a source of animal protein, farmed fish are an economical alternative to beef or pork and are on par with chicken. While 4 kilograms of grain are required to produce each kilogram of pork and 7 for each kilogram of beef, only 2 kilograms of grain are needed for a kilogram of chicken or fish. In addition only 40 percent of the weight of sheep is eaten and 50 percent of pigs and chicken, while 65 percent of finfish (as opposed to shellfish) is actually consumed. (Because fish are supported by water they have little bone structure; therefore, more of their weight is edible.) Fish are also low in fat and cholesterol, an advantage over other meats.

Contamination of Fish

Noncommercially caught fish and wildlife are sometimes contaminated with chemicals, such as mercury, polychlorinated biphenyls (PCBs), and DDT. In order to protect consumers from health risks associated with consuming such pollutants, the EPA and the states issue consumption advisories to inform the public that high concentrations of contaminants have been found in local specimens. In May 2003 the EPA published its annual publication Update: National Listing of Fish and Wildlife Advisories. During 2002 there were 2,800 fish consumption advisories in effect around the country. (See Figure 6.11 in Chapter 6.)


Materials extracted from the Earth are needed to provide humans with food, clothing, and housing and to continually upgrade the standard of living. Some of the materials needed are renewable resources, such as agricultural and forestry products, while others are nonrenewable, such as minerals.

The USGS reported in Materials Flow and Sustainability (1998) that a significant trend is the decreasing use of renewable resources and the increasing demand for nonrenewable resources. Since 1900 the use of construction materials such as stone, sand, and gravel, has soared.

The large-scale exploitation of minerals began in earnest with the Industrial Revolution around 1760 in England and has grown rapidly ever since. In a world economy based on fossil fuels, minerals and oil are valuable. The value increases in proportion to demand—which is increasing—and supply—which is decreasing. The result is that the search for minerals and fuel sources has become very aggressive and may be detrimental to the environment.

Mining has always been a dirty industry. As early as 1550, German mineralogist and scholar Georgius Agricola wrote: "The fields are devastated by mining operations … the woods and groves cut down … then are exterminated the beasts and birds.… Further, when the ores are washed, the water that has been used poisons the streams, and either destroys the fish or drives them away."

Centuries later mining still pollutes the environment, only on a larger scale. The Clean Air Act (PL 101-576), the Clean Water Act (PL 92-500), and the Resource Conservation and Recovery Act of 1976 (PL 94-580) regulate certain aspects of mining but, in general, the states are primarily responsible for regulation, which varies widely from state to state.

Gold Mining

An extraction process in which cyanide is used for the retrieval of gold from tailings or residues left over from other mining operations has become quite controversial. A series of mishaps around the world have left some communities with polluted lakes, rivers, and streams. A major disaster occurred in Romania on January 30, 2000, when an overflow of polluted mud and wastewater from the Aurul Gold smelter dam sent 100,000 cubic meters of cyanide-tainted wastewater into the adjacent Lapus and Somes Rivers. The cyanide was subsequently carried downstream to the Danube River in Yugoslavia. The spill contaminated drinking water for 2.5 million people and killed more than 100 tons of fish.

Oil in the Arctic

The search for oil has led to the exploration of the Alaskan wilderness. Since the oil supply from the existing North Slope Reserve will steadily decline and then eventually disappear, exploratory oil drillers are focusing their attention on the National Petroleum Reserve in Alaska (NPRA) in the Arctic wilderness. The NPRA is a 23-million-acre area in northwestern Alaska. (See Figure 9.9.) Geologists consider northern Alaska to be the last, great untapped oil field in North America. Environmental experts fear that oil and gas development will seriously harm the area.

In 2002 the USGS assessed the NPRA and found a significantly greater supply of petroleum (5.9 to 13.2 billion barrels) than previously estimated. Only up to 5.6 billion barrels of this petroleum are technically and economically recoverable at existing market prices. The USGS suspects that there may be as much as 83.2 trillion cubic feet of undiscovered natural gas in the same area. Transportation of this gas to markets would require a new pipeline. There is already a pipeline system in place for oil—the Trans-Alaska Pipeline System (TAPS), which lies between the NPRA and the Arctic National Wildlife Refuge (ANWR) as shown in Figure 9.9. The ANWR is a 19-million-acre area of pristine wilderness along the Alaska-Canada border. It, too, is being considered for oil exploration, a move strongly opposed by environmentalists.

The future of the refuge lies in the hands of the federal government. The administration of George H. W. Bush made drilling there a major foundation of the national energy policy. Under the Clinton administration oil and mineral development was prohibited within the wildlife refuge. In April 2002, following heated debate, the U.S. Senate killed a proposal by the administration of George W. Bush to let oil companies drill in ANWR. Republicans raised the issue again in the fall of 2003, citing the need for the nation to reduce its dependence on oil imported from the Middle East. As of April 2004 the U.S. Congress has not yet approved drilling in ANWR.

Antarctic Resources—Regulate or Prohibit?


Dispute is ongoing over another polar area—Antarctica—as the southern polar region attracts new interest as a source of petroleum and minerals. Antarctica covers an area of 5.4 million miles—one-tenth of the Earth's land surface—and is larger than the United States and Mexico combined. Geologists believe that considerable quantities of mineral deposits probably exist there, as in all large landmasses. Based on the geology of the region, geologists believe they can find base metal (copper, lead, and zinc) and precious metal (gold and silver) deposits. There are already some known mineral deposits in Antarctica. The huge mass of ice would make recovery difficult, especially in some areas and seasons.


In 1959, 12 countries (Argentina, Australia, Norway, South Africa, Chile, the United Kingdom, Sweden, France, New Zealand, Belgium, Japan, and the United States) agreed to preserve the region south of 60 degrees south latitude, which includes Antarctica, as an area for scientific research and as a zone of peace. They concluded the Antarctic Treaty, giving equal participation in governance to the signing countries "in the interests of all mankind." The treaty established provisions for new member nations; 39 countries representing more than three-fourths of the world's population are party to the treaty.

Seven nations claim territorial sovereignty in Antarctica—Argentina, Australia, Chile, France, Great Britain, New Zealand, and Norway. A 1991 agreement prohibits all mining exploration and development for 50 years, protects wildlife, regulates waste disposal and marine pollution, and provides for increased scientific study of the continent.

Environmentalists want to ban all mining in Antarctica indefinitely. Critics of mining believe the ultimate solution to the problem of mining's destruction of the environment lies in changes in mineral use and a shift from fossil fuels to renewable energy sources. These changes, however, would represent huge transformations in the way people live. Whether these changes are justified, and whether many people are prepared to make them, will be a matter of debate for years to come.


The indebtedness and poverty of many developing countries reduce opportunities for conservation. Local, national, and international efforts must be linked to deal effectively with the underlying pressures on the ecosystems that support biological diversity. Some international efforts include "debt-for-nature" programs and ecotourism (travel oriented around natural sites, native species, and traditional cultural practices).

Since the 1980s a number of debt forgiveness programs have involved debt-for-nature swaps, where governments or conservation groups buy back, or forgive, a portion of a country's debt, usually at a discounted market price, in exchange for the commitment to fund conservation programs.

Another approach to stemming biodiversity-depleting exploitation is to support alternative, less harmful ways for people to earn their livelihoods. Ecotourism is one alternative economic activity that can use nature, if done carefully, with minimal harm. Ecotourism has spurred communities to protect rare ecological sites and has been modestly successful at generating currency for developing countries.


Every year the Gallup Organization conducts a comprehensive poll of Americans on environmental issues. The latest poll was conducted in March 2004. Poll participants were asked to express their level of

Great deal %Fair amount %Only a little %Not at all %No opinion %
2004 Mar 8–11352623151
2003 Mar 3–539292111*
2002 Mar 4–7382721122
2001 Mar 5–744321581
2000 Apr 3–951251491
1999 Apr 13–1449301461
1991 Apr 11–14422521102
1990 Apr 5–8402419143
1989 May 4–7422518123
source: "Please tell me if you personally worry about this problem a great deal, a fair amount, only a little, or not at all. The loss of tropical rain forests?," in Poll Topics and Trends: Environment, The Gallup Organization, Princeton, NJ, March 17, 2004 [Online] [accessed March 30, 2004]

concern about two issues related to natural resources: loss of tropical rain forests and extinction of plant and animal species.

As shown in Table 9.2 only 35 percent of the respondents expressed a great deal of concern about the loss of tropical rain forests. This value is down from a high of 51 percent recorded in 2000. Concern about this issue has varied over the years, but made a noticeable drop in priority over the last three years. In 2002 just over a quarter of those asked (26 percent) expressed a fair amount of concern about the loss of tropical rain forests, while 23 percent felt a little concern, and 15 percent expressed no concern at all.

Poll participants were slightly more worried about the extinction of plant and animal species. (See Table 9.3.) In 2004 more than a third (36 percent) indicated they felt a great deal of worry about this issue, while 26 percent expressed a fair amount of worry, and 23 percent felt a little concerned. Only 15 percent of those asked expressed no worry at all. In 2000 the percentage of people expressing a great deal of concern about this issue was 45 percent.

In 2004 Gallup pollsters also asked people to express their approval or disapproval over opening up the Arctic National Wildlife Refuge in Alaska for oil exploration. As shown in Figure 9.10 a majority (55 percent) of people are opposed to the idea, while 41 percent support it. These values are very similar to the results obtained in Gallup polls conducted during 2001 and 2002.

Great deal %Fair amount %Only a little %Not at all %No opinion %
2004 Mar 8-1136262315*
2003 Mar 3-5343221121
2002 Mar 4-7353022121
2001 Mar 5-743301971
2000 Apr 3-94533148*
source: "Please tell me if you personally worry about this problem a great deal, a fair amount, only a little, or not at all. Extinction of plant and animal species?," in Poll Topics and Trends: Environment, The Gallup Organization, Princeton, NJ, March 17, 2004 [Online] [accessed March 30, 2004]