sev-eral levels on the food chain, it has been suggestedthat a higher world population could be supported by humans moving down the food chain and becoming only vegetarians.. While peopl
Trang 1As early as 1789, naturalists such as Gilbert White
de-scribed the many sequences of animals eating plants,
and animals being eaten by other animals However,
the use of the term “food chain” dates from 1927,
when Charles S Elton described the implications of
the food chain and food web concept in a clear
man-ner His solid exposition advanced the study of two
im-portant biological concepts: the complex
organiza-tion and interrelatedness of nature, and energy flow
through ecosystems
Food Chains in Ecosystem Description
Stephen Alfred Forbes, founder of the Illinois Natural
History Survey, contended in 1887 that a lake
com-prises a system in which no organism or process can
be understood unless its relationship to all the parts is
understood Forty years later, Elton’s food chains
pro-vided an accurate way to diagram these relationships
Since most organisms feed on several food items, food
chains were cross-linked into complex webs with
pre-dictive power For instance, algae in a lake might
sup-port an insect that in turn is food for bluegill If
unfa-vorable conditions eliminate this algae, the insect
might also disappear However, the bluegill, which
feeds on a wider range of insects, survives because the
loss of this algae merely increases the pressure on the
other food sources This detailed linkage of food
chains advanced agriculture and wildlife management
and gave scientists a solid overview of living systems
When Arthur G Tansley penned the term
“ecosys-tem” in 1939, it was food-chain relationships that
de-scribed much of the equilibrium of the ecosystem
Most people still think of food chains as the basis
for the “balance of nature.” This phrase dates from
the controversial 1960 work of Nelson G Hairston,
Frederick E Smith, and Lawrence B Slobodkin They
proposed that if only grazers and plants are present,
grazing limits the plants However, with predators
present, grazers are limited by predation, and the
plants are free to grow to the limits of the nutrients
available Such explanations of the “balance of nature”
were commonly taught in biology books throughout
the 1960’s and 1970’s
Food Chains in Production Biology
Elton’s explanation of food chains came only one year
after Edgar Nelson Transeau of Ohio State University
presented his calculations on the efficiency with which
corn plants converted sunlight into plant tissue
Ecol-ogists traced this flow of stored chemical energy up the food chain to herbivores that ate plants and on to carnivores that ate herbivores Food chains therefore undergirded the new “production biology” that placed all organisms at various trophic levels and calculated the extent to which energy was lost or preserved as it passed up the food chain
With data accumulating from many ecologists, Elton extended food chains into a pyramid of num-bers The food pyramid in which much plant tissue supports some herbivores that are in turn eaten by fewer carnivores is still referred to as an “Eltonian pyr-amid.” In 1939, August Thienemann added “decom-posers” to reduce unconsumed tissues and return the nutrients of all levels back to the plants Early pyra-mids were based on the amount of living tissues or bio-mass
Calculations based on the amount of chemical en-ergy at each level, as measured by the heat released (calories) when food is burned, provided even more accurate budgets Because so much energy is lost at each stage in a food chain, it became obvious that this inefficiency is the reason food chains are rarely more than five or six links long and why large, fierce animals are uncommon It also became evident that because the Earth intercepts a limited amount of sunlight en-ergy per year, there is a limit on the amount of plant life—and ultimately upon the amount of animal life and decomposers—that can be fed Food chains are also important in the accounting of carbon, nitrogen, and water cycling
Value of Food Chains in Environmental Science
Unlike calories, which are dramatically reduced at each step in a food chain, some toxic substances be-come more concentrated as the molecules are passed along The concentration of molecules along the food chain was first noticed by the Atomic Energy Commis-sion, which found that radioactive iodine and stron-tium released in the Columbia River was concentrated
in tissue of birds and fish However, the pesticide dichloro-diphenyl-trichloroethane (DDT) provided the most notorious example of biological magnifica-tion: DDT was found to be deposited in animal body fat
in ever-increasing concentrations as it moved up the food chain to ospreys, pelicans, and peregrine falcons High levels of DDT in these birds broke down steroid hormones and interfered with eggshell formation Because humans are omnivores able to feed at
Trang 2sev-eral levels on the food chain, it has been suggested
that a higher world population could be supported by
humans moving down the food chain and becoming
only vegetarians A problem with this argument is that
much grazing land worldwide is unfit for cultivation,
and therefore the cessation of pig or cattle farming
does not necessarily free up substantial land to grow
crops
While the food chain and food web concepts are
convenient theoretical ways to summarize feeding
in-teractions among organisms, real field situations have
proved far more complex and difficult to measure
Animals often switch diets between larval and adult
stages, and they are often able to shift food sources
widely In real life, it is often difficult to draw the
boundaries of food chains and food webs
John Richard Schrock
Further Reading
Colinvaux, Paul “The Efficiency of Life.” In Why Big
Fierce Animals Are Rare: An Ecologist’s Perspective.
Princeton, N.J.: Princeton University Press, 1978
Golley, Frank Benjamin A History of the Ecosystem
Con-cept in Ecology: More than the Sum of the Parts New
Ha-ven, Conn.: Yale University Press, 1993
Lowenfels, Jeff, and Wayne Lewis Teaming with
Mi-crobes: A Gardener’s Guide to the Soil Food Web
Port-land, Oreg.: Timber Press, 2006
Pimm, Stuart L Food Webs New York: Chapman and
Hall, 1982 Reprint Chicago: University of
Chi-cago Press, 2002
Rooney, N., K S McCann, and D L G Noakes, eds
From Energetics to Ecosystems: The Dynamics and
Struc-ture of Ecological Systems Dordrecht, the
Nether-lands: Springer, 2007
Schilthuizen, Menno The Loom of Life: Unravelling
Eco-systems Berlin: Springer, 2008.
See also: Biosphere; Carbon cycle; Ecology;
Ecosys-tems; Lithosphere; Nitrogen cycle; Phosphorus cycle;
Sulfur cycle
Food shortages
Category: Social, economic, and political issues
Throughout human history, civilizations have been
plagued by malnutrition, hunger, and famine The
growth of the human population, the ecological disas-ters the world is facing, and continued warfare and civil strife have all been named as contributors to the problem in modern times.
Background The procurement of food is one of the necessities of all societies For thousands of years this was accom-plished by hunting and gathering While people were able to find and to use a variety of types of food, they were not always able to acquire the items they needed
in the quantities that were required With the onset of the agricultural revolution and the advent of orga-nized farming, the problem was alleviated to a certain extent Individuals and societies had more control over what their food supply might be at a given time While this fact did not eradicate the problems caused
by natural disasters that could destroy food sources, it did help to mitigate those catastrophes
Other important developments were the scientific and technological advances that occurred beginning
in the sixteenth century The results of this scientific progress were applied to agricultural endeavors, med-ical practice, and industry The knowledge gleaned from science enabled farmers to grow additional crops and to increase the productivity of the land on which they grew them The advances in medical science in-creased the life expectancy of people and thus created additional demands for the foodstuffs that were pro-duced The Industrial Revolution also led to the in-vention of fuels and machines These fuels provided the energy to run the factories that created farm equipment and machinery They later served as a source of energy for farm equipment
Population
By 2009, the global population was approximately 6.8 billion Very poor people continue to have large fami-lies for a variety of cultural and religious reasons Large families provide labor; in some countries chil-dren as young as six years of age are part of the family’s labor pool Besides providing more income, having many family members may mean more clout in com-munity affairs Extra children also provide additional hands to care for parents in their old age
It would be tempting simply to blame the problem
of food shortages on the world’s increasing popula-tion, but population increase alone is by no means re-sponsible for the hunger that exists in the world Rather, food shortages are caused by a combination of
Trang 380 70
60 50
40 30
20 10
Source: United Nations, Millennium Development Goals Indicators, 2009.
Congo, Democratic Republic of the
Eritrea Burundi Haiti Comoros Sierra Leone Angola Ethiopia Zambia Central African Republic
Liberia Rwanda Zimbabwe Chad Mozambique Madagascar Togo Tanzania Tajikistan Djibouti Guinea-Bissau Kenya North Korea Yemen Gambia
76 68 63 58 52 47 46 46 45 43 40 40 40 39 38 37 37 35 34 32 32 32 32 32 30
Undernourished Population (%)
World’s Hungriest Nations, 2004
Trang 4elements that contribute to block access to the tools
that would enable people or cultural groups to break
the cycle of hunger
Extent and Causes of Hunger
Estimates indicate that at least one billion people are
hungry at any given time Almost sixteen thousand
children die of hunger-related diseases each day
Mal-nutrition, or not getting the proper nutrients, is one
of these related syndromes Malnutrition often leads
to other diseases, such as goiter, as is the case in
Ban-gladesh, where people have great iodine deficiencies
Pellagra, another malnutrition-related
disease, is caused by a lack of the amino
acid tryptophan Pellagra is found in
countries where the diet consists mainly
of maize and jowah, a type of sorghum
eaten mainly in India Nutritional
blind-ness also is a side effect of malnutrition
Infantile marasmus and kwashiorkor are
two protein-deficiency diseases that cause
lethargy, edema, and a number of other
medical problems These are brought on
by a lack of protein in the diet and are
prevalent in West Africa
One of the easiest methods of
ascer-taining the extent of hunger worldwide is
to examine infant mortality rates In
coun-tries where hunger is greatest, the infant
mortality rate tends to be high It is often
as high as 50 deaths per every 1,000 births;
in Angola, the infant mortality rate is 180
In developed countries, in contrast, the
rate is far lower Singapore has the lowest
rate at 2.31 In less developed countries,
the infant mortality rate averages 90 per
1,000; in more developed countries it
av-erages 8 (In all countries the rate varies
from area to area.) The developed, or
highly industrialized, countries are able
to feed their own populations and
gener-ally have additional supplies of food to
send to other nations Developing
coun-tries, however, include more than
two-thirds of the world’s population and
ac-count for more than 90 percent of the
hunger that exists in the world Estimates
indicate that 14 to 18 million people die
each year from hunger The World Health
Organization states that more than 820
million people in developing countries suffer from malnutrition
There are a number of explanations for hunger throughout the world Many experts believe that hun-ger arises not so much from overpopulation as from the inequitable distribution of food supplies In other words, a small number of people are responsible for the production of food and are obliged to apportion
it to the world Political scientist Susan George argues this viewpoint and states that it is not only the ineffec-tive or inequitable distribution of food that leads
to hunger; in addition, the inequitable income
distri-Women in Pakistan buy rice discounted for Ramadan The reduced price of the rice
is a humanitarian gesture by the government of a country beset by food shortages.
(Mohsin Raza/Reuters/Landov)
Trang 5bution among the peoples of the world leads to the
in-ability to purchase food Poverty leads to hunger, and
the causes of poverty throughout the world are many
Large numbers of people are poor because they have
no access to land or to the means of production Many
people have no way to earn a living, and many are
forced to migrate to other places—which often offer
no relief for their suffering Hunger occurs when there
are societal dislocations; Arline T Golkin summarizes
these as “disorders in food production, distribution,
earning capacity, medical care, and levels of
develop-ment.” Hunger exists in rich nations as well as poor
Environmental factors such as soil erosion,
defor-estation, and desertification lead to a diminution of
farmland, a situation that eventually leads to food
shortages and hunger Deforestation leads to the
wash-ing away of soil Forests are often destroyed to provide
fuel; in other cases, forests are reduced or washed
away completely by flooding The Food and
Agricul-ture Organization of the United Nations estimates
that some 70 percent of global drylands, which are
30 percent of the globe, are already degraded, with
much of the farmland becoming desert annually
De-sertification is caused by periods of exceptional
dry-ness in an already tenuous climate Desertification is
found in a number of African countries as well as in
Russia, Ecuador, Nepal, and other nations For all
these reasons there is a shortage of usable farmland,
which translates into hunger as a chronic condition
for millions of people throughout the world
When hunger persists in a region for an extended
period of time and leads to increased mortality from
disease or starvation, famine exists These periods can
last for several years, and often more than a food
shortage is involved Major famines have occurred
throughout history Since 1970, famines have occurred
in Ethiopia, Nigeria, the Democratic Republic of the
Congo, Sudan, the Sahel region in northern Africa,
and North Korea In Ethiopia, the cause was drought
In the Democratic Republic of the Congo and
Nige-ria, civil war was primarily responsible Frequently, a
famine is indicative of many underlying structural
malfunctions within a society A long and deep
reces-sion in a rural area, for example, can cause dislocation
in employment, income, and production The people
who are most subject to displacement by this process
are those who own no land, artisans, and those who
trade in goods and services
In times of famine, people are unable to pay for
ar-tisans’ services and products As John Osgood Field
states, “famine occurs not only because a chain of events disposes to a famine outcome but also because nothing, or at least nothing effective, is done to break the process.” Most of the countries that are subject to famine do not have the resources with which to break the cycle of famine, and often the ecosystem is out of balance in a number of ways While societal problems may lead to famines, they can also be the outgrowth of famines When groups of people suffer from famine, they frequently migrate elsewhere if they are able; they then become part of the throng of people in overcrowded cities The result can be significant num-bers of people hoarding, huge increases in the price
of food, and concomitant violence
Judy Arlis Chesen
Further Reading
Bennett, Jon The Hunger Machine: The Politics of Food.
New York: Polity Press in association with B Black-well, 1987
Devereux, Stephen, ed The New Famines: Why Famines Persist in an Era of Globalization New York:
Rout-ledge, 2007
Field, John Osgood, ed The Challenge of Famine: Recent Experience, Lessons Learned West Hartford, Conn.:
Kumarian Press, 1993
George, Susan How the Other Half Dies: The Real Rea-sons for World Hunger New York: Penguin, 1976 George, Susan, and Nigel Paige Food for Beginners.
New York: W W Norton, 1982
Golkin, Arline T Famine, a Heritage of Hunger: A Guide
to Issues and References Claremont, Calif.: Regina
Books, 1987
Patel, Rajeev Stuffed and Starved: Markets, Power, and the Hidden Battle for the World Food System Toronto:
HarperCollins, 2007
Roberts, Paul The End of Food Boston: Houghton
Miff-lin, 2008
Southgate, Douglas, Douglas H Graham, and Luther
Tweeten The World Food Economy Malden, Mass.:
Blackwell, 2007
Stanford, Claire, ed World Hunger Bronx, N.Y.: H W.
Wilson, 2007
See also: Desertification; Developing countries; Drought; Earth First!; Earth Summit; Environmental degradation, resource exploitation and; Green Revo-lution; Land ethic; Land-use regulation and control; United Nations Convention to Combat Desertifica-tion
Trang 6Ford, Henry
Category: People
Born: July 30, 1863; Springwells township (now
Dearborn), Michigan
Died: April 7, 1947; Dearborn, Michigan
The “automobile age” of the twentieth century owes its
existence largely to Henry Ford’s vision of the
automo-bile as a utility vehicle for the masses rather than as
a wealthy individual’s luxury Ford’s development of
the Model T instituted some of the greatest and most
rapid changes in the history of modern civilization.
Biographical Background
Henry Ford’s conception of mass-produced
automo-biles manufactured at a rapid rate changed the
world’s concept of crucial resources An American
inventor, world-famous industrialist, and
technologi-cal genius, Ford learned about internal combustion
engines when he was nineteen In 1896, he built his
first “horseless carriage,” the four-horsepower
Quad-ricycle In 1899, he formed the Detroit Automobile
Company (later reorganized as the Henry Ford
Com-pany) and built several racing cars, including the
“999.”
Ford left the Detroit Automobile Company to start
the Ford Motor Company, which was incorporated in
1903 The company’s first automobile on the market
was the Model A, built in 1903 Realizing the Model A
was not the car that he believed the United States
needed, he declared, “I will build a motor car for the
great multitude.” In October, 1908, he announced
the birth of the Model T, an automobile that was built
with the most advanced production technology
con-ceived to that point The car arrived on the market the
following year
The establishment of a constantly moving main
production line in Highland Park, Michigan, that
eventually reduced the assembly time of a car from
twelve hours to one and one-half was the cause of the
spectacular success of the Model T, of which nearly
seventeen million were sold over a period of nineteen
years It took a number of years to perfect this
assem-bly line Ford’s production methods were intensively
studied In 1914, after the Model T was a success, Ford
startled the world by announcing a $5 daily wage
(compared with an average of $2.34)
Ford established small village factories and built
schools that emphasized vocational training His hold-ings eventually went into the Ford Foundation, the richest private foundation in the world Henry Ford worked intuitively, and he spent most of his life mak-ing headlines, both positive and negative
Impact on Resource Use Without the twenty-four-hour assembly line and its utilization in the creation of millions of affordable au-tomobiles, resources such as petroleum, rubber (both natural and artificial), and the metals used to produce automotive components would not have the impor-tance they do in contemporary society Ford’s influ-ence reached far beyond the automotive world, in that other industries adapted his efficient assembly-line technique to their own needs
Mysore Narayanan
See also: Gasoline and other petroleum fuels; Inter-nal combustion engine; Oil industry; Rockefeller, John D.; Rubber, natural; Steel
Henry Ford’s technological contribution to the transportation in-dustry helped generate America’s love affair with the automobile.
(Library of Congress)
Trang 7Forest fires
Category: Environment, conservation, and
resource management
Forest fires can be natural or caused by humans They
destroy life and property and devastate thousands of
hectares, but they are also vital to the health of the
forest.
Background
Evidence of forest fires is routinely found in soil
sam-ples and tree borings The first major North American
fires in the historical record were the Miramichi and
Piscataquis fires of 1825 Together, they burned more
than 1 million hectares in Maine and New Brunswick
Other U.S fires of significance were the Peshtigo fire
in 1871, which raged over 500,000 hectares and took
fourteen hundred lives in Wisconsin; the fire that
dev-astated northern Idaho and northwestern Montana
in 1910 and killed at least seventy-nine firefighters; a
series of fires that joined forces to sweep across a third
of Yellowstone National Park in 1988; and the “Station
Fire” of 2009, the largest in the history of Los Angeles
County
Fire Behavior
Fires need heat, fuel, and oxygen They spread
hori-zontally by igniting particles at their edge At first,
flames burn at one point, then move outward,
accu-mulating enough heat to keep burning on their own
Topography and weather affect fire behavior Fires go
uphill faster than downhill because warm air rises and
preheats the uphill fuels Vegetation on south- and
west-facing slopes receives more sunlight and so is
drier and burns more easily Steep, narrow canyons
will pull heat up them like a chimney, increasing heat
intensity
For several reasons, only one-third of the
vegeta-tion within a large fire usually burns This mosaic
ef-fect may be caused by varied tree species that burn
dif-ferently, old burns that stop fire, strong winds that
blow the fire to the leeward side of trees, and varied
fuel moisture
Forest Management
One of the early criteria of forest management was
fire protection In the second quarter of the twentieth
century, lookout towers, firebreaks, and trails were
built to locate fires as quickly as possible Low fires that typically would have burned through the forest at ground level and cleared out brush every five to twenty-five years were suppressed As a result, the nat-ural cycle of frequent fires moving through an area was broken Fallen trees, needles, cones, and other debris collected as kindling on the forest floor rather than being incinerated every few years
It took foresters and ecologists fifty years to realize that too much fire suppression was as bad as too little Accumulated kindling burns hot and fast and ex-plodes into treetops The result is a devastating crown fire, a large fire that advances as a single front Burning embers of seed cones, as well as sparks borne by hot, strong winds created within the fire, are tossed into unburned areas to start more fires
In the 1970’s, prescribed burning was added to forest management techniques used to keep forests healthy Fires set by lightning are allowed to burn when the weather is cool, the area isolated, and the risk of the fire exploding into a major fire low More than 70 percent of prescribed burning takes place in the southeastern states, where natural fires would burn through an area more frequently than in the West
Causes of Fires Forest fires may be caused by natural events or human activity Most natural fires are started by lightning strikes Dozens of strikes can be recorded from one lightning storm When a strike seems likely, fire spot-ters watch for columns of smoke, and small spotter planes will fly over the area looking for smoke Many
of the small fires simply smolder and go out, but if the forest is dry because of drought or any period of hot, dry weather, multiple fires can erupt from a single lightning storm
The majority of forest fires are human-caused, and most are the result of carelessness rather than arson Careless campers may leave a campsite without squelching their campfire completely, and winds may then whip the glowing embers into flames; a smoker may toss a cigarette butt from a car window; sparks from a flat tire riding on the hub may set fire to vegeta-tion alongside the highway; and the Sun shining through a piece of broken glass left by litterers may ig-nite dry leaves
Prescribed fires may be natural or human-caused
In some areas they are set in an attempt to re-create the natural sequence of fire, as in Florida, where
Trang 8prescribed burns provide wildlife habitat and open
up groves to encourage healthy growth Other
pre-scribed fires start accidentally but are allowed to burn
until they reach a predetermined size
Benefits of Fire
Some tree species require very high temperatures for
their seed casings to split for germination When fire
periodically sweeps through the forest, seeds will
ger-minate Other species, such as the fire-resistant
pon-derosa pine, require a shallow layer of decaying
vege-table matter in which to root Fires burn excess debris
and small trees of competing species, leaving an open
environment suitable for germination Dead material
on the forest floor is processed into nutrients more
quickly by fire than by decay, and in a layer of rich soil,
plants will sprout within days to replace those
de-stroyed in the fire, thus providing feed for wildlife
Fire intervals vary Without human intervention,
spacious ponderosa pine forests will burn every five to
twenty-five years Lodgepole pine, which grows in
dense stands, will burn every two hundred to four
hundred years Southern pines, if fire is not
sup-pressed, are cleared every three to five years
Disadvantages
Erosion is one of the devastating effects of a fire If
the fuels burn hot, tree oils and resins can be baked
into the soil, creating a hard shell
that will not absorb water When it
rains, the water runoff gathers mud
and debris, creating flash floods
and extreme stream sedimentation
Culverts and storm drains fill with
silt, and streams flood and change
course Fish habitat is destroyed,
veg-etation sheltering stream banks is
ripped away, and property many
kilo-meters downstream from the forest
is affected
When a fire passes through
tim-ber, it generally leaves pockets of
green, although weakened, stands
Forest pests such as the bark beetle
are attracted to the burned trees and
soon move to the surviving trees,
weakening them further and
destroy-ing them Healthy trees outside the
burn area may also fall to pest
infes-tation unless the burned trees are
salvaged before pests can take hold The ash and smoke from hot, fast-burning forest fires can be trans-ported for kilometers, affecting the air quality of cities many kilometers from the actual fire
Relationship to Timber Resources Although a prescribed fire is an attempt to duplicate natural fire, it is not as efficient, because private and commercial property within the fire path must be pro-tected Once a fire has occurred, burned timber dete-riorates quickly, through either insect infestation or blueing—a mold that stains the wood Private land-owners can move quickly to salvage fire-damaged trees and plant new seedlings to harness erosion On federal land, regulations governing the salvage of trees can delay logging of the burned snags until dete-rioration makes it uneconomical to harvest them
Fire Fighting Bulldozers are used to cut fire lines ahead of the ap-proaching fire, and fuels between this line and the fire are backburned Helicopters and tanker planes drop water with a fire-retardant additive or bentonite, a clay, at the head of the fire to smother fuels Fire-fighters are equipped with fire shelters in the form of aluminized pup tents, which they can pull over them-selves if a fire outruns them Despite technological ad-vances, one of the best tools for fighting fires—along
A firefighter gives directions as a backfire is set during the devastating Station Fire that burned uncontrollably in the Los Angeles National Forest during the summer of 2009.
(AP/Wide World Photos)
Trang 9with the shovel—remains the Pulaski, a combination
ax and hoe, first produced commercially in 1920 This
tool, in the hands of on-the-ground firefighters, is
used to cut firebreaks and to throw dirt on smoldering
debris
Public Policy and Public Awareness
Beginning in the early twentieth century, forest fires
engendered public policy In the aftermath of major
fires in 1903 and 1908 in Maine and New York, state
fire organizations and private timber protective
asso-ciations were formed to provide fire protection These,
in turn, contributed to the Weeks Act of 1911, which
permitted cooperative fire protection between
fed-eral and state governments
People who make their homes in woodland
set-tings in or near forests face the danger of forest fire,
and government agencies provide information to help
the public safeguard themselves and their property
Homes near forests should be designed and
land-scaped with fire safety in mind, using fire-resistant,
noncombustible materials on the roof and exterior
Landscaping should include a clear safety zone
around the house, and hardwood trees, less
flamma-ble than conifers, should be planted
Jill A Cooper
Further Reading
Carle, David Burning Questions: America’s Fight with
Nature’s Fire Westport, Conn.: Praeger, 2002.
Fuller, Margaret Forest Fires: An Introduction to
Wild-land Fire Behavior, Management, Firefighting, and
Pre-vention New York: Wiley, 1991.
Omi, Philip N Forest Fires: A Reference Handbook Santa
Barbara, Calif.: ABC-CLIO, 2005
Pyne, Stephen J Awful Splendour: A Fire History of
Can-ada Vancouver: University of British Columbia Press,
2007
_ Fire in America: A Cultural History of Wildland
and Rural Fire 1982 Reprint Princeton, N.J.:
Princeton University Press, 1988
_ Smokechasing Tucson: University of Arizona
Press, 2003
Rothman, Hal K Blazing Heritage: A History of Wildland
Fire in the National Parks New York: Oxford
Univer-sity Press, 2007
Wuerthner, George, ed The Wildfire Reader: A Century
of Failed Forest Policy Washington, D.C.: Island Press,
2006
Web Site National Interagency Fire Center Fire Information: Wildland Fire Statistics http://www.nifc.gov/fire_info/fire_stats.htm See also: Erosion and erosion control; Fires; Forest management; Forestry
Forest management
Category: Environment, conservation, and resource management
Forest management is the process of planning, organiz-ing, and implementing activities designed to produce and maintain a mix of resources in the forest that will meet the goals and objectives of landowners and so-ciety.
Background
In 1967, the Society of American Foresters defined forestry as “the science, the art, and the practice of managing and using for human benefit the natural re-sources that occur on and in association with for-estlands.” In 1971, the same organization redefined forest management as “generally, the application of scientific, economic, and social principles to the ad-ministration and working of a forest estate for speci-fied objectives” and “more particularly, the branch of forestry concerned with a) the overall administrative, economic, legal, and social aspects, and b) with the es-sentially scientific and technical aspects, especially silviculture, protection, and forest regulation.” Forests include or provide many things of value to humans: water, wildlife, grazing, timber, and recre-ation Forest structure and composition can be de-signed to produce different mixtures of these things; one aspect of forest management is the determina-tion of the mixture of goods and services that will best satisfy the goals and objectives of landowners and soci-ety Forest managers have the responsibility to plan, schedule, and implement activities in the forest to achieve the management objectives
Silviculture
Ralph Nyland, in Silviculture: Concepts and Applications
(2d ed., 2001), defines silviculture as “the science and art of growing and tending forest crops” and
Trang 10particu-larly as “the theory and practice of controlling the
es-tablishment, composition, character, and growth of
forest stands to satisfy specific objectives.” Silviculture
is distinct from forest management Forest
ment is concerned with the establishment of
manage-ment goals and objectives and the administrative
ac-tivity to support the achievement of these goals, while
silviculture is concerned with the detailed
prescrip-tions for individual forest management units required
to achieve the goals set for the larger area The types
of resources to emphasize and the mix of goods and
services to produce are forest management decisions;
specific measures to achieve these goals and the
devel-opment of prescriptions for individual areas are the
province of silviculture
Protection Forest protection is the branch of forestry concerned with minimizing damage to forests from both abiotic and biotic factors Abiotic factors such as wind, floods, and fire can directly kill trees and affect the achieve-ment of manageachieve-ment goals Biotic factors such as pests, pathogens, herbivores, livestock, and humans also affect tree mortality and health The amount and type of material and human resources to allocate to fire protection, for example, are management deci-sions Forest management is concerned with the allo-cation of financial, material, and human resources to manage all of these risk factors in such a way as to bal-ance the costs of control measures with the benefits of maintaining forest health and productivity
Environmental Effects of Select Silvicultural Methods
Silvicultural methods
Converting mixed forest stands to monoculture Soil acidification
Fertilizing Increased leaching of nutrients,
especially nitrogen Forest machines leave
the residues in heaps, often on wet sites
Clear-cutting Increased water runoff Soil erosion
Soil scarification
Draining Increased amount of organic
material and metals (Fe, Al, Hg) in water and ecosystems; secondary effects on fish
Decreased number of
plant and animal species
of the forests, mires, and fens Short rotation intervals
Decreased number of old and dead trees
Foreign species Decreased number of forest
plant and animal species
Source:Adapted from I Stjernquist, “Modern Wood Fuels,” inBioenergy and the Environment, edited by Pasztor and Kristoferson, 1990.