If a student were to ask me what the single greatest threat to the environment was, I would answer with the exponential growth of the human population. As we near a global population of seven billion people, the growth is showing signs of slowing, but is still continuing. More people mean more resources used, more pollution produced, and more threats to other species. Because of this, human population growth is a cause of all of the three categories of environmental problems.
Due to its influence on all environmental problems, human population growth is the first unit that I teach my environmental science class after our introductory unit. This topic is often also included in a biology, ecology, or even social studies curriculum. We begin with a look at human population growth throughout history. This is a great way to emphasize the interdisciplinary nature of environmental science as you can see many major historical events reflected in the exponential growth curve of the human population. Throughout most of human history, the population remained small as hunter-gatherers. Around the time of the Agricultural Revolution, you can see an increase in the global population as people moved into cities and more food supported larger populations. The growth remains constant and slow through many millennia. The part of this growth curve that I particularly emphasize is the dramatic population increase that occurs around the time of the Industrial Revolution. World human population did not reach its first billion until the 1800s. It took only about 100 years to double the population, and doubling time has been decreasing rapidly ever since. It is this increase in population, affluence, and technology that has caused the increased environmental impact of humans on the environment.
After this discussion, I introduce the concept of carrying capacity. I ask students how many people they think the Earth can support. This question makes for an interesting discussion since even scientists are unsure of the answer. Since we have discussed the ecological footprint of individuals on the world previously, students understand that the number of people that the planet can support depends on the lifestyle of those people. We do not have the resources and energy to support the current global population in the lifestyle that we have as Americans.
Once students understand the exponential growth and potential carrying capacity of the Earth for humans, I introduce the concept of demographic transition. The demographic transition model shows how populations increase as modern sanitation and health care allow historically high death rates to decrease. Since birth rates do not automatically decrease to match the decreasing death rates, populations grow rapidly. As birth rates decrease to once again match death rates, a country is said to undergo its demographic transition.
Students may not understand the cultural reasons why certain countries still have high birth rates and are undergoing the demographic transition slowly. Since I cannot personally take my classes to visit countries around the world to gain this perspective, I use the Nova film, “World in the Balance: Population Paradox.” This film does an excellent job of explaining the various cultures in the world and how they contribute to the population issue. It also emphasizes the exponential growth curve and demographic transition model that we have already discussed, as well as introduces the concept of population pyramids.
You can also use role plays to show students the differences in population around the world. You can give groups of students a country to research. Then you can have students plot the population pyramid of their country on a poster board. Based on their research, students can write a skit to portray some of the cultural issues in that country that contribute to its population issues. To give a variety of perspectives, try some of the following countries – India, China, Kenya, Japan, Germany, the United States, and Russia.
My goal for this unit is to give my class a broader perspective of population issues and the complexity of their solutions. The lessons below will help you do to the same with your students.
Human Population Growth Lesson Plans:
In this lesson students learn about population pyramids, which show the age distribution of individuals in a country. The shape of the pyramid can tell us if the population is growing or shrinking, or if there are particular problems in the country, such as an AIDS epidemic. Having students compare population pyramids for various countries will help them learn about the value of these diagrams.
Students explore factors that change human population growth in a biology simulation for seven countries including the United States, China, Egypt, Germany, Italy, India, and Mexico. Factors such as age at which women begin having children, fertility rate and death rate are examined.
Students explore population growth, discuss potential issues associated with the world's growing population, evaluate public policy in the area of population growth, and create population pyramids.
Students examine the changes in the population in Idaho over a specific amount of time. In groups, they use a digital atlas to identify the trends in the population and describe why and how they exist. To end the lesson, they compare and contrast human population growth limits from the past and today.
Students use this lesson to focus on population growth and the threat of overpopulation. In groups, they analyze the world birth and death rates to determine the growth rate of the population. As a class, they discuss the causes and consequences of a growing population on the land space and resources available. They pretend with a partner to have a discussion about adding a new baby to their family and how it would affect Connecticut as a whole. This could be adapted for use with any geographic region.
Students examine the changes in the population in Idaho over a specific amount of time. In groups, they use the digital atlas to identify the trends in the population and describe why and how they exist. To end the lesson, they compare and contrast the human population growth limits from the past and today.
Students make a variety of mathematical calculations designed to illustrate the current size and growth rate of the human population. They analyze a graph that shows human population growth over time.