Landscape change in tidal floodplains near the mouth of the Amazon River

Recent analyses of human impacts on Amazonian landscapes have focused primarily on upland forests that have been deforested as roads have penetrated the frontier. In contrast, relatively little priority has been given to documenting and understanding landscape changes in the roughly 400 000 km 2 of Amazônia’s floodplains, where an extensive network of waterways has long provided the transportation infrastructure. Amazonian floodplains generally support higher rural population densities than the uplands and provide critical habitat and food for fish and shrimp species, a principal source of protein for millions of rural and urban Amazonians. We examined cover type changes in a 52 304 ha tidal floodplain near the mouth of the Amazon River in Amapá, Brazil ( tidal range =2–3 m) . We found five major cover types discernible in both black-and-white infrared aerial photographs taken in October–November 1976, and Landsat Thematic Mapper (TM) data from November 1991. The cover types were: (1) water and unvegetated banks, (2) herbaceous cover, both natural and agricultural, (3) early regrowth or degraded forest, (4) palm forest, and (5) mixed species várzea forest. From 1976 to 1991, the areal extent of the aquatic, herbaceous, early regrowth and degraded forest, and palm forest cover types increased from 2833 to 3406, 10708 to 15074, 3842 to 5446, and 1250 to 3208 ha, respectively, while the areal extent of the mixed species várzea forest decreased from 33 671 to 25 170 ha. Logging, heart-of-palm extraction and agricultural conversion are interacting disturbances which, combined with the rapid regrowth that occurs in the tidal floodplains of Amazônia, have produced a landscape characterized by a high rate of cover type transitions and a substantial loss of the mixed species várzea forest. The annualized forest conversion rate is comparable to that reported elsewhere for upland Amazonian landscapes.