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FIGURE 6.6 Scenarios of the future of the Brazilian Amazon [after Laurance et al. (2001)]. (a) Optimistic scenario. (b) Pessimistic scenario. The intensity of shading reflects the relative intensity of human impacts. See text for description of these impacts. (c) Relative sizes of species ranges for some highly abundant species, on same scale as maps of the Brazilian Amazon.

FIGURE 6.6 Scenarios of the future of the Brazilian Amazon [after Laurance et al. (2001)]. (a) Optimistic scenario. (b) Pessimistic scenario. The intensity of shading reflects the relative intensity of human impacts. See text for description of these impacts. (c) Relative sizes of species ranges for some highly abundant species, on same scale as maps of the Brazilian Amazon.

must proceed. Whatever the accuracy of our extinction rate estimates, we believe that estimates informed by theory on the distribution of relative tree-species abundance and species range sizes are likely to be more accurate than estimates not based on such information. The two most difficult issues are: (i) we do not know where the species whose ranges we can estimate are physically located in the Amazon and (ii), perhaps more important, we do not know how each of these tree species will respond to each of the land-use categories.

Faced with these information challenges, we have taken the following approach. With regard to the first problem, the best we can currently do is to perform a large ensemble of stochastic simulations in which we assign locations of all species in the metacommunity randomly throughout the Brazilian Amazon and then average the extinction results over these simulations. In each stochastic simulation, we assigned the centroids of the species ranges at random locations and then calculated the number of pixels of each land-use category that lay within the calculated range size for the species of a given abundance. For species with <102 individu-



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