358 CHAPTER 14 Agriculture and Food Resources
Industrialized agriculture has favored the replace-
ment of traditional family farms with large agribusiness
conglomerates. In the United States, most cattle, hogs,
and poultry are now grown in feedlots and livestock
factories (Figure 14.10c). The large concentrations
of animals in livestock factories create many environ-
mental problems, including air and water pollution
(Figure 14.10d).
Many insects, weeds, and disease-causing organ-
isms have developed or are developing resistance to
pesticides. Pesticide resistance forces farmers to apply
progressively larger quantities
of pesticides (Figure 14.10e).
Pesticide residues contaminate
our food supply and reduce the
number and diversity of benefi-
cial microorganisms in the soil.
Fishes and other aquatic organ-
isms are sometimes killed by pes-
ticide runoff into lakes, rivers,
and estuaries.
Land degradation is a reduc-
tion in the potential productiv-
ity of land. Soil erosion, which
is exacerbated by large-scale
mechanized operations, causes
a decline in soil fertility, and the
eroded sediments damage water quality. Other types
of degradation are compaction of soil by heavy farm
machinery and waterlogging and salinization (salting)
of soil from improper irrigation methods.
Clearing grasslands and forests and draining
wetlands to grow crops result in habitat fragmentation
that reduces biological diversity. Many species are endan-
gered or threatened as a result of habitat loss to agricul-
ture. The most dramatic example of habitat loss in North
America is tallgrass prairie, more than 90 percent of
which has been converted to agriculture.- What is happening to the number of
domesticated plant and animal varieties? Why? - What is the green revolution? What are some of
its benefits and problems? - What are the major environmental problems
associated with industrialized agriculture?
Increasing Livestock Yields
The use of hormones and antibiotics, although contro-
versial, increases animal production. Hormones, usually
administered by ear implants, regulate livestock bodily
functions and promote faster growth. Although U.S. and
Canadian farmers use hormones, the European Union
(EU) currently restricts imports of hormone-treated beef
because of health concerns for human consumers. EU
regulators cite studies which suggest that these hormones
or their breakdown products, both found in trace amounts
in meat and meat products, could cause cancer or affect
the growth of young children. In 1999 an international
scientific committee organized by the FAO and WHO con-
cluded that the trace amounts of hormones found in beef
are safe because they are very low compared to the normal
hormone concentrations found in the human body.
Modern agriculture has also embraced the routine
addition of low doses of antibiotics to feed for healthy
pigs, chickens, and cattle. These animals gain 4 to 5 per-
cent more weight than untreated animals, presumably
because they expend less energy fighting infections.
Several studies link the indiscriminate use of antibiot-
ics in humans and livestock to the evolution of bacterial
strains that are resistant to antibiotics (Figure 14.10a).
When an antibiotic is used to treat a bacterial infection,
a few bacteria may survive because they are genetically
resistant to the antibiotic, and they pass these genes to
future generations. As a result, the bacterial population
contains a larger percentage of antibiotic-resistant bacte-
ria than before.
Because there is increasing evidence that the use of
antibiotics in agriculture reduces their medical effective-
ness for humans, WHO recommended in 2003 that rou-
tine use of antibiotics in livestock be eliminated. Many
European countries have complied, but the United States
and many other countries continue the practice.
Environmental Impacts
Industrialized agriculture has many environmental effects
(Figure 14.10b). The agricultural use of fossil fuels and
pesticides produces air pollution. Untreated animal
wastes and agricultural chemicals such as fertilizers and
pesticides cause water pollution, which reduces biologi-
cal diversity, harms fisheries, and leads to outbreaks of
nuisance species. According to the Environmental Pro-
tection Agency, agricultural practices are the single larg-
est cause of surface water pollution in the United States.
pesticide A toxic
chemical used to kill
pests.
degradation (of
land) Natural or
human-induced
reduction in the
potential ability of the
land to support crops
or livestock.
habitat
fragmentation The
breakup of large areas
of habitat into small,
isolated patches.