Deforestation affects biological diversity in three ways.
The destruction of habitat forces species out of areas, or causes them to die. Isolation or fragmentation restricts their range, exposing them to disease or predators with whom they are not accustomed. Edge effects create boundary zones, where they are exposed to wind, to extremes of temperature, and there is access to the forest by non-forest animals, livestock, and humans. The result of this is the net loss of plant and animal species, especially in edge areas. While deforestation is the most easily seen problem, isolation and edge effects compound its impact, and aggravate the extinction of species.