ABSTRACT
Global forest cover is estimated to have decreased by around 40% since preagricultural times (Bryant, Nielson, and Tangley 1997). However, because defining deforestation is problematic, one should not rely too heavily on any exact figure. Some authors focus on forest degradation, which refers to any decrease in density or disturbance of the forest ecosystem. It is not uncommon for loggers to remove some (particularly valuable) trees, which then opens up an area to ecological and economic changes such as road building, which brings immigration, agriculture, and additional forest clearing. Fewer than 40% of forests globally are relatively undisturbed by human action.
