Environmental Encyclopedia

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Environmental Encyclopedia 3

High-solids reactor

brief controversy when he suggested tearing down O’S-

haughnessy Dam. See also Economic growth and the envi-

ronment; Environmental law; Environmental policy

[Teresa C. Donkin]

ESOURCES

OOKS

Jones, Holway R. John Muir and the Sierra Club: The Battle for Yosemite.

San Francisco: Sierra Club, 1965.

Nash, Roderick. “Conservation as Anxiety.” In The American Environment:

Readings in the History of Conservation. 2nd ed. Reading, Mass: Addison-

Wesley Publishing Company, 1976.

Heterotroph

A heterotroph is an organism that derives its nutritional

carbon

and energy by oxidizing (i.e., decomposing) organic

materials. The higher animals,

fungi

, actinomycetes, and

most bacteria are heterotrophs. These are the biological con-

sumers that eventually decompose most of the organic matter

on the earth. The

decomposition

products then are available

for chemical or biological

recycling

. See also Biogeochemical

cycles; Oxidation reduction reactions

High-grading (mining, forestry)

The practice of high-grading can be traced back to the early

days of the California gold rush, when miners would sneak

into claims belonging to others and steal the most valuable

pieces of ore. The practice of high-grading remains essen-

tially unchanged today. An individual or corporation will

enter an area and selectively mine or harvest only the most

valuable specimens, before moving on to a new area. High-

grading is most prevalent in the mining and timber indus-

tries. It is not uncommon to walk into a forest, particularly an

old-growth forest

, and find the oldest and finest specimens

marked for harvesting. See also Forest management; Strip

mining

High-level radioactive waste

High-level

radioactive waste

consists primarily of the by-

products of nuclear

power plants

and defense activities.

Such wastes are highly radioactive and often decay very

slowly. They may release dangerous levels of radiation for

hundreds or thousands of years. Most high-level radioactive

wastes have to be handled by remote control by workers who

are protected by heavy shielding. They present, therefore, a

serious health and environmental hazard. No entirely satis-

factory method for disposing of high-level wastes has as yet

717

been devised. Currently, the best approach seems to involve

immobilizing the wastes in a glass-like material and then

burying them deep underground. See also Low-level radioac-

tive waste; Radioactive decay; Radioactive pollution; Radio-

active waste management; Radioactivity

High-solids reactor

Solid waste

disposal is a serious problem in the United

States and other developed countries. Solid waste can consti-

tute valuable raw materials for commercial and industrial

operations, however, and one of the challenges facing scien-

tists is to develop an economically efficient method for utiliz-

ing it.

Although the concept of bacterial waste conversion is

simple, achieving an efficient method for putting the tech-

nique into practice is difficult. The main problem is that

efficiency of conversion requires increasing the ratio of solids

to water in the mixture, and this makes mixing more difficult

mechanically. The high-solids reactor was designed by scien-

tists at the

Solar Energy

Research Institute (SERI) to solve

this problem. It consists of a cylindrical tube on a horizontal

axis, and an agitator shaft running through the middle of

it, which contains a number of Teflon-coated paddles ori-

ented at 90 degrees to each other. The pilot reactors operated

by SERI had a capacity of 2.6 gal (10 l).

SERI scientists modeled the high solids reactor after

similar devices used in the

plastics

industry to mix highly

viscous materials. With the reactor, they have been able to

process materials with 30–35% solids content, while existing

reactors normally handle wastes with five to eight% solid

content. With higher solid content, SERI reactors have

achieved a yield of

methane

five to eight times greater than

that obtained from conventional mixers. Researchers hope

to be able to process wastes with solid content ranging any-

where from zero to 100%. They believe that they can eventu-

ally achieve 80% efficiency in converting

biomass

methane.

The most obvious application of the high-solids reac-

tor is the processing of municipal solid wastes. Initial tests

were carried out with

sludge

obtained from

sewage treat-

ment

plants in Denver, Los Angeles, and Chicago. In all

cases, conversion of solids in the sludge to methane was

successful, and other applications of the reactor are also

being considered. For example, it can be used to leach out

uranium

from mine wastes:

anaerobic

bacteria in the reac-

tor will reduce uranium in the wastes and the uranium will

then be absorbed on the bacteria or on

ion exchange

resins.

The use of the reactor to clean

contaminated soil

is also

being considered in the hope is that this will provide a

desirable alternative to current processes for cleaning

soil

Environmental Encyclopedia 3

Hiroshima, Japan

which create large volumes of contaminated water. See also

Biomass fuel; Solid waste incineration; Solid waste recycling

and recovery; Solid waste volume reduction; Waste man-

agement

[David E. Newton]

ESOURCES

ERIODICALS

“High Solids Reactor May Reduce Capital Costs.” Bioprocessing Technology

(June 1990).

“SERI Looking for Partners for Solar-Powered High Solids Reactor.” Waste

Treatment Technology News (October 1990).

High-voltage power lines

see

Electromagnetic field

High-yield crops

see

Borlaug, Norman E.; Consultative

Group on International Agricultural Research

Hiroshima, Japan

Hiroshima is a beautiful modern city located near the south-

western tip of the main Japanese island of Honshu. It had

been a military center with the headquarters of the Japanese

southern army and a military depot prior to the end of World

War II. The city is now a manufacturing center with a

major university and medical school. It is most profoundly

remembered because it was the first city to be exposed to

the devastation of an atomic bomb.

At 8:15

A.M.

on the morning of August 6, 1945, a

single B29 bomber flying in from Tinian Island in the Mari-

nas released the bomb at 2,000 ft (606.6 m) above the city.

The target was a “T"-shaped bridge near the city center.

The only surviving building in the city center after the atomic

bomb blast was a domed cement building at ground zero,

just a few yards from the bridge. An experimental bomb

developed by the Manhattan Project had been exploded at

Alamagardo, New Mexico, only a few weeks earlier. The

Alamagardo bomb had the explosive force of 15,000 tons

of TNT. The Hiroshima uranium-235 bomb, with the ex-

plosive power of 20,000 tons of TNT, was even more power-

ful than the New Mexico bomb. The immediate effect of

the bomb was to destroy by blast, winds, and fire an area

of 4.4 mi

(7 km

). Two-thirds of the city was destroyed.

A portion of Hiroshima was protected from the blast by

hills, and this is all that remains of the old city. Destruction

of human lives was caused immediately by the blast force

718

of the bomb or by burns or

radiation sickness

later. Sev-

enty-five thousand people were killed or were fatally

wounded; there was an equal number of wounded survivors.

Nagasaki, to the south and west of Hiroshima, was bombed

on August 9, 1945, with much loss of life. The bombing of

these two cities brought World War II to a close. The lessons

that Hiroshima (and Nagasaki) teach are the horrors of war

with its random killing of civilian men, women, and children.

That is the major lesson—war is horrible with its destruction

of innocent lives.

The why of Hiroshima should be taken in the context

of the battle for Okinawa which occurred only weeks before.

America forces suffered 12,000 dead with 36,000 wounded

in the battle for that small island 350 mi (563.5 km) from

the mainland of Japan. The Japanese were reported to have

lost 100,000 men. The determination of the Japanese to

defend their homeland was well known, and it was estimated

that the invasion of Japan would cost no less than 500,000

American lives. Japanese casualties were expected to be

larger. It was the military judgment of the American Presi-

dent that a swift termination of the war would save more

lives than it would cost; both American and Japanese.

Whether this rationale for the atomic bombing of Hiroshima

was correct, i.e., whether more people would have died if

Japan was invaded, will never be known. However, it cer-

tainly is a fact that the war came to a swift end after the

bombing of the two cities.

The second lesson to be learned from Hiroshima is

that

radiation exposure

is hazardous to human health and

radiation damage results in radiation sickness and increased

cancer

risk. It had been known since the development of x

rays at the turn of the century that radiation has the potential

to cause cancer. However, the thousands of survivors at

Hiroshima and Nagasaki were to become the largest group

ever studied for radiation damage. The Atomic Bomb Casu-

alty Commission, now referred to as the Radiation Effects

Research Foundation (RERF), was established to monitor

the health effects of radiation exposure and has studied these

survivors since the end of World War II. The RERF has

reported a 10–15 times excess of all types of

leukemia

among the survivors compared with populations not exposed

to the bomb. The leukemia excess peaked four to seven years

after exposure but still persists among the survivors. All

forms of cancer tended to develop more frequently in heavily

irradiated individuals, especially children under the age of

10 at the time of exposure. Thyroid cancer was also increased

in these children survivors of the bomb.

War is destructive to human life. The particular kind

of destruction at Hiroshima, due to an atomic bomb, contin-

ues to be relentlessly destructive. The city of Hiroshima is

known as a Peace City.

[Robert G. McKinnell]

Environmental Encyclopedia 3

Holistic approach

A painting by Yasuko Yamagata depicting the Japanese city of Hiroshima after the atomic bomb was dropped

on it. (Reproduced by permission.)

Holistic approach

First formulated by Jan Smuts, holism has been traditionally

defined as a philosophical theory that states that the de-

termining factors in

nature

are wholes which are irreducible

to the sum of their parts and that the

evolution

of the

universe is the record of the activity and making of such

wholes. More generally, it is the concept that wholes cannot

be analyzed into parts or reduced to discrete elements with-

out unexplainable residuals. Holism may also be defined by

what it is not: it is not synonymous with organicism; holism

does not require an entity to be alive or even a part of

living processes. And neither is holism confined to spiritual

mysticism, unaccessible to scientific methods or study.

The holistic approach in

ecology

and

environmental

science

derives from the idea proposed by Harrison Brown

that “a precondition for solving [complex] problems is a

realization that all of them are interlocked, with the result

that they cannot be solved piecemeal.” For some scholars

holism is the rationale for the very existence of ecology. As

719

David Gates notes, “the very definition of the discipline of

ecology implies a holistic study.”

The holistic approach has been successfully applied

to environmental management. The United States

Forest

Service

, for example, has implemented a multi-level ap-

proach to management that takes into account the complex-

ity of forest ecosystems, rather than the traditional focus on

isolated incidents or problems.

Some people believe that a holistic approach to nature

and the world will counter the effects of “reductionism"—

excessive individualism, atomization, mechanistic

worldview, objectivism, materialism, and anthropocentrism.

Advocates of holism claim that its emphasis on connectivity,

community, processes, networks, participation, synthesis,

systems, and emergent properties will undo the “ills” of

reductionism. Others warn that a balance between reduc-

tionism and holism is necessary. American ecologist Eugene

Odum mandated that “ecology must combine holism with

reductionism if applications are to benefit society.” Parts and

wholes, at the macro- and micro-level, must be understood.

Environmental Encyclopedia 3

Homeostasis

The basic lesson of a combined and complementary parts-

whole approach is that every entity is both part and whole—

an idea reenforced by Arthur Koestler’s concept of a holon.

A holon is any entity that is both a part of a larger system

and itself a system made up of parts. It is essential to recog-

nize that holism can include the study of any whole, the

entirety of any individual in all its ramifications, without

implying any organic analogy other than organisms them-

selves. A holistic approach alone, especially in its extreme

form, is unrealistic, condemning scholars to an unproductive

wallowing in an unmanageable complexity. Holism and re-

ductionism are both needed for accessing and understanding

an increasingly complex world. See also Environmental ethics

[Gerald L. Young Ph.D.]

ESOURCES

OOKS

Bowen, W. “Reductions and Holism.” In Thinking About Nature: An Investi-

gation of Nature, Value and Ecology. Athens: University of Georgia Press,

1988.

Johnson, L. E. “Holism.” In A Morally Deep World: An Essay on Moral

Significance and Environmental Ethics. Cambridge: Cambridge University

Press, 1991.

Savory, A. Holistic Resource Management. Covelo, CA: Island Press, 1988.

ERIODICALS

Krippner, S. “The Holistic Paradigm.” World Futures 30 (1991): 133–40.

Marietta Jr., D. E. “Environmental Holism and Individuals.” Environmental

Ethics 10 (Fall 1988): 251–58.

McCarty, D. C. “The Philosophy of Logical Wholism.” Synthese 87 (April

1991): 51–123.

Van Steenbergen, B. “Potential Influence of the Holistic Paradigm on the

Social Sciences.” Futures 22 (December 1990): 1071–83.

Homeostasis

Humans, all other organisms, and even ecological systems,

live in an

environment

of constant change. The persistently

shifting, modulating, and changing milieu would not permit

survival, if it were not for the capacity of biological systems

to respond to this constant flux by maintaining a relatively

stable internal environment. An example taken from mam-

malian biology is temperature which appears to be “fixed”

at approximately 98.6°F (37°C). While humans can be ex-

posed to extreme summer heat, and arctic mammals survive

intense cold, body temperature remains constant within vary

narrow limits. Homeostasis is the sum total of all the biologi-

cal responses that provide internal equilibrium and assure

the maintenance of conditions for survival.

The human

species

has a greater variety of living

conditions than any other organism. The ability of humans

to live and reproduce in such diverse circumstances is due

720

to a combination of homeostatic mechanisms coupled with

cultural (behavioral) responses.

The scientific concept of homeostasis emerged from

two scientists: Claude Bernard, a French physiologist, and

Walter Bradford Cannon, an American physician. Bernard

contrasted the external environment which surrounds an

organism and the internal environment of that organism.

He was, of course, aware that the external environment

fluctuated considerably in contrast to the internal environ-

ment which remained remarkably constant. He is credited

with the enunciation of the constancy of the internal environ-

ment ("La fixite

du milieu inte

rieur...") in 1859. Bernard

believed that the survival of an organism depended upon

this constancy, and he observed it not only in temperature

control but in the regulation of all of the systems that he

studied. The concept of the stable “milieu inte

rieur” has been

accepted and extended to the many organ systems of all

higher vertebrates. This precise control of the internal envi-

ronment is effected through hormones, the autonomic ner-

vous system, endocrines, etc.

The term “homeostasis,” derived from the Greek ho-

moios meaning similar and stasis meaning to stand, suggests

an internal environment which remains relatively similar or

the same through time. The term was devised by Cannon

in 1929 and used many times subsequently. Cannon noted

that, in addition to temperature, there were complex controls

involving many organ systems that maintained the internal

stability

within narrow limits. When those limited are ex-

ceeded, there is a reaction in the opposite direction that

brings the condition back to normal, and the reactions re-

turning the system to normal is referred to as negative feed-

back. Both Bernard and Cannon were concerned with hu-

man physiology. Nevertheless, the concept of homeostasis

is applied to all levels of biological organization from the

molecular level to ecological systems, including the entire

biosphere

. Engineers design self-controlling machines

known as servomechanisms with feedback control by means

of a sensing device, an amplifier which controls a servomotor

which in turn runs the operation of the device. Examples

of such devices are the thermostats which control furnace

heat in a home or the more complicated automatic pilots

of aircraft. While the human-made servomechanisms have

similarities to biological homeostasis, they are not consid-

ered here.

As indicated above, temperature is closely regulated

in humans and other homeotherms (birds and mammals).

The human skin has thermal receptors sensitive to heat or

cold. If cold is encountered, the receptors notify an area of

the brain known as the hypothalamus via a nerve impulse.

The hypothalamus has both a heat-promoting center and a

heat-losing center, and, with cold, it is the former which

is stimulated. Thyroid-releasing hormone, produced in the

Environmental Encyclopedia 3

Homeostasis

hypothalamus, causes the anterior pituitary to release thyroid

stimulating hormone which, in turn, causes the thyroid gland

to increase production of thyroxine which results in increased

metabolism

and therefore heat. Sympathetic nerves from

the hypothalamus stimulate the adrenal medulla to secrete

epinephrine and norepinephrine into the blood which also

increases body metabolism and heat. Increased muscle activ-

ity will generate heat and that activity can be either voluntary

(stamping the feet for instance) or involuntary (shivering).

Since heat is dissipated via body surface blood vessels, the

nervous system causes surface vasoconstriction to decrease

that heat loss. Further, the small quantity of blood that does

reach the surface of the body, where it is chilled, is reheated

by countercurrent heat exchange resulting from blood vessels

containing cold blood from the limbs running adjacent to

blood vessels from the body core which contain warm blood.

The chilled blood is prewarmed prior to returning to the

body core. A little noted response to chilling is the voluntary

reaching for a jacket or coat to minimize heat loss.

The body responds with opposite results when exces-

sive heat is encountered. The individual tends to shed unnec-

essary clothing, and activity is reduced to minimize metabo-

lism. Vasodilation of superficial blood vessels allows for

radiation of heat. Sweat is produced, which by evaporation

reduces body heat. It is clear that the maintenance of body

temperature is closely controlled by a complex of homeostasis

mechanisms.

Each step in temperature regulation is controlled by

negative feedback. As indicated above, with exposure to cold

the hypothalamus, through a series of steps, induces the

synthesis and release of thyroxine by the thyroid gland. What

was not indicated above was the fact that elevated levels of

thyroxine control the level of activity of the thyroid by nega-

tive feedback inhibition of thyroid stimulating hormone. An

appropriate level of thyroid hormone is thus maintained. In

contrast, with inadequate thyroxine, more thyroid stimulat-

ing hormone is produced. Negative feedback controls assure

that any particular step in homeostasis does not deviate too

much from the normal.

Historically, biologists have been particularly impres-

sed with mammalian and human homeostasis. Lower verte-

brates have received less attention. However, while internal

physiology may vary more in a frog than in a human, there

are mechanisms which assure the survival of

frogs

. For

instance, when the ambient temperature drops significantly

in the autumn in northern latitudes, leopard frogs move into

lakes or rivers which do not freeze. Moving into lakes and

rivers is a behavioral response to a change in the external

environment which results in internal temperature stability.

The metabolism and structure of the frog is inadequate to

protect the frog from freezing, but the specific heat of the

water is such that freezing does not occur except at the

721

surface of the overwintering lake or river. Even though life

at the bottom of a lake with an ice cover moves at a slower

pace than during the warm summer months, a functioning

circulatory system is essential for survival. In general, frog

blood (not unlike crankcase oil prior to the era of multiviscos-

ity oil) increases in viscosity with as temperature decreases.

Frog blood, however, decreases in viscosity with the pro-

longed autumnal and winter cold temperatures, thus assuring

adequate circulation during the long nights under an ice

cover. This is another control mechanism that assures the

survival of frogs by maintaining a relatively stable internal

environment during the harsh winter. With a return of a

warm external environment, northern leopard frogs leave

cold water to warm up under the spring sun. Warm tempera-

ture causes frog blood viscosity to increase to summer levels.

It may be that the behavioral and physiological changes do

not prevent oscillations that would be unsuitable for warm

blooded animals but, in the frog, the fluctuations do not

interfere with survival, and in biology, that is all that is

essential.

There is homeostasis in ecological systems. Popula-

tions of animals in complex systems fluctuate in numbers,

but the variations in numbers are generally between limits.

For example, predators survive in adequate numbers as long

as prey are available. If predators become too great in num-

ber, the population of prey will diminish. With fewer prey,

the numbers of predators plummet through negative feed-

back thus permitting recovery of the preyed upon species.

The situation becomes much more complex when other food

sources are available to the predator.

Many organisms encounter a negative feedback on

growth rate with crowding. This density dependent popula-

tion control has been studied in larval frogs, as well as many

other organisms, where excretory products seem to specifi-

cally inhibit the crowded species but not other organisms in

the same environment. Even with adequate food, high den-

sity culture of laboratory mice results in negative feedback

on reproductive potential with abnormal gonad development

and delayed sexual maturity. Density independent factors

affecting populations are important in population control

but would not be considered homeostasis.

Drought

is such

a factor, and its effects can be contrasted with crowding.

Populations of tadpoles will drop catastrophically when

breeding ponds dry. Instead of fluctuating between limits

(with controls), all individuals are affected the same (i.e.,

they die). The area must be repopulated with immigrants

at a subsequent time, and the

migration

can be considered

a population homeostatic control. The inward migration

results in maintenance of population within the geographic

area and aids in the survival of the species.

[Robert G. McKinnell]

Environmental Encyclopedia 3

Homestead Act (1862)

ESOURCES

OOKS

Hardy, R. N. Homeostasis. London: Edward Arnold, Ltd., 1976.

Langley, L. L. Homeostasis. New York: Reinhold Publishing Co., 1965.

Tortora, G. J., and N. P. Anagnostakos. Principles of Anatomy and Physiology.

5th ed. New York: Harper and Row, 1987.

Homestead Act (1862)

The Homestead Act was signed into law in 1862. It was

a legislative offer on a vast scale of free homesteads on

unappropriated public lands. Any citizen (or alien who filed

a declaration of intent to become a citizen), who had reached

the age of 21, and was the head of a family could acquire

title to a stretch of

public land

of up to 160 acres (65 ha)

after living on it and farming it for five years. The only

payment required was administrative fees. The settler could

also obtain the land without the requirement of residence

and cultivation for five years, against payment of $1.25 per

acre. With the advent of machinery to mechanize farm labor,

160-acre (65 ha) tracts soon became uneconomical to oper-

ate, and Congress modified the original act to allow acquisi-

tion of larger tracts. The Homestead Act is still in effect,

but good unappropriated land is scarce. Only Alaska still

offers opportunities for homesteaders.

The Homestead Act was designed to speed develop-

ment of the United States and to achieve an equitable distri-

bution of wealth. Poor settlers, who lacked the capital to

buy land, were now able to start their own farms. Indeed,

the act contributed greatly to the growth and development

of the country, particularly in the period between the Civil

War and World War I, and it did much to speed settlement

west of the Mississippi River. In all, well over a quarter

of a billion acres of land has been distributed under the

Homestead Act and its amendments. However, only a small

percentage of land granted under the act between 1862 and

1900 was in fact acquired by homesteaders. According to

estimates, only at most 1 of every 6 acres (0.4 of every 2.4

ha) and possibly only 1 in 9 acres (0.4 in 3.6 ha) passed into

the hands of family farmers.

The railroad companies and land speculators obtained

the bulk of the land, sometimes through gross fraud using

dummy entrants. Moreover, the railroads often managed to

get the best land while the homesteaders, ignorant of farming

conditions on the Plains, often ended up with tracts least

suitable to farming. Speculators frequently encouraged set-

tlement on land that was too dry or had no sources of water

for domestic use. When the homesteads failed, many settlers

sold the land to speculators.

The environmental consequences of the Homestead

Act were many and serious. The act facilitated railroad devel-

722

opment, often in excess of

transportation

needs. In many

instances, competing companies built lines to connect the

same cities. Railroad development contributed significantly

to the destruction of

bison

herds, which in turn led to the

destruction of the way of life of the Plains Indians. Cultiva-

tion of the Plains caused wholesale destruction of the vast

prairies, so that whole ecological systems virtually disap-

peared. Overfarming of semi-arid lands led to another envi-

ronmental disaster, whose consequences were fully experi-

enced only in the 1930s. The great

Dust Bowl

, with its

terrifying dust storms, made huge areas of the country un-

livable.

The Homestead Act was based on the notion that

land held no value unless it was cultivated. It has now become

clear that reckless cultivation can be self-destructive. In many

cases, unfortunately, the damage can no longer be undone.

[William E. Larson and Marijke Rijsberman]

ESOURCES

ERIODICALS

Shimkin, M. N. “Homesteading on the Republican River.” Journal of the

West 26 (October 1987): 58–66.

Horizon

Layers in the

soil

develop because of the additions, losses,

translocations, and transformations that take place as the

soil ages. The soil layers occur as a result of water percolating

through the soil and

leaching

substances downward. The

layers are parallel to the soil surface and are called horizons.

Horizons will vary from the surface to the

subsoil

and from

one soil to the next because of the different intensities of

the above processes. Soils are classified into different groups

based on the characteristics of the horizons.

Horseshoe crabs

The horseshoe crab (Limulus polyphemus) is the American

species

of a marine animal that is only a distant relation of

crustaceans like crabs and lobsters. Horseshoe crabs are more

closely related to spiders and scorpions. The crabs have been

called “living fossils” because the genus dates back millions

of years, and Limulus evolved very little over the years.

Fossils found in British Columbia indicate that the

ancestors of horseshoe crabs were in North America about

520 million years ago. During the late twentieth century,

the declining horseshoe crab population concerned environ-

mentalists. Horseshoe crabs are a vital food source for dozens

of species of birds that migrate from South America to the

Arctic Circle. Furthermore, crabs are collected for medical

Environmental Encyclopedia 3

Horseshoe crabs

research. After blood is taken from the crabs, they are re-

turned to the ocean.

American horseshoe crabs live along the Atlantic

Ocean coastline. Crab

habitat

extends south from Maine

to the Yucata

n in the Gulf of Mexico. Several other crab

species are found in Southeast Asia and Japan.

The American crab is named for its helmet-like shell

that is shaped like a horseshoe. Limulus has a sharp tail

shaped like a spike. The tail helps the crab move through

the sand. If the crab tips over, the tail serves as a rudder so

the crab can get back on its feet. The horseshoe crab is

unique; its blood is blue and contains

copper

. The blood

of other animals is red and contains iron.

Mature female crabs measure up to 24 inches in length.

Males are about two-thirds smaller. Horseshoe crabs can

live for 19 years, and they reach sexual maturity in 10 years.

The crabs come to shore to spawn in late May and early

June. They spawn the during the phases of the full and new

moon. The female digs nests in the sand and deposits from

200 to 300 eggs in each pit. The male crab fertilizes the

eggs with sperm, and the egg clutch is covered with sand.

During the spawning season, a female crab could de-

posit as many as 90,000 eggs. This spawning process coin-

cides with the

migration

of shorebirds. Flocks of birds like

the red knot and the sandpiper eat their fill of crab eggs

before continuing their northbound migration.

Through the years, people found a variety of uses

for horseshoe crabs. During the sixteenth century, Native

Americans in South Carolina attached the tails to the spears

that they used to catch fish. In the nineteenth century, people

ground the crabs up for use as

fertilizer

or food for chickens

and hogs.

During the twentieth century, researchers learned

much about the human eye by studying the horseshoe crab’s

compound eye. Furthermore, researchers discovered that the

crab’s blood contained a special clotting agent that could be

used to test the purity of new drugs and intravenous solu-

tions. The agent called Limulus Amoebocyte Lysate is obtained

by collecting horseshoe crabs during the spawning season.

Crabs are bled and then returned to the beach.

Horseshoe crabs are also used as bait. The harvesting

of crabs increased sharply during the 1990s when people in

the fishing industry used crabs as bait to catch eels and

conch. The annual numbers of crabs harvested jumped from

the thousands to the millions during the 1990s, according

to environmental groups and organizations like the

National

Audubon Society

The declining horseshoe crab population could affect

millions of migrating birds. The Audubon Society reported

seeing fewer birds at the Atlantic beaches where horseshoe

723

A horseshoe crab (

Limulus polyphemus

). (©John

M. Burnley, National Audubon Society Collection. Photo

Researchers Inc. Reproduced by permission.)

crabs spawn. In the spring of 2000, scientists said that birds

appeared undernourished. Observers doubted that they

would complete their journey to the Arctic Circle.

The Audubon Society and environmental groups have

campaigned for state and federal regulations to protect horse-

shoe crabs. By 2002, coastal states and the Atlantic States

Marine Fisheries Commission had set limits on the amount

of crabs that could be harvested. The state of Virginia made

bait bags mandatory when fishing with horseshoe crab bait.

The mesh bag made of hard plastic holds the crab. That

made it more difficult for predators to eat the crab so fewer

Limuluscrabs were needed as bait.

Furthermore, the federal government created a 1,500-

square-mile refuge for horseshoe crabs in Delaware Bay.

The refuge extends from Ocean City, New Jersey to north

of Ocean City, Maryland. As of March of 2002, harvesting

was banned in the refuge. People who took crabs from the

area faced a fine of up to $100,000, according to the National

Marine Fisheries Service.

As measures like those were enacted, marine biologists

said that it could be several decades before the crab popula-

tion increased. One reason for slow

population growth

was that it takes crabs 10 years to reach maturity.

[Liz Swain]

Environmental Encyclopedia 3

Household waste

ESOURCES

OOKS

Fortey, Richard. Trilobite!: Eyewitness to Evolution. New York: Alfred A.

Knopf, 2000.

Tanacredi, John, Ed. Limulus in the Limelight: 350 Million Years in the

Making and in Peril? New York: Kluwer Academic Publishers, 2001.

RGANIZATIONS

Atlantic States Marine Fisheries Commission., 1444 Eye Street, NW, Sixth

Floor, Washington, D.C. 20005 (202) 289-6400, Fax: (202) 289-6051,

Email: comments@asmfc.org, http://www.asmfc.org

National Audubon Society Horseshoe Crab Campaign., 1901 Pennsylvania

Avenue NW, Suite 1100, Washington, D.C. 20006 (202) 861-2242, Fax:

(202) 861-4290, Email: pplumart@audubon.org, http://www.audubon.org/

campaign/horseshoe/contacts.htm

National Marine Fisheries Service., 1315 East West Highway, SSMC3,

Silver Spring, MD 20910 (301) 713-2334, Fax: (301) 713-0596, Email:

cyber.fish@noaa.gov, hhttp://www.nmfs.noaa.gov

Hospital wastes

see

Medical waste

Household waste

Household waste is commonly referred to as

garbage

trash. As the population of the world expands, so does the

amount of waste produced. Generally, the more automated

and industrialized human societies become, the more waste

they produce. For example, the industrial revolution intro-

duced new manufactured products and new manufacturing

processes that added to household

solid waste

and indus-

trial waste. Modern consumerism and the excess packaging

of many products also contribute significantly to the increas-

ing amount of solid waste.

Much of the trash Americans produce (about 40%) is

paper and paper products. Paper accounts for more than 71

million tons of garbage. Yard wastes are the next most com-

mon waste, contributing more than 31 million tons of solid

waste. Metals account for more than 8% of all household

waste, and

plastics

are close behind with another 8% or 14

million tons. America’s trash also contains about 7% glass

and nearly 20 million tons of other materials like

rubber

textiles, leather, wood, and inorganic wastes. Much of the

waste comes from packaging materials. Other types of waste

produced by consumers are durable goods such as tires,

appliances, and furniture, while other household solid waste

is made up of non-durable goods such as paper, disposable

products, and clothing. Many of these items could be recy-

cled and reused, so they also can be considered a non-utilized

resource.

In less industrialized times and even today in many

developing countries, households and industries disposed of

unwanted materials in bodies of water or in land dumps.

724

However, this practice creates undesirable effects such as

health hazards and foul odors. Open dumps serve as breeding

grounds for disease-carrying organisms such as rats and in-

sects. As the

first world

became more alert to environmental

hazards, methods for waste disposal were studied and im-

proved. Today, however, governments, policymakers, and

individuals still wrestle with the problem of how to improve

methods of waste disposal, storage, and

recycling

In 1976, the United States Congress passed the

Re-

source Conservation and Recovery Act

(RCRA) in an

effort to protect human health and the

environment

from

hazards associated with waste disposal. In addition, the act

aims to conserve energy and

natural resources

and to re-

duce the amount of waste Americans generate. Further, the

RCRA promotes methods to manage waste in an environ-

mentally sound manner. The act covers regulation of solid

waste,

hazardous waste

, and underground storage tanks

that hold

petroleum

products and certain

chemicals

Most household solid waste is removed from homes

through community garbage collection and then taken to

landfills. The garbage in landfills is buried, but it can still

produce noxious odors. In addition, rainwater can seep

through

landfill

sites and leach out pollutants from the

landfill trash. These are then carried into nearby bodies of

water. Pollutants can also contaminate

groundwater

, which

in turn leads to contamination of drinking water.

In order to fight this problem, sanitary landfills were

developed. Clay or plastic liners are placed in the ground

before garbage is buried. This helps prevent water from

seeping out of the landfill and into the surrounding environ-

ment. In sanitary landfills, each time a certain amount of

waste is added to the landfill, it is covered by a layer of

soil

At a predetermined height the site is capped and covered

with dirt. Grass and trees can be planted on top of the

capped landfill to help prevent

erosion

and to improve the

look of the site. Sanitary landfills are more expensive than

open pit dumps, and many communities do not want the

stigma of having a landfill near them. These factors make

it politically difficult to open new landfills. Landfills are

regulated by state and local governments and must meet

minimum requirements set by the United States

Environ-

mental Protection Agency

(EPA). Some household haz-

ardous wastes such as paint, used motor oil, or insecticides

can not be accepted at landfills and must be handled sepa-

rately.

Incineration

(burning) of solid waste offers an alterna-

tive to disposal in landfills. Incineration converts large

amounts of solid waste to smaller amounts of ash. The ash

must still be disposed of, however, and it can contain toxic

materials. Incineration released

smoke

and other possible

pollutants into the air. However, modern incinerators are

equipped with smokestack

scrubbers

that are quite effective

Environmental Encyclopedia 3

Hubbard Brook Experimental Forest

in trapping toxic emissions. Many incinerators have the

added benefit of generating electricity from the trash they

burn.

Composting

is a viable alternative to landfills and

incineration for some

biodegradable

solid waste. Vegetable

trimmings, leaves, grass clippings, straw, horse manure,

wood chippings, and similar plant materials are all biode-

gradable and can be composted. Compost helps the environ-

ment because it reduces the amount of waste going into

landfills. Correct composting also breaks down biodegrad-

able material into a nutrient-rich soil additive that can be

used in gardens or for landscaping. In this way, nutrients vital

to plants are returned to the environment. To successfully

compost biodegradable wastes, the process must generate

high enough temperatures to kill seeds or organisms in the

composted material. If done incorrectly, compost piles can

give off foul odors.

Families and communities can help reduce household

waste by making some simple lifestyle changes. They can

reduce solid waste by recycling, repairing rather than replac-

ing durable goods, buying products with minimal packaging,

and choosing packaging made from recycled materials. Re-

ducing packaging material is an example of source reduction.

Much of the responsibility for source reduction with manu-

facturers. Businesses need to be encouraged to find smart

and cost effective ways to manufacture and package goods

in order to minimize waste and reduce the toxicity of the

waste created. Consumers can help by encouraging compa-

nies to create more environmentally responsible packaging

through their choice of products. For example, consumers

successfully pressured McDonalds to change from serving

their sandwiches in non-biodegradable Styrofoam boxes to

wrapping them in biodegradable paper.

For individual households can reduce the amount of

waste they send to landfills by recycling. Paper,

aluminum

glass, and plastic containers are the most commonly recycled

household materials. Strategies for household recycling vary

from community to community. In some areas materials

must separated by type before collection. In others, the sepa-

ration occurs after collection.

Recycling preserves natural resources by providing an

alternative supply of raw materials to industries. It also saves

energy and eliminates the emissions of many toxic gases and

water pollutants. In addition, recycling helps create jobs,

stimulates development of more environmentally sound

technologies, and conserves resources for

future genera-

tions

. For recycling to be successful, there must be an end

market for goods made from recycled materials. Consumers

can support recycling by buying “green” products made of

recycled materials.

Battery recycling

is also becoming increasingly com-

mon in the United States and is required by law in many

725

European countries. In 2001, a nonprofit organization called

Rechargeable Battery Recycling Corporation (RBRC) began

offering American communities cost-free recycling of porta-

ble rechargeable batteries such as those used in cell phones,

camcorders, and laptop computers. These batteries contain

cadmium

, which is recycled back into other batteries or

used in certain coatings or color pigments.

Household waste disposal is an international problem

that is being attacked in many ways in many countries. In

Tripoli, Libya, a plant exploits household waste, converting

it to organic

fertilizer

. The plant recycles 500 tons of house-

hold waste, producing 212 tons of fertilizer a day. In France,

a country with less available space for landfills than the

United States, incineration is proving a desirable alternative.

The French are turning household waste into energy through

combustion

and are developing technologies to control the

residues that occur from incineration.

In the United States, education of consumers is a key

to reducing the volume and toxicity of household waste. The

EPA promotes four basic principles for reducing solid waste:

reduce the amount of trash discarded,

reuse

products and

containers, recycle and compost, and reconsider activities

that produce waste.

[Teresa G. Norris]

ESOURCES

THER

“Communities Invited to Recycle Rechargables Cost Free.” Environmental

News Network. October 11, 2001 [cited July 2002]. <http://www.enn.-

com/news>.

RGANIZATIONS

U.S. Environmental Protection Agency Office of Solid Waste, 1200

Pennsylvania Avenue NW, Washington, DC USA 20460 (703) 412-9810,

Toll Free: (800) 424-9346, , <http://www.epa.gov>

HRS

see

Hazard Ranking System

Hubbard Brook Experimental Forest

The Hubbard Brook Experimental Forest is located in West

Thornton, New Hampshire. It is an experimental area estab-

lished in 1955 within the White Mountains

National Forest

in New Hamphire’s central plateau and is administered by

the U.S.

Forest Service

. Hubbard Brook was the site of

many important ecological studies beginning in the 1960s

which established the extent of

nutrient

losses when all the

trees in a

watershed

are cut.

Hubbard Brook is a north temperate watershed cov-

ered with a mature forest, and it is still accumulating

bio-

Environmental Encyclopedia 3

Hudson River

mass

. In one early study, vegetation cut in a section of

Hubbard Brook was left to decay while nutrient losses were

monitored in the

runoff

. Total

nitrogen

losses in the first

year were twice the amount cycled in the system during a

normal year. With the rise of nitrate in the runoff, concentra-

tions of calcium, magnesium, sodium, and potassium rose.

These increases caused eutrophication and

pollution

of the

streams fed by this watershed. Once the higher plants had

been destroyed, the

soil

was unable to retain nutrients.

Early evidence from the studies indicated that total

losses in the

ecosystem

due to the

clear-cutting

were a

large number of the total inventory of

species

. The site’s

ability to support complex living systems was reduced. The

lost nutrients could accumulate again, but

erosion

of pri-

mary minerals would limit the number of plants and animals

sustained in the area.

Another study at the Hubbard Brook site investigated

the effects of forest cutting and

herbicide

treatment on

nutrients in the forest. All of the vegetation in one of Hub-

bard Brook’s seven watersheds was cut and then the area

was treated with the herbicides. At the time the conclusions

were startling:

deforestation

resulted in much larger runoffs

into the streams. The

of the

drainage

stream went from

5.1 to 4.3, along with a change in temperature and electrical

conductivity of the stream water. A combination of higher

nutrient concentration, higher water temperature, and

greater solar radiation due to the loss of forest cover produced

algal bloom

, the first sign of eutrophication. This sig-

naled that a change in the ecosystem of the watershed had

occurred. It was ultimately demonstrated at Hubbard Brook

that the use of herbicides on a cut area resulted in their

transfer to the outgoing water.

Hubbard Brook Experimental Forest continues to be

an active research facility for foresters and biologists. Most

current research focuses on

water quality

and nutrient ex-

change. The Forest Service also maintians an

acid rain

monitoring station, and conducts research on old-growth

forests. The results from various studies done at Hubbard

Brook have shown that mature forest ecosystems have a

greater ability to trap and store nutrients for

recycling

within

the ecosystem. In addition, mature forests offer a higher

degrees of

biodiversity

than do forests that are clear-cut.

See also Aquatic chemistry; Cultural eutrophication; Decline

spiral; Experimental Lakes Area; Nitrogen cyle

[Linda Rehkopf]

ESOURCES

OOKS

Bormann, F. H. Pattern and Process in a Forested Ecosystem: Disturbance

Development and the Steady State Based on the Hubbard Brook Ecosystem

Study. New York: Springer-Verlag, 1991.

726

Botkin, D. B. Forest Dynamics: An Ecological Model. New York: Oxford

University Press, 1993.

ERIODICALS

Miller, G. “Window Into a Water Shed.” American Forests 95 (May-June

1989): 58–61.

Hudson River

Starting at Lake Tear of the Clouds, a two-acre (0.8-ha)

pond in New York’s

Adirondack Mountains

, the Hudson

River runs 315 miles (507 km) to the Battery on Manhattan

Island’s southern tip, where it meets the Atlantic Ocean.

Although polluted and extensively dammed for hydroelectric

power, the river still contains a wealth of aquatic

species

including massive sea sturgeon (Acipenser oxyrhynchus) and

short-nosed sturgeon (A. brevirostrum). The upper Hudson is

fast-flowing trout stream, but below the Adirondack Forest

Preserve,

pollution

from municipal sources, paper compa-

nies, and industries degrades the water. Stretches of the

upper Hudson contain so-called warm water fish, including

northern pike (Esox lucius), chain pickerel (E. niger),

smallmouth bass (Micropterus dolomieui), and largemouth

bass (M. salmoides). These latter two fish swam into the

Hudson through the

Lake Erie

and Lake Champlain canals,

which were completed in the early nineteenth century.

The Catskill Mountains dominate the mid-Hudson

region, which is rich in fish and

wildlife

, though dairy

farming, a source of

runoff

pollution, is strong in the region.

American shad (Alosa sapidissima), historically the Hudson’s

most important commercial fish, spawn on the river flats

between Kingston and Coxsackie. Marshes in this region

support snapping turtles (Chelydra serpentina) and, in the

winter, muskrat (Ondatra zibethicus) and mink (Mustela vi-

son). Water chestnuts (Trapa natans) grow luxuriantly in

this section of the river.

Deep and partly bordered by mountains, the lower

Hudson resembles a fiord. The unusually deep lower river

makes it suitable for navigation by ocean-going vessels for

150 miles (241 km) upriver to Albany. Because the river’s

surface elevation does not drop between Albany and Man-

hattan, the tidal effects of the ocean are felt all the way

upriver to the Federal Lock and Dam above Albany. These

powerful tides make long stretches of the lower Hudson

saline or

brackish

, with saltwater penetrating as high as 60

miles (97 km) upstream from the Battery.

The Hudson contains a great variety of botanical spe-

cies. Over a dozen oaks thrive along its banks, including red

oaks (Quercus rubra), black oaks (Q. velutina), pin oaks (Q.

palustris), and rock chestnut (Q. prinus). Numerous other

trees also abound, from mountain laurel (Kalmia latifolia)

and red pine (Pinus resinosa) to flowering dogwood (Cornus