Abstract
The Amazon Basin contains the largest extent of tropical forest on Earth, over 5 × 106 km2, and accounts for a large proportion of the planefs animal and plant species. It also contains over 2 × 106 km2 of savanna Vegetation to the north and to the south of the domain of the tropical forest. The annual discharge of the River Amazon into the Atlantic Ocean of more than 200 000 m3 s-1 contributes about 18% of the global flow of fresh water into the oceans. It is thought that humans have inhabited tropical South America for at least 12 000 years, but their impact on the Vegetation cover was quite small from immemorial times to about 1950. By the time the Europeans arrived in this continent 500 years ago, there were several million indigenous people living in Amazonia. Their impact on the Vegetation cover was negligible because they practised small-scale shifting and burning agriculture. Because many tribes selected useful plant species to grow near their dwellings (for instance, the Kayapo “gardening”), it is thought that the species composition and distribution have gradually changed from pre-historical times but with little overall effect on the Vegetation cover. For most of the last 500 years, the forests of Amazonia were left untouched, including the period known as the “rubber boom” (second half of the 19U1 Century to about 1910). During that period, the river System was used to bring hundreds of thousand of workers to the far-distant portions of the forest to tap the rubber tree,but land Clearing was not significant. In fact, after the demise of the rubber boom by 1910 many workers settled along the river corridors, and borrowed many of the habits from the indigenous tribes that they had displaced such as adopting small-scale shifting and burning agriculture, and having fish as their main protein source. In summary, they caused only negligible disturbance to the forest and by the 1950s only about 1% of the forest of Amazonia had been cleared.