Earth Science: Geology, the Environment, and the Universe

Chapter 27: Human Impact on Earth Resources

Problem of the Week

Human Carrying Capacity: What’s the Limit?

Carrying capacity, is defined as, "the number of organisms that any given environment can support" (pg. 714 in text). In each environment, and on Earth in general, there is a limited supply of resources. As long as the resources remain available, groups of organisms or populations, can continue to exist in that environment. In times of abundance, populations thrive and increase; in times of great scarcity, populations crash. What usually happens, is that resources remain fairly stable and populations of organisms in an environment fluctuate up and down "around" the carrying capacity for that organism. Each element of the resource "bank" can act as a limiting factor. If a resource runs out, the population's growth is limited by its absence.

Some scientists believe that the human population may have already gone far above the "actual" carrying capacity of Earth, and that we are playing on borrowed time and resources. At the time of this writing, the world population was estimated at 6,113,980,320 people and growing. As humans we have the ability to manipulate our resource supplies, and the environment, to allow us to go beyond what the environment can actually support.

Check out the following Web site to see how much the population has increased since this problem was written. Put in your age to see what the population was when you were born. Look at the difference. http://www.popexpo.net/eMain.html

Things to Think About:

1. Which environmental factors normally act as limiting factors?


2. What factors control or may control the limits of human populations?


3. Ways in which humans manipulate these factors to "outwit" nature.

Problem:

The data table below shows some predictions. Based on a steady increase every twenty years, what would the predicted figures be for the year 2030. Discuss with a classmate, or as a group, whether growth at this rate is sustainable, or will the resources run out?

Source: Postel, S. "Carrying Capacity: Earth’s Bottom Line." State of the World, 1994.