Summary

Educational Significance

Global change occured before the first humans appeared on Earth. There were Ice Ages long before human populations were of consequence. Natural catastrophes such as volcanic eruptions and explosions or impacts between Earth and asteroids may have caused sudden and dramatic changes to the planetary environment in the past. However, at this point in the history of the Earth, human activities are the most significant agents of global changes.

The human population is large, larger than it has ever been before and it is growing exponentially. Many students and adults have difficulty understanding the nature of exponential growth. Thus, activities or models which can help to develop this understanding will be useful.

All biological populations depend on the environment for the requirements of life. All organisms draw their life requirements from natural systems and in the course of doing so they often modify that environment. Thus, over time, as a population grows its impact on the environment becomes more and more significant. If a population grows rapidly it can outstrip the capacity of the environment to supply its needs and can degrade its habitat even further. Unchecked growth of populations will eventually surpass the capacity of the environment to sustain the species. When this happens, the species may suddenly decline through starvation, lack of shelter, available water, or lack of any other critical factor. Only one critically needed component of the environment has to be exhausted or in short supply to become a check on further growth of the population which depends on it. Such factors are called limiting factors. Thus, the concepts of Carrying Capacity and Limiting Factors are important to an understanding of this chapter and students' understanding of them should be developed through a number of teaching/learning activities.

The exponential growth of the human population is creating an important impact on the Earth's systems. We do not live lightly on the land, especially in the developed, industrialized world. We use technology to exploit and store energy and material resources. We think we have been able to escape some of the environmental limits imposed on early humans and other species. But the escape may be very temporary. Our use of technology and energy stored as fossil fuels has greatly contributed to global change caused by human activity. We have degraded the very systems on which we depend to support our large, and growing human population.

The developed world tends to blame many environmental problems on more populated, less developed regions. In doing so we fail to note that it is the resource-consuming lifestyles in the developed nations which have caused many of the environmental problems not only in our own lands, but also in the rest of the world. Many of the environmental problems of the developing world are connected to poverty, lack of basic services and education, and denial of human rights. Many of these problems are indirectly or directly caused by the demands of the developed nations.

Our use of natural resources has deep roots in human values and culture. Students need to see the connections between social, economic, political, and environmental realities instead of dealing with global change purely as a series of biological, scientific or technological issues . This fact strongly recommends a thematic, multi-disciplinary approach to the study of global change as a curriculum topic.

Learning Outcomes

• define and describe limiting factors and carrying capacity and use graphs, models, or written examples to illustrate their descriptions;
• illustrate the exponential growth of populations using graphs or other examples;
• describe the growth of the human population over history and discuss the implications of this growth pattern in terms of carrying capacity and limiting factors;
• discuss the ways in which humans have used technology to escape, at least temporarily, direct environmental regulation of the population size of our species;
• describe, using appropriate examples, the consequences of human population size and human use of energy and material resources;
• debate the proposition that the real problem of human population is not size but the environmental demands of a consumer lifestyle on the part of the inhabitants of the developed, industrialized nations; and
• critique the proposal that the long-term solution to the problems of human activities causing global change is to change human values and the economic system.