Mangrove forest is a productive ecosystem and constitutes
a natural barrier against storm surges and strong
winds. It serves as nursery and feeding grounds for
many commercially important aquatic species. During
the past 32 years (1961–1993), social and economic development
have caused severe destruction of mangrove
forests in Thailand. The existing mangrove forest area in
Thailand has decreased more than 50% in the past 32
years (Kongsangchai, 1995). Changes of the areas are
shown in Table 9. The deterioration of mangroves in the
past and at present is approximately 6.2 thousand ha/
year. The major causes are economic, political, and social
pressures which can be separated into many activities
as show in Table 10. It is clearly seen that the
conversion of mangrove forests to shrimp farming is
one of the most severe problems and has tremendous
impacts on the coastal ecosystem. For example the
removal of tree-cover, loss of nutrient-supply from the
forest to the sea, obstruction of tidal flushing and fresh
water runoff, coastal erosion and the discharge of waste
from ponds lead to change in the natural equilibrium
and ultimately to the ecosystem destruction. Human
activities can directly cause catastrophic mortality on
reefs through dredging, dynamite fishing, and/or pollution.
ONEB (1992) reported on the status of the coral
reefs in the Thai waters during the period of 1987–1992
that only 36% remained in good condition, 33% in fair
condition, 30% in poor condition (Table 11). It is expected
that the destruction of the coral reefs will be
more severe if preventive measures are not promptly
taken.
The rapid expansion of the marine fishery industry
since the early 1960s has put tremendous pressure on the
available resources in the Gulf of Thailand. The exploitation
of fish resources in the Gulf of Thailand has
exceeded maximum sustainable level and caused adversely
affects on the fish stocks in the Gulf, resulting in
the drastic decrease from about 300 to 30 kg/h. However,
another serious problem affecting fish resources is
pollution, especially in the inner Gulf of Thailand. It is
evident that the increasingly deteriorating conditions in
the marine environment of the inner Gulf of Thailand
have threatened the existence of several economically
important organisms in the area. Thus, better management
of marine resources is a prerequisite to any improvement
to the existing situation.