Environmental Encyclopedia

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Environmental Encyclopedia 3

Precycling

A prairie dog. (U.S. Fish and Wildlife Service. Repro-

duced by permission.)

More than 200 other

wildlife

species are associated

with prairie dog colonies, resulting in the increased biological

diversity seen in prairie lands with colonies. Some of these

animals are prairie dog predators, such as hawks, eagles,

snakes, and coyotes, while others use the colonies as their

habitat

. The reduction and/or spread of certain insects and

plants is also dependent on prairie dogs.

However, prairie dog populations have been greatly

reduced, in some cases to one to two percent of their histori-

cal numbers. This decrease in prairie dog populations was,

and continues to be, due to

poisoning

hunting

, and exter-

mination campaigns by some ranchers who believe that prai-

rie dogs compete for livestock forage. Long-term

overgraz-

ing

by livestock has resulted in loss of grasses that prairie

dogs depend on, as well as in

erosion

and destruction of

prairie dog habitat. Additional habitat losses are due to

development of lands for human housing and other uses.

Prairie dogs are also susceptible to diseases, including the

plague

, which can wipe out entire colonies.

The

IUCN—The World Conservation Union

lists the

black-tailed and Utah prairie dogs at low risk and the Mexi-

can prairie dog is already endangered. Environmental and

citizen’s groups are beginning to act to preserve prairie dog

1127

habitats throughout the western grassland areas that serve

as their home lands.

[Judith L. Sims]

ESOURCES

OOKS

Graves, Russell A. The Prairie Dog: Sentinel of the Plains. Lubbock: Texas

Tech University Press, 2001.

Hoogland, John L. The Black-Tailed Prairie Dog: Social Life of a Burrowing

Mammal (Wildlife Behavior and Ecology). Chicago: University of Chicago

Press, 1995.

Long, Kim. Prairie Dogs: A Wildlife Handbook. Boulder: Johnson Books,

2002.

Patent, Dorothy Hinshaw, and William Munoz. Prairie Dogs. Boston:

Houghton Mifflin Company, 1999.

Precision

Precision refers to the ability to repeat the same measurement

and arrive at the same value. In

statistics

, precision refers

to the difference between repeated measurements of the

same quantity, where the closer the measurements are to

each other; the greater the precision of the estimate of the

quantity. Precise measurements are not necessarily accurate

measurements, because the repeated measurements can be

very close to the same value and still be far from correct. As

an example, if the differences in ten measurements of the

same distance are very close to each other, the distance-

measuring device is considered to be precise. However, there

is no surety that the distance measured is correct unless the

device is also accurate.

[Marie H. Bundy]

Precycling

Precycling is source reduction and

reuse

. In most

waste

management

planning the hierarchy is Reduce, Reuse, and

Recycle. Reduction and reuse are the first lines of defense

against increasing waste volume. Precycling are those actions

that can be taken before

recycling

becomes an option. It is

the decision on the part of a consumer to not purchase an

unnecessary product or the decision to purchase a reusable

as opposed to a disposable item. Precycling is using the china

plates in the cupboard for a party instead of purchasing paper

or plastic plates. It is also the decision to buy in bulk or to

buy refillable containers and then purchasing the product in

a bulk container that can refill a dispenser. Precycling is

thinking ahead to the ultimate destination of the containers

and packaging of products are bought and making the deci-

sion to reduce those that might end up in a

landfill

.In

addition to individual decisions to reduce waste before it

Environmental Encyclopedia 3

Predator control

happens there is the decision on the part of industry to reuse

chemicals

and to buy from parts suppliers that take back

packaging and reuse it. Precycling is stopping waste before

it happens. See also Green packaging; Green products;

Solid waste

Predator control

Predator control is a

wildlife management

policy specifi-

cally aimed at reducing populations of predatory

species

either to protect livestock or boost populations of game

animals. Coyotes, bobcats, grey and red

wolves

, bears, and

mountain lions have been the most frequent targets. Histori-

cally, efforts were centered in government-run programs to

hunt, trap, or poison predators, while bounties offered for

particular predatory species encouraged private citizens to

do the same. Over time, however, it has become apparent

that predator control is disruptive of ecosystems and often

inefficient.

Predator control is based on a lack of understanding

of the complex interactive mechanisms by which natural

environments sustain themselves. Control efforts take the

position that prey populations benefit when predators are

removed. In the long term, however, removing predators is

generally bad for the prey species and their ecosystems. The

conservationist

Aldo Leopold

, noticing the devastating ef-

fects of

overgrazing

by deer, realized as early as the 1920s

that shooting wolves, although it led to an immediate in-

crease in the deer population, ultimately posed a threat to

the deer themselves as well as other

fauna

and

flora

their

environment

. Another example can be found in the

undesirable consequences of killing significant numbers of

coyotes. Immediate benefits rebound not only to livestock

but also to populations of rabbits and other rodents, which

are normally controlled by predation. Since rabbits compete

with livestock for the same rangeland, an explosion in the

rabbit population simply means that the land can sustain

fewer livestock animals.

In 1940, the

U.S. Department of the Interior

initiated

a large-scale program against livestock predators, particularly

aiming at the

coyote

and relying heavily on poisons. The

poison most widely used in bait was sodium fluoroacetate,

also called “compound 1080,” which is highly persistent and

wreaks havoc on many animals besides the coyote, including

threatened and

endangered species

. Moreover, when a

poisoned coyote dies, the carrion enters the

food chain/

web

, with lethal effects primarily on scavengers. Eagles,

including the rare

bald eagle

, are particularly hard-hit by

efforts to poison coyotes.

Rising environmental awareness has caused continuing

controversy over predator control. By 1972, the government-

1128

appointed Committee on Predator Control concluded that

the use of poisons had unacceptably harmful consequences.

Government agencies discontinued the use of poisons, and

poison was banned on public lands. Nevertheless, private

citizens, mostly ranchers and hunters who feel that their

interests have been sorely overlooked, have continued using

poisons with little regard for the law. In the 1980s the

government started taking a less progressive stance, and in

1985 the Reagan administration reinstituted the use of com-

pound 1080 in “livestock collars.” While nonpredatory spe-

cies will not fall victim immediately, the poison still enters

the food chain with every coyote killed.

In spite of aggressive methods, the fight against coy-

otes has mostly been unsuccessful. Even after decades of

predator control, total annual losses are given in the hundreds

of thousands of animals (mostly sheep and goats) by ranchers

who claim they lose as much as 25 percent of their lambs

to predators each year. Conservationists and supporters of

wildlife

say these numbers are inflated, but, even if they are

accurate, the cost of lost livestock is significantly lower than

the cost of the government’s predator control programs.

Conservation

groups argue that it would be much cheaper

to give up on predator control and reimburse ranchers for

livestock lost to predation.

Besides killing predators, ranchers also have a number

of other options when it comes to protecting their livestock.

Sheep can be protected by letting it graze together with

cattle or other animals too big for coyotes to handle. Llamas

and donkeys have also been suggested for the purpose.

Trained guard dogs are an effective deterrent to coyotes

as well.

Although predator control can clearly have devastating

consequences, it is by no means a thing of the past. Recently,

Alaska began implementing a program to shoot 1000 wolves

(out of a total population of 7000 wolves in the state). The

program, which is to remove the wolves from a vast, centrally

located stretch of

wilderness

over a period of five years,

will have government agents tracking and shooting packs of

wolves from the air. Private citizens are also allowed to shoot

wolves. The object is to boost moose and caribou herds for

hunting

and tourist purposes. The view that the value of

animal resources lies primarily in their usefulness to human

beings still motivates many government policies and individ-

ual behaviors.

[David A. Duffus and Marijke Rijsberman]

ESOURCES

OOKS

Dasmann, R. Environmental Conservation. New York: Wiley, 1984.

Gilbert, F. F., and D. G. Dodds. The Philosophy and Practice of Wildlife

Management. Malabar, FL: R. E. Kreiger, 1987.

Environmental Encyclopedia 3

Prescribed burning

Rolston III, H. Philosophy Gone Wild. Buffalo, NY: Prometheus Books,

1989.

Wilson, E. O. Biophilia. Cambridge: Harvard University Press, 1984.

Predator-prey interactions

The relationship between predators and their prey within

ecosystem

is often a quite complex array of offenses

and defenses. Predation is the consumption of one living

organism by another. Predators must have ways of finding,

catching, and eating their prey (the offensive strategies), and

prey organisms must have ways of avoiding or discouraging

this activity (the defensive strategies). Predator-prey interac-

tions are often simply thought of as one animal, a carnivore,

catching and eating another animal, another carnivore or an

herbivore. The interrelationships of predators and their prey

is much more involved than this and encompasses all levels

within an ecological

food chain/web

, from plant-herbivore

systems to herbivore-carnivore systems to three-way interac-

tions of interdependent plant-herbivore-carnivore systems.

Even though a plant may not be killed outright, remov-

ing leaves, stems, roots, bark, or the sap from plants will

reduce its fitness and ultimately its ability to survive. The

younger, more tender leaves and stems of a plant are typically

consumed by herbivores. Because these are sites of active

growth, the plants send stores of nutrients from roots and

other tissues to these developing regions. When they are

eaten the plant is losing a disproportionate amount of nutri-

ents that will be difficult to replenish. Severe

defoliation

results in a tremendous loss of vigor and the loss of the

ability to photosynthesize and store energy reserves for the

dormant season. Without this energy store available, the

plants are more vulnerable to insect or disease attack the

following year.

Plants have responded to herbivory in a variety of ways.

Some plants have developed spines or thorns, whereas others

have developed the ability to produce chemical products

which deter herbivory by making the plant unpalatable,

barely digestible, or toxic. Many herbivores have found ways

to circumvent these defenses, however. Some insects are able

to absorb or metabolically detoxify these

chemicals

from

the plants. Other insects have learned to cut trenches in the

leaves of plants before they eat them, which stops the flow

of these chemical substances to the leaves. Other animals

have developed digestive modifications, such as bacterial

communities that break down cellulose, to enable them to

ingest less nutritious, but more abundant, vegetation.

A classic example of predator-prey interactions in car-

nivores is the relationship of the lynx, snowshoe hare, and

woody browse of northern coniferous forests. The hare feeds

on buds and twigs of conifer, aspen, alder, and willow trees.

Excessive browsing, as the hare population increases, de-

1129

creases the subsequent year’s growth, initiating a decline in

the hare population. The lynx population follows that of the

snowshoe hare, having greater reproductive success when

more prey are available, then declining as hare populations

drop. This relationship is cyclical and follows its course over

a ten-year period.

The prey of carnivores, both herbivores and other car-

nivores, have developed a variety of defensive mechanisms

to avoid being detected, caught, or eaten. Some employ

chemicals, such as odorous secretions, stored toxic substances

ingested from plants, or synthesized venom or poisons.

Other animals have taken to hiding from predators through

cryptic coloration, patterns, shapes, and postures. Mimicry,

widespread in the animal kingdom, is a system whereby one

animal, a palatable

species

, mimics an inedible species, and

is thus avoided by the predator. Additional means of predator

avoidance or discouragement involves the employment of

armor coats or shells, the use of quills or spines, or living

in groups. However, predators can benefit prey populations

by removing sick or inferior individuals. Subtle, long-term

interactions, in fact, can benefit both predator and prey as

they co-evolve together into more highly adapted or finely-

tuned forms. See also Evolution; Population biology

[Eugene C. Beckham]

ESOURCES

OOKS

Predators and Predation: The Struggle for Life in the Animal World. New

York: Facts on File, 1989.

Predator-Prey Relationships: Perspectives and Approaches From the Study of

Lower Vertebrates. Chicago: University of Chicago Press, 1986.

Taylor, R. J. Predation. New York: Chapman and Hall, 1984.

van Lawick, H. Among Predators and Prey. San Francisco: Sierra Club

Books, 1986.

ERIODICALS

Sunquist, F. “The Strange, Dangerous World of Folivory.” International

Wildlife 21 (1991): 4–11.

Prescribed burning

Intentional burning, usually in forests, prairies, and savannas,

in order to maintain desired ecological conditions or prevent

major wildfires that could result from accumulated dry,

woody debris. Prescribed burning, also called controlled

burning, has become a widely recognized component of

modern

ecosystem management

in recent decades as ecol-

ogists and managers have recognized the role of fire in natural

ecosystems. In practice, though, prescribed burning is still

used only on a small portion of public and private lands. In

a forest, prescribed burning is usually aimed at removing

accumulated fuel—fallen branches, pine needles, and other

Environmental Encyclopedia 3

Prescribed burning

dry debris. In a

prairie

savanna environment

, pre-

scribed burns may be used to prevent encroachment of trees,

to reduce populations of nonnative grassland

species

, and

to enhance the health of native grassland vegetation that is

adapted to periodic fires.

The principle of prescribed burning is that fire is a

normal component of ecosystems, and that frequent small

fires can serve both to maintain species diversity and to

prevent large, catastrophic wildfires. Under natural condi-

tions wildfires, usually ignited by lightning, occur frequently

in many forest and grassland biomes. Proponents of pre-

scribed burning argue that these natural fires would usually

be small and cool, occurring too frequently to allow excessive

accumulation of fallen branches, dead grass, and other fuel.

Frequent, low-intensity fires should do little damage either

to mature trees or to the root systems of most plants. At

the same time, by clearing away debris every few years, and

by a natural fire regime should provide fresh ground, exposed

to sunlight and freshly fertilized by ashes, to encourage new

germination and plant growth.

Deliberate burning is also an age-old method of main-

taining grazing lands in many parts of the world. Periodic

forest burning to maintain pasturage and to clear farm plots

has probably been practiced for millennia in Africa and South

America. In North America,

indigenous peoples

used fire

to maintain open forests and prairies that provide grazing

for game animals such as deer and

bison

. In some areas,

especially New England and the rural South, early European

immigrants to the New World adopted Indian methods of

burning. These practices differ from what is usually consid-

ered a prescribed burn, however, because they are often

carried out without the planning and the careful fire control

usually exercised in a controlled or prescribed burn. In most

of North America, traditional burning practices have also

disappeared as more and more forests have come under

professional management for timber production.

The introduction of prescribed burning to professional

land management strategies in the United States is often

attributed to

Aldo Leopold

, who pointed out in 1924, while

he was serving as a forester and firefighter in Arizona, that

fire control programs were producing brush-choked forests

susceptible to extreme

wildfire

. Leopold argued that decades

of fire suppression had actually increased the

probability

of severe fires, and that forests were healthier when subject

to regular, natural fires. Since Leopold began arguing for

prescribed burning in the 1920s,

ecosystem

managers have

widely recognized the ecological benefits of fire. The amount

of prescribed burning carried out still remains modest, how-

ever. Between 1983–1994, prescribed burns were carried out

on only about 0.1% of public lands in the United States

each year, as compared to 0.3% burned annually by wildfires

in the same interval.

1130

Proponents of prescribed burning sometimes argue fire

suppression techniques--bulldozed fire breaks, tree felling,

air drops of chemical fire retardants, and other measures--

cause more damage than the fires they are meant to control.

In addition, these expensive, and dangerous, tactics may

ultimately have little effect. Prescribed burn proponents ar-

gue that most large natural fires die out as a result of rainfall,

cooler weather, or a lack of fuel, not because of the efforts

of fire fighters. These opponents of standard military-style

fire suppression programs propose that it would be more

effective to use fire control budgets for planned burns than

for impressive but useless shows of force against large forest

fires. However events such as the

Yellowstone National

Park

fires of 1988, a series of highly publicized fires that

led to loud criticism from the media and politicians that

Park officials were negligent in their duties to protect the

park, demonstrate that the public is unlikely to settle for

inactivity during a forest fire. During fires such as those in

Yellowstone, the public is quick to criticize officials for doing

nothing even if there is nothing to be done. Most of us

would rather see a campaign to fight fires even if wastes

money and causes serious damage to the forest.

Benefits of Prescribed Fires

Fire has many ecological benefits. By clearing patches

of forest, fire allows tree seeds to germinate. The seedlings

of many trees, including Douglas fir (Pseudotsuga menziesii)

and white pine (Pinus strobus), both prized for timber, require

the strong sunlight of an open patch in the forest to begin

growing. Other species, such as jack pine (Pinus banksiana)

require intense heat, such as that produced by a fire or

extremely hot sun, to release the seeds from their resin-sealed

cones. These trees are considered fire-adapted, because they

reproduce best, or only, when seedlings can grow in the full

sun and fresh ashes of recently burned patches of forest.

Many prairie grasses and flowers are also fire adapted, thriv-

ing best when periodic fires remove dead stem litter and

release stored nutrients to the

soil

Fire plays an important role in cleaning out damaged

or diseased regions of a forest. Where

parasites

, fungus,

or disease have damaged stands of trees, a fire can locally

eliminate the

pest

population, reducing the risk of parasite

or disease spread, at the same time as it removes standing

dead trees and makes room for new seedlings to replace the

damaged trees. Land managers in southern Alaska, faced

with the worst spruce beetle outbreak ever in the United

States, have recently begun to consider using prescribed fire

to control beetles.

Undesirable species encroaching on

grasslands

and

savannas can also be controlled with fire. Opportunistic trees

and brush such as aspen, buckthorn, juniper and sumac,

introduced European grasses, as well as nuisance species

such as poison oak and poison ivy can all be set back by

Environmental Encyclopedia 3

Prescribed burning

periodic burning. At the same time, prescribed burns can

rejuvenate fire-adapted plant populations by clearing debris

and releasing nutrients to the soil. In a burned area increased

sunlight can extend the growing season, an important advan-

tage in cold climates. In addition, periodic patchy burns

help maintain

habitat

diversity by producing a mosaic of

landscape types and different-aged tree stands. Because many

animal species utilize a variety of environments for feeding

and nesting, a mosaic landscape maintained by fire can bene-

fit

wildlife

populations.

Methods

A prescribed burn is a fire set under conditions that

should allow control of the fire. Usually this means identi-

fying the limits of an area that should be burned and creating

or identifying fire breaks that will prevent the uncontrolled

spread of the fire once it has been lit. Often a backfire is

used. A backfire is line of fire burned on the downwind

edge of the area to be burned. The backfire is kept low and

forced to burn upwind until it has created a swath of land

clear of any combustible fuel. Flank fires, similarly, clear

combustible materials from strips along the flanks of the

burn area. The main fire, moving forward in a downwind

direction, will die out due to a lack of fuel when it reaches

the blacked zone created by the backfire. In addition to these

precautions, prescribed burning usually requires selecting a

day with high humidity and light winds, to keep the fire

relatively low.

Ideally areas should be burned periodically in order to

mimic the pattern of natural fires. Fire ecologists and manag-

ers usually attempt to burn areas with the frequency they

estimate would occur in local ecosystems under natural con-

ditions. In some areas natural fire frequency might be as

often as every 2-3 years; elsewhere natural fires might nor-

mally occur as infrequently as every 10-20 years. Or managers

may simply burn any areas in which debris has accumulated

to dangerous levels.

Prescribed Natural Fires

Sometimes a prescribed burn policy means establishing

a rule to let naturally ignited fires, usually started by light-

ning, burn themselves out. When rules establish that fires

should be allowed to burn, fires that occur are referred to

as prescribed natural fires. “Let-burn” policies are widely

applied in national parks and forests in the United States.

Seventy-five percent of

Yosemite National Park

, for exam-

ple, is treated as a prescribed natural fire zone. In large part

this is because it is more politically palatable to allow

nature

to take its course than it is to deliberately burn a park. In

addition, it is less costly to let fires burn naturally than to

maintain a burn crew, design burn plans and fire breaks,

and carry out and monitor a regular program of prescribed

burns. Usually a prescribed natural fire policy sets limits on

the conditions and size of fires that will be allowed to burn,

1131

and any natural fires that do occur are closely monitored to

ensure that they do not become too large or dangerous.

History of Prescribed Burning in the United States

Two factors influenced the development of prescribed

burning in the United States. One was the observation that

despite decades of fire suppression, the number and intensity

of wildfires has actually increased since the advent of major

fire suppression programs. One United States

Forest Service

study showed that total acreage burned, after declining from

1917 to 1955, increased steadily from the 1960s to the 1990s.

The other factor was a transition in ecological theory toward

understanding ecosystems as complex and dynamic, not

static structures that should be maintained a single, undis-

turbed, optimal climax state. The shift in ecological theory

developed partly from the observation that ecosystems main-

tained rigorously by managers were not necessarily healthier,

than those that underwent periodic catastrophic events such

as floods and fires. In fact, according to this theory, ecosys-

tems may require periodic change and disruption in order

to remain healthy.

The Nature Conservancy

, which maintains scattered

patches of native prairie, savanna, and other ecosystems, was

one of the pioneers of prescribed burning. Since it conducted

its first prescribed burn on a North Dakota prairie in the

1970s, the Nature Conservancy has expanded its prescribed

burning program to a current level of over 40,000 acres

(16,400 ha) of native habitat each year. The organization’s

objectives are controlling invasive plant species and main-

taining the vigor of native fire-adapted plant communities.

Controversy over Prescribed Burns

Prescribed burning is controversial for several reasons.

First, decades of education about fire suppression, both in the

general public and among land management professionals,

makes burning seem intuitively wrong to many people. Cul-

tural icons such as Smokey Bear and Bambi, both fictional

characters who suffered from forest fires, have symbolized

the trauma and destruction of fires. The idea that fire might

rejuvenate a forest is often harder to explain than the idea

that fire destroys a forest. Second, people living near forests

and grasslands fear that a controlled burn may escape and

damage their property--an event that occurs rarely but is

always a potential risk. Property owners are understandably

nervous about the possibility of a fire escaping. On the other

hand, prescribed burns have sometimes been used to protect

property. A number of homes adjacent to the Wenatchee

National Forest

in Washington State were spared from the

Tyee Creek fire of 1994 because previous burns had reduced

fuel levels in the surrounding forest.

In addition to objections to fire danger, the

smoke

resulting from a prescribed fire is unpleasant and sometimes

hazardous. There can be a real health risk for people with

Environmental Encyclopedia 3

President’s Council on Sustainable Development

Prescribed burning of a prairie in South Dakota

for land management purposes. (Photograph by

Stephen J. Krasemann. National Audubon Society Collec-

tion/Photo Researchers, Inc. Reproduced by permission.)

lung ailments or

asthma

if they are exposed to concentrated

smoke. In addition, a deliberately set fire often violates

air

quality

laws, making fires technically illegal in many popu-

lated areas. If the fire occurs near a road,

visibility

is also

reduced, so that the road must often be closed while a burn

is in progress. Although the smoke produced by a series of

prescribed fires may be less than the smoke from a single

large wildfire, prescribed fires are sensitive because the indi-

vidual or group responsible for the fire is also liable for any

damage or injury it causes.

Controversy over the use of prescribed burns has be-

come especially serious in areas where human settlement is

encroaching on natural areas. Where cities and suburbs

spread into forested areas or reach the edges of preserves

that are managed with fire, residents of new subdivisions

usually object to the potential risks and inconvenience im-

posed by fire near their property. This problem is especially

severe in the

chaparral

country of southern and central

California. Chaparral is a fire-adapted ecosystem with highly

combustible, dry vegetation that normally burns as every 30

years or so. As suburban development, with its high real

estate values, moves into the chaparral, the economic and

environmental costs of fire control have risen sharply. In

wildlife and habitat preserves near metropolitan areas land

1132

managers have sometimes had to abandon successful fire

management programs because of suburban sprawl.

[Mary Ann Cunningham Ph.D.]

ESOURCES

OOKS

de V. Booysen, P., and N. Tainton, eds. Ecological Effects of Fire in South

African Ecosystems. Ecological Studies vol. 48. New York: Springer-Ver-

lag, 1995.

Pyne, S. J. Fire in America. Princeton, NJ: Princeton University Press, 1982.

United States Forest Service. The Use of Fire in Forest Restoration. USFS

General Technical Report INT-GTR-341. Washington, D.C.: General

Printing Office, 1996.

ERIODICALS

Babbit, B. “To Take up the Torch.” American Forests 101 (July/August

1995):17–18, 59.

McLean, H. “Fighting Fire with Fire.” American Forests 101 (July/August

1995):13–16, 56–7.

President’s Council on Sustainable

Development

An environmental advisory group created by President Bill

Clinton in June 1993 to develop new approaches for combin-

ing environmental protection in the United States with eco-

nomic development. The council is composed of 25 members

drawn from government, industry, and environmental

groups. One of the primary mandates of the President’s

Council on

Sustainable Development

is to develop plans

for the United States to fulfill its role in the

biodiversity

global warming, and other accords negotiated at the 1992

United Nations Earth Summit

Price-Anderson Act (1957)

The Price-Anderson Act, passed in 1957, limits the liability

of civilian producers of

nuclear power

in the case of a

catastrophic nuclear accident. In the case of such an accident,

damages would be recovered from two sources: private insur-

ance covering each plant and a common fund created by

contributions from each nuclear power plant. This common

fund would cover the difference in damages between the

private insurance and the liability limit.

The act, named for its chief sponsors, Senator Clinton

Anderson (NM) and Representative Melvin Price (IL), was

passed to encourage private investment in nuclear power

production. It was part of a general strategy to encourage

and stimulate nuclear power production in the private sector.

Without such liability limitations, the risk of nuclear power

for utilities and manufacturers would be too great. Private

insurance companies were not willing to underwrite the risks

Environmental Encyclopedia 3

Primary pollutant

due to the uncertainty involved and the potential magnitude

of damages.

The law requires the private operators to carry the

maximum amount of private insurance available ($65 million

in the late 1950s). The upper limit for liability was set at

$560 million per accident for personal damages, with the

common fund covering the difference (between $65 million

and $560 million). Once the liability limit is reached this

law protects the operator from further financial liability.

In addition to setting liability limits, the law establishes a

common fund for victims to draw on if the utility did not

have the ability to pay damages up to the liability limit. In

return for this limited liability, utilities had to accept sole

responsibility for accidents; equipment manufacturers would

not be liable for any damages.

The Price-Anderson Act serves as a subsidy to the

nuclear power industry. If it were not for this liability limita-

tion, it is unlikely that any private firms would have become

involved in the production of nuclear power. As a further

incentive to private industry, the federal government set the

liability limits at a very low level. This was done despite a

1957 government estimate of the damages due to a cata-

strophic accident: 3,000 immediate deaths and $7 billion in

property damage.

In 1977, the Carolina Environmental Study Group

filed a lawsuit, claiming that the Price-Anderson Act was

unconstitutional because it was a taking of private property

without just compensation, a violation of the Fifth Amend-

ment. If a nuclear accident did occur and compensation was

limited, the argument went, a taking of private property had

occurred and compensation was limited in advance. A federal

district court ruled for the environmental group: the act

was unconstitutional. In 1978, however, the Supreme Court

overturned this ruling, maintaining the constitutionality of

the Price-Anderson Act.

The 1988 amendments to the act increased the liability

limit per accident from $720 million to $7.2 billion, with

the utilities continuing to contribute to a common fund to

help pay for any damages if a major accident did occur. The

private insurance coverage was set at $160 million per plant,

with the common fund to make up the over $7 billion

difference. These liability limits will last through 2003. De-

spite this tremendous increase in liability limits, the nuclear

power industry was pleased to retain any liability limit in

the face of significant opposition. The amendments also

protect

U.S. Department of Energy

nuclear contractors

from damage claims and limit the liability for nuclear waste

accidents to $7 billion. See also Environmental law; Environ-

mental liability; Nuclear fission; Radioactive waste; Radioac-

tivity; Three Mile Island Nuclear Reactor

[Christopher McGrory Klyza]

1133

ESOURCES

OOKS

Jasper, J. M. Nuclear Politics: Energy and the State in the United States,

Sweden, and France. Princeton: Princeton University Press, 1990.

Kruschke, E. R., and B. M. Jackson. Nuclear Energy Policy. New York:

ABC-Clio, 1990.

Mazuzan, G. T., and J. S. Walker. Controlling the Atom: The Beginnings

of Nuclear Regulation 1946–1962. Berkeley: University of California

Press, 1985.

Primary pollutant

Primary pollutants cause

pollution

by their direct release

into the

environment

. The substance released may already

be present in some quantities, but it is considered a

primary pollutant if the additional release brings the total

quantity of the substance to pollution levels. For example,

carbon dioxide

is already naturally present in the

atmo-

sphere

, but it becomes toxic when additional releases

cause it to rise above its natural concentrations. The rise

in levels of

carbon

dioxide is one contributing factor to

the

greenhouse effect

The direct release into the atmosphere of a chemical

that is not normally present in the air is also classified as a

primary pollutant.

Hydrogen

fluoride, for example, is re-

leased from some coal-fired furnaces, but the compound is

not usually present in unpolluted air.

A primary pollutant can be generated by many sources:

pesticide

dust sprayed intensively in agricultural areas, emis-

sions from car and industrial exhausts, or dust kicked about

from mining operations, to name a few. Some primary pol-

lutants are composed of

particulate

matter that is not easily

dispersed.

Smoke

, soot, dust, and liquid droplets released

into the air either by the burning of fuel or other industrial

or agricultural processes, are considered primary pollutants.

Primary pollutants also originate from natural sources.

Volcanic ash, as well as grit and dust from volcanic explosions

belong to this category. Salt dust blown inland by strong

oceanic winds or gaseous pollution that originates from bogs,

marshes, and other decomposing matter can also be classified

as primary pollutants.

When two or more primary pollutants react in the

atmosphere and cause additional atmospheric pollution, the

result is called secondary pollution.

Nitrogen oxides

, for

instance, can react with volatile organic compounds to from

smog

, a secondary pollutant. See also Air pollution; Air

pollution index; Air quality criteria; National Ambient Air

Quality Standard

[Linda Rehkopf]

Environmental Encyclopedia 3

Primary productivity (gross and net)

ESOURCES

OOKS

Ney, R. E. Where Did That Chemical Go? A Practical Guide to Chemical

Fate and Transport in the Environment. New York: Van Nostrand Rein-

hold, 1990.

Shineldecker, C. L. Handbook of Environmental Contaminants: A Guide for

Site Assessment. Boca Raton: Lewis, 1992.

Primary productivity (gross and net)

Primary producers (or autotrophs) are organisms that syn-

thesize their own biochemical constituents using simple in-

organic compounds and an external energy source to drive

the process. The amount of energy fixed by autotrophs is

known as primary production, and the rate of fixation is

primary productivity. Both primary productivity and primary

production may be measured in units of

carbon dioxide

(CO

) fixed, energy fixed (as calories or joules), or

biomass

produced. Productivity in terrestrial ecosystems is often ex-

pressed in such units as kilograms of dry biomass (or its

energy equivalent) per hectare per year (e.g., kg/ha.yr or kJ/

ha.yr), while aquatic productivity is often measured on a

volumetric basis (e.g., kg/m

.yr). Many studies have been

made of the primary productivity of various kinds of eco-

systems.

Most primary producers are photoautotrophs that use

sunlight as the external source of energy to drive

photosyn-

thesis

. Photoautotrophs capture solar radiation using photo-

synthetic pigments, such as chlorophyll. Green plants are

the most abundant photosynthetic organisms, along with

algae and some bacteria. A much smaller number of auto-

trophs are chemoautotrophs, which capture some of the

energy content of certain inorganic

chemicals

to drive their

chemosynthesis

. For example, Thiobacillus thiooxidans is a

bacterium that oxidizes sulfide minerals to sulfate, utilizing

some of the energy liberated during this reaction to drive

its chemosynthesis.

The total fixation of solar (or chemical) energy by

primary producers within an

ecosystem

is known as gross

primary production (or GPP). Some of this production is

utilized by autotrophs in support of their own

respiration

(R). Respiration involves physiological functions needed to

maintain organisms in a healthy condition. Its complex reac-

tions involve the metabolic oxidation of biochemicals, which

requires a supply of oxygen and releases

carbon

dioxide and

water as waste products. Net primary production (NPP)

refers to the fraction of gross primary production that re-

mains after primary producers have utilized some of their

GPP for their own respiration. In other words, NPP =

GPP-R.

For example, studies of an oak-pine forest in New

York found that the total fixation of

solar energy

by vegeta-

1134

tion (i.e., the gross primary productivity) was about 48.1-

thousand kilojoules per hectare per year. This fixation rate

was equivalent to less than 0.01% of the input of solar

radiation to the forest. Because the plants utilized 27.2-

thousand kJ/ha.yr in support of their respiration, the net

primary productivity was 20.9-thousand kJ/ha.yr, occurring

as the accumulating biomass of trees.

The NPP of primary producers supports the produc-

tivity of all other organisms, known as heterotrophs, in eco-

systems. Heterotrophs can only utilize living or dead biomass

as food, and they rely on other organisms to supply this

fixed energy. Animal heterotrophs that feed on plants are

known as herbivores (or primary consumers). Animals that

kill and eat other animals are known as carnivores (or second-

ary consumers). Animals that feed on both plant and animal

biomass are known as omnivores. Many heterotrophs feed

on dead organic matter, and are called

decomposers

detritivores

[Bill Freedman Ph.D.]

ESOURCES

OOKS

Begon, M., C. R. Townsend, and J. L. Harper. Ecology: Individuals, Popula-

tions and Communities. London: Blackwell Science Inc., 1998.

Lieth, H. and R. H. Whittaker, eds. Primary Productivity of the Biosphere.

New York: Springer-Verlag.

Odum, E. P. Basic Ecology. New York: Saunders College Publishing.

Primary sewage treatment

see

Sewage treatment

Primary standards

Primary standards are numerical limits of allowable air and

water pollutants designed to protect human health but not

necessarily other parts of the

environment

. Primary stan-

dards differ from

secondary standards

, which are those

that protect against all adverse effects on the environment,

such as those on animals and vegetation. While the term

primary standards usually relates to

air pollution

air

quality

, there are federal primary standards for the drinking

water supply.

The

Clean Air Act

is the major piece of legislation

that protects and enhances the nation’s air quality. As part

of the act, Congress required the

Environmental Protection

Agency

(EPA) to establish National Ambient Air Quality

Standards (NAAQS) for air pollutants, which were charac-

terized by wide dispersal and

emission

from many sources.

The NAAQS, or primary air quality standards, define

the level of air quality to be achieved and maintained nation-

Environmental Encyclopedia 3

Primary standards

wide for six criteria pollutants:

sulfur dioxide

carbon mon-

oxide

nitrogen oxides

ozone

particulate

matter, and

lead

. In general, these standards are not permitted to be

exceeded more than once a year. In addition, the EPA is

required to identify local hazardous air pollutants which

could increase

mortality

or result in serious illnesses such as

cancer

, and establish national standards for them. Although

hundreds of potentially hazardous air pollutants exist, only

eight had been listed as of 1990:

mercury

, beryllium,

asbes-

tos

vinyl chloride

benzene

, radioactive substances, coke

oven emissions, and inorganic

arsenic

The Clean Air Act set a deadline of December 1987

for cities in the United States to meet federal primary stan-

dards. Some cities did meet the standards, increasing

auto-

mobile

emission inspections and instituting tighter regula-

tions for incinerators, but some sixty cities could not comply.

There has been a measurable increase in

nitrogen

oxide

emissions in recent years, and more than 100 areas nation-

wide have exceeded standards at least part of the time for

ozone and

carbon

monoxide levels. The EPA has estimated

that 100 million people live in areas exceeding these stan-

dards. The most heavily-polluted areas of the

Los Angeles

Basin

, Houston, and the New York corridor may take years

to meet the air quality standards. Suggestions to hasten

compliance have included plans to shut down industrial

plants, ration gas, and restrict automobile use.

The 1990 Clean Air Act Amendments include provi-

sions to tighten

pollution control

requirements in cities

that have not attained the National Ambient Air Quality

Standards. These provisions include, among others, require-

ments for stringent automobile

emission standards

. The

new act also requires a 50 percent reduction in sulfur dioxide

emissions, and it sets primary and secondary standards for

dozens of

chemicals

that were not mentioned in the original

act or amendments.

Primary standards are not consistent from country to

country. For example, standards are defined for different

average times, at varying numerical limits. In thirteen coun-

tries the sulfur dioxide standard ranges from 0.30 to 0.75

mg/m

for a 30-minute average, and from 0.05 to 0.38 mg/

for a 24-hour average. Since

pollution

does not stay in

once place, and since

acid rain

is often a source of contro-

versy between bordering countries, the lack of international

standards will continue to contribute to air pollution

problems.

In the United States, concern about

water pollution

has resulted in higher standards for water cleanliness. These

standards have been adopted by state and federal agencies,

but the involvement of so many different agencies on differ-

ent levels has contributed to a lack of agreement on some

water standards.

1135

The primary law to protect the integrity of the nation’s

water is the

Clean Water Act

(1972). The act requires the

EPA to set

water quality

criteria based on the most recent

scientific information. Under the Clean Water Act Reautho-

rization (1987), the EPA is required to publish revised water

quality criteria, stress new programs to combat water pollu-

tion from toxics, and restrict waivers from national standards

that had been easily obtained by discharges.

Criteria are not rules; they are a compilation of data

about pollutants that can be used to formulate standards.

Congress intended for the EPA to set the criteria and for

the states to set the

water quality standards

. By 1990 the

EPA had established criteria for 126 priority pollutants. Of

these, 109 dealt with primary standards and thirty-four with

secondary standards. But although these criteria have been

published, few states have actually established standards for

toxic pollutants or have incorporated these standards into

the regulation of toxic

discharge

Under the Safe Drinking Water Reauthorization Act

(1986), the EPA is not only required to set standards for

contaminants in drinking water, but it also must monitor

public drinking water for unregulated contaminants and set

deadlines for the issuance of new standards. By 1990, the

EPA had set primary standards for drinking water that cov-

ered the inorganic chemicals arsenic, barium,

cadmium

chromium, lead, mercury, nitrate, selenium, silver, and fluo-

ride. Primary drinking water standards are measured in terms

of maximum contaminant levels (MCLs), which are the

maximum permissible level of a contaminant in water at the

tap; they are health related and legally enforceable.

Organic chemicals regulated by primary standards for

drinking water include the pesticides Endrin, Lindane, Me-

thoxychlor, and

Toxaphene

; the herbicides

2,4-D

and

2,4,5-T

Silvex; and the organics benzene, carbon tetrachlo-

ride, p-dichlorobenzene, 1,2-dichlorobenzene, 1,2-dichlor-

oethane, 1,1-dichloroethylene, 1,1,1-trichloroethane, tri-

chloroethylene, vinyl chloride, and an organic compound

referred to as total

trihalomethanes

. Microbiological stan-

dards for drinking water have been set for coliform bacterium

such as

Escherichia coli

, which is present in sewage and

which can cause gastroenteric infections, dysentery, hepati-

tis, and other diseases. Standards have also been set for

turbidity, the murkiness of treated water that can interfere

with disinfection processes. Radionuclides regulated by pri-

mary standards include beta particles and photon activity,

gross alpha particles, and Radium-226 and -228.

As is the case with primary standards for air quality, an

international comparison of primary standards for drinking

water reveals a collection of confusing numbers. While the

United States and Canada seem to agree on standards for

organic compounds, this is where the similarity ends. As of

1990, the Canadian government had no primary drinking

Environmental Encyclopedia 3

Prince William Sound

water standards for radionuclides other than radium, and it

had not set primary standards for volatile organic chemicals

such as benzene and vinyl chloride. By 1990, the European

Economic Community had set primary drinking water stan-

dards only for total pesticides and trihalomethanes. The

World Health Organization (WHO) has recommended pri-

mary standards only for the organics 2,4-D, methoxychlor,

and trihalomethanes, beta and alpha radionuclides, and five

of the eight volatile organic chemicals regulated in the United

States.

In the United States, there is evidence that primary

standards regarding air and water pollutants have had some

impact on air and water quality. Some of the nation’s surface

waters have improved since the implementation of the Clean

Water Act.

Coliform bacteria

counts and

dissolved solids

have been reduced, and

dissolved oxygen

levels have in-

creased enough to permit the reestablishment of plants and

animals that had died out in polluted waters.

Air quality standards have led to an overall 20 percent

reduction in emissions of particulates, sulfur dioxide, and

carbon monoxide during the 1980s. Los Angeles, which

suffers as much or more than any American city from air

pollution, has proposed an air quality plan that would surpass

the EPA’s standards, requiring lifestyle changes to help com-

bat air pollution.

Implementing laws and regulations to enforce water

and air standards that will protect the health of humans will

be expensive: The yearly price tag just for implementation

of the Clean Air Act of 1990 is estimated to be $25 billion.

But many believe the savings in health costs and environ-

mental damage to be incalculable. See also Air pollution

index; Air Quality Control Region; Air quality criteria; At-

tainment area; Nitrates and nitrites; Nonattainment area;

Radioactive waste; Safe Drinking Water Act; Sewage treat-

ment; Toxic substance

[Linda Rehkopf]

ESOURCES

OOKS

Freeman, M. Air and Water Pollution Regulation: Accomplishments and Eco-

nomic Consequences. Westport, CT: Greenwood Publishing Group, 1993.

Harte, John, et al. Toxics A to Z. Berkeley: University of California

Press, 1991.

van der Leeden, F., et al. The Water Encyclopedia. Chelsea, MI: Lewis

Publishers, 1990.

Prince William Sound

British explorer Captain James Cook made the European

discovery of Prince William Sound in 1778. Today, the

25,090-square-mile (65,000-square-kilometer) passage

1136

southeast of Anchorage, Alaska, is the focal point of an on-

going political and environmental issue: whether oil can

be safely transported in extreme climates without seriously

threatening terrestrial and marine habitats or the recre-

ational, agricultural, and industrial interests of the region.

Prince William Sound is bordered on the north and

west by the Chugach and Kenai mountain ranges, on the

east by the

Copper

River, and by the Hinchinbrook Islands

on the south. Ten percent of its area is open water, with

depths ranging from 492-2,952 ft (149-895 m). The remain-

der consists of shallow coastal waters, shoals, and reefs. The

combined 2,980 miles (4,800 km) of mainland and island

shoreline are home to more than 200

species

of birds, among

them approximately 3,000 bald eagles. Ten species of marine

mammals, including

sea lions

seals

whales

, porpoises,

and some 10,000 sea otters thrive in its bountiful waters.

The natural beauty of Prince William Sound is responsible

for the area’s healthy tourism industry.

The Sound is world-renowned for its

salmon

fishery.

More than 300 streams are used by salmon for spawning

and, combined with hatchery inputs, more than one billion

fry are released annually into the Sound. The herring season

brings in an additional 12 million dollars to the area each

year. The inhabitants of the four communities on the Sound

are supported primarily by fishing and its related industries.

For economic reasons, residents of the area are concerned

with preserving the Sound’s

natural resources

In the mid-1970s, the Cordova Island fishermen

fought the oil industry’s plan to build an oil pipeline from

Prudhoe Bay in northern Alaska to Prince William Sound.

The decision was left to the United States Senate which,

despite warnings from scientists and environmental groups,

voted to approve the proposed pipeline route into the Sound.

Natural and man-induced disasters threaten the health

of the Sound.The Alaskan coast makes up the western bound-

ary of the North American continental plate and is, therefore,

subject to considerable seismic activity. On March 24, 1964,

earthquake

centered in the mountains surrounding

Prince William Sound had substantial effects on the Sound.

Twenty-five years later to the day, the oil tanker

Exxon Val-

dez

wrecked on the rocks of the Sound’s Bligh Reef in waters

less than 39 ft (12 m) deep. Approximately 265,000 barrels

(42 million liters) of heavy crude oil leaked into the Sound,

one of the worst oil spills in United States history. The local

sea otter

population was nearly destroyed; many pelagic and

shore bird populations were also heavily impacted. Effects of

the spill and subsequent clean-up efforts on shoreline and sea-

floor communities are unknown, as are the long-term effects

on Prince William Sound and adjacent habitats.

[William G. Ambrose Jr. and Paul E. Renaud]