Page 728 - Environment: The Science Behind the Stories

logistic growth curve A plot that shows how market failure The failure of markets to take methane hydrate An ice-like solid consisting
the initial exponential growth of a population into account the environment’s positive effects of molecules of methane embedded in a crys-
is slowed and finally brought to a standstill by on economies (for example, ecosystem ser- tal lattice of water molecules. Most is found in
limiting factors. vices) or to reflect the negative effects of eco- sediments on the continental shelves and in the
nomic activity on the environment and thereby Arctic. Methane hydrate is a potential alterna-
longline fishing Fishing practice that involves
setting out extremely long lines with up to sev- on people (external costs). tive fossil fuel.
eral thousand baited hooks spaced along their mass extinction event The extinction of a microclimate A small-scale localized pattern
lengths. Kills turtles, sharks, and an estimated large proportion of the world’s species in a of weather conditions.
300,000 seabirds each year as bycatch. very short time period due to some extreme micronutrients Elements and compounds re-
and rapid change or catastrophic event. Earth
low-input agriculture Agriculture that uses quired in relatively small amounts by organ-
smaller amounts of pesticides, fertilizers, has seen five mass extinction events in the past isms. Examples include zinc, copper, and iron.
growth hormones, water, and fossil fuel energy half-billion years. Milankovitch cycle One of three types of vari-
than are used in industrial agriculture. Com- mass transit A public transportation system ations in Earth’s rotation and orbit around the
pare sustainable agriculture; organic agricul- for a metropolitan area that moves large num- sun that result in slight changes in the relative
ture. bers of people at once. Buses, trains, subways, amount of solar radiation reaching Earth’s sur-
streetcars, trolleys, and light rail are types of face at different latitudes. As the cycles pro-
low-pressure system An air mass in which air
moves toward the low atmospheric pressure at mass transit. ceed, they change the way solar radiation is
the center of the system and spirals upward, mass wasting The downslope movement of distributed over Earth’s surface and contribute
typically bringing clouds and precipitation. soil and rock due to gravity. Compare land- to changes in atmospheric heating and circula-
Compare high-pressure system. slide. tion that have triggered glaciations and other
climate changes.
materials recovery facility (MRF) A recy-
cling facility where items are sorted, cleaned, Millennium Development Goals A program
macromolecule A very large molecule, such as shredded, and prepared for reprocessing into of targets for sustainable development set
a protein, nucleic acid, carbohydrate, or lipid. by the international community through the
new items.
macronutrients Elements and compounds matter All material in the universe that has United Nations at the turn of this century.
required in relatively large amounts by organ- mass and occupies space. See law of conserva- mineral A naturally occurring solid element or
isms. Examples include nitrogen, carbon, and tion of matter. inorganic compound with a crystal structure,
phosphorus. a specific chemical composition, and distinct
maximum sustainable yield The maximal physical properties. Compare ore and rock.
magma Molten, liquid rock.
harvest of a particular renewable natural re-
malnutrition The condition of lacking nu- source that can be accomplished while still mining (1) In the broad sense, the extraction
trients the body needs, including a complete keeping the resource available for the future. of any resource that is nonrenewable on the
timescale of our society (such as fossil fuels
complement of vitamins and minerals.
meandering river A river that winds its way or groundwater). (2) In relation to mineral re-
Malthus, Thomas (1766–1834) British econ- across its floodplain, depositing sediment sources, the systematic removal of rock, soil,
omist who maintained that increasing human on the riverbank on the insides of curves and or other material for the purpose of extracting
population would eventually deplete the avail- eroding the riverbanks on the outside of curves. minerals of economic interest.
able food supply until starvation, war, or dis- Compare braided river. mitigation The pursuit of strategies to lessen
ease arose and reduced the population.
meltdown The accidental melting of the ura- the severity of climate change, notably by re-
mangrove A tree with a unique type of roots nium fuel rods inside the core of a nuclear re- ducing emissions of greenhouse gases. Com-
that curve upward to obtain oxygen, which is actor, causing the release of radiation. pare adaptation.
lacking in the mud in which they grow, and mesosphere The atmospheric layer above the mixed economy An economy that combines
that serve as stilts to support the tree in chang- stratosphere, extending 50–80 km (31–56 mi) elements of a capitalist market economy and a
ing water levels. Mangrove forests grow on the above sea level. centrally planned economy.
coastlines of the tropics and subtropics.
metal A type of chemical element, or a mass model A simplified representation of a complex
manipulative experiment An experiment in of such an element, that typically is lustrous, natural process, designed by scientists to help
which the researcher actively chooses and ma- opaque, and malleable and that can conduct understand how the process occurs and to make
nipulates the independent variable. Compare heat and electricity. predictions.
natural experiment.
metamorphic rock One of the three main cat- moderator Within a nuclear reactor, a sub-
mantle The malleable layer of rock that lies egories of rock. Formed by great heat and/or stance, most often water or graphite, that slows
beneath Earth’s crust and surrounds a mostly pressure that reshapes crystals within the rock the neutrons bombarding uranium so that fis-
iron core. sion can begin.
and changes its appearance and physical prop-
marasmus A form of malnutrition that results erties. Common metamorphic rocks include molecule A combination of two or more atoms.
from protein deficiency together with a lack of marble and slate. Compare igneous rock and monoculture The uniform planting of a single
calories, causing wasting or shriveling among sedimentary rock. crop over a large area. Characterizes industrial
millions of children in the developing world.
metapopulation A network of subpopulations, agriculture. Compare polyculture.
marine protected area (MPA) An area of the most of whose members stay within their re- Montreal Protocol International treaty rati-
ocean set aside to protect marine life from fish- spective landscape patches, but some of whom fied in 1987 in which 180 (now 196) signatory
ing pressures. An MPA may be protected from move among patches or mate with members of nations agreed to restrict production of chlor-
some human activities but be open to others. other patches. ofluorocarbons (CFCs) in order to halt strato- GLOSS ARY
Compare marine reserve.
methane (CH ) A colorless gas produced pri- spheric ozone depletion. This was a protocol of
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marine reserve An area of the ocean desig- marily by anaerobic decomposition. The major the Vienna Convention for the Protection of the
nated as a “no-fishing” zone, allowing no ex- constituent of natural gas and a greenhouse Ozone Layer. The Montreal Protocol is widely
tractive activities. Compare marine protected gas that is molecule-for-molecule more potent considered the most successful effort to date
area (MPA). than carbon dioxide. in addressing a global environmental problem. G-13

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