ma-Spain: Resources at a GlanceOfficial name: Kingdom of Spain Government: Parliamentary monarchy Capital city: Madrid Area: 195,139 mi2; 505,370 km2 Population 2009 est.: 40,525,002 Lan
Trang 1In 2009, British scientists presented a design for a
gravity tractor that would fly close to an asteroid
sur-face and, through gravitational influence alone, over
perhaps fifteen years, make changes in the orbital
path of such a body If a near-Earth object or small
as-teroid were on a collision course with Earth, such a
spacecraft placed close to its surface could avert a
deadly global catastrophe A 9-metric-ton gravity
trac-tor, however, could not be used to bring a
resource-laden asteroid into Earth proximity for convenient
mining operations
Charles W Rogers and David G Fisher
Further Reading
Clarke, Arthur C The Snows of Olympus: A Garden on
Mars London: Victor Gollancz, 1994.
Davidson, Frank Paul, Katinka I Csigi, and Peter E
Glaser Solar Power Satellites: A Space Energy System for
Earth New York: Wiley & Sons, 1998.
Elbert, Bruce R Introduction to Satellite Communication.
3d ed New York: Artech House, 2008
Fogg, Martyn J Terraforming: Engineering Planetary
En-vironments Warrendale, Pa.: Society of Automotive
Engineers, 1995
Handberg, Roger International Space Commerce:
Build-ing from Scratch Gainesville: University Press of
Florida, 2006
Harris, Philip Robert Space Enterprise: Living and
Working Offworld in the Twenty-first Century New
York: Praxis, 2009
Johnson, Richard D., and Charles Holbrow, eds Space
Settlements: A Design Study Washington, D.C.:
Na-tional Aeronautics and Space Administration, 1977
Karl, John Celestial Navigation in the GPS Age New
York: Paradise Cay, 2007
Kendall, Henry W., and Steven J Nadis, eds Energy
Strategies—Toward a Solar Future: A Report of the Union
of Concerned Scientists Cambridge, Mass.: Ballinger,
1980
Lewis, John S Mining the Sky: Untold Riches from the
As-teroids, Comets, and Planets Reading, Mass.:
Addi-son-Wesley, 1996
Olla, Phillip, ed Commerce in Space: Infrastructures,
Technologies, and Applications Hershey, Pa.:
Infor-mation Science Reference, 2008
Olsen, R C Remote Sensing from Air and Space New
York: SPIE Press, 2007
Pop, Virgiliu Who Owns the Moon? Extraterrestrial
As-pects of Land and Mineral Resources Ownership
Dor-drecht, the Netherlands: Springer, 2009
Ride, Sally K Mission, Planet Earth: Our World and Its Climate—And How Humans Are Changing Them New
York: Flash Point, 2009
Robinson, Ian S Measuring the Oceans from Space: The Principles and Methods of Satellite Oceanography New
York: Springer, 2004
Schmitt, Harrison Return to the Moon: A Practical Plan for Going Back to Stay New York: Springer, 2005.
Web Site National Aeronautics and Space Administration
Using Space Resources http://ares.jsc.nasa.gov/HumanExplore/
Exploration/EXLibrary/docs/ISRU/00toc.htm See also: Aerial photography; Greenhouse gases and global climate change; Landsat satellites and satellite technologies; Ozone layer and ozone hole debate; Re-mote sensing; Solar energy; Weather and resources
Spain
Categories: Countries; government and resources
Spain tends to import more commodities than it ex-ports It once exported iron but now exports products made from iron and steel The country is a large and increasingly important exporter of olives and olive oil, sweet oranges, mandarins (especially clementines), wine, and various fruits and vegetables Most exports
go to France, Germany, Portugal, Italy, the United Kingdom, and the United States.
The Country Spain is located in the southwest corner of Europe on the Iberian Peninsula between the Atlantic Ocean and the Mediterranean Sea The dominant physical feature is the Meseta, a vast, somewhat barren table-land that has an average elevation of 600 meters and slopes gently to the west Three major rivers flow from the Meseta to the Atlantic: the Douro, Tagus, and Guadiana The high and broad Pyrenees are on the northern border with France The Cantabrian Moun-tains run behind the north coast The Betic Cordillera stretches from the Gibraltar highlands at the penin-sula’s southern tip east to the province of Alicante Less dramatic sierras punctuate the Meseta Two
Trang 2ma-Spain: Resources at a Glance
Official name: Kingdom of Spain Government: Parliamentary monarchy Capital city: Madrid
Area: 195,139 mi2; 505,370 km2
Population (2009 est.): 40,525,002 Languages: Castilian Spanish Monetary unit: euro (EUR)
Economic summary:
GDP composition by sector (2008 est.): agriculture, 3.4%; industry, 29%; services, 67.6%
Natural resources: coal, lignite, iron ore, copper, lead, zinc, uranium, tungsten, mercury, pyrites, magnesite,
fluorspar, gypsum, sepiolite, kaolin, potash, hydropower, arable land
Land use (2005): arable land, 27.18%; permanent crops, 9.85%; other, 62.97%
Industries: textiles and apparel (including footwear), food and beverages, metals and metal manufactures,
chemicals, shipbuilding, automobiles, machine tools, tourism, clay and refractory products, footwear,
pharmaceuticals, medical equipment
Agricultural products: grain, vegetables, olives, wine grapes, sugar beets, citrus, beef, pork, poultry, dairy products,
fish
Exports (2008 est.): $285.4 billion
Commodities exported: machinery, motor vehicles, foodstuffs, pharmaceuticals, medicines, other consumer goods Imports (2008 est.): $414.5 billion
Commodities imported: machinery and equipment, fuels, chemicals, semifinished goods, foodstuffs, consumer goods,
measuring and medical control instruments
Labor force (2008 est.): 22.85 million
Labor force by occupation (2008 est.): agriculture, 4%; industry, 26.4%; services, 69.5%
Energy resources:
Electricity production (2008 est.): 294.3 billion kWh
Electricity consumption (2008 est.): 276.1 billion kWh
Electricity exports (2007 est.): 14.52 billion kWh
Electricity imports (2007 est.): 8.773 billion kWh
Natural gas production (2007 est.): 88 million m3
Natural gas consumption (2007 est.): 34.43 billion m3
Natural gas exports (2007 est.): 0 m3
Natural gas imports (2007 est.): 34.47 billion m3
Natural gas proved reserves ( Jan 2008 est.): 2.548 billion m3
Oil production (2007 est.): 29,000 bbl/day Oil imports (2005): 1.777 million bbl/day Oil proved reserves ( Jan 2008 est.): 150 million bbl
Source: Data from The World Factbook 2009 Washington, D.C.: Central Intelligence Agency, 2009.
Notes: Data are the most recent tracked by the CIA Values are given in U.S dollars Abbreviations: bbl/day = barrels per day;
GDP = gross domestic product; km 2 = square kilometers; kWh = kilowatt-hours; m 3 = cubic meters; mi 2 = square miles.
Madrid
Spain
France
Portugal
Algeria Morocco
M e d i t e r r a n e a n
S e a
A t l a n t i c
O c e a n
Trang 3jor depressions are between the Meseta and the
mar-ginal ranges: the Ebro, with its namesake river
drain-ing to the Mediterranean, and the Guadalquivir, with
its namesake river flowing to the Atlantic The coastal
plains are few in number and extent Spain’s territory
also includes the Balearic Islands in the western
Medi-terranean; the Canary Islands off the northwest coast
of Africa; Ceuta and Melilla, two autonomous port
cit-ies along the Mediterranean coast of Morocco; and
six small islands off that coast In 2007, Spain had
the world’s eighth largest national economy Key
re-sources are coal, iron and steel, water, olives and olive
oil, citrus fruit, grapevines and wine, and other
miner-als and foodstuffs
Coal
Coal is Spain’s most plentiful natural resource
Bitu-minous and anthracite coals are found in the
north-ern provinces of Asturias and León and in the
south-ern provinces of Ciudad Real and Córdoba Lignite
(brown coal) occurs in the regions of Catalonia and in
Galicia Coal has been important to Spain’s economy
since the last half of the nineteenth century However,
importing coal has been necessary because Spain’s
de-posits tend to be small, with narrow seams and
impuri-ties, and domestic anthracite is not suitable for
con-version into coke for use in the iron and steel industry
Because of these disadvantages, Spain’s coal industry
demanded government protection from competition
with cheaper coal imported from Great Britain This
protection is estimated to have raised industrial prices
in Spain between 2 and 5 percent until the 1960’s,
when the coal industry was largely nationalized
A small amount of domestic black coal is used for
local industry and for heating fuel Brown coal is used
for mine-mouth power stations, but imported steam
coal is increasingly important for power generation
The main use of coal in Spain is the generation of
electric power, especially during times of drought,
when hydroelectric power is less available
Spain has reduced its subsidies to the coal industry
while investing in structural change that will limit coal
mining and government welfare for coal-mining
dis-tricts The Institute for the Restructuring of Coal
Mining and Alternative Development of Mining
Dis-tricts supports projects that create jobs and promotes
alternative development of mining areas Since 1998,
billions of dollars have been invested in hundreds
of mining-district projects, closure of some coal
pro-duction units, early retirement of miners, aid to some
companies, and investment in some companies to guarantee access to coal reserves for reasons of na-tional security
Iron and Steel The iron and steel industry depends on two main re-sources: iron and coal The nineteenth century blast furnaces required about 4 metric tons of coal to pro-cess 1 metric ton of iron This ratio drew iron and steel producers to the coal deposits Because Spanish coal was not competitive in quality and price with foreign coal, the iron and steel producers finally located in the province of Vizcaya From there, ships exported Spain’s iron ore and pig iron to England and returned with inexpensive Welsh coking coal from Cardiff By
1901, 90 percent of Spain’s excavated iron ore was ex-ported to Great Britain Although some of the largest iron-mining companies were subsidiaries of foreign iron manufacturers, most of the profits remained in Spain, helping to develop the iron and steel industry
in Vizcaya and also partially underwriting the indus-trialization of the city of Bilbao In 1902, the three largest iron and steel companies merged to form Altos Hornos de Vizcaya, which became the largest and most profitable industrial enterprise in Spain However, at that time, Spain’s outputs of pig iron and steel were small compared to those of Great Britain and Germany
The domestic industry’s growth resulted largely from tariffs protecting an oligopoly led by Altos Hornos de Vizcaya When demand for iron and steel rose, the oligopoly raised prices before attempting to increase supply Until 1960, the iron and steel indus-try retarded Spain’s economic development
In 1959, Spain adopted an economic stabilization plan and embarked on an industrial revolution in which the industrial sector grew at a faster rate than the gross domestic product (GDP) Much of the dy-namic growth in iron and steel production resulted from the derived demand of a rapidly growing Span-ish automobile industry By the 1970’s, the iron and steel industry, made more competitive by the creation
in 1956 and gradual expansion of the state-owned Empresa Nacional Siderúrgica Sociedad Anónima (ENSIDESA), began to export production
Spain was required to lower its iron and steel out-put upon joining the European Union and the Euro-pean Coal and Steel Community in 1986 Neverthe-less, the industry remains dynamic In 2006, Spain produced 17.8 million metric tons of crude steel, and
Trang 4iron and steel accounted for almost $7 billion in
ex-ports and were the seventh leading export group The
industry also supports exports of machinery, ships,
and other articles of iron and steel, not to mention the
export of vehicles, Spain’s greatest export by value
($44 billion in 2006)
Water
The most industrialized regions of Spain—the Basque
Country and Catalonia—are relatively well endowed
with water However, water is a scarce resource in most
of Spain, large regions of which receive less than 500
millimeters average annual precipitation These
re-gions are dry in the summer months, when their rivers
carry less water for irrigation, processing raw
materi-als for industry, and hydropower Only 8 percent of
Spain’s hydrologic resources are available for use
with-out artificially altering the natural regimen; in the rest
of Europe the comparable figure is 40 percent As a
re-sult, Spain has about twelve hundred large dams and
reservoirs and many canals to alter the natural water
regimen so that an estimated 37 to 47 percent of the
water is available for use
Water management in Spain focuses on the river
basin or watershed Each autonomous community
manages watersheds entirely within its boundaries A
Hydrographic Confederation oversees watersheds that
spread over more than one autonomous community Spain’s dams and reservoirs generate hydroelectric power, provide irrigation water for farming, supply potable water, support recreation, regulate down-stream flow, and make water available for interbasin transfers The large reservoirs have a water storage ca-pacity of about 52 cubic kilometers; about 79 percent
is for agriculture, 15 percent is for potable water in the urban supply network, and 6 percent is for industry The transfers of water from one basin to another
(trasvases) began in 1980 with the Tagus-Segura
aque-duct, which stretches 300 kilometers from the upper Tagus River to the Segura River basin in the provinces
of Albacete and Murcia; most of that water has been used for irrigating citrus orchards The National Hy-drological Plan of 2001 called for transfer of water from the Ebro River to basins along the Mediterra-nean coast, but public outcry led to its replacement with Programa AGUA (2004), a program to build twenty-one desalinization plants in six provinces along the Mediterranean Spain is forging additional poli-cies that support sustainable water management
Olives and Olive Oil Spain has 2.4 million hectares in olive cultivation—as much as in Italy and Greece, the next largest olive growers in Europe, combined Olive trees prefer thin,
Olive trees in Andalusia, Spain Spain is a leading producer of olives and olive oil (©Anton Moiseenko/Dreamstime.com)
Trang 5stony soils with little water and long, hot summers.
The olive tree is intolerant to temperatures less than
−5° Celsius Most of the olive cultivation is in
Anda-lusia, where 58 percent of the total cultivated area is
dedicated to olive trees The province of Jaén is home
to more than one-half of Andalusia’s olive groves,
fol-lowed in importance by the provinces of Córdoba,
Sevilla, Badajoz, and Granada Almost all of this
culti-vation is for oil; only 6 percent is for table olives
Span-iards consume about 0.4 liter of olive oil per person
per week, and olive oil provides most of the fat in their
diets Spain is the world’s largest exporter of olive oil
In recent years, olive oil production has risen in
re-sponse to world demand, which grew 4 percent per
year in the 1990’s Although the traditional form of
ol-ive cultivation has been on small farms of less than 20
hectares, the growing demand has led to more farms
larger than 100 hectares The large groves tend to be
located in flatter areas, use drip irrigation to increase
tree density, and adopt mechanical harvesting The
large groves not only enjoy lower costs of production
per kilogram of olives than small groves but also
bene-fit from European Union subsidies that are correlated
positively with the amount of production The
tradi-tional groves on steeper slopes also can receive aid, but
only if they minimize tillage, keep walls and terraces,
maintain at least 50 percent green cover on the land,
and do not use chemicals The more mountainous
traditional groves try to compensate for their lower
productivity by forming Designation of Origin (DO)
areas The DOs have regulatory councils to ensure
quality, and some of their farms have adopted organic
cultivation As Spain has more than 260 olive cultivars,
there is much room for market differentiation
Olive groves create a distinct landscape In parts of
Andalusia there are little more than olive trees for as
far as the eye can see Olive mills are located on or
near farms, so the harvested olives can be pressed
quickly to prevent an increase in acidity Virgin oil is
bottled at the mill Pomace oil is made in refineries
from olive pomace and pits and is often mixed with
virgin olive oil; it is used in commercial cooking
Lampante oil is refined in cities and is used in industry.
Citrus Fruit
Spain’s citrus crops are, in order of importance, sweet
oranges, mandarins (especially clementines),
lem-ons, grapefruit, and bitter (Seville) oranges They are
grown mainly in Mediterranean coast provinces, from
Castellón to Málaga The center of sweet orange
or-chards has been the province of Valencia; clemen-tines are raised especially in Castellón; lemons and grapefruit prefer the hotter province of Murcia How-ever, citrus production is increasing rapidly in the re-gion of Andalusia Everywhere the trees are irrigated, either through flood irrigation or, in newer orchards, through drip irrigation
The sweet orange accounts for about one-half of Spain’s citrus production The sweet oranges come in many varieties and are typically raised on small farms belonging to cooperatives that supply packinghouses Barring water-supply problems and unusually cold temperature spells, their production is gradually in-creasing
Clementines, a cross between the sweet orange and the Chinese mandarin, are small, seedless citrus of dif-ferent varieties The small clementine tree (around 3 meters tall) is trimmed annually, and the fruit must be clipped by hand; a job for which the cooperatives usu-ally recruit migrant labor Clementine cultivation has expanded significantly, with most new orchards lo-cated in the Guadalquivir Valley and averaging more than 100 hectares Spain is the world’s largest ex-porter of clementines, and U.S imports of the fruit have risen dramatically in recent years
Spain supplies nearly one-half of all the world’s exports of oranges and clementines, which gener-ates about $3 billion per year More than 80 percent
of these exports go to Europe, especially Germany, France, the Netherlands, and the United Kingdom
Grapevines and Wine Grapevines require a dry, well-drained soil, summer temperatures neither too cold nor too hot, and an au-tumn without heavy rain The vines grow in every province of Spain, but most vineyards are located along the Mediterranean coast from near the French border to the province of Almería However, the larg-est wine region is La Mancha (in the provinces of Albacete, Ciudad Real, Cuenca, and Toledo) Spain has more land devoted to the wine grape than does any other country, with 1.2 million hectares under vine cultivation However, the country produces less wine than France and Italy because of its aridity and rainfall variability
Spain’s vineyards traditionally were planted in wide rows, with drought-resistant vines kept low and bushy
to minimize evaporation The resulting wine was ordi-nary to good, with some exceptional wines in the re-gions of Jerez, La Rioja, and Priorat However, growers
Trang 6have been replacing vines with new grape varieties,
adding drip irrigation, and pursuing new methods of
wine making
Spain’s sixty-nine Qualified Designation of Origin
(DOCA) and DO areas produce distinct quality wines
crafted from 146 varieties of grapes Only La Rioja and
Priorat have the DOCA designation Vino de la Tierra
(VdlT) wines come from regions with no special DO
status but have a distinctive character Vino Comarcal
(VC) wines come from areas without any claim to
quality Finally, Vino de Mesa (VdM) table wines are a
blend of wines from different regions and from any
vintage The VC and VdM wines are for domestic
con-sumption, which is considerable, as wine is typically
imbibed with afternoon and evening meals Wine is
integral to the Spanish culture; it has been made
in the country since the fourth millennium before
Christ Today, a number of Spaniards in rural areas
make their own wines and have their own bodegas
(wine cellars), preferably in caves dug into hills near
their homes
Although wine production accounts for only 2
per-cent of Spain’s total agricultural production by value,
it enjoys the fastest growth in net sales of any agrifood
industry About one-half of Spanish wine exports is
bulk, going mainly to France, Italy, and Portugal
where it is used to blend with domestic wines before
bottling Spain’s bottled exports go mainly to
Ger-many, the United Kingdom, the United States, and
the Netherlands, in that order
Other Resources
In the dry interior of the tablelands, wheat and barley
are important crops grown for domestic
consump-tion Both are grown largely in the same areas and
usually secano (without irrigation) Although barley is
hardier, both crops can suffer significantly reduced
yields from droughts and spring storms Other crops
grown mainly for the export market include Spanish
melons, eggplants, tomatoes, lettuce, strawberries,
peppers, and tomatoes They are often grown under
huge sheets of plastic and harvested by migrants living
in nearby encampments
Spain is highly mineralized, and its metal ores
other than iron include alumina, copper, gold, lead,
mercury, nickel, pyrites, silver, tungsten, uranium,
and zinc Industrial minerals include barite, clays,
fluorspar, and potash Energy resources also include
small amounts of petroleum and natural gas
Steven L Driever
Further Reading Harrison, Joseph “The Economic History of Spain
Since 1800.” Economic History Review 43, no 1
(1990): 79-89
Sommers, Brian J The Geography of Wine: How Land-scapes, Cultures, Terroir, and the Weather Make a Good Drop New York: Penguin Group, 2008.
Tortella, Gabriel The Development of Modern Spain: An Economic History of the Nineteenth and Twentieth Cen-turies Translated by Valerie J Herr Cambridge,
Mass.: Harvard University Press, 2000
Viladomiu, Lourdes, and Jordi Rosell “Olive Oil
Pro-duction and the Rural Economy of Spain.” In Sus-taining Agriculture and the Rural Environment: Gover-nance, Policy and Multifunctionality, edited by Floor
Brouwer Northhampton, Mass.: Edward Elgar, 2004
See also: Agricultural products; Agriculture indus-try; Coal; Resources as a medium of economic ex-change; Steel; Steel industry
Species loss
Category: Environment, conservation, and resource management
Species loss, particularly the extinction of species that is caused by human activities, has increasingly con-cerned scientists in a number of fields The Endan-gered Species Act (1973) is the central piece of legisla-tion concerned with preventing species loss in the United States.
Background Public and scientific concern about species loss stems from several factors and encompasses a variety of view-points Ethically, many people believe that species have value in and of themselves and that humankind does not have the right to cause the extinction of any species A species may also have an unknown po-tential to enrich human life and health The latter argument is important in that many synthetic medi-cines and commercial products were first produced
by plants and animals The loss of species could mean the loss of beneficial new products for human soci-ety Species that exist today are the result of millions
of years of evolutionary success, and to lose species
Trang 7is to lose that evolutionary history From a resource
management point of view, ecologists and land
man-agers alike are concerned about the effects that
spe-cies loss may have on the function and stability of
bi-otic communities
The ramifications of species loss are not easily
pre-dictable The food-web relationships among species
in a community may or may not be known and, if
known, may not have been measured Relationships
such as predation, competition, and parasitism link
species into complex community relationships One
way species are linked is by trophic levels within the
community food chain, which is more accurately
de-scribed as a food web Starting with plants at the base
of the web, trophic levels begin with producers,
fol-lowed by several successive levels of consumers:
herbi-vore, first-level carniherbi-vore, second-level carniherbi-vore, and
so on, up to top carnivore Omnivores feed both as
herbivores and as carnivores and thus feed at more
than one trophic level Finally decomposers feed on
dead organisms and their waste products from all
trophic levels
Species-Removal Studies
Species-removal studies provide some indication of
what may occur when a species becomes extinct In
more than 90 percent of predator-removal studies,
population densities of prey species in the trophic
level immediately below the predator have shown a
significant increase or decrease In many cases, the
change in density was twofold Rarely has the removal
of predator species had no effect on the population
density of its prey However, not all studies have shown
the expected increase in prey density; many have
shown an unexpected decrease
For species that possibly compete with one
an-other, more than 90 percent of competitor-removal
studies have shown an increase in the “remaining
competitor” population density Several factors may
influence the strength of community response in
species-removal experiments For example, a
preda-tor may prey more heavily on a large, aggressive prey
species and thus allow the coexistence of a less
ag-gressive, competitor prey species If the predator is
removed, the aggressive prey may increase in density
while the less aggressive one may actually decrease
Studies in aquatic communities indicate that the
higher the trophic level in which species removal
oc-curs, the greater the effect on population densities at
lower trophic levels
The ramifications of species loss can be only par-tially predicted with knowledge of community food webs The size and direction of population density change within a community may or may not be as ex-pected It is safe to predict, however, that species loss will cause changes in most instances
Wildlife Protection and Endangered-Species Legislation
Concern about species loss in North America can be traced back at least as far as 1872, when legislation offering limited protection to the buffalo was passed
by Congress This legislation was passed at the height
of buffalo exploitation by market hunters and dur-ing the U.S Army’s policy of fightdur-ing American In-dian tribes by cutting off their food supply However, President Ulysses S Grant vetoed the legislation, and the buffalo was almost lost Only a few hundred re-mained by 1900 The first National Wildlife Refuge was set aside by President Theodore Roosevelt in 1902
to protect egrets from extinction by feather hunters Three years later, the Wichita Mountain National Wildlife Refuge was set aside to protect one of the small remnant herds of buffalo Several North Ameri-can species and subspecies are now extinct because
of similar exploitations: The passenger pigeon, Caro-lina parakeet, heath hen, Merriam’s elk, and Bad-lands bighorn sheep are some of the best-known ex-amples
During the 1960’s increasing concern about an ac-celerated species extinction rate attributable to human exploitation and disturbance of the environment cul-minated in the first federal protective legislation for endangered species, the Endangered Species Preser-vation Act of 1966 This act was limited to listing en-dangered birds and mammals and funding research
on their population ecology and habitat acquisition This legislation was expanded in 1969 to include all vertebrate animal species and some invertebrates The definitive protection legislation is the 1973 En-dangered Species Act This act set procedures for list-ing threatened and endangered species, called for designation of critical habitats for each threatened
or endangered species, and mandated the develop-ment of recovery plans for these species The act pro-hibits the use of federal funds for projects that would harm threatened or endangered species The cover-age of the 1973 act was also expanded to include plants and invertebrate animals (except pest insects), subspecies, and distinct vertebrate populations
Trang 8Beginning in 1966, the United States Fish and
Wildlife Service (USFWS) assumed the legal
responsi-bility of compiling and maintaining an official
threat-ened and endangered species list There are formal
petitioning processes for placing additional species
on the list and for removing them from the list
Peti-tions may be initiated by the USFWS or by private
organizations Petitions are reviewed by scientific
pan-els using all available information on the species
If sufficient information is available to support the
petition, a proposed addition to the list is published
in the Federal Register and other appropriate places
to solicit public comment Final decisions about
list-ing, “down-listing” (for example, changing a species
designation from “endangered” to “threatened”), or
“delisting” are made by the USFWS The ultimate
goal of the listing process and the implementation
of a recovery plan is to increase the abundance and
distribution of a species to the point of being able
to remove it from the threatened and endangered
species list
James F Fowler
Further Reading
Ellis, Richard The Empty Ocean: Plundering the World’s
Marine Life Washington, D.C.: Island
Press/Shear-water Books, 2003
Garbutt, Nick, and Mike Unwin One Hundred Animals
to See Before They Die Chalfont St Peter, England:
Bradt, 2007
Goodall, Jane, Thane Maynard, and Gail Hudson
Hope for Animals and Their World: How Endangered
Species Are Being Rescued from the Brink New York:
Grand Central, 2009
McGavin, George Endangered: Wildlife on the Brink of
Extinction Buffalo, N.Y.: Firefly Books, 2006.
Maclaurin, James, and Kim Sterelny What Is
Biodiver-sity? Chicago: University of Chicago Press, 2008.
Pimm, Stuart L The Balance of Nature? Ecological Issues
in the Conservation of Species and Communities
Chi-cago: University of Chicago Press, 1991
Ricklefs, Robert E., and Dolph Schluter, eds Species
Di-versity in Ecological Communities: Historical and
Geo-graphical Perspectives Chicago: University of
Chi-cago Press, 1993
Strong, Donald R., Jr., et al., eds Ecological
Commu-nities: Conceptual Issues and the Evidence Princeton,
N.J.: Princeton University Press, 1984
Wilson, Edward O The Future of Life New York: Alfred
A Knopf, 2002
Web Sites Environment Canada: Canadian Wildlife Service
Species at Risk http://www.cws-scf.ec.gc.ca/
theme.cfm?lang=e&category=12 U.S Fish and Wildlife Service Endangered Species Program http://www.fws.gov/endangered See also: Biodiversity; Conservation; Conservation biology; Endangered species; Endangered Species Act; Fish and Wildlife Service, U.S.; Nature Conservancy; Plants as a medical resource
Steam and steam turbines
Categories: Energy resources; obtaining and using resources
A steam boiler converts the chemical energy in fuel into the thermal energy of steam A steam turbine converts this thermal energy into the mechanical energy of a ro-tating shaft This shaft can drive an electric generator
or other device.
Background Fossil fuels such as oil and coal contain chemical en-ergy Uranium contains nuclear enen-ergy Either of these forms of energy can be converted into thermal energy (heat), and this thermal energy can be used to make steam in a boiler A steam turbine can be used to convert the thermal energy of steam into the mechan-ical energy of a rotating shaft When the turbine shaft
is used to drive an electric generator, electricity is pro-duced Although electric generators can be driven by diesel engines, gas turbines, and other devices, most electricity is generated using steam turbines
Principles of Turbine Operation High-pressure, high-temperature steam enters a steam turbine through a throttle valve Inside the turbine the steam flows through a series of nozzles and rotat-ing blades As it flows through a nozzle, the pressure and temperature of the steam decrease, and its speed increases The fast-moving steam is directed against rotating blades, which work something like the blades
Trang 9on a pinwheel The steam is deflected as it passes over
the rotating blades, and in response the steam pushes
against the blades and makes them rotate As the
steam flows over the rotating blades its speed
de-creases
Large turbines are composed of many stages Each
stage has a ring of nozzles followed by a ring of
ing blades The slow-moving steam leaving the
rotat-ing blades of one stage enters the nozzles of the next
stage, where it speeds up again This arrangement is
called pressure compounding The energy of the
steam is converted to mechanical work in small steps
Less of the steam’s thermal energy is wasted or lost if it
is converted in small steps
The amount of power produced by a turbine
de-pends on the amount of steam flowing through it and
on the inlet and outlet steam pressures Steam flow is
constantly regulated by the throttle valve, but the
steam pressures are fixed by the
de-sign of the system Inlet steam
pres-sure is determined by the operating
pressure of the boiler that supplies
it Outlet pressure is determined by
where the steam goes when it leaves
the turbine If the steam simply
es-capes into the atmosphere, the
out-let pressure is atmosphere If the
outlet steam pressure is made lower
than atmospheric pressure, the
tur-bine produces more power This is
accomplished by having the steam
leaving the turbine flow into a
con-denser
Cooling water passing through
tubes inside the condenser removes
heat from the steam flowing around
the tubes and causes it to condense
and become liquid water Since water
occupies a much smaller volume as a
liquid than as steam, condensing
cre-ates a vacuum When a turbine is
connected to a condenser, the outlet
steam pressure can be far below one
atmosphere
Details of Turbine
Construction
Inside the steel turbine casing,
sta-tionary partitions called diaphragms
separate one turbine stage from the
next Each diaphragm has a hole at the center for the rotor shaft to pass through Nozzle passages are cut through the diaphragms near their outer rims, and the steam is forced to pass through these nozzles to get to the next stage
The rotor of a turbine is made up of solid steel disks that are firmly attached to a shaft Rotating blades are mounted around the rims of the disks Where the shaft extends from the casing at each end, it is sup-ported by journal bearings and a thrust bearing The journal bearings are stationary hollow cylinders of soft metal that support the weight of the rotor A thrust bearing consists of a small disk on the shaft of the turbine that is trapped between two stationary disks supported by the casing If the rotor tries to move forward or back along its own axis, the rotating disk presses against one of the stationary disks Thrust and journal bearings must be lubricated by a constant
Steam fields in Sonoma County, California, feed the McCabe power plant, churning tur-bines that create steam-powered electricity (AP/Wide World Photos)
Trang 10flow of oil that forms a thin film between the rotating
and stationary parts of the bearing and prevents them
from making direct contact Without this film of oil,
the bearing would wear out in a few seconds
A seal must be provided where the shaft of the
tur-bine passes through the casing At one end of the
cas-ing the steam pressure inside is high Outside the
casing the air pressure is only one atmosphere If
there were no seal, steam would rush out through the
space between the casing and the shaft At the other
end of the turbine, the pressure inside may be below
atmospheric Here air would rush in if there were no
seal around the shaft
Electric Power Generation
Most electric power is produced by steam turbines
driving electric generators This is true whether the
source of the steam is a nuclear reactor or a boiler
burning fossil fuel The turbines in power stations are
extremely large In nuclear plants the turbines may
produce as much as 1,300 megawatts of power Power
stations are often located near rivers so that water
from the river can be used as cooling water in the
con-densers that receive steam from the large turbines
Edwin G Wiggins
Further Reading
Avallone, Eugene A., Theodore Baumeister III, and
Ali M Sadegh “Steam Turbines.” In Marks’
Stan-dard Handbook for Mechanical Engineers 11th ed.
New York: McGraw-Hill, 2007
Blank, David A., Arthur E Bock, and David J
Richard-son Introduction to Naval Engineering 2d ed
Annap-olis, Md.: Naval Institute Press, 1985
Bloch, Heinz P Steam Turbines: Design, Applications,
and Rerating 2d ed New York: McGraw-Hill, 2009.
McBirnie, S C Marine Steam Engines and Turbines 4th
ed Boston: Butterworths, 1980
Peng, William W “Steam Turbines.” In Fundamentals
of Turbomachinery Hoboken, N.J.: J Wiley, 2008.
Termuehlen, Heinz One Hundred Years of Power Plant
Development: Focus on Steam and Gas Turbines as Prime
Movers New York: ASME Press, 2001.
Web Site
How Stuff Works
How Steam Technology Works
http://science.howstuffworks.com/steam-technology.htm
See also: Coal; Electrical power; Metals and metal-lurgy; Nuclear energy; Oil industry; Steam engine; Steel; Uranium
Steam engine
Category: Obtaining and using resources
A steam boiler converts the chemical energy in fuel into the thermal energy of steam A steam engine converts this thermal energy into the mechanical energy of a ro-tating shaft This shaft can drive an electric generator
or pump.
Background The chemical energy that is contained within fossil fu-els such as oil and coal can be converted into thermal energy (heat) by burning the fuel This thermal en-ergy can be used to create steam in a boiler A steam engine converts the thermal energy of steam into the mechanical energy of a rotating shaft, and this shaft can drive a pump, a ventilating fan, a ship’s propeller, and many other devices
History Although there were attempts to use steam to drive mechanical devices as early as 60 c.e by Hero of Alex-andria, the first real steam engine was designed and built by Thomas Newcomen in 1712 That year New-comen successfully used a steam engine to pump water from a coal mine near Dudley Castle, England
In 1765, as he walked across Glasgow Green in the city
of Glasgow, Scotland, James Watt conceived the idea
of connecting the steam engine to a separate denser The first full-size engines based on this con-cept were built in 1776: one at John Wilkinson’s blast furnace near Broseley, England, and the other at Bloomfield coal mine near Tipton, England New-comen’s design and Watt’s early designs used steam at constant pressure Over the course of his life, Watt vented many improvements to the steam engine, in-cluding rotary engines, a device for measuring engine performance, and engines in which the steam ex-panded during the piston stroke Expanding steam engines soon drove the earlier type off the market, be-cause the fuel consumption associated with the boiler
of an expanding steam engine is far less than that of a constant pressure engine While modern steam