It affects climate significantly, in part because the forest plays a major role in the water cycle, recycling rain back into the clouds as it receives rainfall. As a result, when the land is cleared, flooding and drought become serious problems, as rainwater travels quickly through the ground without the forest to regulate it. It threatens the existence of indigenous peoples. There have been more extinctions of tribal peoples in this century than any other, with Brazil losing 87 tribes between 1900 and 1950. Deforestation robs the world of countless species, destroying crucial biodiversity and losing species with potential uses in medicine, agriculture and industry.
Biodiversity is important because it contributes to resiliency.
A world without biodiversity would be fragile and likely to amplify disturbance into catastrophe through the collapse of ecosystems that had lost keystone species. Thus, biodiversity reduction, combined with climate change, has the potential to spin out of control and to threaten the prosperity of global civilization. Already the scale of biodiversity caused by the present generation of human activities ranks with the great prehistoric extinctions. Recovery from this level of disturbance will require tens of millions of years. At the close of the twentieth century, the world finds itself undergoing the most rapid and complete deforestation it has ever expierenced under the human hand.