A zone around a star where the temperature would be in the range 0-100 °C to sustain liquid water on the surface of rocky planets (or sufficiently large moons). Water is thought to be a necessary comp
onent to the formation and evolution of Earth-type life. This zone depends on the parent star's luminosity and distance; it will be farther from hotter stars. A more accurate definition of a Habitable Zone needs to include other factors, such as orbital eccentricity, heat sources other than stellar irradiation, and atmospheric properties.
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 org
anism'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.
A strong wind and sandstorm or duststorm in northern and central Sudan, especially around Khartoum, where the average number is about 24 a year. The name comes from the Arabic word habb, meaning ?wind
.? Haboobs are most frequent from May through September, especially in June, but they have occurred in every month except November. Their average duration is three hours; they are most severe in April and May when the soil is driest. They may approach from any direction, but most commonly from the north in winter and from the south, southeast, or east in summer. The average maximum wind velocity is over 13 m s-1 (30 mph) and a speed of 28 m s-1 (62 mph) has been recorded. The sand and dust form a dense whirling wall that may be 1000 m (3000 ft) high; it is often preceded by isolated dust whirls. During these storms, enormous quantities of sand are deposited. Haboobs usually occur after a few days of rising temperature and falling pressure.