Botkin Environmental Science Earth as Living Planet 8th txtbk

Glossary G-11
cooler than it is today. During the Little Ice Age, glaciers
expanded in mountainous regions. Cold, wet years during
the Little Ice Age, may have contributed to the devastation
caused by the Black Plague.
Littoral drift Movement caused by wave motion in nearshore
and beach environment.
Local extinction The disappearance of a species from part of
its range but continued persistence elsewhere.
Logistic carrying capacity In terms of the logistic curve, the
population size at which births equal deaths and there is no
net change in the population.
Logistic equation The equation that results in a logistic growth
curve; that is, the growth rate dN/dt rN[(K N)/N],
where r is the intrinsic rate of increase, K is the carrying
capacity, and N is the population size.
Logistic growth curve The S-shaped growth curve that is
generated by the logistic growth equation. In the logistic,
a small population grows rapidly, but the growth rate
slows down, and the population eventually reaches a
constant size.
Low-level radioactive waste Waste materials that contain sufficiently
low concentrations or quantities of radioactivity
so as not to present a significant environmental hazard if
properly handled.
Luz solar electric generating system Solar energy farms
comprising a power plant surrounded by hundreds of solar
collectors (curved mirrors) that heat a synthetic oil, which
flows through heat exchangers to drive steam turbine
generators.
Macronutrients Elements required in large amounts by living
things. These include the big six—carbon, hydrogen, oxygen,
nitrogen, phosphorus, and sulfur.
Made lands Man-made areas created artificially with fill,
sometimes as waste dumps of all kinds and sometimes to
make more land available for construction.
Magma A naturally occurring silica melt, a good deal of
which is in a liquid state.
Malnourishment The lack of specific components of food,
such as proteins, vitamins, or essential chemical elements.
Manipulated variable See Variable, independent.
Marasmus Progressive emaciation caused by a lack of protein
and calories.
Marginal cost In environmental economics, the cost to reduce
one additional unit of a type of degradation; for example,
pollution.
Marginal land An area of Earth with minimal rainfall or
otherwise limited severely by some necessary factor, so
that it is a poor place for agriculture and easily degraded
by agriculture. Typically, these lands are easily converted
to deserts even when used for light grazing and crop
production.
Mariculture Production of food from marine habitats.
Marine evaporites With respect to mineral resources, refers
to materials such as potassium and sodium salts resulting
from the evaporation of marine waters.
Materially closed system Characterized by a system in
which no matter moves in and out of the system, although
energy and information may move across the system’s
boundaries. For example, Earth is a materially closed system
for all practical purposes.
Materials management In waste management, methods
consistent with the ideal of industrial ecology, making
better use of materials and leading to more sustainable use
of resources.
Matter Anything that occupies space and has mass. It is the
substance of which physical objects are composed.
Maximum lifetime Genetically determined maximum
possible age to which an individual of a species can live.
Maximum sustainable population The largest population
size that can be sustained indefinitely.
Maximum sustainable yield (MSY) The maximum usable
production of a biological resource that can be obtained in
a specified time period without decreasing the ability of the
resource to sustain that level of production.
Mediation A negotiation process between adversaries, guided
by a neutral facilitator.
Medieval Warming Period (MWP) A period of approximately
300 years from A.D. 950 to 1250 when Earth’s
surface was considerably warmer than the normal that we
experience today. The warming was particularly relevant
and important in Western Europe and the Atlantic Ocean
where the MWP was a time of flourishing culture and activity,
as well as expansion of population.
Megacities Urban areas with at least 8 million inhabitants.
Meltdown A nuclear accident in which the nuclear fuel
forms a molten mass that breaches the containment of
the reactor, contaminating the outside environment with
radioactivity.
Methane (CH 4 ) A molecule of carbon and four hydrogen
atoms. It is a naturally occurring gas in the atmosphere,
one of the so-called greenhouse gases.
Methane hydrate A white icelike compound made up of
molecules of methane gas trapped in “cages” of frozen
water in the sediments of the deep seafloor.
Microclimate The climate of a very small local area. For
example, the climate under a tree, near the ground within
a forest, or near the surface of streets in a city.
Micronutrients Chemical elements required in very small
amounts by at least some forms of life. Boron, copper, and
molybdenum are examples of micronutrients.
Micropower The production of electricity using smaller
distributed systems rather than relying on large central
power plants.
Migration The movement of an individual, population, or
species from one habitat to another or more simply from
one geographic area to another.
Migration corridor Designated passageways among parks
or preserves allowing migration of many life-forms among
several of these areas.
Mineral A naturally occurring inorganic material with a definite
internal structure and physical and chemical properties that
vary within prescribed limits.
Mineral resources Elements, chemical compounds, minerals,
or rocks concentrated in a form that can be extracted to
obtain a usable commodity.