Landscape change in
tidal floodplains near the mouth of the Amazon River
Daniel J. Zarin, Valeria F. G. Pereira, Hugh Raffles,
Fernando G. Rabelo, Miguel Pinedo-Vasquez
and Russell G. Congalton
Summary of Points:
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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 km2 of
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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.
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The study examined cover type changes in a 52,304 ha tidal
floodplain near the mouth of the
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We found five major cover types discernible in both
black-and-white infrared aerial photographs taken in OctoberŻNovember
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.
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From 1976 to 1991, the areal extent of
the aquatic, herbaceous, early regrowth and degraded
forest, and palm forest cover types increased from 2,833 to 3,406, 10,708 to
15,074, 3,842 to 5,446, and 1,250 to 3,208 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.
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