What initiates primary succession in an ecosystem?

Primary succession starts in an area devoid of soil and life, such as after a volcanic eruption, glacial retreat, or the formation of a new island. This process begins when a substantial disturbance occurs in uninhabited land, allowing pioneer species like lichens and mosses to colonize the bare substrate. These organisms can withstand extreme conditions and help in soil formation by breaking down the rock and contributing organic material as they die and decompose. This eventual buildup of soil supports the growth of more complex plant species, leading to a more diverse ecosystem over time.

In contrast, smaller disturbances to existing ecosystems, human activities, or seasonal changes do not typically initiate primary succession. Instead, they may lead to secondary succession, where ecosystems recover and rebuild after disturbances but still retain some soil and life. In primary succession, the absence of existing biological communities is crucial, as it sets the stage for a completely new ecological framework to develop from scratch.