> The Forest > Reproduction Methods > Clearcut > Hot Topic: Edge Effects
An edge effect refers to how the local environment
changes along some type of boundary, or "edge."
As humans we deal with many types of
environmental "edges," such as the cold blast
of air upon entering an air-conditioned building from a
hot street, or entering a treed, shaded city park after
biking along a broad, treeless avenue. The edge is the change
in temperature and humidity that we feel, and an edge effect
is our reaction to the change in temperature (e.g. putting
on a sweater, or searching out a patch of sun).
The edge effect we most often hear
about in forestry refers to the forest edges that are
created when we harvest trees, particularly when we
choose to clearcut. Tree canopies provide the ground
below with lots of shade, while a clearcut allows sun
to reach the ground; tree canopies maintain a cooler,
moister environment below, while a clearcut is warmer
and drier when the sun is out. As time passes and a
stand of young trees emerges on a clearcut, the environment
in the young stand changes and the edge begins to fade.
As a mature forest develops, the edge fades away. The
edge effect is the result of two different conditions
influencing the plants and animals that live on the
Some animals, deer
and elk for example, like the forest edges because they
can find food in the clearing and hiding cover in the
trees they are called "edge species," because
they can thrive on the edge and benefit by having various
habitats near one another. Other animals, like the spotted
owl, prefer areas with a lot of canopy and few edges.
Edges for this and other plants and animals, can be
dangerous. Research suggests, however, that the dangerous
edges occur when a forest shares an edge with agricultural
or suburban development lands, and not when the forest
lands remain in forest use the edge between an old
and young forest is not an obstacle as is an edge between
a forest and an agricultural field, or a forest and
If we are managing our land with most
plants and animals in mind, then should we be mindful of
our edges caused by harvesting timber? It may be that edges
are less important to the success of our forest animals
than is the total area of forest habitat suitable for them.
While there is no ideal forest patch size for all animals,
we do need to manage our forested landscape to include a
mix of forest types, and a sufficient area of each type,
that will meet the needs of the greatest number of species.
When we plan to harvest trees from an
area, we need to consider what will result from the removal
of an older forest structure and subsequent creation of
a younger one. Will we hurt animals that we want to protect
by reducing habitat? Will we provide forage for animals
that we want to grow strong? Will fragile plants disappear
? Will desirable plants flourish in their new environment?
That is life in the forest mosaic, and as we learn more
about plants and animals in the forest, we'll be better
able to both protect our forest resources and harvest trees.