Geography Reference
In-Depth Information
design new sites. In the United States landfi ll capacity has
been reached or will soon be reached in about a dozen
States, most of them in the Northeast and Mid-Atlantic
regions, and those States must now buy space from other
States for this purpose. Trucking or sending garbage by
rail to distant landfi lls is very expensive, but there are few
alternatives.
Similar problems arise on a global scale. The
United States, the European Union, and Japan export
solid (including hazardous) wastes to countries in Africa,
Middle and South America, and East Asia. While these
countries are paid for accepting the waste, they do not
always have the capacity to treat it properly. So the waste
often is dumped in open landfi lls, where it creates the very
hazards that the exporters want to avoid. In the late 1980s,
the wealthier countries' practice of “managing” waste by
exporting it became a controversial issue, and in 1989 a
treaty was drawn up to control it. The treaty did not (as
many poorer countries wished) prohibit the exporting of
hazardous waste, although it did place some restrictions
on trade in hazardous materials.
It is useful to differentiate between
toxic wastes
, in
which the danger is caused by chemicals, infectious mate-
rials, and the like, and
radioactive wastes
, which are of
two types: low-level radioactive wastes, which give off
small amounts of radiation and are produced by industry,
hospitals, research facilities, and nuclear power plants;
and high-level radioactive wastes, which emit strong
radiation and are produced by nuclear power plants and
nuclear weapons factories. In the United States, low-level
radioactive wastes have for many years been disposed of in
steel drums placed in six special government-run landfi lls,
three of which are now closed.
High-level radioactive waste is extremely dangerous
and diffi cult to get rid of. Fuel rods from nuclear reactors
will remain radioactive for thousands of years and must be
stored in remote places where they will not contaminate
water, air, or any other part of the environment. In fact, no
satisfactory means or place for the disposal of high-level
radioactive waste has been found. Among many suggested
disposal sites are deep shafts in the bedrock, chambers dug
in salt deposits (salt effectively blocks radiation), ice cham-
bers in Antarctica, sediments beneath the ocean fl oor, and
volcanically active midocean trenches. Meanwhile, spent
fuel rods (which last only about three years in the reactor)
are put in specially designed drums and stored in one of
about 100 sites, all of them potentially dangerous.
There is a related problem: transportation of waste.
Even if secure and safe storage can be found for high-level
radioactive waste, the waste has to be transported from its
source to the disposal site. Such transportation presents
an additional hazard; a truck or train accident could have
disastrous consequences.
The dimensions of the waste-disposal problem are
growing and globalizing. The threat to the planet's envi-
ronment is not just over the short term but can exist for
centuries, indeed millennia.
Biodiversity
A signifi cant change that is related to all of the develop-
ments discussed so far is the accelerating loss of
biodiver-
sity
. An abbreviation of “biological diversity,” biodiver-
sity refers to the diversity of all aspects of life found on the
Earth. Although the term is commonly used when refer-
ring to the diversity of species, it encompasses the entire
range of biological diversity, from the genetic variability
within individuals of a species to the diversity of ecosys-
tems on the planet.
How many species are there? Estimates range from
10 million to 100 million, and no one is quite sure how
many. So far only some 1.75 million species have been
identifi ed, and new species, particularly new species of
insects, are being discovered regularly. Yet species are
also becoming extinct at a rapid rate. It is diffi cult to say
exactly how quickly extinctions are occurring, since we
do not know how many species there are. What is clear,
however, is that although extinction is a natural process,
humans have dramatically increased rates of extinction,
particularly over the last few hundred years. Estimates
from the United Nations Environment Program's Global
Biodiversity Assessment indicate that 8 percent of plants,
5 percent of fi sh, 11 percent of birds, and 18 percent of the
world's mammal species are currently threatened.
Where is biodiversity most threatened? Whether a
species is threatened with extinction depends on the range
of the species, its scarcity, and its geographic concentra-
tion. If a species with a small range, a high degree of scar-
city, and a small geographic concentration has its habitat
threatened, extinction can follow. Because most species
have small ranges, change in a small area can affect a spe-
cies. A 2005 report in
Scientifi c American
explained that
“Clearing a forest, draining a wetland, damming a river
or dynamiting a coral reef to kill its fi sh can more readily
eliminate species with small ranges than more widespread
species.”
Human impacts on biodiversity have increased over
time. The domestication of animals, followed by the agri-
cultural domestication of plant life, caused signifi cant
changes in our relationship with other species. Large ver-
tebrates have always been particularly hard hit by human
activities. Many birds and mammals have been hunted
not only for food but also for their skins, feathers, and so
forth. During the eighteenth and nineteenth centuries,
beaver populations in North America were drastically
reduced as the beavers were trapped and skinned for their
pelts. Many bird species were hunted for their feathers,
which were sold to decorate fashionable hats. Worldwide,
elephants and walruses continue to be hunted for their
