ECOLOGICAL REASONS

Deforestation results in declines in biodiversity.[38] The removal or destruction of areas of forest cover has resulted in a degraded environment with reduced biodiversity.[39] Forests support biodiversity, providing habitat for wildlife;[40] moreover, forests foster medicinal conservation.[41] With forest biotopes being irreplaceable source of new drugs (such as taxol), deforestation can destroy genetic variations (such as crop resistance) irretrievably.[42]
Since the tropical rainforests are the most diverse ecosystems on Earth[43][44] and about 80% of the world's known biodiversity could be found in tropical rainforests,[45][46] removal or destruction of significant areas of forest cover has resulted in a degraded[47] environment with reduced biodiversity.[48]
Scientific understanding of the process of extinction is insufficient to accurately make predictions about the impact of deforestation on biodiversity.[49] Most predictions of forestry related biodiversity loss are based on species-area models, with an underlying assumption that as forest are declines species diversity will decline similarly.[50] However, many such models have been proven to be wrong and loss of habitat does not necessarily lead to large scale loss of species.[51] Species-area models are known to overpredict the number of species known to be threatened in areas where actual deforestation is ongoing, and greatly overpredict the number of threatened species that are widespread.[52]SOURCEhttp://en.wikipedia.org/wiki/Deforestation