Environmental Engineering Reference
In-Depth Information
Control and Reclamation Act (SMCRA); the Clean Water Act (CWA); the Clean Air Act (CAA); the Safe
Drinking Water Act (SDWA); the Resource Conservation and Recovery Act (RCRA); CERCLA; and many
others.
Since minerals are nonrenewable resources, sustainable use is an important aspect of managing them. This can
be accomplished through recycling and reuse of products, as well as by thoughtful purchasing of products with
the goal of reducing consumption.
Fishing
Throughout history people have fished Earth's oceans and freshwater sources. In modern times, however, these
waters are being over-fished and depleted, mainly due to the use of techniques capable of harvesting large
numbers of fish to meet the demand of our increasing global population. The excessive consumption of fish,
combined with the destruction of aquatic habitats and ecosystems, has brought some fish populations close to
extinction, with other populations declining rapidly, and many species are considered to be endangered or
threatened. Ultimately, the balance of entire ecosystems and food webs can be dramatically altered by overfish-
ing, with the potential for devastating ecosystem collapse.
Fishing Techniques
Modern fishing practices are designed to catch the most fish as quickly as possible and as cheaply as possible.
As a result, these techniques tend to be both efficient and destructive. The three main industrial fishing tech-
niques include bottom trawling, long-lining, and drift netting.
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Bottom trawling
includes dragging a large net along the bottom to capture organisms. This can crush
coral reefs and other organisms. It also can stir up sediment and decrease the amount of sunlight that
reaches the deeper parts of the ocean. Other types of trawling target species that are either just above the
benthic zone or in the pelagic zone (mid-ocean). Many nations have placed restrictions on when, where,
or how trawling can be conducted.
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Long-lining
involves dragging a long fishing line with baited hooks along its length behind a boat or at-
taching it to an anchor. Long-lining is used to catch surface fish such as swordfish or can be deployed
closer to the ocean floor to catch benthic fish such as cod. One side effect of this fishing method is the
high rate of bycatch, or fish and other organisms caught unintentionally while trying to catch a particular
species of fish. Organisms commonly caught as bycatch include sea turtles and a variety of birds. Re-
cently, the fishing industry has started making modifications to the lines in order to reduce bycatch.
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Drift netting
is the practice of dragging large nets through the water to catch fish. The primary negative
environmental impact of this technique is the large amount of bycatch, including sharks, dolphins, sea
turtles, and whales. In some regions, the use of drift nets is regulated, with limits set on the size of the
net. In other regions, this practice has been banned, either for particular species or altogether.
Overfishing
The extensive fishing of the oceans and freshwater sources allowed by large-scale commercial fishing methods
has caused a dramatic decline in fishery numbers. Many fisheries are now collapsing, meaning the numbers are
very low and continue to decrease. Because of the decline in populations of the larger, more desirable fish,
fleets have started fishing the smaller, less desirable, less valuable fish. This process has been termed "fishing
down the food chain," reflecting the literal change from harvesting larger fish, to medium-size fish, to smaller
fish, similar to the progression down the aquatic food chain.
