This past Friday in class we began our study of the human population, also known as demographics.
As many Environmental Science textbooks say, the number one environmental problem is that there are too many humans. The current world population is quickly approaching 7.1 billion, but for the AP exam, the world population is about 6.8 billion, since the exam was written a couple of years ago. Serving as evidence that the human population is the main issue, all of the threats to biodiversity (HICOP) are caused by humans. The map below shows which countries have the most people by depicting them as larger. It is called a cartogram.
By looking at the cartogram, you can see that some smaller countries appear to be much larger than other countries with more geographical area. For example, on the cartogram, China is depicted as much larger than Russia, but we all know that Russia is Geographically much bigger than China. This leads us into our next discussion: Population Density Issues.
In class we listed the top 5 most populated countries and the top 5 largest countries.
For population we have: 1. China (1.3 billion); 2. India (1.2 billion); 3. United States (.3 billion); 4. Indonesia (.25 billion); 5. Brazil (.2 billion).
For land area: 1. Russia; 2. Canada; 3. China; 4. United States; 5. Brazil.
These statistics show that Indonesia and India are in trouble because they have extremely large populations, but they are not even in the top 5 largest countries. This means that the population is much more dense than other countries.
Next, we watched a video that showed the human population growth from 1 AD to 2030 AD.
In class we talked about the causes for the two biggest population jumps in history. The causes are the Industrial Revolution, and the use of Modern Medicine. This image from one of Mr. Willard’s slides shows the human population growth curve:
By looking at the human population growth curve, you can see that the rate of growth drastically increases around the time of the industrial revolution. This leads us into our next discussion about the doubling time of our population. The following picture shows the human population at certain years and the rate of growth for several intervals of time. By using the rule of 70, we calculated the rate of growth for several intervals of time.
The diagram shows that the doubling time for our population is getting smaller and smaller as our population grows bigger and bigger. This is a very important lesson. As population grows exponentially, doubling time decreases.
Lastly, we discussed the fact that the human population continues to grow exponentially because humans have essentially gotten rid of some density dependent limiting factors such as disease, parasites, and predation.
Humans have worked around disease by creating vaccines to prevent diseases, and antibiotics to treat them. We have avoided parasites by learning to cook our food and to boil our water before ingesting it. And we have eliminated predation by developing countless ways to avoid and protect ourselves from dangerous animals. The only density dependent limiting factor that humans have not worked around is competition, which we still experience in the form of wars.
For whoever was absent last Friday, I hope this helps.