Desertification refers to the gradual ecosystem degradation, where plants and animals, and geological resources such as water and soil, are stressed beyond their ability to adjust to changing conditions.
Desertification is caused by by various factors such as overgrazing, urbinization, overdrafting of ground water, deforestation, tillage practices and natural disasters among other factors.
<em>Desertification affects the ground water reserves, topsoil, human, surface runoff, animal and plant populations.</em>
Topsoil is usually the riches soil in terms of nutrient is important in support of plant vegetation. It is rich because it contains humus and other decomposed materials that recycle nutrients. When the topsoil is washed away, the local region becomes barren in that it cannot support vegetation. This causes the area to turn into a desert.
The main difference between cells and viruses is that viruses need another cell to infect so that they can reproduce. Cells on the other hand can reproduce on their own.
