| Destruction and alteration of
habitat are recognized as the greatest threat to
biodiversity. Marine scientists looking at the problems of
oceans and coastal areas at the start of the new
millennium declared: "Habitats, of course, have changed
naturally since long before the appearance of humanity,
but the sheer scale of the present onslaught is
unprecedented." The destruction comes from physical
alterations, pollution, and invasions of alien species as
well as other biological threats such as eutrophication
and red tides. Some phenomena are natural events. But many
result from human activities, and most impacts are from
land-based activities.
The closer the seas come to people, the greater is the
damage. Ill-planned (and often unplanned) coastal
development is one of the main driving forces behind the
environmental problems of the oceans. Apart from
overfishing, the greatest harm is caused by what we do on
land and particularly at the coasts rather than at sea.
The crisis is deepest where the waters are shallowest.
It is here that pollution is at its worst, habitats are
most readily destroyed, and much of the depletion of
fisheries takes place. More and more of the narrow
strip of land along the world’s coasts and its habitats has been ruined by a host of poorly planned and badly
regulated activities, from the explosive growth of coastal
cities and towns to the increase in tourism, from industrialisation to the expansion of fish farming, from
the development of ports to measures taken to try to
control flooding. The pressures are particularly
exacerbated along the coasts of many developing countries,
where rapid population growth combines with persistent
poverty, and there is little capacity to manage the
situation. But developed country coastlines are often
overdeveloped too, as people and businesses demand
ocean-front properties.
 Coastal development, say marine scientists, is one of
the main causes of the ocean's environmental problems. In
a survey of the marine environment produced for the new
millennium, the experts brought together by the UN pointed
out : "Apart from overfishing, the greatest harm is caused
by what we do on land – and particularly at the coasts –
rather than at sea."
Yet
one-third of the world's population already lives within
100 km of the sea, and the growth rate in coastal areas is
increasing, not to speak of the boom in coastal tourism.
Among the coastal ecosystems, the marine scientists
have singled out five as being at direct risk from
development, as distinct from pollution or overfishing,
though many suffer from these problems, too: wetlands,
seagrass beds, coastal lagoons, mangroves and shorelines.
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