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landed, extinctions (especially of birds) and wholesale habitat destruction have shortly followed.

RESULTS AND DISCUSSION

Species Loss vs. Human Population Growth

The numbers of megafauna species lost were modest until the human growth curve began its rapid exponential rise between 15.5 and 11.5 kyr B.P. (Fig. 12.2). Then, species losses accelerated, primarily in the Americas, until the non-human megafauna baseline leveled off at 183 species, where it more or less remains today. However, human population continued to rise dramatically even after the counts of non-human megafauna species stabilized.

Biomass Crash

When converted to biomass, the inverse relationship between humans and non-human megafauna is evident (Fig. 12.3). Non-human megafauna biomass fell dramatically between 15.5 and 11.5 kyr B.P., concomitant with the initial steep rise in human biomass.

Summing the biomass calculated for humans and nonmegafauna species provides a way to track changes in overall megafauna biomass through time (Fig. 12.4). The results suggest that biomass loss from the early megafauna extinctions in Australia and the first pulse of extinc-

FIGURE 12.2 Number of non-human megafauna species that went extinct through time plotted against estimated population growth of humans.

FIGURE 12.2 Number of non-human megafauna species that went extinct through time plotted against estimated population growth of humans.



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