Generally speaking, a positive relationship exists
between habitat size and species diversity; the larger the size of an area
the more diversity of organisms. However, because of human activities
much of the natural landscape has experienced great size reduction, and
habitat fragmentation results in much of the land hospitable to native
plants and animals being surrounded by land not hospital to their survival.
The result is series of habitat islands, and
corridors which connect them left to make up our current natural habitat
inventory. The study, survival, and growth of this inventory is of
central importance to this module, and we hope a focus for your students
environmental education.
It should be noted that the shape as well as
the size of these islands and corridors is important. Some
species are interior species which need a buffer zone of natural vegetation
between them and the habitat border to survive, thus favoring larger areas.
But the shape is also critical. Long, thin portions of habitat have
less interior space and a greater portion of edge. Other edge species
may be edge sensitive in a positive way, and prefer edge habitat.
This may be because they can use both the natural habitat and the surrounding
areas, or because they don't have to compete with the interior species,
or a number of other reasons. In many cases this has resulted in
a shift in species abundance, which favors edge species over interior species.
This is called the edge effect.
Ecotone
Edge effect
Edge species
Habitat fragmentation
Interior species
Niche