Figure 3.

Extinction risks are hierarchical: they conspire to determine the risk of extinction for individual species. The transition from the mostly plaid ecosystems accompanying the tumultuous climatic regime of the ice age to the striped ecosystems of the climatically stable Holocene may have lowered the extinction thresholds for many megafaunal species because their life forms and life‐history strategies were no longer as adaptive as they had been during the ice age. Once these thresholds were lowered, individual species became more vulnerable to a variety of proximate threats, many of which had been only minor threats before.