Debate on the theory
Environment
SLOSS
Richness
and size
Reserve
design
Environment
One
argument against the Theory of Island Biogeography is that when it comes
to habitat islands they are not normally isolated in a completely inhospitable
matrix. It is usually the case that some species can cross the matrix
to a certain degree. Stepping stones often exist across the landscape.
These take the form of suitable intervening habitats that reduce the effect
of isolation.
Other arguments against the 'Theory' come from species-area relationships.
The 'Theory' has been applied to the design of nature reserves and treats
patches in reserves as being like 'islands' in a sea of less favourable
habitat.
SLOSS
The
controversy comes from the idea of favouring one large patch as a reserve
for species over several small ones. This led to the SLOSS (single large
or several small) debate. The SLOSS debate is concerned with whether one
large reserve would preserve more species than several small ones (Higgs,
1981).
Typically large islands support more species than small ones, so complying
with species area relationships and the 'Theory' managers should support
the establishment of single large reserves. However, some studies suggest
that two reserves of half the size are actually better for maintaining
species.
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Which do you think might be more important, one single reserve or several small reserves linked spatially? | |
Richness
and size
Despite
the dispute over the applicability of the 'Theory' to terrestrial habitat
islands and species area relationships, a correlation has been shown to
exist between species richness, and island size and isolation.
Reserve
design
Whatever
side of the debate landscape ecologists sit, the importance of size and
shape of remnants is not disputed. However, it should be noted that the
use of species area relationships alone do not give any information on
which habitats contribute most to species richness, or which species are
most likely to be lost from a remnant which are important issues for environmental
management.
Although in an ideal world managers would choose the size and shape of
patches in their reserve system, there is often no opportunity to design
a reserve network. The best mangers can do is to work with the remnant
patches that have been left after a disturbance has taken place.
