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Learning Outcomes�

By the end of this chapter, you will be able to:

Identify the impact that farming has on the environment
Identify the impact that our eating choices have on the environment

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I know that every time something eats, something else dies. I recognize the Earth is little more than a revolving buffet with weather. -Comedian George Carlin

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Ancient Egyptian farmer, tomb of Sennedjem, via Wikimedia Creative Commons.

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How destructive is farming?

VERY.
Globally, farmland was a bit over 37% of the earth's landmass in 2015. We can only expect that number to grow as the human population increases.
When we farm, we're taking a naturally occurring ecosystem and turning it into an ecosystem that is designed for human needs. In other words, we're exploiting the land.
When we farm, we're taking an ecosystem that is full of many different species and turning it into an ecosystem that lacks diversity.
When we farm, we're taking things out of a system.

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We all produce unwanted byproducts in nearly everything we do. According to the Environmental Protection Agency (EPA), the United States produces 11 billion tons of solid waste each year. That's roughly 3.6 tons per person. Nearly half of that amount consists of agricultural waste, such as crop residues and animal manure, which are generally recycled into the soil on the farms where they are produced.

Industrial waste—other than mining and mineral production—amounts to some 400 million metric tons per year in the United States. Most of this material is recycled, converted to other forms, disposed of in private landfills or deep injection wells. About 60 million metric tons of industrial waste fall in a special category of hazardous and toxic waste, which we will discuss later in this chapter.

Municipal solid waste, the garbage we produce in our houses, offices, and cities, accounts for a small percentage of total waste by weight, but it is hard to re-use and recycle because it contains so many different materials. A combination of household and commercial refuse, municipal solid waste —amounts to about 250 million metric tons per year in the United States (fig. 13.2).

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Exploitation and the Dust Bowl

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Exploitation and the Dust Bowl

Homestead Act (1862), the Kinkaid Amendment (1904), and the Enlarged Homestead Act (1909)
Designed to reduce power of plantations
Usually semi-arid, but a few wet years around that time

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Exploitation and the Dust Bowl

Soil Conservation Service (1935)

Now Natural Resource Conservation Service

Shelterbelt

Great Wall of Trees or Tree Army
Roosevelt
Not natural – CCC and WPA workers
Effects unknown

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Crop Rotation�Crop rotation in practice, Ward 4, Murewa, Zimbabwe by CIMMYT via Flickr Creative Commons

Grow a series of different crops on the same field

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Crop Rotation�Soybean Root Nodules by IITA Image Library

Build healthy soil

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Crop Rotation�Western corn rootworm by Patrick Dockens, Flickr Creative Commons

Reduce pest problems
Pest or pathogen will not survive if its host is not present

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Species Diversity and the Four Pests

Humans must conquer Nature. - Maoist slogan

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Species Diversity and the Four Pests

1958: Chairman Mao Zedong
War on: Mosquitoes, flies, rats, and sparrows
Each sparrow can eat 4.5 kg of grain seeds
Chinese scientists estimated that killing a million sparrows could feed an extra 60,000 citizens
Sparrows killed by poisoning, crushing eggs, exhaustion

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What else do sparrows eat besides grain?

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Species Diversity and the Four Pests

Great Chinese Famine (1958-61)
30 million dead
China began to import sparrows

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Genetic Diversity and the Gros Michel

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Genetic Diversity and the Gros Michel

If you've studied evolution, you might remember that natural selection will occur when three things are present:

Members of a population have heritable variations
More offspring are produced than can be supported
Competition results in the better-adapted variations surviving at a higher rate

Farming is in conflict with variation. Why?

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The oceans are vast, but they're not so large enough to absorb our waste without harm. Every year

some 25,000 metric tons (55 million lbs) of packaging, including half a millions of bottles, cans, and plastic containers, are dumped at sea. Even in remote regions, beaches are littered with the non-degradable flotsam and jetsam. About 150,000 tons (330 million lbs) of fishing gear—including more than 1,000 km (660 mi) of nets—are lost or discarded at sea each year. An estimated that 50,000 northern fur seals are entangled in this refuse and drown or starve to death every year in the North Pacific alone. Until recently, many cities in the United States dumped municipal refuse, industrial waste, sewage, and sewage sludge into the ocean. Federal legislation now prohibits this dumping. New York City, the last to stop offshore sewage sludge disposal, finally ended this practice in

1992.

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Genetic Variation and the Gros Michel�

Bananas popular export food starting in early 1800s
Wars, upheavals, puppet governments (“Banana republics”)
Gros Michel was tasty, intense, and, most importantly, kept from getting damaged in a boat

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Genetic Variation and the Gros Michel�

Susceptible to Panama wilt (fungus)
Estimated cost 2.3 billion in 2000 dollars
By 1960, replaced by Cavendish

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Genetic Variation and the Gros Michel�

Gros Michel and Cavendish “the McDonalds of bananas”
But cheaply and globally available

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Red bananas, image by Sheba_Also 4000 Photos via Creative Commons license

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Stem Rust Pathotype UG99

Fungus, P. graminis
Humans have been battling stem rust as long as we have been growing wheat
1950s- rust resistant varieties
1999 – Virulent Ugandan strain UG99
Spreading globally
Most currently used varieties are susceptible

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Importation and Huanglongbing

Huanglongbing (citrus greening disease)
Insect-vectored bacterial disease
Invasive vector (Asian citrus psyllid)

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Quarantine map for Asian citrus psyllid

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Courtesy USDA

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Quarantines in Texas

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