The dry zones in the world are those zones that lie between 15°to 35° latitude of both hemispheres. A large part of the dry zone is in the North Africa, Central Australia, Western Asia, Western part of North America and Mid-south of the South America.

Latitude controls the climate by determining the slope and incidence of the sunrays. They slant extensively towards far north or far south. Slanting rays spread over and heat larger regions, but has low intensity, as on the poles. But the vertical rays cover and heat a smaller area intensively as on the equator. Here, higher the altitude, less intense is the heat. Indonesia has hotter climate than Nepal because it is near to the equator in comparison to Nepal.

The factors affecting climate are latitude, altitude, land and water distribution, distance from the sea, distance from the sun, prevailing winds and ocean currents, surface covering the land, volcanism, solar constant sunspots, wind direction and nature of mountain chains, mountain barriers.

Deforestation causes adverse effects on environment. They can be presented in the following points:

  1. The habitat of animal decreased and hence they will perish.
  2. The sources of food for human beings decreases and many people die of starvation.
  3. There will be lack of fuel, wood, timber and fodder for the domestic animals.
  4. Ecosystem gets disturbed due to imbalance in the number of living beings.
  5. Environment imbalance occurs owing to the disturbance in living and non-living beings.
  6. Flood, landslide, soil erosion and various kinds of pollution increases due to deforestation.
The nature of vegetation differs in terms of climate variation. Nepal is one suitable example to prove this fact. Nepal is a small country but there is a clear distinction of climatic variation because of the change of altitude. In the plain Terai, it's very hot having tropical type of vegetation with strong and big trees. The deposition of fertile soil makes it capable of having good cultivation.
Similarly, the increment in altitude towards the north brings variation in vegetation. The sloppy, gentle hills have moderate climate with moderate number of vegetation and suitable cash crops like tea, cardamom, potato, Coffee, ginger, etc. The availability of water also makes it normally moderate in vegetation with deciduous trees.
On the other hand, the snow clad and extremely cold climate in the far narth has poor vegetation. Except rare crops in the Himalayan region, we find coniferous trees with soft nature.