ln an attempt to better their lives, people have significantly changed the
environment. For example, the Egyptians built the Aswan High Dam across the Niie
. River to generate electric power, control flooding, and improve irrigation. The
completedam, however, has caused major problems.
.
The dam holds back much ofthe rich silt that fertilized the fields during the
flood season each year. Farmers in Egypt must now use artificial fertilizers, more than
farmers in any other country. In addition, the flow of the Nile's waters to the
Mediterranean Sea held baik the salty sea water. After the dam was built, less water
flowed down to the Meditenanean. Sait water now enters the delta, making some of ..* i
the once fertile land unfit for farming.
Pollution, as well as the search for minerals and other natural resources, has
ruined formerly productive lands. In northern Africa, Arabia, and India, deserts are
expanding at the rate of thousands of square miles each year because of overgrazing
and poor irrigation. Safeguarding the world requires global cooperatio