A guide for planners and managers - IUCN

220 MARINE AND COASTAL
PROTECTED AREAS
– Enabling protection of more species by enabling the survival of different sets of
species on each island.
– Being less susceptible to epidemic disease or similar disasters that could eliminate
an entire species or set of species from a single island.
– Enabling edge species, which thrive at the interfaces between habitats, to thrive
on islands with a higher ratio of perimeter to area.
If one is designing protected areas for maximum “edge” for shore species, such
as turtles, shorebirds, and pinnipeds, then a number of small islands would seem to
best fulfil the objectives. Although, in general, a large island area can better protect
samples of indigenous communities and biological diversity, since many edge species
will survive outside the protected area and require no special management.
With these various ideas in mind, the following guidelines for protecting island
habitats seem important.
Use natural limits for protected areas.
Islands are naturally divided from other lands by the sea. Since their biological
peculiarities and their ecosystems’ vulnerability are largely results of isolation, whole
islands rather than parts of islands should be protected under different management
regimes. The natural isolation of islands can thus be used to prevent or slow the dangers
of alien plant or animal invasions. Where it is not possible to protect whole islands,
natural boundaries, such as contour or climate boundaries or isthmuses that can be
fenced off are the best boundaries for management regimes with different conservation
objectives, just as they are for protected areas on continents. The best approach is
usually to protect habitats rather than species, as elsewhere, and to exploit the natural
isolation that islands present.
Enforce rigorous quarantine on all imports.
Imports of plants, animals and soils need to be quarantined. The more isolated
a landmass, the more vulnerable are its native ecosystems to disruption by introductions
of species. Smaller islands need to exercise quarantine control to exclude troublesome
invading plants such as privet, guava and New Zealand flax, and animals such as
mongooses, goats, and rats, which have become pests on many islands and destroyed
native vegetation and fauna. Exotic diseases of domesticated animals have also been
extremely destructive on islands, when they have infected wild stocks there, as
ornithosis did in Hawaiian native land birds. The importation of any new species to
islands should be regarded from the point of view of possible damage to native
ecosystems and native species as well as to domesticated species. Effective quarantine
control against species that may be aggressive on islands is difficult, but managers
can exploit some of the natural advantages of island isolation by prohibiting the import
of species that might be troublesome in comparable environments.