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ENV510 Landscape Ecology and GIS
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Environment
SLOSS
Richness and size
Reserve design
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.
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.
Think!
Which do you think might be more important, one single reserve or several small reserves linked spatially?
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.
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.
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