Page 270 - Environment: The Science Behind the Stories

Livestock agriculture pollutes water and air

Livestock produce prodigious amounts of manure and urine,
and their waste can pollute surface water and groundwater.
Rich in nitrogen and phosphorus, livestock waste is a com-
mon cause of eutrophication (pp. 126–127, 430) in freshwater
systems. It can also release a wide array of bacterial and viral
pathogens that can sicken people, including Salmonella, E.
coli, Giardia, Microsporidia, Pfiesteria, and pathogens that
cause diarrhea, botulism, and parasitic infections.
The crowded conditions under which animals are often
kept necessitate heavy use of antibiotics to control disease.
Hormones are administered to livestock as well, and feed is
spiked with heavy metals that spur growth. Livestock excrete
most of these chemicals, which end up in wastewater and
may be transferred up the food chain in downstream ecosys- Figure 10.12 People practice many types of aquaculture.
tems. Some of the chemicals that remain in livestock meat Here, fish-farmers tend their animals at a fish farm in China
are transferred to us when we eat the meat. In addition, the
overuse of antibiotics can cause microbes to evolve resistance
to the antibiotics (just as pests evolve resistance to pesticides; We raise seafood with aquaculture
p. 273), making these drugs less effective. All in all, the FAO
estimates that livestock (including both feedlot and grazed Besides growing crops and raising animals on rangeland and
animals) in the United States account for 55% of soil erosion, in feedlots, we rely on aquatic organisms for food. Wild fish
37% of pesticide applications, 50% of antibiotics consumed, populations are plummeting throughout the world’s oceans as
and one-third of the nitrogen and phosphorus pollution in U.S. increased demand and new technologies lead us to overharvest
waterways. marine fisheries (pp. 455–460). As a result, raising fish and
Feedlot impacts can be minimized when properly managed, shellfish on “fish farms” has become necessary to meet our
and both the EPA and the states regulate U.S. feedlots. Waste- growing demand for these foods (Figure 10.12).
water and manure may be stored in lagoons, where it undergoes We call the cultivation of aquatic organisms for food in
a degree of treatment somewhat similar to that of municipal controlled environments aquaculture. Many aquatic species
wastewater (pp. 432–433). The resulting sludge may then be are grown in open water in large, floating net-pens. Others are
applied to farm fields as fertilizer (or injected into the ground raised in ponds or holding tanks. Practiced at small scales,
where plants need it), reducing the need for chemical fertilizers. community-based aquaculture is a focus of sustainable
Raising animals for food also results in air pollution. development efforts in the developing world. At large scales,
Besides the strong odors that emanate from feedlots and waste- industrialized aquaculture produces large amounts of food
water lagoons, livestock are a major source of greenhouse gases but exerts environmental impacts. People pursue aquaculture
that lead to climate change (pp. 502–504). A comprehensive with over 220 freshwater and marine species ranging from
FAO report in 2006 concluded that livestock agriculture contrib- fish to shrimp to clams to seaweeds (Figure 10.13).
utes 9% of our carbon dioxide emissions, 37% of our methane
emissions, and 65% of our nitrous oxide emissions—altogether,
18% of the emissions driving climate change, a larger share Other aquatic animals
than automobile transportation! Livestock release methane (1.1%)
and nitrous oxide in their metabolism and waste. Nitrous oxide Crustaceans CHAPTER 10 • A g R i C ulT u RE , Bi o TECH nology, A nd THE Fu T u RE o F Food
is also released from certain feed crops and from fertilizers (7.3%)
applied to feed crops. Carbon dioxide is released when forests
are cleared for ranching or for growing feed, and when fossil
fuels are burned to grow feed, transport animals, and more.
Molluscs
(17.9%)
Fish
WeIGhING the IssUes (49.6%)

FeedlOts ANd ANIMAl RIGhts Animal rights activists
denounce factory farming because they say it mistreats ani- Aquatic plants
(24.1%)
mals. Chickens, pigs, and cattle are crowded together in small
pens their entire lives, fattened up, and slaughtered. Should
we concern ourselves with the quality of life of the animals
that constitute part of our diet? Do you think animal rights
concerns are as important as the environmental issues? Are Figure 10.13 Aquaculture involves many types of fish, but
conditions at feedlots a good reason for being vegetarian? also a wide diversity of other marine and freshwater organ-
isms. Data from U.N. Food and Agriculture Organization (FAO). 269

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