Most of the world's marine ecosystems,
particularly coastal habitats, are stressed by a combination
of these factors. The Black Sea is dying under the weight
of pollution and over fishing. Land-based pollution in the
form of industrial wastes, sewage, and runoff of pesticides
and fertilisers, combined with oil and other wastes from ship
traffic, have contaminated the entire basin. Eutrophication
has left 90 percent of the Black Sea facing critically low
oxygen levels. The total fish catch within the region declined
by 64 percent between 1986 and 1992. The cost of this damage
is estimated at $500 million annually to the fishing and tourism
industries alone.
The direct factors (pressures) leading to the loss of marine
biodiversity are habitat loss, intense overexploitation, pollution
and sedimentation, species introductions, and climate change.
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Habitat
Loss
Habitat
conversion and degradation are generally thought to be the most
significant threats to terrestrial life. Within marine ecosystems,
they rank along with overexploitation and pollution as major
causes of biodiversity loss.
Coastal development converts mangroves and other wetlands as
a result of urbanization and agricultural expansion. breakwaters,
mining, oil drilling, and dredging and filling all destabilise
the coastal environment. These result both in the destruction
of wetlands and other habitats and in the degradation of nearby
areas, through siltation and changes in water temperature and
flow, salinity, and other physical factors.
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