Figure 23.4 Declining North American mammals. When researchers created species–area curves of North American mammals from different geographic regions before and after human arrival, they discovered that from 11,500 to 500 years ago the number of mammals declined anywhere from 15 to 42 percent, depending on the geographic region examined.

Data from M. A. Carrasco et al., Quantifying the extent of North American mammal extinction relative to the pre-anthropogenic baseline, PLoS One 4 (2009): e8331.