An important component to overall habitat health is called EDGE.
Edge is the transition zone, or ecotone, where one type of plant community “gives way” to another plant community. Wildlife managers like edge because it provides animals with simultaneous access to 2 or more vegetation types – where its likely several welfare factors are located.
Edge zones often support a more diverse wildlife community than the adjoining plant communities which is called the “edge effect”.
So what exactly is an edge? Think of how a mown field meets a forest. Or how your yard meets the trees out back, or a fence. There is an abrupt change from one thing to the next. Edge is a way to gradually transition from one type of vegetation to the next. For example, perhaps in our mown field – instead of mowing straight up to the forest – there are bushes and small trees between the field and the forest. Or in your yard – instead of going from lawn to fence or trees – you have shrubbery or garden beds – these areas are crucial to many species of animals and meet many of the habitat factors we discussed in the last post.
There are a few important characteristics of Edge Zones:
- Variety of Plants: with different types of plants present, edge zones are often sources of year-round food and cover!
- Depth of Edge: areas with little edge (abrupt) provide fewer welfare factors than areas with deeper edge zones.
- Length of Edges: population densities are positively related to the number of feet of edge in the plant community. The best measure of edge effect is through a study of length (or the distance around the plant communities).
Edge increases as an area is elongated from a circle to a narrow rectangle; a circular area has 11% less edge than a square acre. The more strip-like wildlife clearings are, the greater their edge effect will be!
The main functional component of edge is plant composition! With a variety of plants, edge zones are used by many game species – and the best part… you can create more at any time!
But be careful! We must not assume that the creation of more edge in landscapes will always have a positive effect on wildlife! For example:
- Incidents of nest predation and parasitism are HIGHER near edges than in the forest interior
- Edge areas will concentrate predators near edge zones
- Diseases of domestic animals in land adjacent to edges may spread to wild animals concentrated in edge zones more easily.
Some edges result from abrupt changes in soil type, topographic differences, geomorphic differences (such as rock outcrops), and micro-climate changes. Because adjoining vegetation types are determined by long-term natural features, such edges are usually stable and permanent and are called inherent edges.
Edges which develop as the result of disturbance (fires, logging, farming) and can only be maintained by periodic disturbances are called induced edges.
So which edge can you manage for? (Induced!) And between “soft” and “hard” edge which is better? (Soft!) Keep that in mind when creating edge of your own. The benefits are endless!