Because deforestation basically involves killing trees in forests, there are so many effects that can be enumerated as results of the activity. Effects of deforestation can be classified and grouped into effects to biodiversity, environment and social settings.
When forests are cuted down, nature basically requires people to renew the forest. Reforestation is proven to be a much harder effort than deforestation. It is one concept that is in the opposite direction as deforestation.
So the rate of deforestation has not been offset by the rate of reforestation. Thus, the world is now in a troubled state when it comes to issues concerning the environment.
Pollution is rapidly growing along with population. Forests are greatly helping reduce the amount of pollutants in the air. So, the depletion of these groups of trees is greatly increasing the risk that carbon monoxide would reach the atmosphere and result in the depletion of the ozone layer, which in turn results to global warming.
Second is the long process of global climate change. As mentioned above, deforestation has been found to contribute to global warming or that process when climates around the world become warmer as more harmful rays of the sun comes in through the atmosphere.
The ozone layer is a mass of oxygen or O3 atoms that serves as shield in the atmosphere against the harmful ultraviolet rays from the sun. Because ozone is made up of oxygen atoms, oxygen react with carbon monoxide. Such reaction would use up oxygen atoms.
It follows that when there are more carbon monoxide atoms going to the atmosphere, the volume of oxygen would decline. Such is the case of ozone depletion.
The third effect to the environment would be on the water table underneath the ground. Water table is the common source of natural drinking water by people living around forests.
Water table is replenishing. That means, the supply of water underground could also dry up if not replenished regularly. When there is rain, forests hold much of the rainfall to the soil through their roots.
Thus, water sinks in deeper to the ground, and eventually replenishing the supply of water in the water table. Now, imagine what happens when there is not enough forests anymore. Water from rain would simply flow through the soil surface and not be retained by the soil.
Or other than that, the water from rain would not stay in the soil longer, for the process of evaporation would immediately set in. Thus, the water table is not replenished, leading to drying up of wells.
Effect to biodiversity
Through the years, it is estimated that there are millions of plant and extinct animal species that have been wiped out because they have been deprived of home. Thus, biodiversity is significantly lowered because of the savage deforestation practices of some people.
Wildlife advocates have been constantly reminding that several wild animals left in the world could still be saved if deforested forests would only be reforested and the practice of slash and burn of forests would be totally abandoned.
Social effects of deforestation
Deforestation is hardly hitting the living conditions of indigenous people who consider forests as their primary habitats. Imagine how they are rendered homeless when forests are depleted. These natives would be forced to live elsewhere, and are usually left to becoming mendicants in rural and urban areas.
Overall, effects of deforestation cannot be offset by the contribution of the practice to development. While it is logical that progress is very much needed by mankind, it must also be noted that nature knows no defeat. Destruct it and it would certainly retaliate, one way or another.