further biotic pressure. A familiar example from the land is the pattern of development of forests in the southeastern U.S. hardwood forests are the climax community, the end product of a successional sequence of tree communities. If a fire should destroy a forest, the area is recolonized by grasses and then pines, both of which require intense sunlight and cannot grow under a forest canopy. The forest gradually becomes dominated by pines, then by a mixed stand of large pines and young hardwoods until the climax hardwood forest is finally reached. The whole process of recovery to the pre-fire condition through biological succession may take more than a century.

In marine communities succession is generally a much more rapid phenomenon, but recovery through succession may still take several years. On British rocky shores there exists a balanced community of barnacles, mussels, rockweed (large brown algae), and algal grazers, particularly limpets. The grazers keep algal growth firmly in check, restricting the amount of rock surface covered with algae by grazing on algal sporelings. On heavily oiled and vigorously cleaned shores of Cornwall all the limpets were killed and within two or three months they became clothed with green algae, which are otherwise not abundant on these shores (). During the following year, a vigorous growth of the characteristic rockweeds replaced this "green phase." Young limpets began to reappear but were unable to graze the large algae, so that an unusually dense cover of seaweeds persisted three to four years later.

Similarly, the Tampico Maru spill killed many sea urchins that, through grazing on sporelings, had prevented the development of extensive kelp beds prior to the spill (). Following the spill the diminished grazing pressure allowed kelp sporelings to survive and dense kelp beds to form throughout the affected cove. The distribution of kelp in the cove did not return to its pre-spill pattern for six years.

The length of time necessary for successional recovery of an oiled marine community ranges from weeks or months to perhaps a decade. This will depend on the structural complexity of the community and the degree of initial damage. Of course, persistent contamination by petroleum hydrocarbons, frequent spills, or chronic pollution may hinder natural succession, appreciably delaying recovery.