Ecological succession refers to the gradual and predictable process of change in the composition of species in an ecosystem over time. In general, ecological succession tends to lead to an increase in species diversity, meaning that more and more different types of organisms become established and thrive within the ecosystem.
This is because ecological succession typically begins with the colonization of the area by a relatively small number of pioneering species that are well-suited to the harsh conditions of the newly-formed or disturbed environment. Over time, these species modify the environment in ways that make it more hospitable to other, less hardy species, which then begin to colonize the area as well. As this process continues, the number and variety of species within the ecosystem tends to increase, leading to greater overall diversity.
Of course, there are many factors that can influence the course and outcome of ecological succession, and not all successions will result in the same patterns of species diversity. However, in general, an increase in species diversity is one of the most common and noticeable outcomes of ecological succession.