GLO-1

A

A horizon Frequently the top layer of soil, a zone of organic material and minerals that have been mixed together. Also known as topsoil.

abiotic Nonliving.

accuracy How close a measured value is to the actual or true value.

acid A substance that contributes hydrogen ions to a solution.

acid deposition Acids deposited on Earth as rain and snow or as gases and particles that attach to the surfaces of plants, soil, and water.

acid precipitation Precipitation high in sulfuric acid and nitric acid from reactions between water vapor and sulfur and nitrogen oxides in the atmosphere. Also known as acid rain.

acid rain See acid precipitation.

Acquired Immune Deficiency Syndrome (AIDS) An infectious disease caused by the human immunodeficiency virus (HIV).

active solar energy Energy captured from sunlight with advanced technologies.

acute disease A disease that rapidly impairs the functioning of an organism.

acute study An experiment that exposes organisms to an environmental hazard for a short duration.

adaptation A trait that improves an individual’s fitness.

adiabatic cooling The cooling effect of reduced pressure on air as it rises higher in the atmosphere and expands.

adiabatic heating The heating effect of increased pressure on air as it sinks toward the surface of Earth and decreases in volume.

aerobic respiration The process by which cells convert glucose and oxygen into energy, carbon dioxide, and water.

affluence The state of having plentiful wealth including the possession of money, goods, or property.

age structure A description of how many individuals fit into particular age categories in a population.

age structure diagram A visual representation of the number of individuals within specific age groups for a country, typically expressed for males and females.

GLO-2

agribusiness See industrial agriculture.

agroforestry An agricultural technique in which trees and vegetables are intercropped.

air pollution The introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings, or to alter ecosystems.

albedo The percentage of incoming sunlight reflected from a surface.

algal bloom A rapid increase in the algal population of a waterway.

alien species See exotic species.

allergen A chemical that causes allergic reactions.

allopatric speciation The process of speciation that occurs with geographic isolation.

ammonification The process by which fungal and bacterial decomposers break down the organic nitrogen found in dead bodies and waste products and convert it into inorganic ammonium (NH₄⁺).

anaerobic respiration The process by which cells convert glucose into energy in the absence of oxygen.

anemia A deficiency of iron.

annual plant A plant that lives only one season.

anthropocentric worldview A worldview that focuses on human welfare and well-being.

anthropogenic Derived from human activities.

aphotic zone The deeper layer of ocean water that lacks sufficient sunlight for photosynthesis.

aquaculture Farming aquatic organisms such as fish, shellfish, and seaweeds.

aquatic biome An aquatic region characterized by a particular combination of salinity, depth, and water flow.

aqueduct A canal or ditch used to carry water from one location to another.

aquifer A permeable layer of rock and sediment that contains groundwater.

artesian well A well created by drilling a hole into a confined aquifer.

asbestos A long, thin, fibrous silicate mineral with insulating properties, which can cause cancer when inhaled.

ash The residual nonorganic material that does not combust during incineration.

assimilation The process by which producers incorporate elements into their tissues.

asthenosphere The layer of Earth located in the outer part of the mantle, composed of semi-molten rock.

GLO-3

atmospheric convection current Global patterns of air movement that are initiated by the unequal heating of Earth.

atom The smallest particle that can contain the chemical properties of an element.

atomic number The number of protons in the nucleus of a particular element.

autotroph See producer.

B

B horizon A soil horizon composed primarily of mineral material with very little organic matter.

background extinction rate The average rate at which species become extinct over the long term.

base A substance that contributes hydroxide ions to a solution.

base saturation The proportion of soil bases to soil acids, expressed as a percentage.

becquerel (Bq) Unit that measures the rate at which a sample of radioactive material decays; 1 Bq = decay of 1 atom or nucleus per second.

benthic zone The muddy bottom of a lake, pond, or ocean.

bioaccumulation An increased concentration of a chemical within an organism over time.

biocentric worldview A worldview that holds that humans are just one of many species on Earth, all of which have equal intrinsic value.

biochemical oxygen demand (BOD) The amount of oxygen a quantity of water uses over a period of time at specific temperatures.

biodiesel A diesel substitute produced by extracting and chemically altering oil from plants.

biodiversity hotspot An area that contains a high proportion of all the species found on Earth.

biodiversity The diversity of life forms in an environment.

biofuel Liquid fuel created from processed or refined biomass.

biogeochemical cycle The movements of matter within and between ecosystems.

biomagnification The increase in chemical concentration in animal tissues as the chemical moves up the food chain.

biomass The total mass of all living matter in a specific area.

biophilia Love of life.

GLO-4

biosphere reserve Protected area consisting of zones that vary in the amount of permissible human impact.

biosphere The region of our planet where life resides, the combination of all ecosystems on Earth.

biotic Living.

bird flu A type of flu caused by the H5N1 virus.

bitumen A degraded petroleum that forms when petroleum migrates to the surface of Earth and is modified by bacteria.

boreal forest A forest biome made up primarily of coniferous evergreen trees that can tolerate cold winters and short growing seasons.

bottleneck effect A reduction in the genetic diversity of a population caused by a reduction in its size.

bottom ash Residue collected at the bottom of the combustion chamber in a furnace.

broad-spectrum pesticide A pesticide that kills many different types of pest.

brown smog See photochemical smog.

brownfields Contaminated industrial or commercial sites that may require environmental cleanup before they can be redeveloped or expanded.

bycatch The unintentional catch of nontarget species while fishing.

C

C horizon The least-weathered soil horizon, which always occurs beneath the B horizon and is similar to the parent material.

capacity factor The fraction of time a power plant operates in a year.

capacity In reference to an electricity-generating plant, the maximum electrical output.

cap-and-trade An approach to controlling CO₂ emissions, where a cap places an upper limit on the amount of pollutant that can be emitted and trade allows companies to buy and sell allowances for a given amount of pollution.

capillary action A property of water that occurs when adhesion of water molecules to a surface is stronger than cohesion between the molecules.

carbohydrate A compound composed of carbon, hydrogen, and oxygen atoms.

carbon cycle The movement of carbon around the biosphere.

carbon neutral An activity that does not change atmospheric CO₂ concentrations.

GLO-5

carbon offsets Methods of promoting global CO₂ reduction that do not involve a direct reduction in the amount of CO₂ actually emitted by a company.

carbon sequestration An approach to stabilizing greenhouse gases by removing CO₂ from the atmosphere.

carcinogen A chemical that causes cancer.

carnivore A consumer that eats other consumers.

carrying capacity (K) The limit of how many individuals in a population the environment can sustain.

cation exchange capacity (CEC) The ability of a particular soil to absorb and release cations.

cell A highly organized living entity that consists of the four types of macromolecules and other substances in a watery solution, surrounded by a membrane.

cellular respiration The process by which cells unlock the energy of chemical compounds.

cellulosic ethanol An ethanol derived from cellulose, the cell wall material in plants.

chemical energy Potential energy stored in chemical bonds.

chemical reaction A reaction that occurs when atoms separate from molecules or recombine with other molecules.

chemical weathering The breakdown of rocks and minerals by chemical reactions, the dissolving of chemical elements from rocks, or both.

chemosynthesis A process used by some bacteria in the ocean to generate energy with methane and hydrogen sulfide.

child mortality The number of deaths of children under age 5 per 1,000 live births.

chronic disease A disease that slowly impairs the functioning of an organism.

chronic study An experiment that exposes organisms to an environmental hazard for a long duration.

Clean Water Act Legislation that supports the “protection and propagation of fish, shellfish, and wildlife and recreation in and on the water” by maintaining and, when necessary, restoring the chemical, physical, and biological properties of surface waters.

clear-cutting A method of harvesting trees that involves removing all or almost all of the trees within an area.

climate The average weather that occurs in a given region over a long period of time.

closed system A system in which matter and energy exchanges do not occur across boundaries.

GLO-6

closed-loop recycling Recycling a product into the same product.

coal A solid fuel formed primarily from the remains of trees, ferns, and other plant materials preserved 280 million to 360 million years ago.

cogeneration The use of a fuel to generate electricity and produce heat. Also known as combined heat and power.

combined cycle A power plant that uses both exhaust gases and steam turbines to generate electricity.

combined heat and power See cogeneration.

command-and-control approach A strategy for pollution control that involves regulations and enforcement mechanisms.

commensalism A relationship between species in which one species benefits and the other species is neither harmed nor helped.

commercial energy source An energy source that is bought and sold.

community All of the populations of organisms within a given area.

community ecology The study of interactions between species.

competition The struggle of individuals to obtain a shared limiting resource.

competitive exclusion principle The principle stating that two species competing for the same limiting resource cannot coexist.

composting Creation of organic matter (humus) by decomposition under controlled conditions to produce an organic-rich material that enhances soil structure, cation exchange capacity, and fertility.

compound A molecule containing more than one element.

concentrated animal feeding operation (CAFO) A large indoor or outdoor structure designed for maximum output.

cone of depression An area lacking groundwater due to rapid withdrawal by a well.

confined aquifer An aquifer surrounded by a layer of impermeable rock or clay that impedes water flow.

consumer An organism that is incapable of photosynthesis and must obtain its energy by consuming other organisms. Also known as heterotroph.

contaminated water Wastewater from toilets, kitchen sinks, and dishwashers.

contour plowing An agricultural technique in which plowing and harvesting are done parallel to the topographic contours of the land.

GLO-7

control group In a scientific investigation, a group that experiences exactly the same conditions as the experimental group, except for the single variable under study.

control rod A cylindrical device inserted between the fuel rods in a nuclear reactor to absorb excess neutrons and slow or stop the fission reaction.

Convention on Biological Diversity An international treaty to help protect biodiversity.

Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) A 1973 treaty formed to control the international trade of threatened plants and animals.

convergent plate boundary An area where plates move toward one another and collide.

coral bleaching A phenomenon in which algae inside corals die, causing the corals to turn white.

coral reef The most diverse marine biome on Earth, found in warm, shallow waters beyond the shoreline.

core The innermost zone of Earth’s interior, composed mostly of iron and nickel. It includes a liquid outer layer and a solid inner layer.

Coriolis effect The deflection of an object’s path due to the rotation of Earth.

corridor Strips of natural habitat that connect populations.

covalent bond The bond formed when elements share electrons.

cradle-to-grave analysis See life-cycle analysis.

crop rotation An agricultural technique in which crop species in a field are rotated from season to season.

crude birth rate (CBR) The number of births per 1,000 individuals per year.

crude death rate (CDR) The number of deaths per 1,000 individuals per year.

crude oil Liquid petroleum removed from the ground.

crust In geology, the chemically distinct outermost layer of the lithosphere.

crustal abundance The average concentration of an element in Earth’s crust.

CTL (coal to liquid) The process of converting solid coal into liquid fuel.

cultural eutrophication An increase in fertility in a body of water, the result of anthropogenic inputs of nutrients.

curie A unit of measure for radiation; 1 curie = 37 billion decays per second.

GLO-8

D

dam A barrier that runs across a river or stream to control the flow of water.

dead zone In a body of water, an area with extremely low oxygen concentration and very little life.

decomposers Fungi or bacteria that convert organic matter into small elements and molecules that can be recycled back into the ecosystem.

demographer A scientist in the field of demography.

demography The study of human populations and population trends.

denitrification The conversion of nitrate (NO₃^– ) in a series of steps into the gases nitrous oxide (N₂O) and, eventually, nitrogen gas (N₂), which is emitted into the atmosphere.

density-dependent factor A factor that influences an individual’s probability of survival and reproduction in a manner that depends on the size of the population.

density-independent factor A factor that has the same effect on an individual’s probability of survival and the amount of reproduction at any population size.

Department of Energy (DOE) The U.S. organization that advances the energy and economic security of the United States.

desalinization The process of removing the salt from salt water.

desertification The transformation of arable, productive land to desert or unproductive land due to climate change or destructive land use.

detritivore An organism that specializes in breaking down dead tissues and waste products into smaller particles.

developed country A country with relatively high levels of industrialization and income.

developing country A country with relatively low levels of industrialization and income.

development Improvement in human well-being through economic advancement.

die-off A rapid decline in a population due to death.

dike A structure built to prevent ocean waters from flooding adjacent land.

disease Any impaired function of the body with a characteristic set of symptoms.

distillation A process of desalinization in which water is boiled and the resulting steam is captured and condensed to yield pure water.

distribution Areas of the world in which a species lives.

GLO-9

disturbance An event, caused by physical, chemical, or biological agents, resulting in changes in population size or community composition.

divergent plate boundary An area beneath the ocean where tectonic plates move away from each other.

DNA (deoxyribonucleic acid) A nucleic acid, the genetic material that contains the code for reproducing the components of the next generation, and which organisms pass on to their offspring.

dose-response study A study that exposes organisms to different amounts of a chemical and then observes a variety of possible responses, including mortality or changes in behavior or reproduction.

doubling time The number of years it takes a population to double.

E

E horizon A zone of leaching, or eluviation, found in some acidic soils under the O horizon or, less often, the A horizon.

earthquake The sudden movement of Earth’s crust caused by a release of potential energy along a geologic fault and usually causing a vibration or trembling at Earth’s surface.

Ebola hemorrhagic fever An infectious disease with high death rates, caused by the Ebola virus.

ecocentric worldview A worldview that places equal value on all living organisms and the ecosystems in which they live.

ecological economics The study of economics as a component of ecological systems.

ecological efficiency The proportion of consumed energy that can be passed from onetrophic level to another.

ecological footprint A measure of how much an individual consumes, expressed in area of land.

ecological succession The predictable replacement of one group of species by another group of species over time.

ecologically sustainable forestry An approach to removing trees from forests in ways that do not unduly affect the viability of other trees.

economics The study of how humans allocate scarce resources in the production, distribution, and consumption of goods and services.

economies of scale The observation that average costs of production fall as output increases.

ecosystem A particular location on Earth with interacting biotic and abiotic components.

GLO-10

ecosystem engineer A keystone species that creates or maintains habitat for other species.

ecosystem services The processes by which life-supporting resources such as clean water, timber, fisheries, and agricultural crops are produced.

ED50 The effective dose of a chemical that causes 50 percent of the individuals in a dose-response study to display a harmful, but nonlethal, effect.

edge habitat Habitat that occurs where two different communities come together, typically forming an abrupt transition, such as where a grassy field meets a forest.

El Niño–Southern Oscillation (ENSO) A reversal of wind and water currents in the South Pacific.

electrical grid A network of interconnected transmission lines that joins power plants together and links them with end users of electricity.

electrolysis The application of an electric current to water molecules to split them into hydrogen and oxygen.

electromagnetic radiation A form of energy emitted by the Sun that includes, but is not limited to, visible light, ultraviolet light, and infrared energy.

element A substance composed of atoms that cannot be broken down into smaller, simpler components.

emergent infectious disease An infectious disease that has not been previously described or has not been common for at least 20 years.

emigration The movement of people out of a country or region.

eminent domain A principle that grants government the power to acquire a property at fair market value even if the owner does not wish to sell it.

endangered species A species that is in danger of extinction within the foreseeable future throughout all or a significant portion of its range.

Endangered Species Act A 1973 U.S. act designed to protect species from extinction.

endemic species A species that lives in a very small area of the world and nowhere else.

endocrine disruptor A chemical that interferes with the normal functioning of hormones in an animal’s body.

energy The ability to do work or transfer heat.

energy carrier Something that can move and deliver energy in a convenient, usable form to end users.

energy conservation Finding and implementing ways to use less energy.

energy efficiency The ratio of the amount of energy expended in the form you want to the total amount of energy that is introduced into the system.

GLO-11

energy intensity The energy use per unit of gross domestic product.

energy quality The ease with which an energy source can be used for work.

energy subsidy The fossil fuel energy and human energy input per calorie of food produced.

entropy Randomness in a system.

environment The sum of all the conditions surrounding us that influence life.

environmental economics A subfield of economics that examines the costs and benefits of various policies and regulations that seek to regulate or limit air and water pollution and other causes of environmental degradation.

environmental hazard Anything in the environment that can potentially cause harm.

environmental impact statement (EIS) A document outlining the scope and purpose of a development project, describing the environmental context, suggesting alternative approaches to the project, and analyzing the environmental impact of each alternative.

environmental indicator An indicator that describes the current state of an environmental system.

environmental mitigation plan A plan that outlines how a developer will address concerns raised by a project’s impact on the environment.

Environmental Protection Agency (EPA) The U.S. organization that oversees all governmental efforts related to the environment, including science, research, assessment, and education.

environmental science The field of study that looks at interactions among human systems and those found in nature.

environmental studies The field of study that includes environmental science and additional subjects such as environmental policy, economics, literature, and ethics.

environmental worldview A worldview that encompasses how one thinks the world works; how one views one’s role in the world; and what one believes to be proper environmental behavior.

environmentalist A person who participates in environmentalism, a social movement that seeks to protect the environment through lobbying, activism, and education.

epicenter The exact point on the surface of Earth directly above the location where rock ruptures during an earthquake.

epidemic A situation in which a pathogen causes a rapid increase in disease.

erosion The physical removal of rock fragments from a landscape or ecosystem.

GLO-12

ethanol Alcohol made by converting starches and sugars from plant material into alcohol and CO₂.

eutrophic Describes a lake with a high level of productivity.

eutrophication A phenomenon in which a body of water becomes rich in nutrients.

evapotranspiration The combined amount of evaporation and transpiration.

evolution A change in the genetic composition of a population over time.

evolution by artificial selection The process in which humans determine which individuals breed, typically with a preconceived set of traits in mind.

evolution by natural selection The process in which the environment determines which individuals survive and reproduce.

exotic species A species living outside its historical range. Also known as alien species.

exponential growth model (N_t = N₀e^rt) A growth model that estimates a population’s future size (N_t ) after a period of time (t ), based on the intrinsic growth rate (r ) and the number of reproducing individuals currently in the population (N₀ ).

externality The cost or benefit of a good or service that is not included in the purchase price of that good or service.

extinction The death of the last member of a species.

extrusive igneous rock Rock that forms when magma cools above the surface of Earth.

exurb An area similar to a suburb, but unconnected to any central city or densely populated area.

F

family planning The practice of regulating the number or spacing of offspring through the use of birth control.

famine The condition in which food insecurity is so extreme that large numbers of deaths occur in a given area over a relatively short period.

fault A fracture in rock caused by a movement of Earth’s crust.

fault zone A large expanse of rock where a fault has occurred.

fecal coliform bacteria A group of generally harmless microorganisms in human intestines that can serve as an indicator species for potentially harmful microorganisms associated with contaminated sewage.

Ferrell cell A convection current in the atmosphere that lies between Hadley cells and polar cells.

GLO-13

first law of thermodynamics A physical law which states that energy can neither be created nor destroyed but can change from one form to another.

fish ladder A stair-like structure that allows migrating fish to get around a dam.

fishery A commercially harvestable population of fish within a particular ecological region.

fishery collapse The decline of a fish population by 90 percent or more.

fission A nuclear reaction in which a neutronstrikes a relatively large atomic nucleus, which then splits into two or more parts, releasing additional neutrons and energy in the form of heat.

fitness An individual’s ability to survive and reproduce.

flex-fuel vehicle A vehicle that runs on either gasoline or a gasoline/ethanol mixture.

floodplain The land adjacent to a river.

fly ash The residue collected from the chimney or exhaust pipe of a furnace.

food chain The sequence of consumption from producers through tertiary consumers.

food insecurity A condition in which people do not have adequate access to food.

food security A condition in which people have access to sufficient, safe, and nutritious food that meets their dietary needs for an active and healthy life.

food web A complex model of how energy and matter move between trophic levels.

forest Land dominated by trees and other woody vegetation and sometimes used for commercial logging.

fossil carbon Carbon in fossil fuels.

fossil fuel A fuel derived from biological material that became fossilized millions of years ago.

founder effect A change in the genetic composition of a population as a result of descending from a small number of colonizing individuals.

fracking Hydraulic fracturing, a method of oil and gas extraction that uses high-pressure fluids to force open cracks in rocks deep underground.

fracture In geology, a crack that occurs in rock as it cools.

freshwater wetlands An aquatic biome that is submerged or saturated by water for at least part of each year, but shallow enough to support emergent vegetation.

fuel cell An electrical-chemical device that converts fuel, such as hydrogen, into an electrical current.

GLO-14

fuel rod A cylindrical tube that encloses nuclear fuel within a nuclear reactor.

fundamental niche The suite of abiotic conditions under which a species can survive, grow, and reproduce.

G

gene A physical location on the chromosomes within each cell of an organism.

gene flow The process by which individuals move from one population to another and thereby alter the genetic composition of both populations.

genetic diversity A measure of the genetic variation among individuals in a population.

genetic drift A change in the genetic composition of a population over time as a result of random mating.

genetically modified organism (GMO) An organism produced by copying genes from a species with a desirable trait and inserting them into another species.

genotype The complete set of genes in an individual.

genuine progress indicator (GPI) A measure of economic status that includes personal consumption, income distribution, levels of higher education, resource depletion, pollution, and the health of the population.

geographic isolation Physical separation of a group of individuals from others of the same species.

geothermal energy Heat energy that comes from the natural radioactive decay of elements deep within Earth.

global change Change that occurs in the chemical, biological, and physical properties of the planet.

global climate change Changes in the average weather that occurs in an area over a period of years or decades.

global warming The warming of the oceans, land masses, and atmosphere of Earth.

gray smog See sulfurous smog.

gray water Wastewater from baths, showers, bathrooms, and washing machines.

Green Revolution A shift in agricultural practices in the twentieth century that included new management techniques, mechanization, fertilization, irrigation, and improved crop varieties, and that resulted in increased food output.

green tax A tax placed on environmentally harmful activities or emissions in an attempt to internalize some of the externalities that may be involved in the life cycle of those activities or products.

greenhouse effect Absorption of infrared radiation by atmospheric gases and reradiation of the energy back toward Earth.

GLO-15

greenhouse gases Gases in Earth’s atmosphere that trap heat near the surface.

greenhouse warming potential An estimate of how much a molecule of any compound can contribute to global warming over a period of 100 years relative to a molecule of CO₂.

gross domestic product (GDP) A measure of the value of all products and services produced in one year in one country.

gross primary productivity (GPP) The total amount of solar energy that producers in an ecosystem capture via photosynthesis over a given amount of time.

ground source heat pump A technology that transfers heat from the ground to a building.

groundwater recharge A process by which water percolates through the soil and works its way into an aquifer.

gyre A large-scale pattern of water circulation that moves clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

H

Hadley cell A convection current in the atmosphere that cycles between the equator and 30° N and 30° S.

half-life The time it takes for one-half of an original radioactive parent atom to decay.

hazardous waste Liquid, solid, gaseous, or sludge waste material that is harmful to humans or ecosystems.

haze Reduced visibility.

herbicide A pesticide that targets plant species that compete with crops.

herbivore A consumer that eats producers. Also known as primary consumer.

herbivory An interaction in which an animal consumes a producer.

heterotroph See consumer.

Highway Trust Fund A U.S. federal fund that pays for the construction and maintenance of roads and highways.

horizon A horizontal layer in a soil defined by distinctive physical features such as texture and color.

hot spot In geology, a place where molten material from Earth’s mantle reaches the lithosphere.

Hubbert curve A bell-shaped curve representing oil use and projecting both when world oil production will reach a maximum and when the world will run out of oil.

GLO-16

human capital Human knowledge and abilities.

human development index (HDI) A measurement index that combines three basic measures of human status: life expectancy; knowledge and education.

Human Immunodeficiency Virus (HIV) A type of virus that causes Acquired Immune Deficiency Syndrome (AIDS).

human poverty index (HPI) A measurement index developed by the United Nations to investigate the proportion of a population suffering from deprivation in a country with a high HDI.

hydroelectricity Electricity generated by the kinetic energy of moving water.

hydrogen bond A weak chemical bond that forms when hydrogen atoms that are covalently bonded to one atom are attracted to another atom on another molecule.

hydrologic cycle The movement of water through the biosphere.

hydroponic agriculture The cultivation of plants in greenhouse conditions by immersing roots in a nutrient-rich solution.

hypothesis A testable conjecture about how something works.

hypoxic Low in oxygen.

I

igneous rock Rock formed directly from magma.

immigration The movement of people into a country or region, from another country or region.

impermeable surface Pavement or buildings that do not allow water penetration.

inbreeding depression When individuals with similar genotypes—typically relatives—breed with each other and produce offspring that have an impaired ability to survive and reproduce.

incentive-based approach A strategy for pollution control that constructs financial and other incentives for lowering emissions based on profits and benefits.

incineration The process of burning waste materials to reduce volume and mass, sometimes to generate electricity or heat.

indicator species A species that indicates whether or not disease-causing pathogens are likely to be present.

individual transferable quota (ITQ) A fishery management program in which individual fishers are given a total allowable catch of fish in a season that they can either catch or sell.

induced demand The phenomenon in which an increase in the supply of a good causes demand to grow.

GLO-17

industrial agriculture Agriculture that applies the techniques of mechanization and standardization. Also known as agribusiness.

industrial smog See sulfurous smog.

infant mortality The number of deaths of children under 1 year of age per 1,000 live births.

infectious disease A disease caused by a pathogen.

infill Development that fills in vacant lots within existing communities.

innocent-until-proven-guilty principle A principle based on the belief that a potential hazard should not be considered an actual hazard until the scientific data definitively demonstrate that it actually causes harm.

inorganic compound A compound that does not contain the element carbon or contains carbon bound to elements other than hydrogen.

inorganic fertilizer See synthetic fertilizer.

input An addition to a system.

insecticide A pesticide that targets species of insects and other invertebrates that consume crops.

instrumental value Worth as an instrument or a tool that can be used to accomplish a goal.

integrated pest management (IPM) An agricultural practice that uses a variety of techniques designed to minimize pesticide inputs.

integrated waste management An approach to waste disposal that employs several waste reduction, management, and disposal strategies in order to reduce the environmental impact of MSW.

intercropping An agricultural method in which two or more crop species are planted in the same field at the same time to promote a synergistic interaction.

intermediate disturbance hypothesis The hypothesis that ecosystems experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels.

intertidal zone The narrow band of coastline between the levels of high tide and low tide.

intertropical convergence zone (ITCZ) The latitude that receives the most intense sunlight, which causes the ascending branches of the two Hadley cells to converge.

intrinsic growth rate (r) The maximum potential for growth of a population under ideal conditions with unlimited resources.

intrinsic value Value independent of any benefit to humans.

intrusive igneous rock Igneous rock that forms when magma rises up and cools in a place underground.

invasive species A species that spreads rapidly across large areas.

GLO-18

inversion layer The layer of warm air that traps emissions in a thermal inversion.

ionic bond A chemical bond between two ions of opposite charges.

IPAT equation An equation used to estimate the impact of the human lifestyle on the environment: Impact = population × affluence × technology.

isotopes Atoms of the same element with different numbers of neutrons.

J

joule ( J) The amount of energy used when a 1-watt electrical device is turned on for 1 second.

J-shaped curve The curve of the exponential growth model when graphed.

K

keystone species A species that plays a far more important in its community than its relative abundance might suggest.

kinetic energy The energy of motion.

K-selected species A species with a low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity.

Kyoto Protocol An international agreement that sets a goal for global emissions of greenhouse gases from all industrialized countries to be reduced by 5.2 percent below their 1990 levels by 2012.

L

Lacey Act A U.S. act that prohibits interstate shipping of all illegally harvested plants and animals.

latent heat release The release of energy when water vapor in the atmosphere condenses into liquid water.

law of conservation of matter A law of nature stating that matter cannot be created or destroyed; it can only change form.

LD50 The lethal dose of a chemical that kills 50 percent of the individuals in a dose-response study.

leach field A component of a septic system, made up of underground pipes laid out below the surface of the ground.

leachate Liquid that contains elevated levels of pollutants as a result of having passed through municipal solid waste (MSW) or contaminated soil.

leaching The transportation of dissolved molecules through the soil via groundwater.

GLO-19

leapfrogging The phenomenon of less developed countries using new technology without first using the precursor technology.

least concern species Species that are widespread and abundant.

levee An enlarged bank built up on each side of a river.

life expectancy The average number of years that an infant born in a particular year in a particular country can be expected to live, given the current average life span and death rate in that country.

life-cycle analysis A systems tool that looks at the materials used and released throughout the lifetime of a product—from the procurement of raw materials through their manufacture, use, and disposal. Also known as cradle-to-grave analysis.

limiting nutrient A nutrient required for the growth of an organism but available in a lower quantity than other nutrients.

limiting resource A resource that a population cannot live without and that occurs in quantities lower than the population would require to increase in size.

limnetic zone A zone of open water in lakes and ponds.

lipid A smaller organic biological molecule that does not mix with water.

lithosphere The outermost layer of Earth, including the mantle and crust.

littoral zone The shallow zone of soil and water in lakes and ponds where most algae and emergent plants grow.

logistic growth model A growth model that describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment.

London-type smog See sulfurous smog.

Los Angeles–type smog See photochemical smog.

M

macroevolution Evolution that gives rise to new species, genera, families, classes, or phyla.

macronutrient One of six key elements that organisms need in relatively large amounts: nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.

mad cow disease A disease in which prions mutate into deadly pathogens and slowly damage a cow’s nervous system.

magma Molten rock.

malnourished Having a diet that lacks the correct balance of proteins, carbohydrates, vitamins, and minerals.

GLO-20

mangrove swamp A swamp that occurs along tropical and subtropical coasts, and contains salt-tolerant trees with roots submerged in water.

mantle The layer of Earth above the core, containing magma.

manufactured capital All goods and services that humans produce.

manure lagoon Human-made pond lined with rubber built to handle large quantities of manure produced by livestock.

Marine Mammal Protection Act A 1972 U.S. act to protect declining populations of marine mammals.

market failure When the economic system does not account for all costs.

mass A measurement of the amount of matter an object contains.

mass extinction A large extinction of species in a relatively short period of time.

mass number A measurement of the total number of protons and neutrons in an element.

matter Anything that occupies space and has mass.

maximum contaminant level (MCL) The standard for safe drinking water established by the EPA under the Safe Drinking Water Act.

maximum sustainable yield (MSY) The maximum amount of a renewable resource that can be harvested without compromising the future availability of that resource.

meat Livestock or poultry consumed as food.

mesotrophic Describes a lake with a moderate level of productivity.

metal An element with properties that allow it to conduct electricity and heat energy, and to perform other important functions.

metamorphic rock Rock that forms when sedimentary rock, igneous rock, or other metamorphic rock is subjected to high temperature and pressure.

metapopulation A group of spatially distinct populations that are connected by occasional movements of individuals between them.

microevolution Evolution below the species level.

mineralization The process by which fungal and bacterial decomposers break down the organic matter found in dead bodies and waste products and convert it into inorganic compounds.

mining spoils Unwanted waste material created during mining. Also known as tailings.

modern carbon Carbon in biomass that was recently in the atmosphere.

molecule A particle that contains more than one atom.

GLO-21

monocropping An agricultural method that utilizes large plantings of a single species or variety.

mountaintop removal A mining technique in which the entire top of a mountain is removed with explosives.

multiple-use lands A U.S. classification used to designate lands that may be used for recreation, grazing, timber harvesting, and mineral extraction.

multi-use zoning A zoning classification that allows retail and high-density residential development to coexist in the same area.

municipal solid waste (MSW) Refuse collected by municipalities from households, small businesses, and institutions.

mutagen A type of carcinogen that causes damage to the genetic material of a cell.

mutation A random change in the genetic code produced by a mistake in the copying process.

mutualism An interaction between two species that increases the chances of survival or reproduction for both species.

N

National Environmental Policy Act (NEPA) A 1969 U.S. federal act that mandates an environmental assessment of all projects involving federal money or federal permits.

national wilderness area An area set aside with the intent of preserving a large tract of intact ecosystem or a landscape.

national wildlife refuge A federal public land managed for the primary purpose of protecting wildlife.

native species Species that live in their historical range, typically where they have lived for thousands or millions of years.

natural capital The resources of the planet, such as air, water, and minerals.

natural experiment A natural event that acts as an experimental treatment in an ecosystem.

near-threatened species Species that are very likely to become threatened in the future.

negative feedback loop A feedback loop in which a system responds to a change by returning to its original state, or by decreasing the rate at which the change is occurring.

net migration rate The difference between immigration and emigration in a given year per 1,000 people in a country.

net primary productivity (NPP) The energy captured by producers in an ecosystem minus the energy producers respire.

GLO-22

net removal The process of removing more than is replaced by growth, typically used when referring to carbon.

neurotoxin A chemical that disrupts the nervous systems of animals.

niche generalist A species that can live under a wide range of abiotic or biotic conditions.

niche specialist A species that is specialized to live in a specific habitat or to feed on a small group of species.

nitrification The conversion of ammonia (NH₄⁺) into nitrite (NO₂^– ) and then into nitrate (NO₃^– ).

nitrogen cycle The movement of nitrogen around the biosphere.

nitrogen fixation A process by which some organisms can convert nitrogen gas molecules directly into ammonia.

nomadic grazing The feeding of herds of animals by moving them to seasonally productive feeding grounds, often over long distances.

nondepletable An energy source that cannot be used up.

nonpersistent pesticide A pesticide that breaks down rapidly, usually in weeks or months.

nonpoint source A diffuse area that produces pollution.

nonrenewable energy resource An energy source with a finite supply, primarily the fossil fuels and nuclear fuels.

no-till agriculture An agricultural method in which farmers do not turn the soil between seasons as a means of reducing topsoil erosion.

nuclear fuel Fuel derived from radioactive materials that give off energy.

nuclear fusion A reaction that occurs when lighter nuclei are forced together to produce heavier nuclei.

nucleic acid Organic compounds found in all living cells.

null hypothesis A prediction that there is no difference between groups or conditions, or a statement or an idea that can be falsified, or proved wrong.

O

O horizon The organic horizon at the surface of many soils, composed of organic detritus in various stages of decomposition.

Occupational Safety and Health Administration (OSHA) An agency of the U.S. Department of Labor, responsible for the enforcement of health and safety regulations.

GLO-23

ocean acidification The process by which an increase in ocean CO₂ causes more CO₂ to be converted to carbonic acid, which lowers the pH of the water.

oil sands Slow-flowing, viscous deposits of bitumen mixed with sand, water, and clay.

oligotrophic Describes a lake with a low level of productivity.

open ocean Deep ocean water, located away from the shoreline where sunlight can no longer reach the ocean bottom.

open system A system in which exchanges of matter or energy occur across system boundaries.

open-loop recycling Recycling one product into a different product.

open-pit mining A mining technique that uses a large visible pit or hole in the ground.

ore A concentrated accumulation of minerals from which economically valuable materials can be extracted.

organic agriculture Production of crops without the use of synthetic pesticides or fertilizers.

organic compound A compound that contains carbon-carbon and carbon-hydrogen bonds.

organic fertilizer Fertilizer composed of organic matter from plants and animals.

output A loss from a system.

overnutrition Ingestion of too many calories and a lack of balance of foods and nutrients.

overshoot When a population becomes larger than the environment’s carrying capacity.

oxygenated fuel A fuel with oxygen as part of the molecule.

ozone (O₃) A secondary pollutant made up of three oxygen atoms bound together.

P

pandemic An epidemic that occurs over a large geographic region.

parasitism An interaction in which one organism lives on or in another organism.

parasitoid A specialized type of predator that lays eggs inside other organisms—referred to as its host.

parent material The rock material from which the inorganic components of a soil are derived.

particles See particulate matter.

particulate matter (PM) Solid or liquid particles suspended in air. Also known as particulates; particles.

particulates See particulate matter.

passive solar design Construction designed to take advantage of solar radiation without active technology.

pathogens Parasites that cause disease in their host.

GOL-24

peak demand The greatest quantity of energy used at any one time.

peak oil The point at which half the total known oil supply is used up.

perchlorates A group of harmful chemicals used for rocket fuel.

perennial plant A plant that lives for multiple years.

periodic table A chart of all chemical elements currently known, organized by their properties.

permafrost An impermeable, permanently frozen layer of soil.

persistence The length of time a chemical remains in the environment.

persistent pesticide A pesticide that remains in the environment for a long time.

pesticide A substance, either natural or synthetic, that kills or controls organisms that people consider pests.

pesticide resistance A trait possessed by certain individuals that are exposed to a pesticide and survive.

pesticide treadmill A cycle of pesticide development, followed by pest resistance, followed by new pesticide development.

petroleum A fossil fuel that occurs in underground deposits, composed of a liquid mixture of hydrocarbons, water, and sulfur.

pH The number that indicates the relative strength of acids and bases in a substance.

phenotype A set of traits expressed by an individual.

phosphorus cycle The movement of phosphorus around the biosphere.

photic zone The upper layer of ocean water in the ocean that receives enough sunlight for photosynthesis.

photochemical oxidant A class of air pollutants formed as a result of sunlight acting on compounds such as nitrogen oxides.

photochemical smog Smog that is dominated by oxidants such as ozone. Also known as Los Angeles–type smog; brown smog.

photon A massless packet of energy that carries electromagnetic radiation at the speed of light.

photosynthesis The process by which producers use solar energy to convert carbon dioxide and water into glucose.

photovoltaic solar cell A system of capturing energy from sunlight and converting it directly into electricity.

phylogeny The branching pattern of evolutionary relationships.

physical weathering The mechanical breakdown of rocks and minerals.

phytoplankton Floating algae.

GLO-25

pioneer species A species that can colonize new areas rapidly and grow well in full sunshine.

placer mining The process of looking for minerals, metals, and precious stones in river sediments.

plague An infectious disease caused by a bacterium (Yersinia pestis) that is carried by fleas.

plate tectonics The theory that the lithosphere of Earth is divided into plates, most of which are in constant motion.

point source A distinct location from which pollution is directly produced.

polar cell A convection current in the atmosphere, formed by air that rises at 60° N and 60° S and sinks at the poles, 90° N and 90° S.

polar molecule A molecule in which one side is more positive and the other side is more negative.

polychlorinated biphenyls (PCBs) A group of industrial compounds used to manufacture plastics and insulate electrical transformers, and responsible for many environmental problems.

population density The number of individuals per unit area at a given time.

population distribution A description of how individuals are distributed with respect to one another.

population ecology The study of factors that cause populations to increase or decrease.

population growth models Mathematical equations that can be used to predict population size at any moment in time.

population growth rate The number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period.

population momentum Continued population growth after growth reduction measures have been implemented.

population pyramid An age structure diagram that is widest at the bottom and smallest at the top, typical of developing countries.

population size (N) The total number of individuals within a defined area at a given time.

population The individuals that belong to the same species and live in a given area at a particular time.

positive feedback loop A feedback loop in which change in a system is amplified.

potential energy Stored energy that has not been released.

GLO-26

potentially renewable An energy source that can be regenerated indefinitely as long as it is not overharvested.

power The rate at which work is done.

precautionary principle A principle based on the belief that action should be taken against a plausible environmental hazard.

precision How close the repeated measurements of a sample are to one another.

predation An interaction in which one animal typically kills and consumes another animal.

prescribed burn A fire deliberately set under controlled conditions in order to reduce the accumulation of dead biomass on a forest floor.

primary consumer See herbivore.

primary pollutant A polluting compound that comes directly out of a smokestack, exhaust pipe, or natural emission source.

primary succession Ecological succession occurring on surfaces that are initially devoid of soil.

prion A small, beneficial protein that occasionally mutates into a pathogen.

producer An organism that uses the energy of the Sun to produce usable forms of energy. Also known as autotroph.

profundal zone A region of water where sunlight does not reach, below the limnetic zone in very deep lakes.

prospective study A study that monitors people who might become exposed to harmful chemicals in the future.

protein A critical component of living organisms made up of a long chain of nitrogen-containing organic molecules known as amino acids.

provision A good that humans can use directly.

R

radioactive decay The spontaneous release of material from the nucleus of radioactive isotopes.

radioactive waste Nuclear fuel that can no longer produce enough heat to be useful in a power plant but continues to emit radioactivity.

rain shadow A region with dry conditions found on the leeward side of a mountain range as a result of humid winds from the ocean causing precipitation on the windward side.

range of tolerance The limits to the abiotic conditions that a species can tolerate.

rangeland A dry open grassland.

GLO-27

REACH A 2007 agreement among the nations of the European Union about regulation of chemicals; the acronym stands for registration, evaluation, authorization, and restriction of chemicals.

realized niche The range of abiotic and biotic conditions under which a species actually lives.

recombination The genetic process by which one chromosome breaks off and attaches to another chromosome during reproductive cell division.

recycling The process by which materials destined to become municipal solid waste (MSW) are collected and converted into raw material that is then used to produce new objects.

Red List A list of worldwide threatened species.

reduce, reuse, recycle A popular phrase promoting the idea of diverting materials from the waste stream. Also known as the three Rs.

renewable In energy management, an energy source that is either potentially renewable or nondepletable.

replacement-level fertility The total fertility rate required to offset the average number of deaths in a population in order to maintain the current population size.

replication The data collection procedure of taking repeated measurements.

reproductive isolation The result of two populations within a species evolving separately to the point that they can no longer interbreed and produce viable offspring.

reserve In resource management, the known quantity of a resource that can be economically recovered.

reservoir The water body created by a damming a river or stream.

resilience The rate at which an ecosystem returns to its original state after a disturbance.

resistance A measure of how much a disturbance can affect flows of energy and matter in an ecosystem.

resource conservation ethic The belief that people should maximize use of resources, based on the greatest good for everyone.

resource partitioning When two species divide a resource based on differences in their behavior or morphology.

restoration ecology The study and implementation of restoring damaged ecosystems.

retrospective study A study that monitors people who have been exposed to an environmental hazard at some time in the past.

reuse Using a product or material that was intended to be discarded.

GLO-28

reverse osmosis A process of desalination in which water is forced through a thin semipermeable membrane at high pressure.

Richter scale A scale that measures the largest ground movement that occurs during an earthquake.

RNA (ribonucleic acid) A nucleic acid that translates the code stored in DNA, which makes possible the synthesis of proteins.

rock cycle The geologic cycle governing the constant formation, alteration, and destruction of rock material that results from tectonics, weathering, and erosion, among other processes.

route of exposure The way in which an individual might come into contact with an environmental hazard.

r-selected species A species that has a high intrinsic growth rate, which often leads to population overshoots and die-offs.

run off Water that moves across the land surface and into streams and rivers.

run-of-the-river Hydroelectricity generation in which water is retained behind a low dam or no dam.

S

Safe Drinking Water Act Legislation that sets the national standards for safe drinking water.

salinization A form of soil degradation that occurs when the small amount of salts in irrigation water becomes highly concentrated on the soil surface through evaporation.

salt marsh A marsh containing nonwoody emergent vegetation, found along the coast in temperate climates.

saltwater intrusion An infiltration of salt water in an area where groundwater pressure has been reduced from extensive drilling of wells.

sample size (n) The number of times a measurement is replicated in data collection.

sanitary landfill An engineered ground facility designed to hold municipal solid waste (MSW) with as little contamination of the surrounding environment as possible.

saturation point The maximum amount of water vapor in the air at a given temperature.

scavenger An organism that consumes dead animals.

scientific method An objective method to explore the natural world, draw inferences from it, and predict the outcome of certain events, processes, or changes.

seafloor spreading The formation of new ocean crust as a result of magma pushing upward and outward from Earth’s mantle to the surface.

GLO-29

second law of thermodynamics The physical law stating that when energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes.

secondary consumer A carnivore that eats primary consumers.

secondary pollutant A primary pollutant that has undergone transformation in the presence of sunlight, water, oxygen, or other compounds.

secondary succession The succession of plant life that occurs in areas that have been disturbed but have not lost their soil.

sedimentary rock Rock that forms when sediments such as muds, sands, or gravels are compressed by overlying sediments.

seismic activity The frequency and intensity of earthquakes experienced over time.

selective cutting The method of harvesting trees that involves the removal of single trees or a relatively small number of trees from among many in a forest.

selective pesticide A pesticide that targets a narrow range of organisms.

sense of place The feeling that an area has a distinct and meaningful character.

septage A layer of fairly clear water found in the middle of a septic tank.

septic system A relatively small and simple sewage treatment system, made up of a septic tank and a leach field, often used for homes in rural areas.

septic tank A large container that receives wastewater from a house as part of a septic system.

severe acute respiratory syndrome (SARS) A type of flu caused by a coronavirus.

sex ratio The ratio of males to females in a population.

shifting agriculture An agricultural method in which land is cleared and used for a few years until the soil is depleted of nutrients.

sick building syndrome A buildup of toxic pollutants in an airtight space, seen in newer buildings.

siltation The accumulation of sediments, primarily silt, on the bottom of a reservoir.

siting The designation of a landfill location, typically through a regulatory process involving studies, written reports, and public hearings.

sludge Solid waste material from wastewater.

GLO-30

smart grid An efficient, self-regulating electricity distribution network that accepts any source of electricity and distributes it automatically to end users.

smart growth A set of principles for community planning that focuses on strategies to encourage the development of sustainable, healthy communities.

smog A type of air pollution that is a mixture of oxidants and particulate matter.

soil degradation The loss of some or all of a soil’s ability to support plant growth.

solubility How well a chemical dissolves in a liquid.

source reduction An approach to waste management that seeks to cut waste by reducing the use of potential waste materials in the early stages of design and manufacture.

speciation The evolution of new species.

species A group of organisms that is distinct from other groups in its morphology (body form and structure), behavior, or biochemical properties.

species diversity The number of species in a region or in a particular type of habitat.

species evenness The relative proportion of individuals within the different species in a given area.

species richness The number of species in a given area.

spring A natural source of water formed when water from an aquifer percolates up to the ground surface.

S-shaped curve The shape of the logistic growth model when graphed.

stakeholder A person or organization with an interest in a particular place or issue.

standing crop The amount of biomass present in an ecosystem at a particular time.

steady state A state in which inputs equal outputs, so that the system is not changing over time.

stewardship The careful and responsible management and care for Earth and its resources.

Stockholm Convention A 2001 agreement among 127 nations concerning 12 chemicals to be banned, phased out, or reduced.

stratosphere The layer of the atmosphere above the troposphere, extending roughly 16 to 50 km (10–31 miles) above the surface of Earth.

strip mining The removal of strips of soil and rock to expose ore.

subduction The process of one crustal plate passing under another.

GLO-31

sublethal effect The effect of an environmental hazard that is not lethal, but which may impair an organism’s behavior, physiology, or reproduction.

subsistence energy source An energy source gathered by individuals for their own immediate needs.

subsurface mining Mining techniques used when the desired resource is more than 100 m (328 feet) below the surface of Earth.

subtropical desert A biome prevailing at approximately 30° N and 30° S, with hot temperatures, extremely dry conditions, and sparse vegetation.

suburb An area surrounding a metropolitan center, with a comparatively low population density.

sulfur cycle The movement of sulfur around the biosphere.

sulfurous smog Smog dominated by sulfur dioxide and sulfate compounds. Also known as London-type smog; gray smog; industrial smog.

Superfund Act The common name for the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); a 1980 U.S. federal act that imposes a tax on the chemical and petroleum industries, funds the cleanup of abandoned and non-operating hazardous waste sites, and authorizes the federal government to respond directly to the release or threatened release of substances that may pose a threat to human health or the environment.

surface tension A property of water that results from the cohesion of water molecules at the surface of a body of water and that creates a sort of skin on the water’s surface.

survivorship curve A graph that represents the distinct patterns of species survival as a function of age.

sustainability Living on Earth in a way that allows humans to use its resources without depriving future generations of those resources.

sustainable agriculture Agriculture that fulfills the need for food and fiber while enhancing the quality of the soil, minimizing the use of nonrenewable resources, and allowing economic viability for the farmer.

sustainable development Development that balances current human well-being and economic advancement with resource management for the benefit of future generations.

swine flu A type of flu caused by the H1N1 virus.

symbiotic relationship The relationship between two species that live in close association with each other.

sympatric speciation The evolution of one species into two, without geographic isolation.

GLO-32

synergistic interaction A situation in which two risks together cause more harm than expected based on the separate effects of each risk alone.

synthetic fertilizer Fertilizer produced commercially, normally with the use of fossil fuels. Also known as inorganic fertilizer.

systems analysis An analysis to determine inputs, outputs, and changes in a system under various conditions.

T

tailings See mining spoils.

technology transfer The phenomenon of less developed countries adopting technological innovations developed in wealthy countries.

tectonic cycle The sum of the processes that build up and break down the lithosphere.

temperate grassland/cold desert A biome characterized by cold, harsh winters, and hot, dry summers.

temperate rainforest A coastal biome typified by moderate temperatures and high precipitation.

temperate seasonal forest A biome with warm summers and cold winters with over 1 m (39 inches) of precipitation annually.

temperature The measure of the average kinetic energy of a substance.

teratogen A chemical that interferes with the normal development of embryos or fetuses.

terrestrial biome A geographic region categorized by a particular combination of average annual temperature, annual precipitation, and distinctive plant growth forms on land.

tertiary consumer A carnivore that eats secondary consumers.

the three Rs See reduce, reuse, recycle.

theory A hypothesis that has been repeatedly tested and confirmed by multiple groups of researchers and has reached wide acceptance.

theory of demographic transition The theory that as a country moves from a subsistence economy to industrialization and increased affluence it undergoes a predictable shift in population growth.

theory of island biogeography A theory that demonstrates the dual importance of habitat size and distance in determining species richness.

thermal inversion A situation in which a relatively warm layer of air at mid-altitude covers a layer of cold, dense air below.

thermal mass A property of a building material that allows it to maintain heat or cold.

GLO-33

thermal pollution Nonchemical water pollution that occurs when human activities cause a substantial change in the temperature of water.

thermal shock A dramatic change in water temperature that can kill organisms.

thermohaline circulation An oceanic circulation pattern that drives the mixing of surface water and deep water.

threatened species According to the International Union for Conservation of Nature (ICUN), species that have a high risk of extinction in the future; according to U.S. legislation, any species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.

tidal energy Energy that comes from the movement of water driven by the gravitational pull of the Moon.

tiered rate system A billing system used by some electric companies in which customers pay higher rates as their use goes up.

tipping fee A fee charged for disposing of material in a landfill or incinerator.

topsoil See A horizon.

total fertility rate (TFR) An estimate of the average number of children that each woman in a population will bear throughout her childbearing years.

tragedy of the commons The tendency of a shared, limited resource to become depleted because people act from self-interest for short-term gain.

transform fault boundary An area where tectonic plates move sideways past each other.

transit-oriented development (TOD) Development that attempts to focus dense residential and retail development around stops for public transportation, a component of smart growth.

transpiration The release of water from leaves during photosynthesis.

tree plantation A large area typically planted with a single rapidly growing tree species.

triple bottom line An approach to sustainability that considers three factors—economic, environmental, and social—when making decisions about business, the economy, and development.

trophic levels The successive levels of organisms consuming one another.

trophic pyramid A representation of the distribution of biomass, numbers, or energy among trophic levels.

tropical rainforest A warm and wet biome found between 20° N and 20° S of the equator, with little seasonal temperature variation and high precipitation.

tropical seasonal forest/savanna A biome marked by warm temperatures and distinct wet and dry seasons.

troposphere A layer of the atmosphere closest to the surface of Earth, extending up to approximately 16 km (10 miles).

tuberculosis A highly contagious disease caused by the bacterium Mycobacterium tuberculosis that primarily infects the lungs.

tundra A cold and treeless biome with low-growing vegetation.

turbine A device with blades that can be turned by water, wind, steam, or exhaust gas from combustion that turns a generator in an electricity-producing plant.

Type I survivorship curve A pattern of survival over time in which there is high survival throughout most of the life span, but then individuals start to die in large numbers as they approach old age.

Type II survivorship curve A pattern of survival over time in which there is a relatively constant decline in survivorship throughout most of the life span.

Type III survivorship curve A pattern of survival over time in which there is low survivorship early in life with few individuals reaching adulthood.

U

uncertainty An estimate of how much a measured or calculated value differs from a true value.

unconfined aquifer An aquifer made of porous rock covered by soil out of which water can easily flow.

undernutrition The condition in which not enough calories are ingested to maintain health.

United Nations (UN) A global institution dedicated to promoting dialogue among countries with the goal of maintaining world peace.

United Nations Development Programme (UNDP) An international program that works in 166 countries around the world to advocate change that will help people obtain a better life through development.

GLO-35

United Nations Environment Programme (UNEP) A program of the United Nations responsible for gathering environmental information, conducting research, and assessing environmental problems.

upwelling The upward movement of ocean water toward the surface as a result of diverging currents.

urban area An area that contains more than 385 people per square kilometer (1,000 people per square mile).

urban blight The degradation of the built and social environments of the city that often accompanies and accelerates migration to the suburbs.

urban growth boundary A restriction on development outside a designated area.

urban sprawl Urbanized areas that spread into rural areas, removing clear boundaries between the two.

valuation The practice of assigning monetary value to intangible benefits and natural capital.

volatile organic compound (VOC) An organic compound that evaporates at typical atmospheric temperatures.

V

volcano A vent in the surface of Earth that emits ash, gases, or molten lava.

W

waste Material outputs from a system that are not useful or consumed.

waste stream The flow of solid waste that is recycled, incinerated, placed in a solid waste landfill, or disposed of in another way.

waste-to-energy A system in which heat generated by incineration is used as an energy source rather than released into the atmosphere.

wastewater Water produced by livestock operations and human activities, including human sewage from toilets and gray water from bathing and washing of clothes and dishes.

water footprint The total daily per capita use of fresh water.

water impoundment The storage of water in a reservoir behind a dam.

water pollution The contamination of streams, rivers, lakes, oceans, or groundwater with substances produced through human activities.

water table The uppermost level at which the water in a given area fully saturates rock or soil.

waterlogging A form of soil degradation that occurs when soil remains under water for prolonged periods.

GLO-36

watershed All land in a given landscape that drains into a particular stream, river, lake, or wetland.

weather The short-term conditions of the atmosphere in a local area, which include temperature, humidity, clouds, precipitation, and wind speed.

well-being The status of being healthy, happy, and prosperous.

West Nile virus A virus that lives in hundreds of species of birds and is transmitted among birds by mosquitoes.

wind energy Energy generated from the kinetic energy of moving air.

wind turbine A turbine that converts wind energy into electricity.

woodland/shrubland A biome characterized by hot, dry summers and mild, rainy winters.

World Bank A global institution that provides technical and financial assistance to developing countries with the objectives of reducing poverty and promoting growth, especially in the poorest countries.

World Health Organization (WHO) A global institution dedicated to the improvement of human health by monitoring and assessing health trends and providing medical advice to countries.

Z

zoning A planning tool used to separate industry and business from residential neighborhoods.