When a forest fire destroys hundreds of acres of the biosphere or a volcano erupts and kills all the living organisms around it by burying them under several meters of volcanic rock, the lifeless land does not stay dead for long.

Just months after Mount Saint Helens erupted in 1980, destroying the forests around it for tens of kilometers, new plants started to grow and bring the area back to life. Today, in many of the areas around the volcano, it is possible to find not only young trees but also insects, birds and other animals living where there was once just rock. How did such a transformation happen? The secret is in dispersal.

Dispersal is the name given to the techniques that living organisms use to populate new areas. In order for plants to grow in devastated lands around volcanoes or forest fires, seeds have to be brought there to bring the area back to life. This chapter will explain how plants use seeds and other devices to colonize a new area.

Other Reasons for Dispersal

In order to survive, plants need sunlight, water, and minerals. If a young plant wants to get these things without taking them from its parent plant, it should not grow too close to the parent. For example, a chestnut tree which starts to grow directly under its parent will not get very much sunlight because it is under the shade of the leaves of its parent tree. In addition, any minerals or water in the soil will be taken by the parent tree's roots and not much will be left for the young sapling.

To avoid these problems of competition, plants find different ways of sending their seeds far enough away from the parents so that the new generation of plants will not compete with them for sunlight, water, or minerals. After many generations, a single species of plants can colonize an area and spread out over vast areas. This process of spreading out is called dispersal and it is the best way for living organisms to survive because it allows them to find new sources of water, food, or sunlight.

Plants cannot easily move themselves from place to place in order to disperse. Plants' bodies are not adapted for locomotion. The roots of plants dig into the soil to absorb water and minerals and their branches and leaves spread out to catch the sunlight. For plants to arrive at a new habitat, they need an appropriate method of dispersal.