The Brazilian Amazon is conceived nowadays as a green ocean, containing one of the world's major river systems with a water course network of more than 6500 km and responsible for 20% of the world's river discharge to the oceans (Figure 3.1). The Amazon river system includes a large annually inundated floodplain, or varzea (Richey et al., 1990) which represents an important natural resource base for food and energy production to meet human needs.

The Amazon is presently home to about 20 million people, mainly distributed in large, medium and small size urban and rural developments along the roads and rivers and concentrated heavily in the eastern part of the region (Figure 3.2).

The area of the Brazilian Amazon extends for about 500 million ha (equivalent to about two-thirds the size of the continental United States of America) of which about 80% falls within the tropical forest zone. Deforestation is currently running at around 1.6 million ha per year and its distribution closely follows the road network as illustrated in Figure 3.3 (Alves, 1999).

Schneider et al. (2000), using data from the 1995–6 Agricultural Census, report on land use by rainfall zone in the Brazilian Amazon (Table 3.1). They observe that, of the area under agricultural use, pasture is the dominant system, representing nearly 80%.

The sheer size of the Amazon region gives it global importance but it is also important as one of the last great frontiers for ‘modern man’ where the natural vegetation is largely intact, representing a store of biodiversity and playing an important role in global processes such as climate, carbon and hydrological cycles.