Air is then breathed into the windpipe and lungs, while the mucus is swallowed (figure 3). Other. Other interesting structures associated with the nasal and sinus tract: Tear duct (called the nasolacrimal duct): drains tears from the inside corner of the eye into the nasal cavity (figure 1).
Human activity is the main cause of soil degradation. Agriculture plays a large part in soil degradation, especially clearing, irrigation, the spreading of chemical fertilizer â¦ s and pesticides, overgrazing and even the passage of heavy farming equipment. Tillage and the clearing and deforestation of large plots of land also lead to soil degradation.
More than half of the dry areas worldwide are. affected by land degradation (Dregne and Chou, 1994). Although water erosion is the. dominant human-induced soil degradation process, an extent of 0.8 million km2 suffers from. secondary salinization caused by land mismanagement, with 58% of these in irrigated areas. alone, and nearly 20% of all irrigated land is salt affected (Ghassemi et al ., 1995).