The causes of extinction are (mostly) fairly obvious, and my first set of notes touched on one of the largest ones all ready--habitat destruction and conversion. But let's spend a little time reminding ourselves what the causes of extinction are, because knowing those causes helps us better to understand their consequences.
Wildlife trade, orchids and succulents
Predator control--Until 1952 the Bald Eagle had a price on its head. The grey wolf was eliminated in the United States except in Alaska and a small population in northern Minnesota by federal wildlife agents.6
Dams: Pacific northwest salmon fishery has declined dramatically in the last 50 years. Many runs are now listed (or proposed for listing) under the Endangered Species Act. Nearly 30% of the ca. 1400 historical populations are extinct (14% of populations from coastal regions, 55% from interior regions) .
Deforestation (Table 1) is just one aspect of habitat conversion. Loss of grasslands and savannas may be equally extreme.
Wilcove, Rothstein, Dubow, Phillips, and Losos  surveyed recovery plans for species listed under the United States Endangered Species Act and categorized the threats they identified into one of five categories: habitat degradation/loss, alien species, pollution, overexploitation, and disease. Table 2 shows the percentage of listed species for which each of these five factors was mentioned as a cause contributing to endangerment.7
In short, many species are going extinct now to reasons related to human activities. We are responsible for the elevated rates of extinction, but they don't tell us how many species are going extinct.