A clear example of dispersal: Krakatau.

In 1883 all the plants and animals on the small island of Krakatau (pictured opposite in more recent times) were killed by being covered in the ash from a huge volcanic eruption. Biologists recorded the recolonization of the island: the recolonization was rapid, and provides good evidence for the power of dispersal.

Fifty years later, the island was already re-covered with tropical forest, which supported 271 plant species and 31 bird species. The immigrants mainly came from the neighboring islands of Java (40 km away) and Sumatra (80 km away); the birds would have dispersed by active flight and the plants would have been carried as seeds. Dispersal, therefore, in the right circumstances can have a clear effect on the ranges of species.