Tuesday, February 5, 2013
Human Population Growth
I have spent a lot of time trying to convince you that exponential growth is an unrealistic model of population growth. Interestingly, human populations have experienced exponential-like growth. How can this be?
What makes humans different from other species?
In other species per capita birth rates and per capita deaths rates are density dependent. However, as human populations have increased there has been no corresponding decline in per capita birth rates or increase in per capita death rates. What makes humans different from other species?
Humans have the ability to alter their environment so that they can avoid the density dependent effects on birth and death rates. 1) Humans have increased food production by improvements in agriculture (e.g., irrigation, fertilization, mechanized farming, genetically improved crops). 2) Humans have been able to decrease death rates by improvements in medicine and public health (things as simple as not pooping in the water you drink helps a lot!). 3) Humans have elimnated most human predators (ocassionally, someone gets killed by a shark or a mountain lion).
Where is human population growth occuring?
The rates of human population growth are not the same in all regions. Today, human populations are increasing in size much faster in developing countries (e.g., Mexico, other countries in Central America, Africa, and Southeast Asia) than they are in developed countries (e.g, USA, Canda, Western Europe). The figure at the top of this post shows the patterns of population growth in developed and developing nations.
Thus we see that populations are increasing most rapidly in the countries that are least able to deal with a rapidly increasing population. See "Population Challenges-The Basics" that can be downloaded from the Population Institute's website.
Human Population Growth Problem?
There is a great deal of debate about whether increasing human populations are a problem or not, and if they are what should be done about it. Unfortunately, we don't have time to discuss this issue in very much detail in class. My personal opinion is that we have too many people consuming too many resources and the last thing that we need are billions more people living on the planet. This is an issue that I am always intersted in talking more about if you would like to chat.
The section on Human Population Growth in your textbook is quite good.
Also see the article "Human Population Explosion" from the EoE.
Both of these contain a good discussion of the "demographic transition".
Really Cool Video
Here is a link to a YouTube video on "World Population" The first minute and a half or so is a little boring, so you can skip over it if you wish. However, I think the animation showing when and where human population growth has been occuring is really cool.
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- describe patterns of human population growth in developed and developing nations
- discuss some reasons why the pattern of population growth in humans is so different from that in other species
- describe the demographic transition
- discuss their own personal view of human population growth.
Past Test Questions (answers at bottom of post)
1. In developing countries, why have per capita birth rates not decreased as human populations have increased in size?
(a) because we have increased rates of food production
(b) because of the improvements in education of women
(c) because of improvements in medical care
(d) a and c
(e) a, b, and c
2. Why do some people consider the high growth rates of human populations in developing countries to be of concern?
(a) because many people are born into conditions that do not provide them enough food
(b) because many people are born into conditions without clean water and adequate sanitation
(c) because increasing population sizes have led to increasing habitat destruction
(d) a, b, and c
(e) none of the above
answers- 1.d, 2.d