Environmental Engineering Reference
In-Depth Information
Studies indicate that about three-fourths of the
world's 200 commercially valuable marine fish species
(40% in U.S. waters) are either overfished or fished to
their estimated sustainable yield. One result of the in-
creasingly efficient global hunt for fish is that big fish
in many populations of commercially valuable species
are becoming scarce. Smaller fish are the next targets,
as the fishing industry has begun working its way
down marine food webs. This practice can reduce the
breeding stock needed for recovery of depleted
species, unravel food webs, and disrupt marine ecosys-
tems. Today, we throw away almost one-third of the
fish we catch because they are gathered unintention-
ally in our harvest of commercially valuable species.
According to marine biologists, at least 1,200 ma-
rine species have become extinct in the past few hun-
dred years, and many thousands of additional marine
species could disappear during this century. Indeed,
fish are threatened with extinction by human activities more
than any other group of species
. And, freshwater animals
are disappearing five times faster than land animals.
and threatened aquatic species,
as discussed in Chapter 9.
We can also
establish protected marine sanctuaries.
Since 1986, the World Conservation Union has helped
establish a global system of
marine protected areas
(MPAs), mostly at the national level. Approximately 90
of the world's 350 biosphere reserves include coastal
or marine habitats. In 2004, Australia's Great Barrier
Reef—the world's largest living structure—became
the world's biggest marine protected area when the
government banned fishing and shipping on one-third
of the reef.
Scientific studies show that within fully protected
marine reserves, fish populations double, fish size
grows by almost one-third, fish reproduction triples,
and species diversity increases by almost one-fourth.
Furthermore, this improvement happens within two
to four years after strict protection begins and lasts for
decades.
Unfortunately, less than 0.01% of the world's
ocean area consists of fully protected marine reserves.
In the United States, the total area of fully protected
marine habitat is only 130 square kilometers (50 square
miles). In other words,
we have failed to strictly protect
99.9% of the world's ocean area from human exploitation.
Also, many current marine sanctuaries are too small to
protect most of the species within them and do not
provide adequate protection from pollution that flows
into coastal waters as a result of land use.
In 1997, a group of international marine scientists
called for governments to increase fully protected ma-
rine reserves to at least 20% of the ocean's surface by
2020. A 2003 study by the Pew Fisheries Commission
recommended establishing many more protected ma-
rine reserves in U.S. coastal waters and connecting
them with protected corridors so that fish can move
back and forth between such areas.
We can also establish
integrated coastal management
in which fishermen, scientists, conservationists, citi-
zens, business interests, developers, and politicians
collaborate to identify shared problems and goals.
Then they attempt to develop workable and cost-effec-
tive solutions that preserve biodiversity and environ-
mental quality while meeting economic and social
needs, ideally using adaptive ecosystem management
(Figure 8-25). Currently, more than 100 integrated
coastal management programs are being developed
throughout the world, including the Chesapeake Bay
in the United States.
Another important strategy is to protect existing
coastal and inland wetlands from being destroyed or
degraded. We can also prevent overfishing. Figure 8-30
lists potential measures for managing global fisheries
more sustainably and protecting marine biodiversity.
Most of these approaches rely on some sort of govern-
ment regulation. Finally, we can regulate and prevent
aquatic pollution, as discussed in Chapter 11.
Science, Education, and Politics: Why Is It
Difficult to Protect Marine Biodiversity?
Coastal development, the invisibility and vastness of
the world's oceans, citizen unawareness, and lack of
legal jurisdiction hinder protection of marine
biodiversity.
Protecting marine biodiversity is difficult for several
reasons. One problem is rapidly growing coastal de-
velopment and the accompanying massive inputs of
sediment and other wastes from land into coastal wa-
ter. This practice harms shore-hugging species and
threatens biologically diverse and highly productive
coastal ecosystems such as coral reefs, marshes, and
mangrove forest swamps.
Another problem is that much of the damage to
the oceans and other bodies of water is not visible to
most people. Also, many people incorrectly view the
seas as an inexhaustible resource that can absorb an al-
most infinite amount of waste and pollution.
Finally, most of the world's ocean area lies outside
the legal jurisdiction of any country. Thus, it is an
open-access resource, subject to overexploitation be-
cause of the tragedy of the commons.
Solutions: Protecting and Sustaining
Marine Biodiversity
Marine biodiversity can be sustained by protecting
endangered species, establishing protected
sanctuaries, managing coastal development, reducing
water pollution, and preventing overfishing.
There are several ways to protect and sustain marine
biodiversity. For example, we can
protect endangered
