A guide for planners and managers - IUCN

PART I
The Roles of Protected Areas
Arabian Sea and Gulf of Oman coasts in the northwestern Indian Ocean. The corals
Euphyllia, Tubipora, Goniastrea, and Montastrea are all found alive in a few restricted
locations off the southern Oman coast, but have all died out in the north and central
coasts where they occur only in Pleistocene beach deposits (Salm, 1993). A similar
pattern is demonstrated by the molluscs Cypraeacassis rufa, Lambis lambis, and
Tridacna. While the majority of corals and molluscs were able to survive the changes
accompanying the transition from Pleistocene to present, the few mentioned above
fell victim.
A species must adapt or die out when faced with environmental change. Did
the corals and molluscs in northern Oman die out because the communities there
were less diverse than further south, hence more susceptible to perturbations? Pimm
(1984) suggested that species might be more resilient to environmental change if the
food web is more diverse. However, there is no evidence to show that complex tropical
reef systems are any more resilient than less diverse polar ones.
Genetic resources cannot be preserved in the wild without maintaining ecological
processes and life support systems. Both ecological processes and genetic resources
must be maintained, then, for the sustainable utilization of species and ecosystems.
1.5 Conserving Ecosystems and Maintaining Ecological Processes
MPAs can conserve entire ecosystems that are unique, particularly rich in species,
representative of biogeographical units, or exceptionally productive of seafood. There
may be unique ecosystems that have complements of species that are found nowhere
else, having evolved to live in their specific environmental conditions. These ecosystems
represent a high-risk natural investment of biodiversity and related genetic resources,
all of which may be lost if such habitats are destroyed. Ecosystems rich in species—
of high biodiversity—represent good investments since they yield a high number of
options for the conservation effort expended.
Different ecosystems have, among their complement of species, genetic resources
influenced by different ecological conditions. Some species are confined to specific
biogeographical regions, while others have separate populations in different regions.
Such separate populations may be genetically distinct, each having developed specific
characters favoring survival in the different regions. As Prescott-Allen and Prescott-
Allen (1984) observe, “Not all populations are equally useful; and useful populations
are not distributed evenly throughout the range of the species they comprise.
Consequently it is possible for valuable genotypes to be threatened with extinction
even though the species is widespread and abundant.”
The ecological systems of the sea may have great complexity—as in coral
reefs—or very high bioproductivity—as in “upwelling” areas where nutrient-laden deep
ocean waters rise to the surface. These examples differ from terrestrial systems in many
ways. Three-dimensional phenomena are more marked and important in the ocean,
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