Environmental Encyclopedia

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Environmental Encyclopedia 3

Genetically engineered organism

codes, they said, for some particular amino

acid

, and a long

series of nitrogen bases were codes for a long series of amino

acids or a protein.

Deciphering the genetic code and discovering how it

is used in cells has taken many years of work since that of

Watson and Crick. The basic features of that process, how-

ever, are now well understood. The first step involves the

construction of a RNA (

ribonucleic acid

) molecule in the

nucleus of a cell, using the code stored in DNA as a template.

The RNA molecule then migrates out of the nucleus to a

ribosome in the cell cytoplasm. At the ribosome, the se-

quence of nitrogen bases stored in RNA act as a map that

determines the sequence of amino acids to be used in con-

structing a new protein.

This knowledge is of critical importance to biologists

because of the primary role played by proteins in an organism.

In addition to acting as the major building materials of which

cells are made, proteins have a number of other crucial

functions. All hormones and enzymes, for example, are pro-

teins, and therefore nearly all of the chemical reactions that

occur within an organisms are mediated by one protein or

another.

Our current understanding of the structure and func-

tion of DNA makes it at least theoretically possible to alter

the biological characteristics of an organism. By changing the

kind of nitrogen bases in a DNA molecule, their sequence, or

both, a scientist can change the genetic instructions stored

in a cell and thus change the kind of protein produced by

the cell.

One of the most obvious applications of this knowl-

edge is in the treatment of genetic disorders. A large majority

of genetic disorders occur because an organism is unable

to correctly manufacture a particular protein molecule. An

example is Lesch-Nyhan syndrome. It is a condition charac-

terized by self-mutilation, mental retardation, and cerebral

palsy which arises because a person’s body is unable to manu-

facture an

enzyme

known as hypoxanthine guanine phos-

phoribosyl transferase (HPRT).

The general principles of the techniques required to

make such changes are now well understood. The technique

is referred to as

genetic engineering

or genetic surgery

because it involves changes in an organism’s gene structure.

When used to treat a particular disorder in humans, the

procedure is also called human gene therapy. Developing

specific experimental techniques for carrying out genetic

engineering has proved to be an imposing challenge, yet

impressive strides have been made. A common procedure is

known as recombinant DNA (rDNA) technology.

The first step in an rDNA procedure is to collect a

piece of DNA that carries a desired set of instructions. For

a genetic surgery procedure for a person with Lesch-Nyhan

syndrome, a researcher would need a piece of DNA that

627

codes for the production of HPRT. That DNA could be

removed from the healthy DNA of a person who does not

have Lesch-Nyhan syndrome, or the researcher might be

able to manufacture it by chemical means in the laboratory.

One of the fundamental tools used in rDNA technol-

ogy is a closed circular piece of DNA found in bacteria called

a plasmid. Plasmids are the vehicle or vector that scientists

use for transferring new pieces of DNA into cells. The next

step in an rDNA procedure, then, would be to insert the

correct DNA into the plasmid vector. Cutting open the

plasmid can be accomplished using certain types of enzymes

that recognize specific base sequences in a DNA molecule.

When these enzymes, called restriction enzymes, encounter

the recognized sequence in a DNA molecule, they cleave

the molecule. After the plasmid DNA has been cleaved and

the correct DNA mixed with it, a second type of enzyme is

added. This kind of enzyme inserts the correct DNA into

the plasmid and closes it up. The process is known as gene

splicing.

In the final step, the altered plasmid vector is intro-

duced into the cell where it is expected to function. In

the case of a Lesch-Nyhan patient, the plasmid would be

introduced into the cells where it would start producing

HPRT from instructions in the correct DNA. Many techni-

cal problems remain with rDNA technology, and this last

step has caused some of the greatest obstacles. It has proven

very difficult to make introduced DNA function. Even when

the plasmid vector with its new DNA gets into a cell, it

may never actually begin to function.

Any organism whose cells contain DNA altered by

this or some other technique is called a genetically engineered

organism. The first human patient with a genetic disorder

who is treated by human gene therapy will be a genetically

engineered organism. The use of genetic engineering on

human subjects has gone forward very slowly for a number

of reasons. One reason is that humans are very complex

organisms. Another reason is that changing the genetic

make-up of a human involves more ethical questions and

more difficult questions than does the genetic engineering

of bacteria, mice, or cows.

Most of the existing examples of genetically engi-

neered organisms, therefore, involve plants, non-human ani-

mals, or

microorganisms

. One of the earliest success stories

in genetic engineering involved the altering of DNA in

microorganisms to make them capable of producing

chemi-

cals

they do not normally produce. Recombinant DNA

technology can be used, for instance, to insert the DNA

segment or gene that codes for insulin production into bacte-

ria. When these bacteria are allowed to grow and reproduce

in large fermentation tanks, they produce insulin. The list

of chemicals produced by this mechanism now includes so-

matostatin, alpha interferon, tissue plasminogen activator

Environmental Encyclopedia 3

Genetically modified organism

(tPA), Factor VIII, erythroprotein, and human growth hor-

mone, and this list continues to grow each year.

[David E. Newton]

ESOURCES

ERIODICALS

Hoffman, C. A. “Ecological Risks of Genetic Engineering of Crop Plants.”

BioScience 40 (June 1990): 434–437.

Kessler, D. A., et al. “The Safety of Foods Developed by Biotechnology.”

Science 256 (June 1992): 1747–1749+.

Kieffer, G. H. Biotechnology, Genetic Engineering, and Society. Reston, VA:

National Association of Biology Teachers, 1987.

Mellon, M. Biotechnology and the Environment. Washington, DC: National

Biotechnology Policy Center of the National Wildlife Federation, 1988.

Pimentel, D., et al. “Benefits and Risks of Genetic Engineering in Agricul-

ture.” BioScience 39 (October 1989): 606-614.

Weintraub, P. “The Coming of the High-Tech Harvest.” Audubon 94

(July–August 1992): 92–4+.

Wheale, P. R., and R. M. McNally. Genetic Engineering: Catastrophe or

Utopia? New York: St. Martin’s Press, 1988.

Genetically modified organism

A genetically modified organism, or GMO, is an organism

whose genetic structure has been altered by incorporating a

single gene or multiple genes—from another organism or

species—that adds, removes, or modifies a trait in the orga-

nism by a technique called gene splicing. An organism that

has been genetically modified—or engineered—to contain

a gene from another

species

is also called a transgenic orga-

nism (because the gene has been transferred) or a living

modified organism (LMO). Most often the transferred gene

allows an organism—such as a bacterium, fungus,

virus

plant, insect, fish, or mammal—to express a trait that en-

hances its desirability to producers or consumers of the final

product.

Overview

Plants and livestock have been bred for desired quali-

ties (selective breeding) for thousands of years—long before

people knew anything about the science of genetics. As

technology advanced, however, so did the means by which

people could select desired traits. Modern

biotechnology

represents a significant step in the history of genetic modifi-

cation.

Until the final decades of the twentieth century, breed-

ing techniques were limited to the transfer of desired traits

within the same or closely related species. Genetically modi-

fied organisms, however, may contain traits transferred from

completely dissimilar species. For example, before modern

biotechnology, apple breeders could only cross-breed apples

with apples or other closely related species. So, if a breeder

wanted to make a certain tasty apple variety that was more

628

tolerant to the cold, a cold-tolerant apple variety had to be

hybridized with a tasty variety. This process usually involved

significant trial and error because there was little assurance

the cold-tolerance ability would be transferred in any individ-

ual attempt to hybridize the two varieties.

Development of modern biotechnology

The characteristics of all organisms are determined by

genes—the basic units of heredity. A gene—a segment of

deoxyribonucleic

acid

(DNA)—is capable of replication and

mutation

, occupying a fixed position on a chromosome (a

group of several thousand genes; humans are defined by 22

pairs of chromosomes plus X and Y), and is passed on from

parents to offspring during reproduction. A gene determines

the structure of a protein or a

ribonucleic acid

(RNA)

molecule. Found in all cells, DNA carries the genetic instruc-

tions for creating proteins; RNA decodes those instructions.

Proteins perform diverse biological functions in the body,

from helping muscles contract, to enabling blood to clot, to

allowing biochemical reactions to proceed quickly enough

to sustain life. By modifying a protein, particular phenotypic

(physical) or physiologic changes—such as the color of a

rose or the ability to bioluminesce (glow like a firefly)—are

created.

A fundamental aspect of modern biotechnology is the

belief that the essential genetic elements of all life are the

same. Since the 1950s, molecular biologists have known that

the DNA in every organism is made up of pairs of four

nitrogen-containing bases, or building blocks: adenine (A),

thymine (T), cytosine (C), and guanine (G).

In 1953, scientists James Watson and Francis Crick

discovered that DNA is constructed in a double helix pat-

tern—sort of a twisted ladder. Although A always pairs with

T, and G with C, there is significant variety in how the

pairs stack. The variable sequence of these DNA base pairs

constitutes, in effect, the variety of life. So even all organisms

are made from the same basic building blocks, their differ-

ences are a result of varying DNA sequences. A principle of

modern molecular biology and biotechnology is that because

these genetic building blocks are the same for all species,

DNA can be extracted and inserted across species.

Genetic engineering techniques

The tools of modern biotechnology allow the transfer

of specific genes, hence specific traits, to occur with more

precision

than ever before. The individual gene conveying

a trait can be identified, isolated, replicated, and the inserted

into another organism. This process is called

genetic engi-

neering

, or recombinant DNA (rDNA) technology—that

is, recombining DNA from multiple organisms.

Through such engineering, the apple breeder who

wants the tasty apple variety to be cold-tolerant as well has

the potential to find a gene that conveys cold tolerance and

insert that gene directly into the tasty variety. Although

Environmental Encyclopedia 3

Genetically modified organism

there is still some trial and error in this process, overall,

there is greater precision in the ability to move genes from

one organism to another. The gene that conveys a cold-

tolerance ability does not need to come from another apple

variety; it may come from any other organism. A cold-

tolerant fish, for example, might have a suitable gene.

There are multiple methods by which genetic material

may be transferred from one organism to another. Before a

gene is moved between organisms, however, it is necessary

to identify the individual gene that confers the desired trait.

This stage is often quite time-consuming and difficult be-

cause often it is not clear what gene is needed or where to

find it. Finding the gene entails using or creating a library

of the species’ DNA, specifying the amino acid sequence of

the desired protein, and then devising a probe (any biochemi-

cal agent labeled or tagged in some way so that it can be

used to identify or isolate a gene, RNA, or protein) for that

sequence. As of 2002, isolating the desired gene is one of

the most limiting aspects to creating a GMO.

Once the desired gene has been identified it must be

extracted from the organism, which is usually done with a

restriction endonuclease (an

enzyme

). Restriction endonu-

cleases recognize particular base sequences in a DNA mole-

cule and cut and isolate these sequences in a predictable

and consistent manner. Once isolated, the gene must be

replicated to generate sufficient usable material, as more

than one copy of the gene is needed for the next steps in

the engineering process.

One common method of gene replication is called

polymerase

chain reaction

(PCR). Through the PCR

method, the strands of the DNA are broken apart—in effect,

the ladder is divided down the middle—and then exact copies

of the opposite sides of the ladder are produced, creating

thousands or millions of copies of the complete gene.

After replication, the gene must be inserted into the

new organism via a vector (an agent that transfers material—

typically DNA—from one host to another). A common

vector is Agrobacterium tumefaciens, a bacterium that normally

inserts itself into plants, causing a tumor. By genetically

engineering A. tumefaciens, however, the bacterium can be

used to insert the desired gene into a plant, replacing its

tumor-causing genetic material.

Another vector, called ballistics, involves coating a

microprojectile—usually a heavy metal such as tungsten—

with the desired gene, then literally shooting the micropro-

jectile into material from the new host organism. The micro-

projectile breaks apart the DNA of the host organism. Then

when the DNA reassembles, some of the new, desired ge-

netic material is inserted. Once the DNA has been inserted,

the host organism can be grown, raised, or produced nor-

mally and tests can be performed to observer whether the

desired trait manifests.

629

Varieties of GMOs

In 2000, of the total land planted with GMO crops

worldwide, the United States occupied 68&percnt;, Argen-

tina 23&percnt;, and China 1&percnt;. The United States

produces many types of GMOs for commercial and research

purposes.

Agricultural crops

A common type of GMO is the modified agricultural

seed. Corn, soybeans, and cotton are a few examples of staple

agricultural GMO products grown in the United States.

Genetic modifications to these products may, for example,

alter a crop’s nutritional content, storage ability, or taste.

With the advent of genetic engineering, for example,

common hybrid crops such as the tomato were launched

into a new era. The first food produced from gene splicing

and evaluated by the

Food and Drug Administration

(FDA) was the Flavr Savr Tomato in 1994. Tomatoes usually

get softer as they ripen because of a protein in the tomato

that breaks down the cell walls of the tomato. Because it is

difficult to ship a quality ripe tomato across the country

before the tomato spoils, tomatoes are usually shipped unrip-

ened. Engineers of the Flavr Savr Tomato spliced a gene

into its deoxyribonucleic acid (DNA) to prevent the break-

down of the tomato’s cell walls. The result of adding the

new gene was a firm ripe tomato that was more desirable

to consumers than the tasteless variety typically found on

store shelves, particularly in the winter months.

Genetic modifications may also confer to a species an

ability to produce its own

pesticide

biologically, thereby

potentially reducing or even eliminating the need to apply

external pesticides. For example,

Bacillus thuringiensis

(Bt)

is a soil bacterium that produces toxins against insects

(mainly in the genera Lepidoptera, Diptera, and Coleoptera).-

When they are genetically modified to carry genetic material

from the Bt bacterium, plants such as soybeans will able to

produce their own Bt toxin and be resistant to insects such

as the cornstalk borer and velvetbean catepillar. Researchers

at the Monsanto chemical company estimate that Bt soy-

beans will be commercially available by about 2006.

By means of genetic engineering, a gene from a soil

bacterium called Agrobacterium sp confers glyphosate

resis-

tance

to a plant. Glyphosate (brand names include

Roundup, Rodeo, and Accord) is a broad-spectrum

herbi-

cide

(kills all green plants). As of 2002, Monsanto was the

sole developer of all glyphosate resistant crops on the market.

These crops (often called “Roundup Ready") include corn,

soybeans, cotton, and canola.

Pharmaceuticals

Genetically engineered pharmaceuticals are also useful

GMO products. One of the first GMOs was a bacterium

with a human gene inserted into its genetic code to produce

a very high quality human insulin for diabetes. Vaccines

Environmental Encyclopedia 3

Genetically modified organism

against diseases such as meningitis or hepatitis B, for exam-

ple, are produced by genetically engineered yeast or bacteria.

Other pharmaceuticals produced by using GMO

microbes

include interferon for

cancer

, erythropoetin for

anemia

growth hormone for the treatment of dwarfism, tissue plas-

minogen activator for heart attack victims. Through genetic

engineering, transgenic plants are likely to become a com-

mercially viable source of pharmaceuticals.

Benefits and risks

Although the technological advances that allowed the

creation of GMOs are impressive, as with any new technol-

ogy, the benefits must be weighed against the risks. Useful

pharmaceutical products have been created as a result of

genetic engineering. Also, GMOs have produced and new

and improved agricultural products that are resistant to crop

pests, thus improving production and reducing chemical

pesticide usage. These developments have had a major im-

pact on food quality and nutrition.

The possibility that biotech crops could make a sub-

stantial contribution to providing sufficient food for an ex-

panding world is also a reason given for engaging in the

research that underlies their development. However, the

debate over GMOs continues among scientists and between

consumers and modern agricultural producers throughout

the world regarding issues such as regulation, labelling, hu-

man health risk, and environmental impact.

In the United States, for example, there has been much

controversy over the health risks of canola oil. Canola oil is

genetically engineered rapeseed oil or “LEAR” oil (low erucic

acid rape), a semi-drying industrial oil used as a lubricant,

fuel, soap, and synthetic

rubber

base, and as an illuminant

to give color pages in magazines their slick look. It was first

developed in Canada (thus the name “canola oil").

Canola oil is derived from the mustard family and is

considered a toxic and poisonous weed. In 1998, the EPA

classified canola oil as a biopesticide with “low chronic toxici-

ties,” yet placed it on the “Generally Considered Safe” list

of foods. Proponents, who tout the oil’s health benefits,

claim that due to genetic engineering and irradiation, it is

completely safe, pointing to its unsaturated structure and

digestibility.

Widely used as a cooking oil, and because it is so

inexpensive, it is used in thousands of processed foods in

the United States and North America. Thus, millions of

people have been exposed—most of them unknowingly—

to genetically engineered foods. However, there has been

little research on the potential adverse effects of these prod-

ucts on humans.

When processed, canola oil becomes rancid very easily.

It has been shown to cause health problems such as lung

cancer and has been associated with loss of vision, disruption

of the central nervous system, respiratory illness, anemia,

630

constipation, increased incidence of heart disease and cancer,

low birth weight in infants, and irritability. It has a tendency

to inhibit proper

metabolism

of foods and curbs normal

enzyme function. Generally, rapeseed has a cumulative ef-

fect, often taking nearly ten years for symptoms to manifest.

The dangers of introducing genes that may cause un-

desirable effects in the

environment

is also a concern among

many. For example, when farmers spray an herbicide to

remove weeds growing among crops, the sprayed chemical

often damages the crop plants. If the crop is genetically

engineered to be resistant to the chemical, the weeds are

killed, but the crop plants remain undamaged.

Although this situation appears to be beneficial, it is

likely to lead to greater use of the particular herbicide, which

would have several negative effects: the crop is likely to

contain greater herbicide residues; and the increased spraying

contaminates the rest of the environment. Although not all

herbicides are dangerous, the safer choice seems to minimize

rather than maximize their use. Also, if genes added to

produce pesticide resistance in crop plants jumped to a weed

species, then weeds would thrive and be difficult to control.

Thus, as debate over GMOs rages, it is important to

note that a wide variety of ecological and human health

concerns exist side by side with the new advances made

possible by genetic engineering.

[Paul R. Phifer Ph.D.]

ESOURCES

OOKS

Anderson, Luke. Genetic Engineering, Food, and Our Environment. White

River Junction, VT: Chelsea Green Publishing Co., 1999.

Ho, Mae-Wan. Genetic Engineering Dream or Nightmare: Turning the Tide

on the Brave New World of Bad Science and Big Business. New York: Contin-

uum Publishing Group, 2000.

Kreuzer, H., and A. Massey. Recombinant DNA and Biotechnology: A Guide

for Students, 2nd Edition. Washington, DC: ASM Press, 2001.

ERIODICALS

Brown, K. “Seeds of Concern.” Scientific American (April 2001): 52–57.

Nemecek, S. “Does the World Need GM Foods?” Scientific American (April

2001): 48–51.

Wolfenbarger, L., and P. Phifer. “The Ecological Risks and Benefits of

Genetically Engineered Plants.” Science 290 (2000): 2088–2093.

RGANIZATIONS

Environmental Protection Agency (EPA), 1200 Pennsylvania Avenue,

NW, Washington, DC USA 20460 (202) 260-2090, Email: public-

access@epa.gov, <http://www.epa.gov>

Human Genome Project Information, Oak Ridge National Laboratory,

1060 Commerce Park MS 6480, Oak Ridge, TN USA 37830 (865)

576-6669, Fax: (865) 574-9888, Email: genome@science.doe.gov, <http://

www.ornl.gov/hgmis>

Environmental Encyclopedia 3

Geographic information systems

Geodegradable

The term geodegradable refers to a material that could de-

grade in the

environment

over a geologic time period.

While

biodegradable

generally refers to items that may

degrade within our lifetime, geodegradable material does

not decompose readily and may take hundreds or thousands

of years.

Radioactive waste

, for example, is degraded only

over thousands of years. The glass formed as an end result

of a

hazardous waste

treatment technology known as “in

situ vitrification,” is considered geodegradable only after a

million years. See also Half-life; Hazardous waste site remedi-

ation; Hazardous waste siting; Waste management

Geographic information systems

A Geographic Information System (GIS) is a computer

system capable of assembling, storing, mapping,

modeling

manipulating, querying, analyzing, and displaying geograph-

ically referenced information (i.e., data that are identified

according to their locations). Some practitioners expand the

definition of GIS to include the personnel involved, the data

that are entered into the system, and the uses, decisions,

and interpretations that are made possible by the system.

A GIS can be used for scientific investigations, resource

management, and planning. The development of GIS was

made possible from innovations in many different disci-

plines, including geography, cartography, remote sensing,

surveying, civil engineering,

statistics

, computer science,

operations research, artificial intelligence, and demography.

Even early man used GIS-type systems. Thirty-five

thousand years ago Cro-Magnon hunters in Lascaux,

France, drew pictures of the animals they hunted. Along

with the animal drawings were track lines that are thought

to show

migration

routes. These early records included two

essential elements of modern GIS: a graphic file linked to

an attribute data base.

In a GIS, maps and other data from many different

sources and in many different forms are stored or filed as

layers of information. A GIS makes it possible to link and

integrate information that is difficult to associate through

other means. A GIS can combine mapped variables to build

and analyze new variables. For example, by knowing and

entering data for water use for a specific residence, predic-

tions can be made on the amount of

wastewater

contami-

nants generated and released to the

environment

from that

residence.

The primary requirement for the source data is that

the locations for the variables are known. Any variable that

can be located spatially can be entered into a GIS. Location

may be determined by x, y, and z coordinates of longitude,

631

latitude, and elevation, or by other systems such as ZIP

codes or highway mile markers. A GIS can convert existing

digital information, which may not be in map form, into

forms it can recognize and utilize. For example, census data

can be converted into map form, such that different types

of information can be presented in layers.

If data are not in digital form, (i.e., not in a form that

the computer can utilize), various techniques are available

to capture the information. Maps can be hand traced with

a computer mouse to collect the coordinates of features.

Electronic scanning devices can be used to convert map

lines and points to digits. Data capture, i.e., entering the

information into the system, is the most time-consuming

component of a GIS. Identities of the objects on the map

and their spatial relationships must be specified. Editing of

information that is captured can be difficult. For example,

an electronic scanner will record blemishes on a map just as

it will record actual map features. A fleck of dirt that is

scanned may connect two lines that should not be connected.

Such extraneous information must be identified and removed

from the digital data file.

Different maps may be at different scales, so map

information in a GIS must be manipulated so that it fits

with information collected from other maps. Data may also

have to undergo projection conversion before being inte-

grated into a GIS. Projection, a fundamental component

of map making, is a mathematical means of transferring

information from the earth’s three-dimensional curved sur-

face to a two-dimensional medium (i.e., paper or a computer

screen). Different projections are used for different types of

maps based on the type of projection appropriate for a spe-

cific use. Much of the information in a GIS comes from

existing maps, so the computing power of the GIS can

integrate digital information from different sources with

different projections into a common projection.

Digital data are collected and stored in various ways,

and so different data sources may not be compatible. A GIS

must be able to convert data from one structure to another.

For example, image data from a satellite that has been inter-

preted by a computer to produce a

land use

map can be

entered into the GIS in raster format. Raster format is like

a spreadsheet, with rows and columns into which numbers

are placed. These rows and columns are linked to x,y coordi-

nates, with the intersection of each row and column forming

a cell that corresponds to a specific point in the world. These

cells contain numbers that can represent such features as

elevation, soils, archeological sites, etc. Maps in a raster GIS

can be handled like numbers (e.g., added, subtracted, etc.)

to form new maps. Raster data files can be quickly manipu-

lated by computer but are less detailed and may be less

visually appealing than vector data files, which appear more

like traditional hand-drafted maps. Vector digital data are

Environmental Encyclopedia 3

Geological Survey

captured as points, lines (a series of point coordinates), or

areas (shapes bounded by lines). A Vector GIS output looks

more like a traditional paper map.

A GIS can be used to depict two- and three-dimen-

sional characteristics of the earth’s surface, subsurface, and

atmosphere

from information points. Each thematic map

(i.e., a map displaying information about one characteristic

of a region) is referred to as a layer, coverage, or level. A

specific thematic map can be overlain and analyzed with any

other thematic map covering the same area. Not all analyses

may require using all of the map layers at the same time.

A researcher may use information selectively to consider

relationships among specific layers. Information from two

or more layers may be combined and transformed into a

new layer for use in subsequent analyses. For example, with

maps of

wetlands

, slopes, streams, land use, and soils, a

GIS can produce a new overlay that ranks the wetlands

according to the relative sensitivity to damage from nearby

factories or homes. This process of combining and trans-

forming information from different layers is referred to as

map “algebra,” as it involves adding and subtracting infor-

mation.

Recorded information from off-screen files can be re-

trieved from the maps by pointing at a location, object, or

area on the screen. Conditions of adjacency (what is next to

what) containment (what is enclosed by what), and proximity

(how close something is to something else) can be deter-

mined using a GIS.

A GIS can also be used for “what if” scenarios by

simulating the route of materials along a linear network. For

example, an evaluation could be made on how long it would

take for

chemicals

accidentally released into a river from a

factory to move into a wetland area. Direction and speed

can be assigned to the digital stream, and the contaminants

can be traced through the stream system.

An important component of a GIS is the ability to

produce graphics on the computer screen or to output to

paper (e.g., wall maps) to inform resource decision makers

about the results of analyses. The viewers of such materials

can visualize and thus better understand the results of analy-

ses or simulations of potential events. A GIS can be used

to produce not only maps, but also drawings and animations

that allow different ways of viewing information. These types

of images are especially helpful in conveying technical con-

cepts to non-scientists.

GIS technology is an improvement in the efficiency

and analytical power of cartographic science. Traditional

maps are abstractions of the real world, with important ele-

ments portrayed on a sheet of paper with symbols to repre-

sent physical objects. For example, topographic maps show

the shape of the land surface with contour lines, but the

actual shape of the land can only be imagined. Graphic

632

display techniques in a GIS illustrate more clearly relation-

ships among the map elements, increasing the ability to

extract and analyze information.

Many commercial GIS software systems are available,

some of which are specialized for use in specific types of

decision-making situations. Other programs are more gen-

eral and can be used for a wide number of applications or

can be customized to meet individual requirements.

GIS applications are useful for a wide range of disci-

plines, including urban planning, environmental and natural

resource management, facilities management,

habitat

stud-

ies, archaeological analyses, hazards management, emer-

gency planning, marketing and demographic analyses, and

transportation

planning. The ability to separate informa-

tion in layers and then combine the layers with other layers

of information is the key to making GIS technology a valu-

able tool for the analysis and display of large volumes of

data, thus allowing better management and understanding

of information and increased scientific productivity.

[Judith L. Sims]

ESOURCES

OOKS

Heywood, D. Ian, Ian Heywood, Sarah Cornelius, and Steve Carver. An

Introduction to Geographical Information Systems.: Prentice Hall, 2000.

THER

“GIS WWW Resource List.” University of Edinburgh Web Page. 1996 [cited

June 1, 2002]. <http://www.geo.ed.ac.uk/home/giswww.html>.

“Geographic Information Systems.” United States Geological Survey Web

Page. April 24, 2001 [cited June 1, 2002]. <http://www.usgs.gov/research/

gis/title/html>.

Geographic Information Systems as an Integrating Technology: Context, Con-

cepts, and Definitions.Kenneth E. Foote and Margaret Lynch, The Geogra-

pher’s Craft Project, Department of Geography, University of Colorado at

Boulder, october 12, 1997. [cited June 1, 2002], <http://www.Colora-

do.EDU/geography/gcraft/notes/intro/intro_f.html>.

Geographic Information Systems: Internet Web Sites.Federal Facilities Restora-

tion and Reuse Office, U.S. Environmental Protection Agency, Washing-

ton, DC, November 5, 2000 [cited June 23, 2002], <http://www.epa.gov/

swerffrr/compend/intrnt_b.htm>.

Geological Survey

The United States Geological Survey (USGS) is the federal

agency responsible for surveying and publishing maps of

topography

(giving landscape relief and elevation), geology,

and natural resources—including minerals, fuels, and water.

The USGS, part of the U. S. Department of the Interior,

was formed in 1879 as the United States began systematically

to explore its newly expanded western territories. Today it

has an annual budget of about $700 million, which is devoted

to primary research, resource assessment and monitoring,

Environmental Encyclopedia 3

Georges Bank (collapse of the ground fishery)

map production, and providing information to the public

and to other government agencies.

The United States Geological Survey, now based in

Reston, Virginia, originated in a series of survey expeditions

sent to explore and map western territories and rivers after

the Civil War. Four principal surveys were authorized be-

tween 1867 and 1872: Clarence King’s exploration of the

fortieth parallel, Ferdinand Hayden’s survey of the Rocky

Mountain territories, John Wesley Powell’s journey down

the

Colorado River

and through the Rocky Mountains, and

George Wheeler’s survey of the 100th meridian. Twelve

years later, in 1879, these four ongoing survey projects were

combined to create a single agency, the United States Geo-

logical Survey. The USGS’ first director was Clarence King.

In 1881 his post was taken by John Wesley Powell, whose

name is most strongly associated with the early Survey. It

was Powell who initiated the USGS topographic mapping

program, a project that today continues to produce the most

comprehensive map series available of the United States and

associated territories.

In addition to topographic mapping, the USGS began

detailed surveys and mapping of mineral resources in the

1880s. Mineral exploration led to mapping geologic forma-

tions and structures and a gradual reconstruction of geologic

history in the United States. Research and mapping of glacial

history and fossil records naturally followed from mineral

explorations, so that the USGS became the primary body

in the United States involved in geologic field research and

laboratory research in experimental geophysics and geo-

chemistry. During World Wars I and II, the USGS’ role

in identifying and mapping tactical and strategic resources

increased. Water and fuel resources (

coal

, oil,

natural gas

and finally

uranium

) were now as important as

copper

gold, and mineral ores, so the Survey took on responsibility

for assessing these resources as well as topographic and geo-

logic mapping.

Today the USGS is one of the world’s largest earth

science research agencies and the United States’ most impor-

tant map publisher. The Survey conducts and sponsors ex-

tensive laboratory and field research in geology,

hydrology

oceanography, and cartography. The agency’s three divi-

sions,

Water Resources

, Geology, and National Mapping,

are responsible for basic research. They also publish, in the

form of maps and periodic written reports, information on

the nation’s topography, geology, fuel and mineral resources,

and other aspects of earth sciences and

natural resources

Most of the United States’ hydrologic records and research,

including streamflow rates,

aquifer

volumes, and

water

quality

, are produced by the USGS. In addition, the USGS

publishes information on natural hazards, including earth-

quakes, volcanoes, landslides, floods, and droughts. The Sur-

vey is the primary body responsible for providing basic earth

633

science information to other government agencies, as well

as to the public. In addition, the USGS undertakes or assists

research and mapping in other countries whose geologic

survey systems are not yet well developed.

[Mary Ann Cunningham Ph.D.]

ESOURCES

OOKS

U.S. Geological Survey. Maps for America. Reston, VA: U.S. Government

Printing Office, 1981.

USGS Yearbook: Fiscal Year 1985. Washington, DC: U.S. Government

Printing Office, 1985.

Georges Bank (collapse of the ground

fishery)

Until the 1990s Georges Bank, off the coasts of New En-

gland and Nova Scotia, was one of the world’s most valuable

fisheries. A bank is a plateau found under the surface of

shallow ocean water. Georges Bank is the southernmost and

the most productive of the banks that form the continental

shelf. A majority of the $800 million northeastern fishery

industry comes from Georges Bank. The oval shaped bank

is 149 mi long and 74.5 mi wide (240 km by 120 km).

Georges Bank covers an area larger than the state of Massa-

chusetts. The ocean bottom of Georges Bank formed ideal

habitat

for favorable quantities of groundfish, demersal fin-

fishes, fish which feed off or near the ocean’s floor mdash;

cod, Gadidae, clam, Pelecypoda, haddock, Melanogrammus

aeglefinus, hake, Merlucciidae, herring, Clupea harengus, lob-

ster, Homarus, pollock, Pollachaius, flounder, and scallops,

Pectinidae. But by 1994 the Georges Bank ground fishery

had collapsed.

Cod were by far the most numerous and valuable of

the Georges Bank’s fish. Atlantic cod form distinct stocks

and the Georges Bank stock grows faster than those of the

colder waters further north. They are the world’s largest and

thickest cod. In 1938 a cod weighing 180 lb (82 kg) was

caught off the bank. The cod move in schools from feeding

to spawning grounds, in dense aggregates of hundreds of

millions of fish, making them easy prey for fishing nets.

During the second half of the twentieth century, gi-

gantic trawlers towing enormous nets could haul in 200 tons

(181.4 metric tons) of fish an hour off Georges Bank. At

its peak in 1968, 810,000 tons (734,827 metric tons) of cod

were harvested. By the 1970s, fleets of Soviet, European,

and Japanese factory ships were trawling the cod-spawning

grounds, scooping up the fish before they could reproduce.

If the catch was of mixed

species

or the wrong size, the

nets were dumped, leaving the ocean surface teaming with

dead fish. After the catch was sorted, many species of dead

Environmental Encyclopedia 3

Georges Bank (collapse of the ground fishery)

bycatch

, including young cod, flounder, and crabs, were

discarded. For every three tons of processed fish, at least a

ton of bycatch died. These ships also trawled for herring,

capelin, mackerel, and other small fish that the cod and

other groundfish depend on for food.

The Fisheries Conservation and Management Act of

1976 extended exclusive American fishing rights from 12–

200 mi (19–322 km) offshore. Since much of Georges Bank

is within the 200-mi (322 km) limit of Nova Scotia, conflict

erupted between American and Canadian fishermen. Inter-

national arbitration eventually gave Canada the northeast

corner of the bank. The legislation also established the New

England Fishery Management Council to regulate fishing.

Although the goal was to conserve fisheries as well as to

create exclusive American fishing grounds, the council was

controlled by commercial interests. The result was the devel-

opment of financial incentives and boat-building subsidies

to modernize the fishing fleet.

Soon the New England fleet surpassed the fishing

capacities of the foreign fleets it replaced and every square

foot of Georges Bank had been scraped with the heavy chains

that hold down the trawling nets and stir up fish. This

destroyed the rocky bottom structure of the bank and the

vegetation and marine invertebrates that created habitat for

the groundfish. Cod, pollack, and haddock were replaced

by dogfish and skates, so-called “trash fish.”

During the 1990s tiny hydroids, similar to jellyfish,

began appearing off Georges Bank, in concentrations as high

as 100 per gal of water. Although they were drifting in the

water, they were in their sedentary life-stage form, indicating

that they may have been ripped from their attachments by

storms or commercial trawlers. These hydroids ate most of

the small crustaceans that the groundfish larvae depend on.

They also directly killed cod larvae.

In 1994 the National Marine Fisheries Service found

that the Georges Bank cod stock had declined by 40% since

1990, the largest decline ever recorded. Furthermore, the

yellowtail flounder stock had collapsed. In a given year,

only eight out of 100 flounder survived and the breeding

population had fallen 94% in three years. The last successful

flounder spawning was in 1987; but 60% of the catch from

that year’s group were too small to sell and were discarded. In

response the Fisheries Service closed large areas of Georges

Bank, but fishing continued in the Canadian sector and

western portions of the American sector. With the goal of

annually harvesting only 15% of the remaining stock, each

vessel was restricted to 139 days of ground fishing. Neverthe-

less by 1996, 55% of the remaining Georges Bank cod

stock — the only surviving North Atlantic population —

had been caught. Fishing was restricted to 88 days. A satel-

lite-based vessel monitoring system is used to detect fishing

boats that enter closed areas of Georges Bank.

634

At the time of the cod moratorium, it was argued that

the population would recover in five years; however there

were few signs of recovery as of 2002. Not only is the cod

stock near an all-time low, but so are populations of other

commercial fish and many other species. The average size

of the bottom-dwelling fish of Georges Bank is a fraction

of what it was twenty years ago.

Georges Bank is just one example of a eastern coastal

area negatively affected by excessive trawling. Even though

there is $800 million worth of fish extracted from Georges

Bank and the surrounding area, there is an overall decline

in groundfish stock along the entire boreal and sub-arctic

coast of eastern North America. American and Canadian

moratoriums on gas and oil exploration and extraction from

Georges Bank—activities that could further disrupt the fish-

ery—are in effect until at least 2012.

[Margaret Alic Ph.D.]

ESOURCES

OOKS

Dobbs, David. The Great Gulf: Fishermen, Scientists, and the Struggle to

Revive the World’s Greatest Fishery. Washington, DC: Island Press, 2000.

Kurlansky, Mark. Cod: A Biography of the Fish that Changed the World. New

York: Walker and Company, 1997.

ERIODICALS

Hattam, Jennifer. “Victory at Sea.” Sierra 85, no. 3 (May/June 2000): 91.

Molyneaux, Paul. “Vessel Monitor Convicts New Bedford Scalloper.” Na-

tional Fisherman 82, no. 11 (March 2002): 50.

THER

American Museum of Natural History. Georges Bank—The Sorry Story of

Georges Bank. [cited June 2002]. <http://www.sciencebulletins.amnh.org/

biobulletin/biobulletin/story1209.html>.

Public Broadcasting System. Empty Oceans, Empty Nets. 2002 [cited May

2002]. <http://www.pbs.org/empty oceans>.

Status of the Fishery Resources off the Northeastern United States. Resource

Evaluation and Assessment Division, Northeast Fisheries Science Center.

June 2001 [cited May 2002]. <www.nefsc.nmfs.gov/sos/index.html>.

United States Geological Survey. Geology and the Fishery of Georges Bank.

January 3, 2001 [cite June 2002]. <http://www.marine.usgs.gov/fact-sheets/

georges-bank/title.html>.

RGANIZATIONS

Cape Cod Commercial Hook Fishermen’s Association, 210 Orleans Road,

North Chatham, MA USA 02650 (508) 945-2432, Fax: (508) 945-0981,

Email: enichols@ccchfa.org, <http//www.ccchfa.org>

Coastal Waters Project/Task Force Atlantis, 418 Main Street, Rockland,

ME USA 04841 (207) 594-5717, Email: coastwatch@acadia.net, <http://

www.atlantisforce.org>

Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA

USA 02543-1026 (508) 495-2000, Fax: (508) 495-2258, , <http://

www.nefsc.nmfs.gov>

U.S. GLOBEC Georges Bank Program, Woods Hole Oceanographic

Institution, Woods Hole, MA USA 02543-1127 (508) 289-2409, Fax:

(508) 457-2169, Email: rgroman@whoi.edu, <http://globec.whoi.edu>

Environmental Encyclopedia 3

Geothermal energy

Geosphere

The solid portion of the earth. It is also known as the

lithosphere. From a technical standpoint, the geosphere in-

cludes inner parts of the earth virtually inaccessible to human

study, the inner and outer core and mantle, as well as the

outermost crust. For the most part, however, environmental

scientists are primarily interested in the relatively thin outer

layer of the crust on which plants and animals live, in the

ores and minerals that occur within the crust, and in the

changes that take place in the crust as a result of

erosion

and mountain-building.

Geothermal energy

Geothermal energy is obtained from hot rocks beneath the

earth’s surface. The planet’s core, which may generate tem-

peratures as high as 8,000°F (4,500°C), heats its interior,

whose temperature increases, on an average, by about 1°C

(2°F) for every 60 ft (18 m) nearer the core. Some heat is

also generated in the mantle and crust as a result of the

radioactive decay

uranium

and other elements.

In some parts of the earth, rocks in excess of 212°F

(100°C) are found only a few miles beneath the surface.

Water that comes into contact with the rock will be heated

above its boiling point. Under some conditions, the water

becomes super-heated, that is, is prevented from boiling

even though its temperature is greater than 212°F (100°C).

Regions of this kind are known as wet steam fields. In other

situations the water is able to boil normally, producing steam.

These regions are known as dry steam fields.

Humans have long been aware of geothermal energy.

Geysers and fumaroles are obvious indications of water

heated by underground rock. The Maoris of New Zealand,

for example, have traditionally used hot water from geysers

to cook their food. Natural hot spring baths and spas are a

common feature of many cultures where geothermal energy

is readily available.

The first geothermal well was apparently opened acci-

dentally by a drilling crew in Hungary in 1867. Eventually,

hot water from such

wells

was used to heat homes in some

parts of Budapest. Geothermal heat is still an important

energy source in some parts of the world. More than 99%

of the buildings in Reykjavik, the capital of Iceland, are

heated with geothermal energy.

The most important application of geothermal energy

today is in the generation of electricity. In general, hot steam

or super-heated water is pumped to the planet surface where

it is used to drive a turbine. Cool water leaving the generator

is then pumped back underground. Some water is lost by

evaporation during this process, so the energy that comes

635

from geothermal wells is actually non-renewable. However,

most zones of heated water and steam are large enough to

allow a geothermal mine to operate for a few hundred years.

A dry steam well is the easiest and least expensive

geothermal well to drill. A pipe carries steam directly from

the heated underground rock to a turbine. As steam drives

the turbine, the turbine drives an electrical generator. The

spent steam is then passed through a condenser where much

of it is converted to water and returned to the earth.

Dry steam fields are relatively uncommon. One, near

Larderello, Italy, has been used to produce electricity since

1904. The geysers and fumaroles in the region are said to

have inspired Dante’s Inferno. The Larderello plant is a major

source of electricity for Italy’s electric railway system. Other

major dry steam fields are located near Matsukawa, Japan,

and at Geysers, California. The first electrical generating

plant at the Geysers was installed in 1960. It and companion

plants now provide about 5% of all the electricity produced

in California.

Wet steam fields are more common, but the cost of

using them as sources of geothermal energy is greater. The

temperature of the water in a wet steam field may be any-

where from 360–660°F (180–250°C). When a pipe is sunk

into such a reserve, some water immediately begins to boil,

changing into very hot steam. The remaining water is carried

out of the reserve with the steam.

At the surface, a separator is used to remove the steam

from the hot water. The steam is used to drive a turbine and

a generator, as in a dry steam well, before being condensed to

a liquid. The water is then mixed with the hot water (now

also cooled) before being returned to the earth.

The largest existing geothermal well using wet steam

is in Wairakei, New Zealand. Other plants have been built

in Russia, Japan, and Mexico. In the United States, pilot

plants have been constructed in California and New Mexico.

The technology used in these plants is not yet adequate,

however, to allow them to compete economically with fossil-

fueled

power plants

Hot water (in contrast to steam) from underground

reserves can also be used to generate electricity. Plants of

this type make use of a binary (two-step) process. Hot water

is piped from underground into a heat exchanger at the

surface. The heat exchanger contains some low-boiling point

liquid (the “working fluid"), such as a

freon

or isobutane.

Heat from the hot water causes the working fluid to evapo-

rate. The vapor then produced is used to drive the turbine

and generator. The hot water is further cooled and then

returned to the rock

reservoir

from which it came.

In addition to dry and wet steam fields, a third kind

of geothermal reserve exists: pressurized hot water fields

located deep under the ocean floors. These reserves contain

natural gas

mixed with very hot water. Some experts be-

Environmental Encyclopedia 3

Giant panda

lieved that these geopressurized zones are potentially rich

energy sources although no technology currently exists for

tapping them.

Another technique for the capture of geothermal en-

ergy makes use of a process known as hydrofracturing. In

hydrofracturing, water is pumped from the surface into a

layer of heated dry rock at pressures of about 7,000 lb/in

(500 kg/cm

). The pressurized water creates cracks over a

large area in the rock layer. Then, some material such as

sand or plastic beads is also injected into the cracked rock.

This material is used to help keep the cracks open.

Subsequently, additional cold water can be pumped

into the layer of hot rock, where it is heated just as natural

groundwater

is heated in a wet or dry steam field. The

heated water is then pumped back out of the earth and into

a turbine-generator system. After cooling, the water can be

re-injected into the ground for another cycle. Since water

is continually re-used in this process and the earth’s heat is

essentially infinite, the hydrofracturing system can be re-

garded as a renewable source of energy.

Considerable enthusiasm was expressed for the hydro-

fracturing approach during the 1970s and a few experimental

plants were constructed. But, as oil prices dropped and inter-

est in

alternative energy sources

decreased in the 1980s,

these experiments were terminated.

Geothermal energy clearly has some important advan-

tages as a power source. The raw material—heated water

and steam—is free and readily available, albeit in only certain

limited areas. The technology for extracting hot water and

steam is well developed from petroleum-drilling experiences,

and its cost is relatively modest. Geothermal mining, in

addition, produces almost no

air pollution

and seems to

have little effect on the land where it occurs.

On the other hand, geothermal mining does have its

disadvantages. One is that it can be achieved in only limited

parts of the world. Another is that it results in the release

of gases, such as

hydrogen

sulfide,

sulfur dioxide

, and

ammonia, that have offensive odors and are mildly irritating.

Some environmentalists also object that geothermal mining

is visually offensive, especially in some areas that are other-

wise aesthetically attractive.

Pollution

of water by

runoff

from a geothermal well and the large volume of cooling

water needed in such plant are also cited as disadvantages.

At their most optimistic, proponents of geothermal

energy claim that up to 15% of the United States’ power

needs can be met from this source. Lagging interest and

research in this area over the past decade have made this

goal unreachable. Today, no more than 0.1% of the nation’s

electricity comes from geothermal sources. Only in Califor-

nia is geothermal energy a significant power source. As an

example, GeoProducts Corporation, of Moraga, California,

636

has constructed a $60 million geothermal plant near Lassen

National Park

that generates 30 megawatts of power.

Until the government and the general public becomes

more concerned about the potential of various types of alter-

native energy sources, however, geothermal is likely to re-

main a minor energy source in the country as a whole.

See also Alternative fuels; Fossil fuels; Renewable resources;

Water pollution

[David E. Newton]

ESOURCES

OOKS

Moran, J. M., M. D. Morgan, and J. H. Wiersma. Environmental Science.

Dubuque, IA: W. C. Brown, 1993.

National Academy of Sciences. Geothermal Energy Technology. Washington,

DC: National Academy Press, 1988.

Rickard, G. Geothermal Energy. Milwaukee, WI: Gareth Stevens, 1991.

U.S. Department of Energy. Geothermal Energy and Our Environment.

Washington, DC: U.S. Government Printing Office, 1980.

ERIODICALS

Fishman, D. J. “Hot Rocks.” Discover 12 (July 1991): 22–23.

Giant panda

Today, the giant panda (Ailuropoda melanoleuca) is one of

the best known and most popular large mammals among

the general public. Although its existence was known long

ago, having been mentioned in a 2,500-year-old Chinese

geography text, Europeans did not learn of its existence until

its discovery by a French missionary in 1869. The first living

giant panda did not reach the Western Hemisphere until

1937. The giant panda, variously classified with the true

bears or, often, in a family of its own, once ranged throughout

much of China and Burma, but is now restricted to a series

of 13

wildlife

reserves totaling just over 2,200 mi

(5,700

) in three central and western Chinese provinces. The

giant panda population has been decimated over the past

2,000 years by

hunting

and

habitat

destruction. In the years

since 1987, they have lost more than 30% of their habitat.

Giant pandas are one of the rarest mammals in the world,

with current estimates of their population size at about 1,000

individuals (150 in captivity). Today human pressure on

giant panda populations has diminished, although

poaching

continues. Giant pandas are protected by tradition and senti-

ment, as well as by law in the Chinese mountain forest

reserves. Despite this progress, however, IUCN—The

World Conservation Union—and the U. S.

Fish and Wild-

life Service

consider the giant panda to be endangered.

Some of this species’ unique requirements and habits do

seem to put them in jeopardy.