Environmental Encyclopedia

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Environmental Encyclopedia 3

Mineral Leasing Act (1920)

ronmental law; Food chain/web; Heavy metals and heavy

metal poisoning; Marine pollution; Methylmercury seed

dressings; Water pollution; Xenobiotic

[Frank M. D’Itri]

ESOURCES

OOKS

Harada, M. “Methyl Mercury Poisoning Due to Environmental Contami-

nation (Minamata Disease).” In Toxicity of Heavy Metals in the Environment,

Part 1, edited by F. W. Oehme. New York: Marcel Dekker, 1978.

Ui, J. “Minamata Disease.” In Industrial Pollution in Japan. Tokyo, Japan:

United Nations University Press, 1992.

ERIODICALS

D’Itri, F. M. “Mercury Contamination—What We Have Learned Since

Minamata.” Environmental Monitoring and Assessment 19 (1991): 165–182.

Mine drainage

see

Acid mine drainage

Mine spoil waste

Most human extractions of earth materials, such as clay for

pottery or

coal

for power generation, produce some waste.

The raw materials are rarely pure, so unwanted

detritus

discarded, usually close to the extraction site. Over the last

two centuries, exponential industrial growth has resulted in

huge increases in the production of mine

spoil

waste. The

management of this waste has become an increasingly impor-

tant issue.

New technologies allow the mining of ever lower

grades of ore, with mounting waste as a byproduct. Early

mining actually wasted ore, since only the richest veins were

extracted. However, less waste was generated by this high

grade ore. Now operations tend to remove varying grades

of ore en mass, yielding a higher return, but multiplying the

waste produced. Where concentrations are high, it has even

been profitable to rework older

tailings

Surface mining

accounts for most mining waste, but

underground work also contributes. Metallic ores, sand,

gravel, and building stone, including aggregate for concrete,

are usually extracted from open pit mines.

Strip mining

effective where resources lie in sedimentary layers, and is

particularly used for coal, phosphate, and gypsum. Much

of the waste from strip mining comes from

overburden

removal.

Dredging

is used to extract sand and heavy placer

deposits such as gold and tin; it reinjects large amounts of

fluvial

sediment

into the flowing water. Hydraulic mining

with high pressure hoses is common in gold fields; devasta-

ting effects are still visible in the foothills of California’s

Sierra Nevada Mountains, more than a century later.

907

Environmental impacts of mining include the creation

of new landforms, severe

ecosystem

disruption, and the

formation of dangerous

chemicals

. The scale of operation

varies enormously, but some projects are immense. The holes

and mountains of overburden created may become useful

as chat for railroad beds, sub-base material for roads, or

recreational lakes. But, severe environmental problems are

a more common result. Ecosystem disruption stems mainly

from loss of

topsoil

, rich in organisms and nutrients; sterile

landscapes with high sediment

runoff

are a common

outcome.

The most serious problem resulting from mine wastes

acid drainage

and

leaching

of hazardous substances.

When these wastes are moved from a reducing

environment

(oxygen deficient) to an oxidizing environment, sulfuric acids

are formed by the oxidation of the sulfides in metallic ores or

the sulfur that commonly accompanies coal deposits. These

acids may flow into surface waters or may leach hazardous

metals from the waste. The best solution is to minimize

exposure to oxygen, usually by burial.

Mining presents the dilemma of short term gains ver-

sus long term losses, especially of land suitable for agriculture

or forestry. The goal of sustainability makes

reclamation

of mine spoil wastes imperative. See also Acid mine drainage;

Erosion; Hazardous material; Sustainable development;

Waste management

[Nathan H. Meleen]

ESOURCES

OOKS

Caudill, H. M. Night Comes to the Cumberlands. Boston: Atlantic-Little

Brown, 1963.

Meleen, N. H. “Mining Wastes and Reclamation.” In Magill’s Survey of

Science: Earth Science Series, edited by Frank N. Magill. Pasadena, CA:

Salem Press, 1990.

THER

U.S. Department of the Interior. Surface Mining and Our Environment.

Washington, DC: U.S. Government Printing Office, 1967.

Mineral Leasing Act (1920)

The Mineral Leasing Act of 1920 regulates the exploitation

of fuel and

fertilizer

minerals on the public lands. The act

resulted from the perceived failure of existing federal laws

dealing with

coal

and oil resources. Coal lands had been

managed under an 1873 law, allowing the coal to be mined

for either $10 or $20 per ton on tracts of 160 or 320 acres

(64.8 or 129.6 ha). These acreage limitations led to abuse

of the law, and in 1906 over 65 million acres (26.3 million

ha) of land were withdrawn from coverage under of the coal

lands law. These lands were then reclassified according to

Environmental Encyclopedia 3

Mining, undersea

whether they contained coal or not, and the price for lands

containing coal was increased. The withdrawal and reclassifi-

cation process slowed development and led many to argue

for a new approach. The fate of these coal lands was soon

tied to the fate of oil lands.

Oil resources were being managed based on the Min-

ing Law of 1870 and the Oil Placer Act of 1897. Neither

law, however, sufficiently recognized the difference between

petroleum

and other minerals this in turn resulted in major

problems in the exploitation of petroleum. These problems

included overproduction, market instability, claim jumping,

and national security concerns. In 1909, President William

Howard Taft withdrew over three million acres of

public

land

from oil development in California and Wyoming,

thereby initiating a policy debate over how to manage petro-

leum resources on the public lands.

The first leasing bill, supported by the Taft administra-

tion, was introduced in Congress in 1913, but because it

was so controversial in the western states, the Mineral Leas-

ing Act was not passed until 1920. The law, which applies

to deposits of coal, oil, gas,

oil shale

, phosphate, potash,

sodium, and sulfur on the public lands, has two main fea-

tures: federal regulatory authority and conditional access to

the public lands. Controversy centered on the oil provisions

of the Act. These gave the Secretary of the Interior the

authority to issue permits for prospecting on land that was

not known to have any oil. If oil were discovered, the pros-

pector acquired lease rights for 20 years and paid a royalty

fee of five percent. For proven oil-producing lands, tracts

were offered under a system of competitive bidding based

on royalty payments. The minimum area covered was 640

acres (259.2 ha), and the minimum royalty accepted was

12.5%. These royalties were to be divided among the

Recla-

mation

Fund (for western water projects), the states in which

the land is located (for education and roads), and the federal

government.

Amendments to the act have done away with prospect-

ing permits, increased the size of tracts that can be leased,

and changed the bidding procedures for leases. Most lands

that are not known to contain oil are leased through a lottery

conducted by the U. S. Department of the Interior. For

known oil lands, a competitive bidding procedure is used.

In addition to the bid fee, a 12.5% royalty and an annual

rental fee of $2.00 per acre is also required.

The Mineral Leasing Act was a significant departure

from past mining policy, based on the Mining Law of 1872,

which granted free access to the public lands, the potential

for inexpensive purchase of mineral lands, and included no

royalty payments to the government.

[Christopher McGrory Klyza]

908

ESOURCES

OOKS

Hays, S. P. Conservation and the Gospel of Efficiency: The Progressive Conser-

vation Movement, 1890–1920. New York: Atheneum, 1975.

Mayer, C. J., and G. A. Riley. Public Domain, Private Dominion: A History

of Public Mineral Policy in America. San Francisco: Sierra Club Books, 1985.

Swenson, R. W. “Legal Aspects of Mineral Resources Exploitation.” In

History of Public Land Law Development, by Paul W. Gates. Washington,

DC: U.S. Government Printing Office, 1968.

Minerals, strategic

see

Strategic minerals

Minimum-tillage agriculture

see

Conservation tillage

Mining

see

Acid mine drainage; Ashio, Japan;

Ducktown, Tennessee; Itai-itai disease; Mine

spoil waste; Placer mining; Silver Bay; Strip

mining; Sudbury, Ontario; Surface mining;

Surface Mining Control and Reclamation Act

(1977)

Mining, undersea

Practically all of the mineral and energy resources found on

land are present under the sea. Development, however, is

limited by extraction costs that increase with depth of water,

by the relative abundance of resources on land, and by politi-

cal questions involving ownership of deep ocean resources.

Worth $80 billion, the most valuable undersea com-

modity is oil and

natural gas

, representing 90% of the

resources obtained from the seafloor. Continental-margin

deposits comprise about one-third of the world’s estimated

oil and gas reserves. Large deposits have been found on the

continental shelves in the Gulf of Mexico, the Persian Gulf,

the North Sea, and off the coasts of northern

Australia

southern California, and the Arctic Ocean. Other sites are

promising, and many other continental shelves remain rela-

tively unexplored. The harsh conditions found in the North

Sea have fostered huge investments in colossal offshore rigs.

Extraction costs on the continental shelves are several times

higher than on land, and projected costs in the Arctic Ocean

are several times higher again. Such fields are profitable only

because of their high flow rates and reserves. Oil exploration

continues to push the limits of profitable extraction into

deeper and deeper waters. One commercially promising well

Environmental Encyclopedia 3

Mission to Planet Earth (NASA)

in the Gulf of Mexico was drilled in waters well over 1 mi

(1.6 km).

Nearshore resources are much more likely to be mined

than distant ones. Sand and gravel predominate in volume.

Though in great demand for use in concrete and as fill

material and beach sand, their low value restricts usage to

local areas.

Delta sediments are often mined for valuable deposits

washed from the land, including gold, platinum, tin, dia-

monds, iron, and

uranium

. Japan, an island country with

limited land resources, is especially eager to exploit such

deposits;

coal

beds are also being mined.

Phosphorite is the source rock for phosphate, a key

fertilizer

. Phosphorite deposits occur where upwelling

brings dissolved phosphate to the surface, where, in turn,

rising temperature and

cause them to precipitate out.

Their value comes from their high grade, since they are not

diluted by land-derived sediments.

Manganese nodules were first discovered on the deep-

ocean floor during the 1873–76 voyage of the British ship,

Challenger. Although rich in valuable ferroalloys used in

steelmaking, these potato-like ores have yet to be mined

commercially. The deposits are immense, but the technology

for profitable mining does not currently exist.

Another tantalizing resource is the sulfide ores precipi-

tated out of ocean water around

hydrothermal vents

deep-ocean rift systems. Commercial extraction is being at-

tempted in the Red Sea, and experimental vehicles have

been built for use in the deep ocean, but technological and

economic limitations hinder commercial development.

Economic considerations are one of the greatest limi-

tations to the growth of undersea mining, along with uncer-

tain environmental impact. Only highly profitable ventures,

as in oil and gas extraction, or readily accessible, near-shore,

bulk resources, such as sand and gravel, are currently feasible.

Undersea mining appears to hold great potential

resources

for the future

, when supplies and extraction costs of land-

based resources tip the scales in its favor.

Political considerations, especially questions of owner-

ship and the sharing of profits, are also key factors here,

with developing countries clamoring for their share. During

the 1970s, the United Nations strove for a treaty to regulate

deep-ocean exploitation. The 1982 Law of the Sea Treaty

claimed manganese nodules as the heritage of all humankind,

to be regulated by the United Nations’ seabed authority and

with profits to be shared. The United States chose not to

sign the treaty, and has joined with other developed countries

in a provisional understanding to award exploitation licenses.

These political and environmental issues are insignifi-

cant, so long as the economic realities favor resources on

land. It will be beneficial if the time spent waiting for devel-

909

opment of undersea mining creates the opportunity for more

productive international discussions and agreements.

[Nathan Meleen]

ESOURCES

OOKS

Duxbury, A. C., and A. B. Duxbury. An Introduction to the World’s Oceans.

3rd ed. Dubuque, IA: Wm. C. Brown Publishers, 1991.

Ingmanson, D. E., and W. J. Wallace. Oceanograph. 5th ed. Belmont, CA:

Wadsworth Publishing, 1995.

Mirex

An organic compound that was manufactured for use as an

insecticide against imported

fire ants

and, secondarily, as a

fire retardant for

plastics

rubber

, paint, paper, and electri-

cal products. It has a molecular weight of 545.59 and consists

of twelve

chlorine

atoms attached to a ten

carbon

cage. Its

full name is dodecachloro-octahydro-1,3,4-metheno-1H-

cyclobuta[c,d]pentalene. The United States

Environmental

Protection Agency

(EPA) has classified it as a

carcinogen

Mirex can be degraded to the toxic

pesticide Kepone

the

environment

. Due to discharges from manufacturing

facilities in the state of New York, it is found in the water,

sediments, and biota of Lake Ontario at levels of concern.

See also Cancer; Great Lakes; Toxic substance

Mission to Planet Earth (NASA)

The Mission to Planet Earth (MTPE), now officially called

the Earth Science Enterprise (ESE), is a program of the

National Aeronautics and Space Administration (NASA)

of the U.S. government. The mission is to use spacecraft

and space technology to provide a comprehensive scientific

study of the earth’s living systems as viewed from space.

Using satellites with precise measuring equipment, the mis-

sion will provide information about weather patterns,

cli-

mate

, oceans, coastlines, surface activity, atmospheric condi-

tions, natural disasters,

pollution

, and hundreds of other

measurements. The goals of the program, according to

NASA, are to find out how the living system of the earth

is changing, and to determine the causes and consequences

of this change. NASA also has the goal of using the pro-

gram’s results to develop a “predictive capability” for climate,

weather, and natural hazards. Finally, the program has an

end-to-end strategy of performing studies and gathering

data as well as making the findings readily available to the

public and scientific community. Other countries are also

taking part in the mission, including Canada, Japan, Russia,

Environmental Encyclopedia 3

Mixing zones

and many major European countries, providing funding and

scientific studies.

MTPE was initiated by President George Bush in

1989, on the recommendation of the

National Research

Council

. At first, NASA and the U.S. government were

ambitious about the plan to study the earth from space, and

proposed a budget of $35 billion for its first 15 years. The

original concept of the program was to build a huge observa-

tory that would orbit and monitor the earth. The program

was scaled down during budget battles in the early 1990s

and received about $8 billion for its first decade of operation.

The scientific concept of the program was changed as well

due to the revised budget; MTPE will utilize up to 18 small

satellites that will monitor the earth from space, called the

Earth Observing System, and collect data that will be coordi-

nated by computers. In 1998 NASA changed the name of

MTPE to the Earth Science Enterprise.

By 2002, the program had several satellites and

measuring instruments in space. The Earth Resources

Observation System (EROS) has mapped cities and rec-

orded urban growth and

habitat

destruction. The Geosta-

tionary Environmental Satellite (GOES) has tracked hurri-

canes and weather patterns. The Upper

Atmosphere

Research Satellite was launched in 1991 to study the

ozone

layer. In 1996 a Japanese satellite carried NASA

instruments to study global wind patterns, and in 1997

a joint United States/Japanese satellite was launched to

study how tropical rainfall affects the world’s climate. In

April 1999, NASA launched the Landsat 7 satellite to

map and study environmental changes on the earth’s

surface, including mapping the world’s forest canopy. In

November 2000 a new generation of satellite was launched,

the EO-1, which was only one-seventh the size of the

Landsat satellites. The new satellite had sophisticated

instruments, some of which can measure parameters such

as the earth’s gravity field. This measurement may help

scientists better understand ocean currents and heat move-

ment between the poles. Other governmental departments

besides NASA are also contributing to the project. The

National Oceanic and Atmospheric Administration’s

(NOAA) Polar-orbiting Operational Environmental Satel-

lite is monitoring factors such as global vegetation, ocean

currents, ice warming, weather patterns, the ozone layer,

and solar storms. The MTPE was projected to consist

of 25 measuring instruments on 10 satellites by 2002,

depending on launch schedules and other factors.

NASA plans to make all of the data from MTPE

satellites available to the public on computers. The informa-

tion will be stored in NASA’s Earth Observing System Data

and Information System (EOSDIS). NASA estimates that

MTPE satellites will send enough data back to Earth during

its first 15 years of operation to fill nearly 6.5 million books

910

per day. The management of this information will be as

demanding a project as sending the satellites to space, and

users will be able access the data from the Internet, CD-

ROMs, tapes, microfiche, and photographs. By 2002 MTPE

data was available via the Internet, including live broadcasts

of the earth from satellites. Eventual users of MTPE data

may include atmospheric scientists studying the ozone layer,

meteorologists predicting weather changes, ecologists moni-

toring tropical rain forests, scholars performing environmen-

tal research, and many others interested in environmental

patterns and problems.

[Douglas Dupler]

ESOURCES

OOKS

Burrows, William E. This New Ocean: The Story of the First Space Age. New

York: Random House, 1998.

Walter, William. Space Age. New York: Random House, 1992.

ERIODICALS

Lawler, Andrew. “Climate Warms a Bit for NASA Mission” Science, March

28, 1997, 1870.

Stevens, William K. “NASA Readies a ’Mission to Planet Earth.’” New

York Times, February 17, 1998, B9.

THER

Earth Observing System Project Office. [cited July 2002]. <http://www.eos.na-

sa.gov>.

Earth Science Enterprise Home Page. [cited July 2002]. <http://www.earth.-

nasa.gov>.

Mitsui Mining and Smelting Company

see

Itai-itai disease

Mixing zones

Most

wastewater

treatment plants and industrial facilities

discharge

their

effluent

into the nearest available body of

surface water such as a stream or river. The mixing zone is

the localized area in the receiving stream within which the

mixing, dispersal, or dissipation of the effluent can be de-

tected. For example, cooling water discharges from

power

plants

typically create a mixing zone in the receiving stream

where the temperature is higher than the ambient back-

ground temperature of the stream waters. Environmental

regulations usually require that the mixing zone be limited

in size and not create a nuisance or hazardous conditions.

MMPA

see

Marine Mammals Protection Act

(1972)

Environmental Encyclopedia 3

Modeling (computer applications)

Computer modeling is a mathematical tool used to analyze

complicated systems or to predict events such as floods,

climate

changes, or population changes. Computer models

are applied in many disciplines, from engineering (predicting

the strength of a bridge or dam) to economics (predicting

inflation rates) to

ecology

(describing a

food chain/web

or projecting the survival chances of an

endangered spe-

cies

). A model may consist of a few simple calculations on

a spreadsheet, or it may involve millions of calculations on

hundreds of thousands of input parameters, as in the case

of general circulation models used to describe and predict

climate conditions. Both simple and complex models involve

quantifying input variables and the relationships between

them, in order to produce numeric output that can describe

or predict some real world phenomenon or condition. Mod-

els are often criticized because they can generalize real-world

phenomena unrealistically, or because any errors in initial

assumptions are expanded as assumptions are added and

multiplied together. However, modeling remains a common

tool because it is often the only available method to find

answers to important research questions.

Models let researchers “experiment” with systems that

do not allow manipulative experimentation. You cannot ac-

tually build a power plant just to test its effect on a popula-

tion, and you cannot deliberately change the temperature of

the

atmosphere

in order to see what happens to plant

populations and sea levels. Instead a model can be used to

predict probable outcomes of known conditions. Different

variables can also be easily introduced in a model, for exam-

ple, on the computer a programmer can easily add

pollution

control

equipment to the power plant and observe its effect

on lung disease rates in the surrounding population, or a

modeler can easily reduce worldwide

carbon dioxide

emis-

sions and calculate the impact on atmospheric temperatures.

Computer models have many applications. Some aid in

assessing or visualizing a phenomenon. Three-dimensional

geological models are used to help visualize or approximate

the volume and dimensions of an

aquifer

, an oil reserve, or

a magma chamber beneath a

volcano

. A simple

ecosystem

model can help identify general relationships between popu-

lations and resources, by letting the modeler adjust variables

and see which arrangements most closely approximate ob-

served data. Other models are used to predict the outcome

of known conditions: a demographic model representing

known rates of

population growth

, reproduction, and

death can reasonably predict a country’s population a century

from now. Still other models are used to test “what if”

questions. A

pollution

dispersion model showing how much

pollution could spread from a power plant to a town can be

used to test different scenarios: What if there were a north-

911

west wind for an entire week? What if the power plant

needed to double its energy production? What if the town

expanded in the direction of the power plant? Models used

to describe or visualize a system are known as descriptive

models. Models that project or predict the results of input

conditions are known as predictive models.

Anything that approximates or simulates a real-world

phenomenon could be considered a model. A plaster replica

of a landform, a diagram drawn on paper to describe links

in a food web, or a verbal description of a storm could

be considered models, because each of these describes or

simulates a real phenomenon. Computer models approxi-

mate phenomena in the real world by performing calculations

on input variables. These calculations produce numeric out-

put that predicts the outcome of the variables in the model.

For example, a wolf population model might multiply the

number of breeding adults (A) by the average number of

pups per litter (P) to produce the expected number of young

wolves

in a year (N):AxP=N.

This is a very simple, and not very realistic, mathemati-

cal model. A computer model can produce a more realistic

representation of a wolf population, by incorporating more

variables, by using randomized variables, by performing more

complicated mathematical functions, and by repeating calcu-

lations many times in order to produce a statistically signifi-

cant number of “experiments.”

Models can be composed of variables, parameters, and

constants. A variable is any factor that is changeable. The

number of breeding adults in a wolf population might change

from year to year, as might the number of pups per adult.

Parameters are sometimes distinguished from variables as

input factors that are unlikely to change: the number of

litters in a wolf pack is unlikely to be more than one per

year, or the month in which pups are born might reasonably

be expected not to change from one year to the next. Con-

stants are input factors that are assumed to be unchanging.

In a model of a dam’s structure and strength, the force of

gravity on the water behind the dam would be a constant.

In addition, randomized (stochastic), values can also be used

to introduce an element of chance into the model. For exam-

ple, in a simulation of population change in wolves a realistic

birth rate may be somewhere between 4-9 pups per breeding

female per year. A computer model can randomly select a

number between 4-9, for this variable each time the model

is run. In addition there might be a 70% chance that each

pup would survive its first year. This stochastic variable could

be added to increase the

precision

of the model’s prediction

of population at the end of the year. As the computer pro-

cesses the model it arbitrarily picks a value for the stochastic

variable. Stochastic variables can improve a model by making

it better represent real events that are somewhat random, or

at least unpredictable.

Environmental Encyclopedia 3

Modeling (computer applications)

Deterministic and Stochastic Models

A deterministic model produces a single answer for

each set of variables; that is, the input variables determine

the outcome. Different results can be produced only by

entering different values for the input variables. Determinis-

tic models are useful where the values of input variables are

reliably known. For example, if an engineer knows with

reasonable certainty the strength of a concrete dam and the

force applied by a full

reservoir

, a deterministic model

should be used to calculate the water level that would cause

the dam to break. A stochastic model, in contrast, includes

an element of randomness, so that there will probably be a

different result each time the model is run. For example, a

population model might include a slightly randomized birth

rate, or a reservoir model might include a randomized vari-

able for rainfall, which in fact varies unpredictably from year

to year. An advantage of using a stochastic (random) variable

is that it helps the model approximate the fluctuations that

can occur in a real system: there is no way to predict the

actual number of pups a wolf pack will have each year, but

it is possible to predict with some precision the minimum

and maximum number that is likely. Running a stochastic

model repeatedly can produce a statistically significant sam-

ple of experimental results. Statistical analysis can be used

to assess the

probability

of various outcomes, such as a 25%

probability that a wolf population will rise over the next

100 years.

Development of Modeling

Although mathematical models and analog models

(physical structures such as clay models of landforms or

river

basins

) have been used in environmental problem solving

for a long time, the growth of modern computer modeling

began in the 1960s with the development of computers. One

of the first publicized computer models was a climate model

that calculated climate conditions based on three input pa-

rameters: temperature, air pressure, and wind speed. Since

then models have been used to predict weather, stream

dis-

charge

soil erosion

, population growth, pollution impacts,

and many other occurrences. The ability to use a computer

greatly increased the complexity of models that could be

developed, and the widespread availability of computers in-

creased the number of people developing models for a grow-

ing number of purposes. Models are used in

environmental

monitoring

and management, physics, engineering,

hydrol-

ogy

, economics, demographics, and many other fields. One

reason modeling developed more or less simultaneously in

many disciplines is that the techniques of programming a

computer to simulate real-world variables are highly porta-

ble: the structure of a model used to interpret water flow

might be modified and applied to magma movement in the

earth or to

nutrient

flows through a landscape. Modeling

is now a widespread technique that is used to help explain

912

how natural systems function and to inform public policy

concerning the

environment

, the economy, and many other

issues.

Sensitivity Analysis, Calibration, and Validation

Once a model is developed it is usually tested against

observed events or data to indicate how reliable it is or

where its weaknesses lie. One of the first tests usually run

is sensitivity analysis. A model’s outcome may be more sensi-

tive to changes in one variable or process than another: in

a beach erosion model, for example, the predicted erosion

rate is likely to be influenced more by wave energy than

by sand particle size, even though both factors need to be

considered. It is essential to know to which factors the model

is most sensitive, because error in estimating those factors

could introduce significant error into the results. Sensitivity

analysis involves adjusting variables or processes and then

running the model to see which factors cause the greatest

variability in outcomes.

Once the input variables and relationships in a model

are established, the model can be calibrated, or tuned, to make

it better represent reality. Calibration usually entails adjusting

different parameters in order to produce a result similar to

some observed results in the real world. Calibrating a model

for forest growth, for example, might involve running the

model repeatedly with different growth rates until the model

approximates observed historic growth rates and densities.

Validation is like calibration, in that it involves com-

paring a model’s results to observed data. The objective of

validation, though, is to demonstrate that the model is reli-

able. The assumption of model validation is that if the model

predicts the correct results in a known situation, then it

will probably predict correctly in an unknown, experimental

situation.

General Circulation Models

A type of model that has received much attention

since the mid-1980s is the general circulation model, or

GCM. This is a class of highly complex models designed

to predict with reasonable

accuracy

the behavior of the

earth’s atmosphere (climate) or oceans. GCMs have been

used to predict worldwide global warming as a result of

increased concentrations of

carbon

dioxide in the atmo-

sphere. GCMs are complex because they simulate the behav-

ior of the atmosphere and the oceans, which have complex

three-dimensional movements or flows of air masses or

water. Predicting how changes in heat input at one location

impacts temperatures and flow rates at another location re-

quires thousands of calculations performed on many inter-

related variables at thousands of points in space. Because

GCMs must keep track of so many variables and so many

points in space, they are usually run on supercomputers that

can perform (billions) of calculations per second.

Environmental Encyclopedia 3

Dr. Mario Jose Molina

The appropriate complexity of a model depends on its

intended use. A model designed to describe ocean circulation

over space and time to produce realistic results on which to

base public policy might incorporate many variables. A

model built to test very general relationships between vari-

ables, in order to stimulate a researcher’s insight into a small

aspect of ecosystem functions, may more appropriately be

quite simple, with only a few input parameters and equations.

[Mary Ann Cunningham Ph.D.]

ESOURCES

OOKS

Gordon, S. I. Computer Models in Environmental Planning. New York: Van

Nostrand Reinhold, 1985.

Hardisty, J., D. M. Taylor, and S. E. Metcalfe. Computerised Environmental

Modelling. New York: Wiley, 1993.

Starfield, A. M., K. A. Smith, and A. L. Bleloch. Model It: Problem Solving

for the Computer Age. New York: McGraw-Hill, 1990.

Dr. Mario Jose Molina (1943 – )

Mexican chemist

Mario Molina was born on March 19, 1943, in Mexico. He

received his bachelor’s degree from the National Autono-

mous University of Mexico in 1965 and his Ph.D. in physical

chemistry from the University of California at Berkeley in

1972. After teaching for a year at the National Autonomous

University, he returned to Berkeley as a research associate

for one year.

In 1973, Molina joined the research laboratory of F.

Sherwood Rowland at the University of California at Irvine.

Molina was looking for a topic on which he could do his

post-doctoral research with Rowland, and Rowland was

ready with a suggestion because he had just come from a

scientific meeting where he became interested in the possible

effects of an important commercial chemical, trichlorofluo-

romethane, also known as chlorofluorocarbon-11, or CFC-

11. The compound was a member of a widely-successful

group of

chemicals

, called freons, produced by Dow Chemi-

cal Company.

In particular, the question that interested Rowland

was what effects, if any, this compound would have on

atmospheric gases. CFC-11 was rapidly becoming very pop-

ular as a propellant in hair sprays, spray paints, and other

aerosol

products. By 1974, more than $2 billion of CFC-11

and related

chlorofluorocarbons

were being used each year.

Rowland and Molina developed a theory about the

fate of CFC molecules released in the

troposphere

, the

layer of the

atmosphere

in which we live. They predicted

that those molecules would rise into the

stratosphere

, the

layer of air above the troposphere. There, they said,

solar

913

energy

would cause CFC molecules to decompose, releasing

free

chlorine

atoms.

If that were to happen, they hypothesized, the free

chlorine would be likely to attack

ozone

molecules, con-

verting them to ordinary oxygen. The chlorine oxide formed

in that reaction might then react with single oxygen atoms,

to form more oxygen and regenerate the original chlorine.

Two important conclusions can be drawn from this

series of reactions. First, a single atom of chlorine would be

capable of destroying many (Rowland and Molina predicted

about 100,000) molecules of ozone. Second, since ozone in

the stratosphere absorbs

ultraviolet radiation

, this process

would result in more ultraviolet radiation reaching the earth’s

surface and causing an increase of skin

cancer

among

humans.

When Rowland and Molina first proposed this theory,

no measurements had ever been made of chlorine in the

stratosphere. By 1979, they had carried out the first of those

measurements and obtained results that closely matched

their predictions. An important new environmental problem,

ozone layer depletion

, had been identified.

Molina held positions as a research associate, assistant

professor, and associate professor at the University of Cali-

fornia at Irvine. In 1983, he left Irvine to become Senior

Research Scientist at the Jet Propulsion Laboratory at the

California Institute of Technology in Pasadena. Molina was

awarded the Society of Hispanic Engineers Award in 1983.

He is also the recipient of more than a dozen awards includ-

ing the 1987 American Chemical Society Esselen Award,

the 1988 American Association for the Advancement of

Science Newcomb-Cleveland Prize, the 1989 NASA Medal

for Exceptional Scientific Advancement, and the 1989

United Nations Environmental Programme Global 500

Award. In 1995, he received the Nobel Prize in Chemistry

along with F. S. Rowland and P. Crutzen.

[David E. Newton]

ESOURCES

ERIODICALS

Molina, M. J., et al. “Experimental Study of Intermediates from OH-

initiated Reactions of Toluene.” Journal American Chemical Society 121

(1999): 10225—10226.

———, and M. J. Molina. “Chlorofluoromethanes in the Environment.”

Review of Geophysical Space Research (January 1975): 1–35.

Rowland, F. S. “Atmospheric Chemistry: Causes and Effects.” MTS Journal

(Fall 1991): 12–18.

THER

Mario Molina Web Page. [cited July 2002]. <http://eaps.mit.edu/molina>.

Molluscicide

see

Pesticide

Environmental Encyclopedia 3

Monarch butterfly

Like all butterflies, moths, and other insects with a lifecycle

that involves complete metamorphosis, individual monarch

butterflies (Danaus plexippus) go through four stages from

eggs to larvae (caterpillars) to pupae to adults. Unlike other

insects, as a

species

monarchs also undergo an annual cycle

that involves several generations and a

migration

that covers

thousands of miles.

Monarch butterflies are native to North and South

America, but have were spread by humans throughout much

of the world in the 1800s. They first appeared in Hawaii in

the 1840s, then spread throughout the rest of the South

Pacific in the 1850s and 1860s. In the early 1870s, the first

monarchs were reported in

Australia

and New Zealand.

These different populations have adapted to their new habi-

tats with an amazing range of behaviors, but the annual

migration undergone by the North American monarchs

makes them unique among insects.

It is thought that there are three distinct populations

of monarchs in the United States. One breeds east of the

Rocky Mountains and overwinters in the mountains of cen-

tral Mexico. Another breeds west of the Rocky Mountains

and overwinters on the California coast. These populations

constitute separate breeding pools with little genetic ex-

change. A third population is found in southern Florida.

This population is genetically less isolated and probably re-

ceives significant influx from the eastern population in the

fall and possibly the spring.

The monarch life cycle

An individual monarch’s life cycle begins when a fe-

male lays an egg on a plant in the milkweed family (Asclepi-

adacae). Dozens of milkweed species are found throughout

North America, and most of these are suitable hosts for

monarchs. Common milkweed (Asclepias syriaca) in the

northern United States and Canada, is probably host to more

monarchs than any other species. It is difficult to tell just

how many eggs each butterfly lays during her life, but the

average female in the wild is thought to lay 300–500 eggs.

In captive females average about 700 eggs over two to five

weeks of egg laying. Eggs usually hatch three to seven days

after they are laid.

The newly hatched larva’s first food is its egg-casing,

but it soon begins eating the plant on which it was hatched.

Only after consuming milkweed does the larva develop the

characteristic yellow, white, and black striped pattern recog-

nized by children and adults throughout the world. Monarch

larvae undergo five stages called instars, shedding their old

skin between stages to allow for growth. The main activity

of the larva is eating, and during the larval period of about

eight to 14 days, they increase their mass about 2,000-fold.

914

The third stage in the monarch life cycle is the pupa,

or chrysalis. When the monarch is ready to pupate, it seeks a

protected location and spins a white silk pad using a spinneret

located just under its mouth. It attaches itself to this pad

and dangles head down. About a day later it sheds its skin

for the last time and the gold-spotted green chrysalis, or

pupa, is complete. This stage lasts eight to 15 days. The day

before the adult butterfly emerges, its folded wings are visible

through the pupa case, and it is possible to see the black,

orange and white color pattern that is the monarch’s trade-

mark. This pattern is due to tiny scales that cover the mon-

arch’s wings and body. On the day that the butterfly emerges,

the colors are very distinct and the pupa no longer has any

green coloring.

Adults live for two to six weeks, spending their time

gathering nectar from flowers, mating, and laying eggs. Four

to five generations repeat this cycle throughout the spring

and summer.

The monarch’s annual cycle

Butterflies that emerge in late August and September

put reproduction on hold. Instead of eating, mating, and

laying eggs, the adults fly south. Individuals in the eastern

North American population, live up to nine times as long

as their spring and summer counterparts. They travel to

old growth oyamel fir (Abies religiosa) forests high in the

transvolcanic mountains of Michoacan, Mexico. West coast

monarchs also begin a migration that will end in the eucalyp-

tus and Monterey pine (Pinus radiata)groves of Pacific

Grove, Santa Cruz, and Fremont on the Central Califor-

nia coast.

Starting in early November, the monarchs form com-

pact roosts thickly covering the trunks and branches of hun-

dreds of trees. They remain in a nearly dormant state until

the temperatures warm in February, when they become more

active, mating, and seeking water and nectar. In mid-March,

they fly north to look for the milkweed plants in order to

produce new generations of monarchs that will continue the

migration cycle. Recolonization of the summer breeding

grounds is a two-step process. Monarchs that have overwin-

tered make part of the return trip. Then they lay eggs and

die. Their offspring continue the journey north until the

breeding range is reoccupied by late May or early June.

Because of their incredible yearly migration cycle,

monarchs depend on resources in widely dispersed locations,

making them especially vulnerable to disruption of their

habitat

. In their breeding range throughout the United

States and southern Canada, they need fields, roadsides,

gardens, and prairies filled with milkweed for larvae and

nectar sources for adults. During their fall migration mon-

archs need safe flyways and nectar sources to fuel their long

journey. Finally, the migratory generation requires an intact

habitat in their wintering one that will protect them from

Environmental Encyclopedia 3

Monarch butterfly

temperature and humidity extremes during their winter rest.

Just as with migratory song birds, preserving the monarch’s

migratory life cycle requires international interest, knowl-

edge, and cooperation.

Monarch population size

There are no reliable estimates of monarch population

size during the breeding stage of the annual cycle. However,

estimates of absolute numbers during the overwintering pe-

riod exist. During the winters of 1985 to 2002, researchers

estimated that overwintering monarch densities are approxi-

mately 10 million butterflies per hectare, with 6–12 hectares

of land used for roosting. However, estimates of monarch

mortality

during a major winter storm in 2002 suggested

that this estimate is too low, and that densities may be more

like 50 or 60 million monarchs per hectare of occupied forest.

Sources of monarch mortality

About 90–95% of monarch eggs never reach adult-

hood, and predators, milkweed defenses, and environmental

conditions can all cause mortality during the immature

stages. Predators and environmental conditions can also kill

adults. Habitat destruction limits the number of monarchs

reaching maturity during the summer breeding period, and

also affects the number that survive the overwintering period.

Invertebrate predators such as insects and spiders, and

diseases caused by bacteria, viruses,

fungi

, and other organ-

isms kill many monarchs in natural populations. Invertebrate

predators of monarchs include both native and introduced

flies and wasps that lay eggs in living larvae or on the leaves

that larvae eat. The wasp or fly larvae that emerge from

these eggs ultimately kill the monarch larvae.

Monarchs accumulate

chemicals

called cardenolides

(also called cardiac glycosides) that are present in the milk-

weed. These cardenolides are poisonous to most vertebrates,

and monarchs face little predation from

frogs

, lizards, mice,

or birds during the adult breeding stage. However, vertebrate

predation is a major source of mortality for overwintering

monarchs. Both birds and mice consume significant numbers

of overwintering adults.

The milky latex present in milkweed leaves is con-

tained under pressure in a system of vesicles. When the

plant is punctured, the latex flows out of these vesicles and

coagulates on contact with air. The latex serves as a defense

to the plant, since it is similar to glue after coagulation. It

can kill small larvae by sealing their mandibles or gluing

their entire body to the leaf. While monarch larvae can cut

off latex flow by trenching the leaves, about 25% of first

instar larvae die after becoming mired in the latex of some

milkweed species.

Monarch eggs do not hatch in very dry conditions.

Dry weather can also reduce the population of monarch by

killing milkweed and reducing the amount of nectar in flow-

915

ers. Very hot weather also causes mortality. Studies have

shown that prolonged temperatures above approximately

95°F (35°C) can be lethal to all stages. Likewise, tempera-

tures below freezing can kill monarchs. All stages can survive

if temperatures are only a few degrees below freezing for

short periods, but extended periods of severe cold and wet kill

them. In the overwintering colonies, the highest mortality

occurs when adult monarchs become wet from rain or snow-

fall, then are subjected to freezing temperatures. Since tem-

peratures extremes are likely to be greater in forests that

have been thinned,

logging

can exacerbate the effects of

winter storms.

The most important source of human-caused mortality

in the breeding range of monarch is habitat loss, especially

the destruction of milkweed and nectar sources. Milkweed

is considered a noxious weed by some people, and is often

destroyed. Herbicides used in agriculture and on roadsides

and lawns kill both nectar plants needed by adults and milk-

weed needed by larvae. Monarchs are also exposed to insecti-

cides used to control insects such as mosquitoes. Research

conducted in 2001 found that most monarchs in the upper

Midwest probably originate in agricultural fields, especially

corn and soybean fields. This means that any agricultural

practices that affect milkweed abundance or monarch sur-

vival in these fields could have large impacts on monarch

populations.

There is also concern that genetically corn containing

Bt toxin is a hazard to monarchs. Pollen produced by this

corn contains the toxin. Pollen may be blown onto milkweed

plants growing in and near cornfields. Since many monarchs

that migrate to Mexico breed in the corn belt of the central

United States, and milkweed growing within cornfields con-

stitutes an important food source for these monarchs, expo-

sure to this risk is likely to be high. The most commonly

used Bt strains express levels of toxin in their pollen that

are unlikely to kill monarch larvae outright. Sublethal im-

pacts have not been closely studied.

[Karen S. Oberhauser Ph.D.]

ESOURCES

OOKS

Pyle, R. M. Chasing Monarchs: Migrating with the Butterflies of Passage.

Boston, MA: Houghton Mifflin, 1999.

ERIODICALS

Anderson, J. B., and L. P. Brower. “Freeze-protection of Overwintering

Monarch Butterflies in Mexico: Critical Role of the Forest as a Blanket

and an Umbrella.” Ecological Entomology 21 (1996): 107–116.

Borkin, S. S. “Notes on Shifting Distribution Patterns and Survival of

Immature Danaus plexippus Lepidoptera: Danaidae) on the Food Plant

Asclepias syriaca.” Great Lakes Entomologist (East Lansing) 15

(1982):199–206

Environmental Encyclopedia 3

Monkey-wrenching

Brower, L. P. “Canary in the Cornfield: The Monarch and the Bt Corn

Controversy.” Orion 20 (2001): 32–14.

Brower, L. P. “ Monarch Butterfly Orientation: Missing Pieces of a Magnif-

icent Puzzle.” Journal of Experimental Biology 199 (1996): 93–103.

Heat Stress on Monarch Butterfly (Lepidoptera: Danaidae) Development.”

Dussourd, D. E. “The Vein Drain, or How Insects Outsmart Plants.”

Natural History 90 (1990): 44–49.

Oberhauser, K. S. “Effects of Spermatophores on Male and Female Mon-

arch Butterfly Reproductive Success.” Behavioral Ecology and Sociobiolgy 25

(1989): 237–246.

Oberhauser, K. S., M. D. Prysby, H. R. Mattila, et al. “Temporal and

Spatial Overlap Between Monarch Larvae and Corn Pollen.” Proceedings

of the National Academy of Science 98 (2001):11913–11918.

Prysby, M. D., and K. S. Oberhauser. 1999. Large-scale Monitoring of

Larval Monarch Populations and Milkweed Habitat in North America. In

Proceedings of the 1997 North American Conference on the Monarch Butterfly.

edited by J. L. Hoth, et al., Commission for Environmental Cooperation:

Montreal, Canada. 1997: 379–383.

Wassenaar, L. I., and K. A. Hobson. “ Natal Origins of Migratory Monarch

Butterflies at Wintering Colonies in Mexico: New Isotopic Evidence.”

Proceedings of the National Academy of Sciences 95 (1998):15436–15439.

York, H., and K. S. Oberhauser. “Effects of Duration and Timing of

Journal of the Kansas Entomological Society.

THER

Journey North: Monarch Migration. “Comparative Migration Maps.” 2002

[cited 26 April 2002]. <http://www.learner.org/jnorth/tm/monarch/Migra-

tionMaps.html>.

Monarch Larva Monitoring Project 2002. April 2002 [cited April 2002].

<http://www.mlmp.org>.

Prysby, M. and K. Oberhauser. Temporal and Geographical Variation in

Monarch Densities: Citizen Scientists Document Monarch Population Patterns.

Monkey-wrenching

Also called ecotage (ecological sabotage), monkey-wrenching

refers to techniques used by some radical environmentalists

to stop or slow the machinery used in

logging

strip mining

and other sorts of environmentally destructive activities. The

term was popularized by Edward Abbey’s novel, The Monkey

Wrench Gang (1975) and the concept was developed by

Dave

Foreman

in Ecodefense: A Field Guide to Monkeywrenching

(1987). The techniques of monkey-wrenching include “spik-

ing” old-growth trees to prevent loggers from cutting them

down, “munching” logging roads with nails to puncture the

tires of logging vehicles, pulling up surveyors’ stakes, putting

sand or grinding compound in the gas tanks or oil intakes

(or oatmeal or Minute Rice in the radiators) of bulldozers

and logging trucks, and other forms of disruption or de-

struction.

Mono Lake

Clear, cold water tumbles from snowcapped peaks and alpine

fields at 13,000 ft (4,000 m) down the precipitous eastern

escarpment of California’s Sierra Nevada. The water feeds

916

semi-arid, sagebrush–covered Mono Basin and, at the basin’s

heart, majestic Mono Lake. This is a salt lake with an area

of 60 square miles (155 km

) at an elevation of 6,400 ft

(2,000 m), and mountain waters have flowed to it for at

least the past half million years, making it one of the oldest

lakes in North America.

Mono Basin lies in the

rain shadow

of the Sierra

Nevada; shielded from moist Pacific air masses to the west,

it has a semi-arid

climate

. Being surrounded by higher

ground, it also has no natural outlet. Over the millennia, the

major water loss from Mono Lake has been by evaporation, a

process that removes pure water and leaves dissolved salts

behind, and the water in the lake has become alkaline as a

result and two and a half times saltier than sea water.

The salty, alkaline lake water excludes fish, but it does

provide ideal conditions for several life forms that normally

are uncommon to inland waters. Algae blooms in abundance

during winter, sometimes turning the lake water pea–soup

green, and it provides summer sustenance to a profusion of

brine flies and tiny brine shrimp. Brine flies and brine shrimp

make Mono Lake a summer haven for hundreds of thousands

of nesting and migratory birds. The lake’s islands provide

safe nesting for tens of thousands of California gulls and

snowy plovers. Nearly 90% of the state’s population of Cali-

fornia gulls, which live mainly along the Pacific coast, are

hatched on these islands. More than 70

species

of migratory

birds use Mono Lake—most notably, several hundred thou-

sand eared grebes which stop over during their fall

migra-

tion

, and more than 100,000 phalaropes which come from

South America for the summer.

Mono Lake’s

aquatic chemistry

, combined with its

unusual geologic and topographic

environment

, has given

rise to the lake’s signature feature: tufa towers. Tufa is a

type of limestone which consists of calcium carbonate that

forms around fresh water springs emanating from the lake

bottom. Calcium carried by the spring water combines with

carbonate in the alkaline lake to form soft rock masses that

slowly grow into underwater pinnacles. These towers were

almost entirely covered by water until recently; they were

first exposed when the lake level started dropping in the

early 1940s, because the growing city of Los Angeles had

begun intercepting fresh water from streams feeding the lake

and diverting it south to the city in a 250–mi (400 km) long

aqueduct.

By the mid-1980s, Mono Basin supplied nearly 20%

of the water used by Los Angeles, and the lake level had

dropped more than 40 ft (12 m). As the water level dropped,

the lake’s

salinity

increased and shoreline

habitat

for brine

flies decreased. Tufa formations became more exposed, dust

storms grew more frequent and severe, and predators occa-

sionally found access to island nesting sites. Meanwhile,

California created the Mono Lake Tufa State Reserve, and