| Taiga
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| The northernmost edge of the boreal forest, including species-poor woodland and peat deposits; intergrading with the arctic tundra.
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| Tailings
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| Mining waste left after mechanical or chemical separation of minerals from crushed ore.
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| Taking
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| Unconstitutional confiscation of private property.
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| Tar sands
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| Sedimentary material containing bitumen that can be ¡§melted out¡¨ using heat and then refined in the same way as crude oil.
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| Taxonomy
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| The science of identification and classification of organisms according to evolutionary relationships.
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| TEA (total exposure assessment)
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| The analysis of the impact of air pollutants on people based on the amount of time they spend in different spaces, especially indoors.
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| Technological fix
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| A purely technological answer to a problem. Also called a technical fix.
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| Technological optimists
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| Those who believe that technology and human enterprise will find cures for all our problems. Also called Promethean environmentalism.
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| Technopolis
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| Also called a vertical city; this model of city development proposes that cities grow vertically instead of horizontally.
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| Tectonic plates
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| Huge blocks of the earth¡¦s crust that slide around slowly, pulling apart to open new ocean basins or crashing ponderously into each other to create new, larger landmasses.
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| Temperate deciduous forest
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| Biome located in the eastern United States, Europe, and northeastern China below the taiga. Characterized by deciduous and nondeciduous trees, warm growing season, abundant rainfall, and a rich species diversity.
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| Temperate rainforest
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| The cool, dense, rainy forest of the northern Pacific coast; enshrouded in fog much of the time; dominated by large conifers.
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| Temperature
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| A measure of the speed of motion of a typical atom or molecule in a substance.
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| Temperature inversion
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| The weather phenomenon in which a layer of warm air overlies cooler air near the ground and prevents the rising and dispersion of air pollutants.
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| Temporary threshold shift
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| Momentary dulling of the sense of hearing after exposure to loud sounds. Can lead to permanent threshold shift.
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| Teratogenic
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| Causing birth defects.
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| Teratogens
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| Chemicals or other factors that specifically cause abnormalities during embryonic growth and development.
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| Terracing
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| Shaping the land to create level shelves of earth to hold water and soil; requires extensive hand labor or expensive machinery, but it enables farmers to farm very steep hillsides.
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| Territoriality
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| An intense form of intraspecific competition in which organisms define an area surrounding their home site or nesting site and defend it, primarily against other members of their own species.
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| Tertiary treatment
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| The removal of inorganic minerals and plant nutrients after primary and secondary treatment of sewage.
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| Theory
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| A conceptual formulation that provides a rational explanation or framework for numerous related observations.
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| Thermal plume
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| A plume of hot water discharged into a stream or lake by a heat source, such as a power plant.
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| Thermal pollution
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| The addition of abnormal and undesirable amounts of heat to air or water. It is most significant with respect to discharging waste heat from electric generating plants, especially nuclear power plants, into bodies of water.
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| Thermocline
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| In water, a distinctive temperature transition zone that separates an upper layer that is mixed by the wind (the epilimnion) and a colder, deep layer that is not mixed (the hypolimnion).
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| Thermodynamics
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| A branch of physics that deals with transfers and conversions of energy.
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| Thermodynamics, first law
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| Energy can be transformed and transferred, but cannot be destroyed or created.
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| Thermodynamics, second law
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| With each successive energy transfer or transformation less energy is available to do work.
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| Thermoplastics
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| Soft plastics composed of single-chain, unlinked polymers, such as polyethylene, polypropylene, polyvinylchloride, polystyrene, and polyester, that can be remelted and reformed to make useful products.
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| Thermoset polymers
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| Hard plastics composed of cross-linked molecular networks, such as acrylic, phenolic, or epoxy resins, that cannot be remelted or recycled.
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| Thermosphere
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| The highest atmospheric zone; a region of hot, dilute gases above the mesosphere extending out to about 1600km (1,000 mi) from the earth¡¦s surface.
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| Third principle of ecosystem sustainability
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| The size of consumer populations is maintained such that overgrazing and other forms of overuse do not occur.
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| Third-generation pesticides
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| Newer chemical agents to control pests, such as pheromones and insect hormones.
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| Third World
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| Less-developed countries that are not capitalistic and industrialized (First World) or centrally-planned socialist economies (Second World); not intended to be derogatory.
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| Threatened species
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| While still abundant in parts of its territorial range this species has declined significantly in total numbers and may be on the verge of extinction in certain regions or localities.
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| Threshold level
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| The maximum degree of exposure to a pollutant, drug, or other factors that can be tolerated with no ill effect. The threshold level will vary depending on the species, the sensitivity of the individual, the length of exposure, and the presence of other factors that may produce synergistic effects.
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| Throughput approach
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| A method of solving an environmental problem by recycling and reuse. For example, recycling or reusing hazardous wastes reduces their ouput.
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| Tidal station
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| A dam built across a narrow bay or estuary traps tide water flowing both in and out of the bay. Water flowing through the dam spins turbines attached to electric generators.
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| Tidal wetlands
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| Areas of marsh grasses and reeds along coasts and estuaries where the ground is covered by high tides but drained at low tide.
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| Tied ridges
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| Series of ridges running at right angles to each other so that runoff is blocked in all directions and water is allowed to soak into the soil.
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| Timberline
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| In mountains, the highest-altitude edge of forest that marks the beginning of the treeless alpine tundra.
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| Time preference
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| A measure of the value of an immediate gain in comparison with a long-term gain.
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| Tolerance level (for pesticides)
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| Level of residue on fruits and vegetables permitted by EPA because it is considered ¡§safe¡¨.
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| Tolerance limits
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| See limiting factors.
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| Tool-making revolution
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| The invention of tools ¡V probably first of stone, wood, or bone ¡V sometime in the early Paleolithic period. Knowledge of tool-making and tool-using technologies may have predated modern humans, as evidenced by tool utilization by other primates.
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| Topsoil
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| The first true layer of soil; layer in which organic material is mixed with mineral particles; thickness ranges from a meter or more under virgin prairie to zero in some deserts.
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| Tornado
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| A violent storm characterized by strong swirling winds and updrafts; tornadoes form when a strong cold front pushes under a warm, moist air mass over the land.
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| Total allowable catch (TAC)
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| In fisheries management, a yearly quota set for the harvest of a species by fisheries managers.
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| Total fertility rate
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| The number of children born to an average woman in a population during her entire reproductive life.
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| Total growth rate
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| The net rate of population growth resulting form births, deaths, immigration, and emigration.
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| Total product life cycle
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| Consideration of all steps from the obtaining of raw materials through the manufacture, use, and finally disposal of a product. Consideration of byproducts and pollution resulting from each step.
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| Toxic colonialism
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| Shipping toxic wastes to a weaker or poorer nation.
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| Toxic Substances Control Act (TOSCA)
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| A law requiring the assessment of the potential hazards of a chemical before the chemical is put on the market.
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| Toxicology
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| The study of the impacts of toxic substance on human health and the pathways by which such substances reach humans.
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| Toxics release inventory
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| An annual record of releases of toxic chemicals to the environment and the location and quantities of toxic chemicals to the environment and the locations and quantities of toxic chemicals stored on site, required by the Emergency Plantoxic chemicals stored on site, required by the Emergency Planning and Community Right-to-Know Act (EPCRA) of 1968.
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| Toxins
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| Poisonous chemicals that react with specific cellular components to kill cells or to alter growth or development in undesirable ways; often harmful, even in dilute concentrations.
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| Trace elements
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| Those essential elements that are needed in only very small amounts.
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| Tradable permits
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| Pollution quotas or variances that can be bought or sold.
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| Trade winds
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| The more or less constant winds blowing in horizontal directions over the surface as part of Hadley cells.
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| Traditional agriculture
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| Farming methods as they were practiced before modern industrialized agriculture.
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| Tragedy of the commons
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| An inexorable process of degradation of communal resources due to selfish self-interest of ¡§free riders¡¨ who use or destroy more than their fair share of common property. See open access systems.
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| Trait
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| Any physical or behavioral characteristic or talent that an individual is born with.
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| Transgenic organism
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| Any organism with genes introduced from other species via biotechnology to convey new characteristics.
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| Transitional zone
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| A zone in which populations from two or more adjacent communities meet and overlap.
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| Transpiration
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| The evaporation of water from plant surfaces, especially through stomates.
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| Trapping technique
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| The use of sex attractants to lure male insects into traps.
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| Trauma
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| Injury caused by accident or violence.
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| Treated sludge
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| Solid organic material that has been removed from sewage and treated so that it is nonhazardous.
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| Tree farms
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| Private forests devoted to maximum timber growth an relying heavily on herbicides, insecticides, and fertilizers.
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| Tricking filter system
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| System in which wastewater trickles over rocks or a framework coated with actively feeding microorganisms. The feeding action of the organisms in a well-aerated environment results in the decomposition of organic matter. Used in secondary or biological treatment of sewage.
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| Tritium
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| An unstable isotope of hydrogen that contains two neutrons in addition to the usual single proton in the nucleus. It does not occur in significant amounts naturally but is human-made.
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| Trombe wall
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| An interior, heat-absorbing wall; may be water filled glass tubes that absorb heat rays and let light into interior rooms.
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| Trophic level
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| Step in the movement of energy through an ecosystem; and organism¡¦s feeding status in an ecosystem.
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| Tropical rainforests
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| Forests in which rainfall is abundant ¡V more than 200cm (80 in) per year ¡V and temperatures are warm to hot year-round.
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| Tropical seasonal forest
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| Semievergreen or partly deciduous forests tending toward open woodlands and grassy savannas dotted with scattered, drought-resistant tree species; distinct wet and dry seasons, hot year-round.
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| Tropical structure
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| The major feeding relationships between organisms at the second, within ecosystems, organized into trophic levels.
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| Tropopause
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| The boundary between the troposphere and the stratosphere.
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| Troposphere
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| The layer of air nearest to the earth¡¦s surface; both temperature and pressure usually decrease with increasing altitude.
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| Tsunami
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| Giant seismic sea swells that move rapidly from the center of an earthquake; they can be 10 to 20 meters high when they reach shorelines hundreds or even thousands of kilometers form their source.
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| Tundra
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| Treeless arctic or alpine biome characterized by cold, harsh winters, a short growing season, and potential for frost any month of the year; vegetation includes low-growing perennial plants, mosses, and lichens.
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| Turbid
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| Refers to water purity; means cloudy.
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| Turbine
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| A sophisticated ¡§paddle wheel¡¨ driven at a very high speed by steam, water, or exhaust gases from combustion.
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| Turbogenerator
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| A turbine coupled to and driving an electric generator. Virtually all-commercial electricity is produced by such devices. The turbine is driven by gas, steam, or water.
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