]> The presence of substances in the atmosphere, particularly those that do not occur naturally Air Pollution Phenomenon particularly associated with smog episodes in cities such as Denver, Colorado. Particles suspended, reducing visibility by scattering light; often a mixture of aerosols and photochemical smog. Type of air pollution, such as Los Angeles smog, associated with the buildup of oxidation products formed from the degradation of hydrocarbons, etc. A haze created by the presence of finely divided particles of sea salt in the air, usually derived from the evaporation of sea spray. Reduced visibility in the atmospheric boundary layer caused by suspended particles of soil, mixed into the air during strong winds. A natural fog contaminated by industrial pollutants, a mixture of smoke and fog. The movement of salt water into fresh water aquifers. Process by which saline water underlying freshwater in an aquifer rises upward into the freshwater zone as a result of pumping water from the freshwater zone. Habitat fragmentation is a process of environmental change important in evolution and conservation biology. As the name implies, it describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat). Habitat fragmentation can be caused by geological processes that slowly alter the layout of the physical environment or by human activity such as land conversion, which can alter the environment on a much faster time scale. The former is suspected of being one of the major causes of speciation. The latter is causative in extinctions of many species. Habitat fragmentation is frequently caused by humans when native vegetation is cleared for human activities such as agriculture, rural development or urbanization. Habitats which were once continuous become divided into separate fragments. After intensive clearing, the separate fragments tend to be very small islands isolated from each other by crop land, pasture, pavement, or even barren land. The latter is often the result of slash and burn farming in tropical forests. The term habitat fragmentation can be considered to include six discrete processes: Reduction in the total area of the habitat, increase in the amount of edge, decrease in the amount of interior habitat, isolation of one habitat fragment from other areas of habitat, breaking up of one patch of habitat into several smaller patches, and Decrease in the average size of each patch of habitat.