The boundary where two or more different types of vegetation of successional stages meet is called edge.  Sometimes there is an abrupt change where one type of vegetation stops and another begins.  The change can be less distinct with a gradual transition from one stage to another. 

Is the picture to the right an example of an abrupt or gradual edge?  Mouse over the picture to find the answer.

An edge resembles both successional stages and vegetation types in places where a gradual change occurs.  The amount of edge is narrow where abrupt changes occur.  Edges attract many different species because the variety of food, cover, and other habitat requirements are arranged so close together.

Edges that are produced when extremely different successional stages of vegetation meet are defined as having high contrast.  There is high contrast where an area in stage 2 (annual forbs and grasses) meets an area in stage 6 (tall mature trees) of plant succession (picture above).  A boundary between stages 2 and 3 has low contrast.  Edges with low contrast will benefit those wildlife species that need an interspersion of several successional stages.  Edges with low contrast may have different species of wildlife than edges with high contrast.  In general, edge may benefit wildlife species that have low mobility and do not require large areas.  However, many landscapes already have sufficient edge.  Creation of more edge may be detrimental to some wildlife species, particularly area sensitive species.