winter wheat and summer soybean crops are grown in
some areas of the United States. However, multicropping
can be accomplished only in regions where water sup-
plies are adequate for irrigation. Also, care must be taken
to prevent a decline in soil fertility from such intensive
use and avoid further harm from chemical and energy
inputs.
The negative environmental effects of agriculture,
including loss of soil fertility, soil erosion, aquifer deple-
tion, and soil, water, and air pollution, must be brought
under control (}ÕÀiÊÓ°£Î). Many strategies exist to
retard the loss of topsoil, conserve water, conserve en-
ergy, and reduce the use of agricultural chemicals. For
example, in conservation tillage, residues from previous
crops are left in the soil, partially covering it and helping
to hold topsoil in place.
We must develop sustainable agricultural systems
that provide improved dietary standards, such as the
inclusion of high-quality protein in diets in develop-
ing countries. China’s expanding use of aquaculture is
an example of efficient protein production. The carp
that are raised in Chinese aquaculture are efficient at
converting food into high-quality protein. In China,
fish production by aquaculture now exceeds poultry
production. However, aquaculture, like all other hu-
man endeavors, has negative environmental effects that
must be addressed for it to be sustainable on a large
scale.Recommendation 4:
Mitigate Climate Change
A widely discussed human effect on the environment
is climate change caused by the enhanced green-
house effect. Both highly developed and developing
countries contribute to major increases in CO 2 in the
atmosphere, as well as to the
increasing amounts of meth-
ane, nitrous oxide, tropospheric
ozone, and CFCs. The most im-
portant greenhouse gas, CO 2 , is
produced when we burn fossil
fuels—coal, oil, and natural gas.
Although Earth’s climate has been relatively stable
during the past 10,000 years, human activities are causing
it to change. The average global temperature increased
by over 1° Celsius during the past century; more than
half of that warming occurred since 1975. Precipitation >>}iÊÌÊÃÊÀiÃÕÀViÃÊUÊ}ÕÀiÊÓ°£ÎÊÊ
Erosion is a serious form of soil degradation. Careful stewardship
of the land prevents such damage. Photographed in West Pokot,
Kenya.enhanced
greenhouse
effect The additional
warming produced
by increased levels
of gases that absorb
infrared radiation.An Overall Plan for Sustainable Living 41`ÊÛ>ÌÌÞÊÃViÊÓääÓÊUÊ}ÕÀiÊÓ°£Ó
From 1975 until the end of the last century, global food prices
were mostly in decline. However, beginning in 2002, food prices
have been both increasing and less predictable. Food price index
is the price of food as compared to the price in 2002, adjusted
for inflation.19610501001502002503003504001968 1975 1982 1989 1996 2003 2010
YearFood price indexU.N. Food and Agriculture OrganizationInterpreting Data
In the early 1970s, global energy prices increased
dramatically. What sort of relationship does this
graph suggest between prices of food and energy
at that time?© Alexandra E. Jones; Ecoscene/Corbis