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Chemical contributions to farming and agriculture

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What's your vision of a chicken farm?

In many nations, farming today is industrial, growing the maximum amount of food for the minimum price, often without much thought as to the long-term social or environmental consequences. These industrial food production plants are a long way from natural ecosystems and the farms of the past.

Advances in Agriculture and Population

Hunters and Gatherers

What is Earth’s carrying capacity for humans? Are humans now exceeding Earth’s carrying capacity for our species? Many anthropologists say that the carrying capacity of humans on the planet without agriculture is about 10 million (Figure below). This population was reached about 10,000 years ago. At the time, people lived together in small bands of hunters and gatherers. Typically men hunted and fished; women gathered nuts and vegetables.  In this way humans were just a part of a natural ecosystem, taking only what they needed from the natural environment around them.  In a hunter-gatherer society, people relied on the resources they could find where they lived.  There were wide varieties of plants and animals in any given area.

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Obviously, human populations have blown past this hypothetical carrying capacity. By using our brains, our erect posture, and our hands, we have been able to manipulate our environment in ways that no other species has ever done. What have been the important developments that have allowed population to grow?


About 10,000 years ago, we developed the ability to grow our own food. Farming increased the yield of food plants and allowed people to have food available year round. Animals were domesticated to provide meat. With agriculture, people could settle down, so that they no longer needed to carry all their possessions (Figure below). They could develop better farming practices and store food for when it was difficult to grow. Agriculture allowed people to settle in towns and cities.

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 (a) Like early farmers, subsistence farmers today grow only enough food for their families, with perhaps a bit extra to sell, barter, or trade. (b) More advanced farming practices allowed a single farmer to grow food for many more people.

Farms are actually engineered ecosystems, which rely on humans for maintenance, and usually have much less biodiversity than natural ecosystems. 

The Green Revolution

The Green Revolution has allowed the addition of billions of people to the population in the past few decades. The Green Revolution has improved agricultural productivity by:

  • Improving crops by selecting for traits that promote productivity; recently, genetically engineered crops have been introduced.
  • Increasing the use of artificial fertilizers and chemical pesticides. About 23 times more fertilizer and 50 times more pesticides are used around the world than were used just 50 years ago (Figure below).
  • Agricultural machinery: plowing, tilling, fertilizing, picking, and transporting are all done by machines. About 17% of the energy used each year in the United States is for agriculture.
  • Increasing access to water. Many farming regions depend on groundwater, which is not a renewable resource. Some regions will eventually run out of this water source. Currently about 70% of the world’s fresh water is used for agriculture.

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The Future

The flip side to this is that for the population to continue to grow, more advances in agriculture and an ever increasing supply of water will be needed. We’ve increased the carrying capacity for humans by our genius: growing crops, trading for needed materials, and designing ways to exploit resources that are difficult to get at, such as groundwater. And most of these resources are limited.

The question is, even though we have increased the carrying capacity of the planet, have we now exceeded it (Figure below)? Are humans on Earth experiencing overpopulation?

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There is not yet an answer to that question, but there are many different opinions. In the eighteenth century, Thomas Malthus predicted that human population would continue to grow until we had exhausted our resources. At that point, humans would become victims of famine, disease, or war. This has not happened, at least not yet. Some scientists think that the carrying capacity of the planet is about 1 billion people, not the 7 billion people we have today. The limiting factors have changed as our intelligence has allowed us to expand our population. Can we continue to do this indefinitely into the future?


  • Hunters and gatherers lived off the land, with no agriculture, and reached a total population of no more than around 10 million.
  • Farming allowed people to settle down and allowed populations to grow.


Use this resource to answer the questions that follow.


1. Who was Thomas Malthus?

2. What did Malthus think would happen as population increased?

3. What did Malthus think would limit population?

4. What is the Malthusian limit?

5. What is happening to population growth in some developed countries today?

6. Malthus didn't account for what in his theory?

7. What country is close to the Malthusian limit today?


1. Link major advances in agriculture and industry with changes in the human population.

2. What is carrying capacity? Has the human population exceeded Earth's carrying capacity for humans? If so, how could this have happened?

3. What is the Green Revolution? How has it affected human population?

4. What do you think of Thomas Malthus' prediction? Have we proven Malthus wrong or have we just not gotten to that point yet?



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