Climate change can decrease the carrying capacity of a region.

By Dr. John Hidore

February 23, 2017—The human population has been growing in size and spreading out over the planet ever since its origin in Africa long ago. It is currently growing faster than at any time in history. Today it is equivalent to adding the populations of the earth’s three largest metropolitan areas each year…or between 80 and 90 million people every 12 months. Various estimates place the global population at between seven and seven and a half billion. Of this two billion has been added in just the last 24 years.

Overpopulation Defined

There are a number of concepts being used today in relating the size of the human population to the environment. These are population growth, limits to growth and overpopulation, and they are each related. The basic resources people need are food, water and essentials for clothing and shelter. Ideally, in any region the size of the human population remains below or in balance with the resources available to support it. When in balance it results in the population being sustained for long periods of time. However, we do not live in an ideal world and the sustainable population seldom exists.

Population growth in any region may result in the area no longer having enough resources to sustain the growing number of people at a healthy level. When this occurs either the people, the environment, or both become stressed. The symptoms of population stress include human health problems, resource depletion, migration, and violence. Environmental stress includes a variety of processes, including deforestation, soil erosion and climate change. In any event when human stress or environmental stress takes place the region is overpopulated.

Processes That Create an Unsustainable Population

Even if the population in a region stays fairly constant it can become overpopulated by environmental changes. Climate change can increase the number of people a region can support. Rainfall may increase in a dry region, or temperatures may get warmer or cooler to favor plant growth.

Carrying capacity is the number of organisms a region can support without environmental degradation. Climate change can decrease the carrying capacity of a region. During the last ice age, large areas of what are now dry lands or deserts received more rainfall than they do now. The Sahara Desert and much of the middle east contain the remains of cities that flourished during wetter times, but are abandoned now due to climate change.

Changes in technology can also change the carrying capacity. As technology has progressed through time many regions have been able to support an increasing number of people. However, the effect of technological change tends to be short-lived and ultimately encourage overpopulation. Even with a more favorable climate and the addition of technological advances there is still a limited carrying capacity and overpopulation can occur.

The green revolution of the 20th Century is a good example of how the carrying capacity can be increased. Modifying plant species allowed crop production, particularly grain, to greatly increase and feed a growing population. 

Just as humans can increase the carrying capacity they can also decrease it. Over-grazing by livestock, soil erosion, salinization of soils, deforestation, or human induced climate change can reduce the carrying capacity. This lowers the level of the sustainable population so that overpopulation occurs.

Overpopulation: The Big Question

The big question, “Does overpopulation occur regionally or globally?” Clearly on a regional basis the answer is yes. All the symptoms are there. Whether it is occurring on a global basis in today’s world is not clear. There are symptoms of overpopulation on every continent except the Antarctic.

Many scientists say the evidence of overpopulation is severe. For example: more than a billion people are undernourished. Another billion do not have clean water to drink.

 Climate change is taking place at an astonishing rate. The extinction rate of plant and animal species is the highest in recorded history. It may be that the resources available to us will support a population of only half what it is at the present time. If the latter is the case, immediate, and perhaps extreme, measures must be taken if world stress and turmoil is to be avoided!

The evidence of overpopulation is severe!