A guide for planners and managers - IUCN

8 MARINE AND COASTAL
PROTECTED AREAS
readily replace the particular communities of plants, animals, and microorganisms
that make up the ecosystems associated with so many essential processes. The genetic
variety and compositions of such ecosystems may be crucial for their performance,
and for their response to long-term events like climate change.
The huge coral mortality associated with the 1998 El Niño related coral
bleaching event drives home the value of different physiological responses to stress
by corals, responses that are presumably seated in their genetic differences. In the
western Indian Ocean and West Pacific, for example, adjacent coral colonies responded
differently to the elevated sea water temperatures: they bleached at different rates,
some bleached and died, others bleached and recovered, and yet others barely
bleached at all. But in some places more than 90 percent of the corals died.
Ethical issues of biodiversity relate particularly to species extinction. Human
beings have become a major evolutionary force, lacking the knowledge to control the
biosphere, but having the power to change it radically. We should be committed to
our descendants and to other creatures to act prudently. We cannot predict what species
may prove important, therefore, we should not cause the extinction of a species.
Just as many varieties of domesticated plants and animals are disappearing,
so too are many species of wild plants and animals. An estimated 25,000 plant species
(Lucas and Synge, 1978) and more than a thousand vertebrate species and subspecies
(IUCN, 1975) were already threatened with extinction in the early to mid-1970s. The
most serious threat was considered to be habitat destruction (Lucas and Synge,
1978; Allen and Prescott-Allen, 1978). This destruction took and continues to take many
forms: (1) the replacement of entire habitats by settlements, harbors, and other
human constructions, by cropland, grazing land, and plantations, and by mines and
quarries; (2) the effects of dams (blocking spawning migrations, drowning habitats,
and altering chemical or thermal conditions) (Figure 5) (3) drainage, channelization,
and flood control; (4) pollution and solid waste disposal (from domestic, agricultural,
FIGURE 5.
Dams change river flows and usually have negative effects on coastal
resources.
industrial, and mining sources);
overuse of groundwater aquifers
(for domestic, agricultural, and
industrial purposes); (5) removal
of materials (such as vegetation,
gravel, and stones) for timber,
fuel, construction, and so on;
(6) dredging and dumping; and
(7) erosion and siltation. Since
that time, conversion of coastal
mangroves and related habitats
into brine ponds for salt production
and prawn farms has
emerged as a major issue.