Ecological succession is the process through which ecosystems change and develop over time. It can be either primary or secondary succession. Primary succession occurs in areas where no life existed before, such as on bare rock after a volcanic eruption. Secondary succession occurs in areas where there was previous life, such as following a forest fire. In both cases, the process involves a series of stages where different species gradually replace one another until a stable community is established. This process can take hundreds to thousands of years depending on the ecosystem and environmental conditions.