agriculture and human population growth

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. Weve 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 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?

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 1.5). 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 worlds fresh water is used for agriculture. Rows of a single crop and heavy ma- chinery are normal sights for modern day farms. The Green Revolution has increased the productivity of farms immensely. A century ago, a single farmer produced enough food for 2.5 people, but now a farmer can feed more than 130 people. The Green Revolution is credited for feeding 1 billion people that would not otherwise have been able to live.


the industrial revolution

The next major stage in the growth of the human population was the Industrial Revolution, which started in the late 1700s (Figure 1.4). This major historical event marks when products were first mass-produced and when fossil fuels were first widely used for power.



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 1.2). 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. More advanced farming practices allowed a single farmer to grow food for many more people. When advanced farming practices allowed farmers to grow more food than they needed for their families (Figure



advances in agriculture and population

Every major advance in agriculture has allowed global population to increase. Early farmers could settle down to a steady food supply. Irrigation, the ability to clear large swaths of land for farming efficiently, and the development of farm machines powered by fossil fuels allowed people to grow more food and transport it to where it was needed.

hunters and gatherers

What is Earths carrying capacity for humans? Are humans now exceeding Earths carrying capacity for our species? Many anthropologists say that the carrying capacity of humans on the planet without agriculture is about 10 million (Figure 1.1). 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. 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?


instructional diagrams

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which of these statements is true?

a) 10,000 years ago men hunted and fished, while women gathered nuts and vegetables

b) many anthropologists believe that the carrying capacity of humans without agriculture is about 10 million

c) advances in our brain capacity, erect posture and use of our hands helped advance the human population

-->  d) all of the above

farmers were able to increase the yield of food plants.

-->  a) true

b) false

agriculture allowed people to

a) have food all year round

b) settle down so that they no longer need to carry out all their possessions

c) store food for when it is difficult to grow

-->  d) all of the above

the industrial revolution was a major historical event that allowed ____.

a) people to live an agricultural lifestyle.

-->  b) solar energy stored in fossil fuels to do the work that humans had done.

c) people to make choices about population growth.

d) all of the above

one side benefit of the industrial revolution is that

-->  a) people were free to develop the arts and culture.

b) people no longer have to be scared by dark skies at night.

c) people were freed from boring dangerous labor.

d) none of the above

the use of artificial fertilizers and chemical pesticides has not increased much in the past 50 years.

a) true

-->  b) false

this scientist in the eighteenth century predicted that human population would continue to grow until we had exhausted our resources.

-->  a) thomas malthus

b) thomas edison

c) alfred wegener

d) louis leakey

the green revolution has

a) greatly increased agricultural productivity.

b) allowed the human population to increase by billions more than it would have.

c) use groundwater and fossil fuels in ways that are unsustainable.

-->  d) all of the above.

it is possible that earths carrying capacity for humans is around 1 billion.

-->  a) true

b) false

human population is currently

a) held down by limiting factors.

b) well with the limits of the population that earth can support.

-->  c) very likely exceeding earths carrying capacity for humans.

d) all of the above.

diagram questions

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