The impact of human activity on the biodiversity of the Eastern Amazon is considered, focussing on both terrestrial and aquatic based ecosystems of Pará State, Brazil. Selective logging is the most serious threat to the forest environment and structure, but the establishment of new cattle pastures also results in the complete removal of forest ecosystems. Alteration or complete destruction of the aquatic ecosystem are caused by gold prospecting projects and river damming to establish hydroelectric plants. In addition to the direct impact on individual species at the site of activity more distant pristine ecosystems may also be affected via air or water. The possible reconciliation of development and conservation projects in this region is discussed.