Page 721 - Environment: The Science Behind the Stories

occurred in Western nations as they became dike A long raised mound of earth erected Dust Bowl An area that loses huge amounts of
industrialized. The model holds that industri- along a river bank to protect against floods by topsoil to wind erosion as a result of drought
alization caused these rates to fall naturally by holding rising water in the main channel. and/or human impact. First used to name the
decreasing mortality and by lessening the need directional drilling A drilling technique (e.g., region in the North American Great Plains se-
for large families. Parents would thereafter for oil or natural gas) in which a drill bores verely affected by drought and topsoil loss in
choose to invest in quality of life rather than down vertically and then bends horizontally in the 1930s. The term is now also used to de-
quantity of children. scribe that historical event and others like it.
order to follow layered deposits for long dis-
demography A social science that applies the tances from the drilling site. This enables us to dynamic equilibrium The state reached when
principles of population ecology to the study of extract more fossil fuels with less environmen- processes within a system are moving in oppos-
statistical change in human populations. tal impact at the surface. ing directions at equivalent rates so that their
denitrifying bacteria Bacteria that convert the discounting A practice in neoclassical eco- effects balance out.
nitrates in soil or water to gaseous nitrogen and nomics by which short-term costs and benefits
release it back into the atmosphere. are granted more importance than long-term
density-dependent factor A limiting fac- costs and benefits. Future effects are thereby earthquake A release of energy that occurs as
Earth relieves accumulated pressure between
tor whose effects on a population increase or “discounted,” under the notion that an impact masses of lithosphere and that results in shak-
decrease depending on the population density. far in the future should count much less than ing at the surface.
Compare density-independent factor. one in the present.
ecocentrism A philosophy that considers ac-
density-independent factor A limiting fac- distance effect In island biogeography theory, tions in terms of their damage or benefit to the
tor whose effects on a population are constant the pattern that islands far from a mainland integrity of whole ecological systems, includ-
regardless of population density. Compare host fewer species because fewer species tend ing both living and nonliving elements. For an
density-dependent factor. to find and colonize it.
ecocentrist, the well-being of an individual is
deoxyribonucleic acid (DNA) A double- disturbance An event that affects environmen- less important than the long-term well-being of
stranded nucleic acid composed of four nu- tal conditions rapidly and drastically, resulting a larger integrated ecological system. Compare
cleotides, each of which contains a sugar in changes to the community and ecosystem. anthropocentrism and biocentrism.
(deoxyribose), a phosphate group, and a nitrog- Disturbance can be natural or can be caused ecolabeling The practice of designating on a
enous base. DNA carries the hereditary infor- by people. product’s label how the product was grown,
mation for living organisms and is responsible divergent plate boundary The area where harvested, or manufactured, so that consum-
for passing traits from parents to offspring. tectonic plates push apart from one another ers are aware of the processes involved and
Compare RNA. as magma rises upward to the surface, creat- can judge which brands use more sustainable
dependent variable The variable that is af- ing new lithosphere as it cools and spreads. processes.
fected by manipulation of the independent A prime example is the Mid-Atlantic Ridge. ecological economics A developing school of
variable in an experiment. Compare convergent plate boundary and trans- economics that applies the principles of ecol-
form plate boundary.
deposition The arrival of eroded soil at a new ogy and systems thinking to the description and
location. Compare erosion. DNA See deoxyribonucleic acid. analysis of economies. Compare environmental
desalination (desalinization) The removal doldrums A region near the equator with little economics; neoclassical economics.
of salt from seawater. wind activity. ecological footprint The cumulative area of
descriptive science Research in which scien- dose The amount of toxicant a test animal re- biologically productive land and water required
tists gather basic information about organisms, ceives in a dose-response test. Compare re- to provide the raw materials a person or popu-
materials, systems, or processes that are not sponse. lation consumes and to dispose of or recycle
yet well known. Compare hypothesis-driven dose-response analysis A set of experiments the waste that is produced.
science.
that measure the response of test animals to dif- ecological modeling The practice of construct-
desert The driest biome on Earth, with annual ferent doses of a toxicant. The response is gen- ing and testing models that aim to explain and
precipitation of less than 25 cm. Because de- erally quantified by measuring the proportion predict how ecological systems function.
serts have relatively little vegetation to insu- of animals exhibiting negative effects. ecological restoration Efforts to reverse the
late them from temperature extremes, sunlight dose-response curve A curve that plots the effects of human disruption of ecological sys-
readily heats them in the daytime, but daytime response of test animals to different doses tems and to restore communities to their con-
heat is quickly lost at night, so temperatures of a toxicant, as a result of dose-response dition before the disruption. The practice that
vary widely from day to night and in different analysis. applies principles of restoration ecology.
seasons.
downwelling In the ocean, the flow of warm ecology The science that deals with the distri-
desertification A form of land degradation in bution and abundance of organisms, the in-
which more than 10% of a land’s productivity surface water toward the ocean floor. Down- teractions among them, and the interactions
is lost due to erosion, soil compaction, forest welling occurs where surface currents con- between organisms and their abiotic environ-
removal, overgrazing, drought, salinization, verge. Compare upwelling. ments.
climate change, water depletion, or other fac- drainage basin See watershed.
tors. Severe desertification can result in the ex- driftnet Fishing net that spans large expanses economic development Improvement in the
pansion of desert areas or creation of new ones. of water, arrayed strategically to drift with cur- efficiency of production due to better technolo-
Compare land degradation; soil degradation. rents so as to capture passing fish, and held gies and approaches that allow us to produce
detritivore An organism, such as a millipede or vertical by floats at the top and weights at the more goods with fewer inputs.
soil insect, that scavenges the waste products bottom. Driftnetting results in substantial by- economic growth An increase in an economy’s
or dead bodies of other community members. catch of dolphins, seals, sea turtles, and non- activity—that is, an increase in the production
Compare decomposer. target fish. and consumption of goods and services.
development The use of natural resources for drylands Arid and semi-arid environments economics The study of how we decide to use
economic advancement (as opposed to simple that are prone to desertification and that cover scarce resources to satisfy demand for goods
G-6 subsistence, or survival). about 40% of Earth’s land surface. and services.

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