| Ultimate production
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| Total amount of a nonrenewable resource that could ultimately be extracted at a reasonable price.
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| Ultraviolet radiation
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| Radiation similar to light but with wavelengths slightly shorter than violet light and with more energy. The greater energy causes it to severely burn and otherwise damage biological tissues.
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| Unconventional air pollutants
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| Toxic or hazardous substances, such as asbestos, benzene beryllium, mercury, polychlorinated biphenyls, and vinyl chloride, not listed in the original Clean Air Act because they were not released in large quantities; also called noncriteria pollutants.
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| Unconventional oil
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| Resources such as shale oil and tar sands that can be liquefied and used like oil.
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| Underground storage tanks
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| The tanks used to store pertroleum products at service stations, now subject to mandated protection against leakage. See UST legislation.
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| Undernutrition
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| A form of hunger in which there is a lack of adequate food energy as measured in calories. Starvation is the most severe form of undernutrition.
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| Undernourished
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| Those who receive less than 90 percent of the minimum dietary intake over a long-term time period; they lack energy for an active, productive life and are more susceptible to infectious diseases.
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| Undiscovered resources
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| Speculative or inferred resources or those that we havenˇ¦t even thought about.
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| Universalists
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| Those who believe that some fundamental ethical principles are universal and unchanging. In this vision, these principles are valid regardless of the context or situation.
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| Upwelling
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| Convection currents within a body of water that carry nutrients from bottom sediments toward the surface.
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| Urban area
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| An area in which a majority of the people are not directly dependent on natural resource-based occupations.
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| Urbanization
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| An increasing concentration of the population in cities and a transformation of land use to an urban pattern of organization.
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| Urban blight/decay
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| General deterioration of structures and facilities such as buildings and roadways, in addition to the decline in quality of services such as education, that has occurred in inner city areas where growth has been focused on suburbs and exurbs.
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| Urban renewal
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| Programs to revitalize old blighted sections of inner cities.
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| Urban sprawl
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| The rapid expansion of metropolitan areas through building housing developments and shopping centers farther and farther from urban centers and lacing them together with more and more major highways. Widespread development that has occurred without any overall land-use plan.
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| UST legislation
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| Amendments to the Resources Conservation and Recovery Act of 1976, passed in 1984 to address the mounting problem of leaking underground storage tanks (USTs).
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| Utilitarian conservation
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| A philosophy that resources should be used for the greatest good for the greatest number for the longest time.
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| Utilitarianism
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| See utilitarian conservation.
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