The term for the gradual process of change in ecosystems over time is called ecological succession. This process involves a series of stages where one community of organisms gradually replaces another, often following disturbances such as fires, floods, or human activity. There are two main types of succession: primary succession, which occurs in lifeless areas, and secondary succession, which occurs in areas where a disturbance has destroyed a community but left the soil intact. Succession is essential for ecosystem recovery and regeneration, shaping biodiversity and environmental complexity over time.