A guide for planners and managers - IUCN

180 MARINE AND COASTAL
PROTECTED AREAS
Photo by R. Salm.
as tropical storms, from which reefs recover naturally with time. Human activities
increase the burden of stress and may prevent normal recovery by increasing the
extinction rate or decreasing the immigration rate.
To maintain the balance between immigration and extinction rates we need to
ensure a steady source of propagules (eggs, larvae, and juveniles) to replenish stressed
areas. Large reefs may be self-replenishing. They manage to achieve this because their
large size allows portions of reef damaged by slumping (collapse of the reef slope),
storm surges, prolonged exposure to air, heat, or freshwater, bleaching, crown-of-thorns
starfish, or other stresses to be recolonized by propagules from undamaged parts of
the same reef. Such large reefs are mosaics of patches in different stages of community
development and redevelopment (Connell, 1978).
We have previously stated that, on balance, fewer large protected areas are to
be favored over a greater number of smaller ones. This principle applies in selecting
and delineating coral reef protected areas.
The optimal size of a protected reef area is designed around a strictly controlled
sanctuary zone or core, which encompasses sufficient reef to be self-replenishing for
all species. This is particularly important if preserving biological diversity is the
principal management objective. This design is less important for other objectives—
for example, maintaining the area’s value for recreation, tourism, research, and
education—or safeguarding specific breeding populations of particular species, like
giant clams (Tridacna gigas), that have smaller area requirements (Figure II-13).
The critical minimum core size for protected coral reefs is that smallest reef
size in which all species in the general vicinity are virtually certain to be found. For
example, core areas encompass at least 300 ha for each reef type in the Chagos
Archipelago (Salm, 1980b, 1984).
FIGURE II-13.
The remainder of the reserve
(including reef flats, land, and
intervening and surrounding
waters) functions as a buffer and
is zoned for different uses. In
addition to the core area, there
may be research zones, education
zones, visitor zones (perhaps used
on a rotational basis), and fisheries
zones. All may be planned
within a single reserve.
Tridacna derasa is an endangered giant clam species, an animal
whose survival depends on the protection of suitable reef habitats
(identified protected area, Taka Bone, Rate, Flores Sea, Indonesia).
One possible way to determine
the critical minimum core
size of coral reef protected areas
is outlined below. However, if
urgency or lack of funds and