Final answer:
The current extinction crisis is 500-1000 times higher than the background rate of extinction in Earth's history and is caused by human activity. This event, known as the sixth mass extinction, is comparable in scale to previous mass extinctions but is solely the result of human actions.
Step-by-step explanation:
The current extinction crisis can be understood in a geological context. Biologists estimate that the rate of species extinctions today is 500-1000 times higher than the background rate of extinction in Earth's history.
This high rate of extinction is primarily caused by human activity, such as habitat destruction, introduction of exotic species, and over-harvesting. The current extinction event, referred to as the sixth mass extinction, is comparable in scale to previous mass extinctions, but unlike those events, it is solely the result of human actions.