| Lacey Act.
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| The first national act, passed in 1900, that gave protection to wildlife by forbidding interstate commerce in illegally killed wildlife.
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| Lag effect
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| The tendency for a population to continue growing even after it has reached replacement-level fertility. Caused by an expanding number of women reaching reproductive age.
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| Land ethic
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| View that extends ethical concerns beyond humans to the ecosystem.
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| Land reform
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| Democratic redistribution of landownership to recognize the rights of those who actually work the land to a fair share of the products of their labor.
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| Land subsidence
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| The phenomenon whereby land gradually sinks. It may result from removing groundwater or oil, which is frequently instrumental in supporting the overlying rock and soil.
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| Land trust
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| Land that is purchased and held by various private organizations specifically for the purpose of protecting its natural environment and biota that inhabit it.
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| Landfills
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| Land disposal sites for solid waste; operators compact refuse and cover it with a layer of dirt to minimize rodent and insect infestation, wind-blown debris, and leaching by rain.
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| Landscape ecology
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| The study of the reciprocal effects of spatial pattern on ecological processes. A study of the ways in which landscape history shapes the features of the land and the organisms that inhabit it as well as our reaction to, and interpretation of, the land.
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| Landscape
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| A group of interacting ecosystems occupying adjacent geographical areas.
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| Landslide
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| The sudden fall of rock and earth from a hill or cliff. Often triggered by an earthquake or heavy rain.
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| Land-use planning
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| Process whereby land uses are matched with the needs of the community and environmental considerations, for example, need for open space and agricultural land and for control of water and air pollution.
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| Larva, pl. larvae
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| A free-living immature form that occurs in the life cycle of many organisms and that is structurally distinct from the adult. For example, caterpillars are the larval stage of months and butterflies.
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| Laterite
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| Soil found in some tropical rain forests. Rich in iron and aluminum but generally of poor fertility. Turns bricklike if exposed to sunlight.
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| Law of conservation of energy
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| See first law of thermodynamics.
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| Law of conservation of matter
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| Law stating that in chemical reactions, atoms are neither created, changed, nor destroyed; they are only rearranged.
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| Law of limiting factors
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| Also known as Liebig¡¦s law of minimums. A system may be limited by the absence or minimum amount (in terms of that needed) of any required factor. (See limiting factor.)
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| LD50
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| A chemical does lethal to 50 percent of a test population.
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| Leachate
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| The mixture of water and materials that are leaching.
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| Leaching
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| The process in which materials in or on the soil gradually dissolve and are carried by water seeping through the soil. It may result in the removal of valuable nutrients from the soil, or it may result in the removal of valuable nutrients from the soil, or it may carry buried wastes into groundwater, thereby contaminating it.
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| Legumes
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| The group of pod-bearing land plants that is virtually alone in its ability to fix nitrogen; includes such common plants as peas, beans, clovers, alfalfa, and locust trees but no major cereal grains. (See nitrogen fixation.)
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| Less-developed countries (LDC)
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| Nonindustrialized nations characterized by low per capita income, high birthrates and death rates, high population growth rates, and low levels of technological development.
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| Liebig¡¦s law of minimums
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| See law of limiting factors.
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| Life span
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| The longest period of life reached by a type of organism.
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| Lifeboat ethic
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| An argument that suggests we should limit the amount of food aid to high-population countries in order to prevent further population growth.
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| Life-cycle analysis
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| Evaluation of material and energy inputs and outputs at each stage of manufacture, use, and disposal of a product.
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| Life-expectancy
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| The average age that a newborn infant can expect to attain in a particular time and place.
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| Light water reactor
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| Most common fission reactor for generating electricity. Water bathes the core of the reactor and is used to generate steam, which turns the turbines that generate electricity. Contrast with liquid metal fast breeder.
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| Light year
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| Astronomical unit that measured the distance that light can travel in a year.
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| Lignite
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| Soft, brown to black coal of low BTU value with original plant components still discernible.
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| Limiting factor
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| A factor primarily responsible for determining the growth and/or reproduction of an organism or a population. The limiting factor may be a physical factor such as temperature or light, a chemical factor such as a particular nutrient, or a biological factor such as a competing species. The limiting factor may differ at different times and places.
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| Limits of tolerance
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| The extremes of any factor, e.g., temperature, that an organism or a population can tolerate and still survive and reproduce.
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| Limnetic zone
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| Open water zone of lakes through which sunlight penetrates; contains algae and other microscopic organisms that feed on dissolved nutrients.
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| Lipid
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| A nonpolar organic compound that is insoluble in water but soluble in solvents, such as alcohol and ether; includes fats, oils, steroids, phospholipids, and carotenoids.
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| Liquefaction
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| Production of liquid fuel from coal.
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| Liquid metal fast breeder
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| A nuclear power plant that converts uranium 238 to plutonium 239; thus, it creates more nuclear fuel than it consumes. Because of the extreme heat and density of its core, the breeder uses liquid sodium as a coolant.
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| Lithosphere
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| Crust of the earth. Contrast with hydrosphere and atmosphere.
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| Litter
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| In an ecosystem, the natural cover if dead leaves, twigs, and other dead plant material. This natural litter is subject to rapid decomposition and recycling in the ecosystem, whereas human litter, such as bottles, cans and plastics, is not.
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| Littoral drift
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| Movement of beach sand parallel to the shoreline. Caused by waves and longshore currents parallel to the beach.
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| Littoral zone
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| Shallow waters along a lakeshore where rooted vegetation often grows.
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| Livability
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| A subjective index of how viable a city is for enjoyable living.
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| Loam
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| A solid consisting of a mixture of about 40% sand, 40% silt, and 20% clay.
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| Logistic growth
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| Growth rates regulated by internal and external factors that establish an equilibrium with environmental resources. See S curve.
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| Longevity
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| The length or duration of life; compare to survivorship.
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| Low-head hydropower
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| Small-scale hydro technology that can extract energy from small headwater dams; causes much less ecological damage.
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| Low-quality energy
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| Diffuse, dispersed energy at a low temperature that is difficult to gather and use for productive purposes.
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| LULU (¡§locally unwanted land use¡¨)
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| Expresses and difficulty in siting a facility that is necessary but which no one wants in the immediate locality.
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