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

Recent analyses of human impacts on Amazonian landscapes have focused prima rily on upland forests that have been deforested as roads have penetrated t he frontier. In contrast, relatively little priority has been given to docu menting and understanding landscape changes in the roughly 400 000 km(2) of Amazonia's floodplains, where an extensive network of waterways has long p rovided the transportation infrastructure. Amazonian floodplains generally support higher rural population densities than the uplands and provide crit ical habitat and food for fish and shrimp species, a principal source of pr otein for millions of rural and urban Amazonians. We examined cover type ch anges in a 52 304 ha tidal floodplain near the mouth of the Amazon River in Amapa, Brazil (tidal range = 2-3 m). We found five major cover types disce rnible in both black-and-white infrared aerial photographs taken in October -November 1976, and Landsat Thematic Mapper (TM) data from November 1991. T he 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 varzea forest. From 1976 to 1991, the ar eal extent of the aquatic, herbaceous, early regrowth and degraded forest, and palm forest cover types increased from 2833 to 3406, 10708 to 15074, 38 42 to 5446, and 1250 to 3208 ha, respectively, while the areal extent of th e mixed species varzea forest decreased from 33 671 to 25 170 ha. Logging, heart-of-palm. extraction and agricultural conversion are interacting distu rbances which, combined with the rapid regrowth that occurs in the tidal fl oodplains of Amazonia, have produced a landscape characterized by a high ra te of cover type transitions and a substantial loss of the mixed species va rzea forest. The annualized forest conversion rate is comparable to that re ported elsewhere for upland Amazonian landscapes. (C) 2001 Elsevier Science B.V. All rights reserved.