Humans have not
always been careful with natural resources. For example, we waste water by
letting faucets run and by watering lawns. We pollute rivers, streams, and
groundwater with garbage and toxic wastes. Fumes from our vehicles and
factories pollute the air. High levels of these fumes in the atmosphere may be
changing the climate of the entire planet. Earth’s temperature may be rising. This
“global warming” can create many problems. For instance,
glaciers
are shrinking, and the polar ice caps are melting. Rising sea
levels may eventually flood coastal areas. Floods, drought, hurricanes, and tornadoes
are among the natural disasters that can be caused by changes in the earth’s
climate. Toxins in the air and other chemicals may be damaging the ozone layer.
The ozone layer of the atmosphere protects living things from the
sun’s harmful rays.
Without this protection, many life-forms—including humans—are in danger.
In the name of
progress, we have changed the landscape. We have cut down whole forests for
lumber and to create farmland. This action destroys wildlife habitat. It causes
erosion and flooding. We have dammed rivers to produce electricity.
Lakes formed by dams have flooded
huge areas. Fish
stopped by the dams can’t reach their breeding grounds. We have changed
the course of rivers to water farmland. This has formed deserts where the water
used to flow. It has added salt to the soil, making the land barren. We
have filled in swamps and built malls. The many animals and plants that lived
in the swamps are gone. Why have we been so careless? Part of the problem is
that we often don’t know the harm we are doing until it is too late. Two
examples are the building of the Aswan Dam and the clearing of the Amazon rain
forest.
In the 1960s,
President Nasser of Egypt dammed the Nile River. The reason was to control its
yearly flooding and to produce electricity. “The miracle has been wrought,” he
said. The dam did stop the floods. However, it also blocked the flow of silt
that enriched the soil of farms along the Nile. This meant that farmers had
to start using chemical fertilizers. The lack of the silt that flowed from the
Nile into the Mediterranean Sea caused many problems. It increased erosion
along the coast and it harmed wildlife. Sardines and shrimp were two species
that lived in the
sea. After the dam
was built, they could not get their normal food— organic matter in the
silt. As a result, the fish died. Egypt’s sardine industry failed.
Rodents that had been
kept in control by the yearly floods increased in numbers. Sewage systems that
were cleansed by the floods became clogged. Farmland below the dam no longer
drained properly. It became salty and useless. Farm production was cut in half.
The “miracle” turned
out to be a disaster
for Egypt.
