Ecological succession is the process that describes how the structure of a biological community (that is, an interacting group of various species in a desert, forest, grassland, marine environment, and so on) changes over time. Species that arrive first in a newly created environment (such as an island rising out of the sea) are called pioneer species, and they, through their interactions with one another, build a rather simple initial biological community. The structure of this community becomes more complex as new species arrive on the scene.
At every stage there are certain species that have evolved life histories to exploit the particular conditions of the community. This situation imposes a partially predictable sequence of change in the physical environment and species composition of communities.