Global Change and Our Common Future Papers from a Forum (1989) / Chapter Skim
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15. Deforestation and Its Role in Possible Changes in the Brazilian Amazon
15. Deforestation and Its Role in Possible Changes in the Brazilian Amazon
Pages 159-171
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From page 159... ...
The Amazon, the richest and most diverse ecosystem on the planet, is presently undergoing rapid transformations due to the expansion of new settlements undertaking diverse activities. CAUSES FOR DEFORESTATION In the beginning of the colonization of Brazil by Europeans in 1530, and in the centuries thereafter, deforestation in Amazonia was the consequence of very few and small-scale human activities.
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From page 160... ...
THE EXTENT OF DEFORESTATION One of the most controversial issues recently in the literature, and in the past few months in the Brazilian and international press, has been the extent to which the Amazon region is being deforested. The increastng international concern, as well as the increasing scientific awareness of the role of the tropical forest in future environmental global changes, is the major driving force behind these discussions.
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From page 161... ...
Assuming the above to be realistic and that the pattern will continue, curve extrapolations show that by the year 2000 most of the Amazonian states will have had their territory completely cleared. DEFORESTATION AND ITS POSSIBLE PHYSICAL AND BIOLOGICAL CONSEQUENCES Biodiversity As stated by Myers (1988a)
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From page 162... ...
This enormous diversity should serve as the basis for not considering tropical forests as mere sources of wasteful exploitation; much more attention should be paid to what this environment represents to our planet and to the necessity to preserve it. Apart from soil protection and balance of the hydrological cycle, forests are not only sources of timber and fuel wood, but they also can provide many other products like resins, essential and edible oils, fruits and nuts, natural fibers, and
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From page 163... ...
1 600 400 2nn Total Legal Amazon t 1970 1 975 1980 1985 1990 YEAR FIGURE 15.1 Deforestation trends in selects (Data extracted from Mahar, 1988.) d areas of the Amazon region.
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From page 164... ...
, where a substantial part of the region has already been completely cleared. Hydrological Cycle and Climate Figure 15.2 schematically shows the water balance for the Amazon basin, including an area of approximately 6 million km2 from the river mouth at Marajo Island to the headwaters at "Cordilheira dos Andes.' The data shown in Figure 15.2, although carrying uncertainties and errors due to the lack of a measuring network with a good spatial distribution over the basin, were obtained through successive approaches using different methods and techniques (Salati, 1986~.
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From page 165... ...
For example, although it was difficult to predict at the time, the sedimentological studies done for the construction of the Samuel power dam in Rondonia did not take into account the possible changes in land use and their consequences for the sediment load of the Rio Jamari. Studies that are currently being carried out using the 210Pb technique to calculate the sedimentation rate in a lake near the dam are showing increases in the rates that might be closely correlated with deforestation and/or tin mining activities in the basin (B.
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From page 166... ...
It should be noted, however, that Rondonia rivers carry very little sediment and could therefore be useful if used as monitors of the rapid deforestation that is occurring in their basins. Carbon Dioxide Emissions Changing the forest cover to other land use systems transfers substantial quantities of carbon stored in the biomass to the atmosphere, potentially increasing the greenhouse effect (Houghton et al., 1987~.
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From page 167... ...
(tons/km2 per yr) Amazon Vargem Grande 47.9 647 571 Obidos 159.0 1156 250 Tributaries Iga 7.4 19 127 Jutai 1.4 2 23 Jurua 3.0 26 116 Japura 13.9 23 79 Purus 10.8 29 78 Negro 30.8 6 8 Madeira Main channel Tributaries Pimenta Bueno Jiparana 29.2 488 357 0.245 0.17 0.875 0.75 Jaru 0.081 0.03 14 23 6 200 tons of carbon per hectare if it is assumed that biomass contains 50 percent carbon.
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From page 168... ...
It is therefore still difficult to visualize the entire Amazonian ecosystem as a whole. The lack of knowledge of the basic functioning mechanisms of the Amazonian ecosystem and of the most suitable methods for sustainable development of the region are the main reasons for the failure of many of the agricultural and cattle ranching
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From page 169... ...
o An expansion of international support to research groups and institutions dedicated to the study of the basic functioning mechanisms of the ecosystem, especially those with programs already under way for a considerable time. o The design of integrated interdisciplinary regional programs to study the factors affecting the steady state equilibrium of the entire ecosystem.
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From page 170... ...
1989. Avaliagao da alteragao da cobertura florestal na Amazonia utilizando sensoriamento remoto orbital.
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From page 171... ...
1987. Censos Demograficos das Unidades que compoem a Amazonia Legal.
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