McGraw-Hill OnlineMcGraw-Hill Higher EducationLearning Center
Student Center | Instructor Center | Information Center | Home
Career Opportunities
Lab Exercises
ESP Essential Study Partner
Simple Animations
Animations & Quizzing
Government Contacts
How to Write a Term Paper
Chart of Common Elements
The Metric System
Regional Perspectives
Global Issues Map
Glossary A-D
Glossary E-L
Glossary M-R
Glossary S-Z
Help Center

Environmental Science: A Global Concern, 7/e
William P. Cunningham, University of Minnesota
Mary Ann Cunningham, Vassar College
Barbara Woodworth Saigo, St. Cloud State University

Glossary M-R

magma  Molten rock from deep in the earth's interior; called lava when it spews from volcanic vents.
magnetic confinement  A technique for enclosing a nuclear fusion reaction in a powerful magnetic field inside a vacuum chamber.
malignant tumor  A mass of cancerous cells that have left their site of origin, migrated through the body, invaded normal tissues, and are growing out of control.
malnourishment  A nutritional imbalance caused by lack of specific dietary components or inability to absorb or utilize essential nutrients.
Malthusian growth  A population explosion followed by a population crash; also called irruptive growth.
Man and Biosphere (MAB) program  A design for nature preserves that divides protected areas into zones with different purposes. A highly protected core is surrounded by a buffer zone and peripheral regions in which multiple-use resource harvesting is permitted.
mantle  A hot, pliable layer of rock that surrounds the earth's core and underlies the cool, outer crust.
marasmus  A widespread human protein deficiency disease caused by a diet low in calories and protein or imbalanced in essential amino acids.
marginal costs  The cost to produce one additional unit of a good or service.
marine  Living in or pertaining to the sea.
market equilibrium  The dynamic balance between supply and demand under a given set of conditions in a "free" market (one with no monopolies or government interventions).
marsh  Wetland without trees; in North America, this type of land is characterized by cattails and rushes.
mass burn  Incineration of unsorted solid waste.
matter  Anything that takes up space and has mass.
mediation  An informal dispute resolution process in which parties are encouraged to discuss issues openly but in which all decisions are reached by consensus and any participant can withdraw at any time.
Mediterranean climate areas  Specialized landscapes with warm, dry summers; cool, wet winters; many unique plant and animal adaptations; and many levels of endemism.
megacity  See megalopolis.
megalopolis  Also known as a megacity or supercity; megalopolis indicates an urban area with more than 10 million inhabitants.
megawatt (MW)  Unit of electrical power equal to 1,000 kilowatts or 1 million watts.
mesosphere  The atmospheric layer above the stratosphere and below the thermosphere; the middle layer; temperatures are usually very low.
metabolism  All the energy and matter exchanges that occur within a living cell or organism; collectively, the life processes.
metamorphic rock  Igneous and sedimentary rocks modified by heat, pressure, and chemical reactions.
methane hydrate  Small bubbles or individual molecules of methane (natural gas) trapped in a crystalline matrix of frozen water.
micro-hydro generators  Small power generators that can be used in low-level rivers to provide economical power for four to six homes, freeing them from dependence on large utilities and foreign energy supplies.
Milankovitch cycles  Periodic variations in tilt, eccentricity, and wobble in the earth's orbit; Milutin Milankovitch suggested that it is responsible for cyclic weather changes.
milpa agriculture  An ancient farming system in which small patches of tropical forests are cleared and perennial polyculture agriculture practiced and is then followed by many years of fallow to restore the soil; also called swidden agriculture.
mineral  A naturally occurring, inorganic, crystalline solid with definite chemical composition and characteristic physical properties.
mitigation  Repairing or rehabilitating a damaged ecosystem or compensating for damage by providing a substitute or replacement area.
mixed perennial polyculture  Growing a mixture of different perennial crop species (where the same plant persists for more than one year) together in the same plot.
molecule  A combination of two or more atoms.
monitored, retrievable storage  Holding wastes in underground mines or secure surface facilities such as dry casks where they can be watched and repackaged, if necessary.
monkey wrenching  Environmental sabotage such as driving large spikes in trees to protect them from loggers, vandalizing construction equipment, pulling up survey stakes for unwanted developments, and destroying billboards.
monoculture agroforestry  Intensive planting of a single species; an efficient wood production approach, but one that encourages pests and disease infestations and conflicts with wildlife habitat or recreation uses.
monsoon  A seasonal reversal of wind patterns caused by the different heating and cooling rates of the oceans and continents.
montane coniferous forests  Coniferous forests of the mountains consisting of belts of different forest communities along an altitudinal gradient.
moral agents  Beings capable of making distinctions between right and wrong and acting accordingly. Those whom we hold responsible for their actions.
moral extensionism  Expansion of our understanding of inherent value or rights to persons, organisms, or things that might not be considered worthy of value or rights under some ethical philosophies.
moral subjects  Beings that are not capable of distinguishing between right or wrong or that are not able to act on moral principles and yet are capable of being wronged by others.
morals  A set of ethical principles that guide our actions and relationships.
morbidity  Illness or disease.
more-developed countries (MDC)  Industrialized nations characterized by high per capita incomes, low birth and death rates, low population growth rates, and high levels of industrialization and urbanization.
mortality  Death rate in a population; the probability of dying.
Müellerian mimicry  Evolution of two species, both of which are unpalatable and, have poisonous stingers or some other defense mechanism, to resemble each other.
mulch  Protective ground cover, including both natural products and synthetic materials that protect the soil, save water, and prevent weed growth.
multiple use  Many uses that occur simultaneously; used in forest management; limited to mutually compatible uses.
mutagens  Agents, such as chemicals or radiation, that damage or alter genetic material (DNA) in cells.
mutation  A change, either spontaneous or by external factors, in the genetic material of a cell; mutations in the gametes (sex cells) can be inherited by future generations of organisms.
mutualism  A symbiotic relationship between individuals of two different species in which both species benefit from the association.
NAAQS  National Ambient Air Quality Standard; federal standards specifying the maximum allowable levels (averaged over specific time periods) for regulated pollutants in ambient (outdoor) air.
natality  The production of new individuals by birth, hatching, germination, or cloning.
natural history  The study of where and how organisms carry out their life cycles.
natural increase  Crude death rate subtracted from crude birthrate.
natural resources  Goods and services supplied by the environment.
natural selection  The mechanism for evolutionary change in which environmental pressures cause certain genetic combinations in a population to become more abundant; genetic combinations best adapted for present environmental conditions tend to become predominant.
neo-classical economics  A branch of economics that attempts to apply the principles of modern science to economic analysis in a mathematically rigorous, noncontextual, abstract, predictive manner.
neo-Luddites  People who reject technology as the cause of environmental degradation and social disruption. Named after the followers of Ned Ludd who tried to turn back the Industrial Revolution in England.
neo-Malthusian  A belief that the world is characterized by scarcity and competition in which too many people fight for too few resources. Named for Thomas Malthus, who predicted a dismal cycle of misery, vice, and starvation as a result of human overpopulation.
net energy yield  Total useful energy produced during the lifetime of an entire energy system minus the energy used, lost, or wasted in making useful energy available.
neurotoxins  Toxic substances, such as lead or mercury, that specifically poison nerve cells.
neutron  A subatomic particle, found in the nucleus of the atom, that has no electromagnetic charge.
new towns  Experimental urban environments that seek to combine the best features of the rural village and the modern city.
nihilists  Those who believe the world has no meaning or purpose other than a dark, cruel, unceasing struggle for power and existence.
NIMBY  Not In My BackYard: the rallying cry of those opposed to LULUs.
nitrate-forming bacteria  Bacteria that convert nitrites into compounds that can be used by green plants to build proteins.
nitrite-forming bacteria  Bacteria that combine ammonia with oxygen to form nitrites.
nitrogen cycle  The circulation and reutilization of nitrogen in both inorganic and organic phases.
nitrogen-fixing bacteria  Bacteria that convert nitrogen from the atmosphere or soil solution into ammonia that can then be converted to plant nutrients by nitrite- and nitrate-forming bacteria.
nitrogen oxides  Highly reactive gases formed when nitrogen in fuel or combustion air is heated to over 650 °C (1,200 °F) in the presence of oxygen or when bacteria in soil or water oxidize nitrogen-containing compounds.
noncriteria pollutants  See unconventional air pollutants.
nongovernmental organizations (NGOs)  A term referring collectively to pressure and research groups, advisory agencies, political parties, professional societies, and other groups concerned about environmental quality, resource use, and many other issues.
nonpoint sources  Scattered, diffuse sources of pollutants, such as runoff from farm fields, golf courses, construction sites, etc.
nonrenewable resources  Minerals, fossil fuels, and other materials present in essentially fixed amounts (within human time scales) in our environment.
North/South division  A description of the fact that most of the world's wealthier countries tend to be in North America, Europe, and Japan while the poorer countries tend to be located closer to the equator.
nuclear fission  The radioactive decay process in which isotopes split apart to create two smaller atoms.
nuclear fusion  A process in which two smaller atomic nuclei fuse into one larger nucleus and release energy; the source of power in a hydrogen bomb.
nucleic acids  Large organic molecules made of nucleotides that function in the transmission of hereditary traits, in protein synthesis, and in control of cellular activities.
nucleus  The center of the atom; occupied by protons and neutrons. In cells, the organelle that contains the chromosomes (DNA).
nuées ardentes  Deadly, denser-than-air mixtures of hot gases and ash ejected from volcanoes.
numbers pyramid  A diagram showing the relative population sizes at each trophic level in an ecosystem; usually corresponds to the biomass pyramid.
ocean shorelines  Rocky coasts and sandy beaches along the oceans; support rich, stratified communities.
ocean thermal electric conversion (OTEC)  Energy derived from temperature differentials between warm ocean surface waters and cold deep waters. This differential can be used to drive turbines attached to electric generators.
oceanic islands  Islands in the ocean; formed by breaking away from a continental landmass, volcanic action, coral formation, or a combination of sources; support distinctive communities.
offset allowances  A controversial component of air quality regulations that allows a polluter to avoid installation of control equipment on one source with an "offsetting" pollution reduction at another source.
oil shale  A fine-grained sedimentary rock rich in solid organic material called kerogen. When heated, the kerogen liquefies to produce a fluid petroleum fuel.
old-growth forests  Forests free from disturbance for long enough (generally 150 to 200 years) to have mature trees, physical conditions, species diversity, and other characteristics of equilibrium ecosystems.
oligotrophic  Condition of rivers and lakes that have clear water and low biological productivity (oligo = little; trophic = nutrition); are usually clear, cold, infertile headwater lakes and streams.
omnivore  An organism that eats both plants and animals.
open access system  A commonly held resource for which there are no management rules.
open canopy  A forest where tree crowns cover less than 20 percent of the ground; also called woodland.
open range  Unfenced, natural grazing lands; includes woodland as well as grassland.
open system  A system that exchanges energy and matter with its environment.
optimum  The most favorable condition in regard to an environmental factor.
orbital  The space or path in which an electron orbits the nucleus of an atom.
organic compounds  Complex molecules organized around skeletons of carbon atoms arranged in rings or chains; includes biomolecules, molecules synthesized by living organisms.
overburden  Overlying layers of noncommercial sediments that must be removed to reach a mineral or coal deposit.
overnutrition  Receiving too many calories.
overshoot  The extent to which a population exceeds the carrying capacity of its environment.
oxygen cycle  The circulation and reutilization of oxygen in the biosphere.
oxygen sag  Oxygen decline downstream from a pollution source that introduces materials with high biological oxygen demands.
ozone  A highly reactive molecule containing three oxygen atoms; a dangerous pollutant in ambient air. In the stratosphere, however, ozone forms an ultraviolet absorbing shield that protects us from mutagenic radiation.
Pacific Decadal Oscillation (PDO)  A large pool of warm water that moves north and south in the Pacific Ocean every 30 years or so and has large effects on North America's climate.
parabolic mirrors  Curved mirrors that focus light from a large area onto a single, central point, thereby concentrating solar energy and producing high temperatures.
paradigm  A model that provides a framework for interpreting observations.
parasite  An organism that lives in or on another organism, deriving nourishment at the expense of its host, usually without killing it.
parsimony  If two explanations appear equally plausible, choose the simpler one.
particulate material  Atmospheric aerosols, such as dust, ash, soot, lint, smoke, pollen, spores, algal cells, and other suspended materials; originally applied only to solid particles but now extended to droplets of liquid.
parts per billion (ppb)  Number of parts of a chemical found in 1 billion parts of a particular gas, liquid, or solid mixture.
parts per million (ppm)  Number of parts of a chemical found in 1 million parts of a particular gas, liquid, or solid mixture.
parts per trillion (ppt)  Number of parts of a chemical found in 1 trillion (1012) parts of a particular gas, liquid, or solid mixture.
passive heat absorption  The use of natural materials or absorptive structures without moving parts to gather and hold heat; the simplest and oldest use of solar energy.
patchiness  Within a larger ecosystem, the presence of smaller areas that differ in some physical conditions and thus support somewhat different communities; a diversity-promoting phenomenon.
pathogen  An organism that produces disease in a host organism, disease being an alteration of one or more metabolic functions in response to the presence of the organism.
peat  Deposits of moist, acidic, semidecayed organic matter.
pellagra  Lassitude, torpor, dermatitis, diarrhea, dementia, and death brought about by a diet deficient in tryptophan and niacin.
peptides  Two or more amino acids linked by a peptide bond.
perennial species  Plants that grow for more than two years.
permafrost  A permanently frozen layer of soil that underlies the arctic tundra.
permanent retrievable storage  Placing waste storage containers in a secure building, salt mine, or bedrock cavern where they can be inspected periodically and retrieved, if necessary.
persistent organic polutants (POPs)  Chemical compounds that persist in the environment and retain biological activity for long times.
pest  Any organism that reduces the availability, quality, or value of a useful resource.
pesticide  Any chemical that kills, controls, drives away, or modifies the behavior of a pest.
pesticide treadmill  A need for constantly increasing doses or new pesticides to prevent pest resurgence.
pest resurgence  Rebound of pest populations due to acquired resistance to chemicals and nonspecific destruction of natural predators and competitors by broadscale pesticides.
pH  A value that indicates the acidity or alkalinity of a solution on a scale of 0 to 14, based on the proportion of H+ ions present.
phosphorus cycle  The movement of phosphorus atoms from rocks through the biosphere and hydrosphere and back to rocks.
photochemical oxidants  Products of secondary atmospheric reactions. See smog.
photodegradable plastics  Plastics that break down when exposed to sunlight or to a specific wavelength of light.
photosynthesis  The biochemical process by which green plants and some bacteria capture light energy and use it to produce chemical bonds. Carbon dioxide and water are consumed while oxygen and simple sugars are produced.
photosynthetic efficiency  The percentage of available light captured by plants and used to make useful products.
photovoltaic cell  An energy-conversion device that captures solar energy and directly converts it to electrical current.
physical or abiotic factors  Nonliving factors, such as temperature, light, water, minerals, and climate, that influence an organism.
phytoplankton  Microscopic, free-floating, autotrophic organisms that function as producers in aquatic ecosystems.
pioneer species  In primary succession on a terrestrial site, the plants, lichens, and microbes that first colonize the site.
plankton  Primarily microscopic organisms that occupy the upper water layers in both freshwater and marine ecosystems.
plasma  A hot, electrically neutral gas of ions and free electrons.
poachers  Those who hunt wildlife illegally.
point sources  Specific locations of highly concentrated pollution discharge, such as factories, power plants, sewage treatment plants, underground coal mines, and oil wells.
policy  A societal plan or statement of intentions intended to accomplish some social good.
policy cycle  The process by which problems are identified and acted upon in the public arena.
political economy  The branch of economics concerned with modes of production, distribution of benefits, social institutions, and class relationships.
pollution  To make foul, unclean, dirty; any physical, chemical, or biological change that adversely affects the health, survival, or activities of living organisms or that alters the environment in undesirable ways.
pollution charges  Fees assessed per unit of pollution based on the "polluter pays" principle.
polycentric complex  Cities with several urban cores surrounding a once dominant central core.
population  A group of individuals of the same species occupying a given area.
population crash  A sudden population decline caused by predation, waste accumulation, or resource depletion; also called a dieback.
population explosion  Growth of a population at exponential rates to a size that exceeds environmental carrying capacity; usually followed by a population crash.
population momentum  A potential for increased population growth as young members reach reproductive age.
postmaterialist values  A philosophy that emphasizes quality of life over acquisition of material goods.
post-modernism  A philosophy that rejects the optimism and universal claims of modern positivism.
potential energy  Stored energy that is latent but available for use. A rock poised at the top of a hill or water stored behind a dam are examples of potential energy.
power  The rate of energy delivery; measured in horsepower or watts.
precautionary principle  The decision to leave a margin of safety for unexpected developments.
precedent  An act or decision that can be used as an example in dealing with subsequent similar situations.
precycling  Making environmentally sound decisions at the store and reducing waste before we buy.
predation  The act of feeding by a predator.
predator  An organism that feeds directly on other organisms in order to survive; live-feeders, such as herbivores and carnivores.
prevention of significant deterioration  A clause of the Clean Air Act that prevents degradation of existing clean air; opposed by industry as an unnecessary barrier to development.
price elasticity  A situation in which supply and demand of a commodity respond to price.
primary pollutants  Chemicals released directly into the air in a harmful form.
primary productivity  Synthesis of organic materials (biomass) by green plants using the energy captured in photosynthesis.
primary standards  Regulations of the 1970 Clean Air Act; intended to protect human health.
primary succession  An ecological succession that begins in an area where no biotic community previously existed.
primary treatment  A process that removes solids from sewage before it is discharged or treated further.
principle of competitive exclusion  A result of natural selection whereby two similar species in a community occupy different ecological niches, thereby reducing competition for food.
producer  An organism that synthesizes food molecules from inorganic compounds by using an external energy source; most producers are photosynthetic.
production frontier  The maximum output of two competing commodities at different levels of production.
prokaryotic  Cells that do not have a membrane-bounded nucleus or membrane-bounded organelles.
promoters  Agents that are not carcinogenic but that assist in the progression and spread of tumors; sometimes called cocarcinogens.
pronatalist pressures  Influences that encourage people to have children.
proteins  Chains of amino acids linked by peptide bonds.
proton  A positively charged subatomic particle found in the nucleus of an atom.
proven resources  Those that have been thoroughly mapped and are economical to recover at current prices with available technology.
public trust  A doctrine obligating the government to maintain public lands in a natural state as guardians of the public interest.
pull factors (in urbanization)  Conditions that draw people from the country into the city.
push factors (in urbanization)  Conditions that force people out of the country and into the city.
radioactive  An unstable isotope that decays spontaneously and releases subatomic particles or units of energy.
radioactive decay  A change in the nuclei of radioactive isotopes that spontaneously emit high-energy electromagnetic radiation and/or subatomic particles while gradually changing into another isotope or different element.
radionucleides  Isotopes that exhibit radioactive decay.
rainforest  A forest with high humidity, constant temperature, and abundant rainfall (generally over 380 cm [150 in] per year); can be tropical or temperate.
rain shadow  Dry area on the downwind side of a mountain.
rangeland  Grasslands and open woodlands suitable for livestock grazing.
rational choice  Public decision making based on reason, logic, and science-based management.
recharge zone  Area where water infiltrates into an aquifer.
reclamation  Chemical, biological, or physical cleanup and reconstruction of severely contaminated or degraded sites to return them to something like their original topography and vegetation.
recoverable resources  Those accessible with current technology but not economical under current conditions.
re-creation  Construction of an entirely new biological community to replace one that has been destroyed on that or another site.
recycling  Reprocessing of discarded materials into new, useful products; not the same as reuse of materials for their original purpose, but the terms are often used interchangeably.
red tide  A population explosion or bloom of minute, single-celled marine organisms called dinoflagellates. Billions of these cells can accumulate in protected bays where the toxins they contain can poison other marine life.
reduced tillage systems  Systems, such as minimum till, conserve-till, and no-till, that preserve soil, save energy and water, and increase crop yields.
reformer  A device that strips hydrogen from fuels such as natural gas, methanol, ammonia, gasoline, or vegetable oil so they can be used in a fuel cell.
refuse-derived fuel  Processing of solid waste to remove metal, glass, and other unburnable materials; organic residue is shredded, formed into pellets, and dried to make fuel for power plants.
regenerative farming  Farming techniques and land stewardship that restore the health and productivity of the soil by rotating crops, planting ground cover, protecting the surface with crop residue, and reducing synthetic chemical inputs and mechanical compaction.
regulations  Rules established by administrative agencies; regulations can be more important than statutory law in the day-to-day management of resources.
rehabilitate land  A utilitarian program to make an area useful to humans.
rehabilitation  To rebuild elements of structure or function in an ecological system without necessarily achieving complete restoration to its original condition.
relative humidity  At any given temperature, a comparison of the actual water content of the air with the amount of water that could be held at saturation.
relativists  Those who believe moral principles are always dependent on the particular situation.
remediation  Cleaning up chemical contaminants from a polluted area.
renewable resources  Resources normally replaced or replenished by natural processes; resources not depleted by moderate use; examples include solar energy, biological resources such as forests and fisheries, biological organisms, and some biogeochemical cycles.
renewable water supplies  Annual freshwater surface runoff plus annual infiltration into underground freshwater aquifers that are accessible for human use.
residence time  The length of time a component, such as an individual water molecule, spends in a particular compartment or location before it moves on through a particular process or cycle.
resilience  The ability of a community or ecosystem to recover from disturbances.
resistance (inertia)  The ability of a community to resist being changed by potentially disruptive events.
resource  In economic terms, anything with potential use in creating wealth or giving satisfaction.
resource partitioning  In a biological community, various populations sharing environmental resources through specialization, thereby reducing direct competition. See also ecological niche.
resource scarcity  A shortage or deficit in some resource.
restoration  To bring something back to a former condition. Ecological restoration involves active manipulation of nature to re-create conditions that existed before human disturbance.
restoration ecology  Seeks to repair or reconstruct ecosystems damaged by human actions.
riders  Amendments attached to bills in conference committee, often completely unrelated to the bill to which they are added.
rill erosion  The removing of thin layers of soil as little rivulets of running water gather and cut small channels in the soil.
risk  Probability that something undesirable will happen as a consequence of exposure to a hazard.
risk assessment  Evaluation of the short-term and long-term risks associated with a particular activity or hazard; usually compared to benefits in a cost-benefit analysis.
RNA  Ribonucleic acid; nucleic acid used for transcription and translation of the genetic code found on DNA molecules.
rock  A solid, cohesive, aggregate of one or more crystalline minerals.
rock cycle  The process whereby rocks are broken down by chemical and physical forces; sediments are moved by wind, water, and gravity, sedimented and reformed into rock, and then crushed, folded, melted, and recrystallized into new forms.
ruminant animals  Cud-chewing animals, such as cattle, sheep, goats, and buffalo, with multichambered stomachs in which cellulose is digested with the aid of bacteria.
runoff  The excess of precipitation over evaporation; the main source of surface water and, in broad terms, the water available for human use.
run-of-the-river flow  Ordinary river flow not accelerated by dams, flumes, etc. Some small, modern, high-efficiency turbines can generate useful power with run-of-the-river flow or with a current of only a few kilometers per hour.
rural area  An area in which most residents depend on agriculture or the harvesting of natural resources for their livelihood.