for another. Physical environmental change in both
fragment and ‘matrix’ habitats has not generally
been given enough attention in the theoretical liter-
ature. Successional change and altered disturbance
regimes may have long-term implications for
species persistence in altered landscapes. The evi-
dence for ‘relaxation’, i.e. stochastically driven
decline in species number, is surprisingly thin.
Species composition and richness are liable to
change in fragmented systems: species are indeed
lost. However, in relation both to SLOSS and
metapopulation scenarios, it is apparent that much
turnover may well be deterministic in nature and
explicable in relation to specific ecological processes
such as succession or meso-predator release.
Various lines of data suggest strong structure to the
disassembly as well as to the assembly of systems.
For instance, many systems and species are
strongly nested in their distributions, and this can,
it seems, be produced in either colonization- or
extinction-dominated systems.
It appears possible to predict the types of species
that will be in greatest difficulty in fragmented
landscapes, and it is these species that require
primacy in relation to reserve configuration, popu-
lation monitoring, and management planning. The
consequences of fragmentation can be severe, but
they are poorly predicted by classical island
theories, which assume stochastic demographic
effects to dominate in a system of fragments search-
ing for a new equilibrium in a sea of altered habi-
tats. The nature of the connectivity of habitat
patches may be crucial. In some cases, corridors
and short dispersal distances may be beneficial,
whereas in other circumstances isolated reserves
may actually provide the best chance of survival for
a threatened species. Some species thrive in edge
habitats, others are disadvantaged by increased
edge effects. The ‘filtering’ properties of the matrix
can be crucial and require careful assessment in
conservation planning. Landscape effects may be
complex, with the same linear feature acting as
corridor, barrier, and lethal hazard for different
organisms. Moreover, some species are mobile, sea-
sonally or aseasonally, and their protection may
require a more extensive approach to conservation
than provided for by any reserve system on its own.
These considerations demand a re-evaluation of
the place of island biogeography within conserva-
tion biology. The equilibrium island theory turns
out to provide rather equivocal guidance, and
appears to have often been invoked as a basis for
predictions of species loss where there is a logical
disconnection between theory and prediction.
Some of the effects traditionally associated with
island approaches may actually be fairly weak in
general, but other features of insularity may pro-
vide powerful and fairly immediate influences on
species persistence and system change. The role of
hierarchical ecological relationships, e.g. between
plants and their dispersers, between vegetation
change and altering habitat space for butterflies,
between understorey insectivores and their
predators, and so forth, may be crucial to the
consequences of fragmentation. Such successional
and food-web controls may be the most powerful
forms of expression of islandness in the altered
landscapes, and they typically involve interactions
and exchanges between the fragments and the
surrounding matrix. The attention being paid to the
effects of the matrix on persistence in remnants, and
to the use of matrix habitats by native species,
signals an on-going switch in emphasis from
island thinking to what some term ‘countryside
biogeography’, i.e. to the importance of incorporat-
ing conservation concerns in managing whole land-
scapes, not just isolated reserves.
A line must be drawn somewhere in any text, and
in this chapter discussion stops short on alternative
approaches to conservation problems, and on
themes such as the implication of large-scale cli-
mate change under global warming scenarios.
Neither is any attempt made to draw out guiding
principles for conservation from island studies. The
grand hopes for simple unifying principles have
proven to be as illusory as the end of the rainbow.
It is nonetheless important to appreciate how these
ideas have influenced conservation theory, just as it
is important to tackle the ecological complexities of
increasing insularity within real landscapes.SUMMARY 289