# Understanding Population Growth, Population Density, And Their Effect

This article pertains to population overall, including population growth, population density, overpopulation, and demographics. Population is defined as the number of people that live in a given geographic region such as a town, city, parish, village, country, or even a group of countries such as the European union. For example: New York City has a population of 8,175,133 people as of 2010. Meaning that 8,175,133 people lived in New York City in 2010.

## Population History

The world’s population growth normally follows a sharp upward trend, and the rate of population growth also increases sharply. According to a University of Michigan lecture, the world’s population was 1 billion in 1804. 123 years later, it exceeded two billion, and then sixty years later it increased to 5 billion. That is a 250% increase.

Then it exceeded 6 billion in 1999. Between 1804 and 1999 (a 195 year period) it grew by 600%, and between 1927 and 1999, it increased by 300% in only 72 years (that is a much faster growth rate). As the world’s population grows, the rate at which it grows increases with it.

As you can see, it grew more than ever during even shorter time periods. The bar chart below provides you with a clear view of the world population count (in billions) for each year. Source: University of Michigan.

World population growth between 1804 and 1999.

## Population Density

The population density of an area such as a city, for example, is the average number of people living in each square mile of that area. Each square mile of the area will have a different population density, but the total population of the entire area is used to calculate the average for each square mile. In other words, this can be obtained by dividing the total population by the number of square miles in the area. If the area is less than a square mile, you can still calculate that, so if the area is only half a square mile, then you would use the figure 0.5 square miles to make your calculation.

A country’s overall population density is not nearly as useful as the population density of individual areas in most cases. Some countries, such as the U.S for example have significantly varying population densities depending on the county. I was prompted to write this here because some people believe that the U.S population density is much lower than that of Japan, therefore Florida does not need high speed rail. The U.S population density is not the same as Florida’s.

Look at the map below and you will see that almost all of the U.S has a population density of less than 50 persons per square mile (pale yellow and orange areas), and then look at Florida, it is actually in the top 4 states with the most red areas which have a high population density of more than 250 persons per square mile.

The palest yellow areas are the largest fraction of the U.S and they have a population density of less than 10 people per square mile.

My point is that the low population density of the vast rural areas in the United States of less than 10 people per square mile lowers America’s average population density significantly. What matters in this case is Florida’s population density, not the entire country, more specifically the population density of the area in Florida that the rail project would be constructed.

Click the map to view a larger and clearer version of it.
Image obtained with thanks from the U.S Census Bereau.

Lightly coloured map of U.S states. Image obtained with thanks from Nationalatlas.gov.

# Effects of Population Growth

Population growth causes many things to grow, including demand for raw materials such as iron ore, copper, silver, gold, alumina, and more. It also causes the number of job seekers to grow, but at the same time, it causes the number of available job positions to grow because a greater population translates to a greater demand for basically anything, so manufacturers and service providers have to expand to compensate for that, and they require more employees to expand to work on assembly lines, as customer service representatives, etc.

Bear in mind that not everything grows with the world’s population. Water sources such as rivers, lakes, and rain do not grow. The amount of land available does not grow either, it shrinks. There is more information about the effects of population growth below.

## Relationship Between Population Growth, Shrinkage and Population Age

Money derived from taxation helps to pay elderly peoples’ pensions, yet a significant solution to the population growth issues mentioned below is for most people to have less children. If people reproduce less, then there will be less workers to pay taxes, and hence less tax money available to fund pension schemes, but also, the need for everything else reduces that much.

It may, at first seem as if the population would age more if people had less children, and hence there would be more old people and less young people  to grow up, get jobs, and contribute tax money to the economy, but:

The less the population reproduces, the less people there are to get old. More reproduction would actually, in the long run, increase the need for pension funds because all of the new children would get old eventually, and hence, will need pensions too.

## Water Supply

If water demand increases beyond river supply, then there will be a water deficit. In this case, it is assumed that the river mentioned is the only source of freshwater. Desalination is sometimes used to supplement shortfalls in water supply. As you can see below, the white area just above the water on the surrounding rock walls of the dam is a sign of a decreased water level. It is also referred to as a “bath tub line”.

Lake Mead at Hoover Dam. Click the image to see a larger version of it. Obtained with thanks from Cmpxchg8b on Wikimedia Commons.

An example of an attempt to supplement shortfalls in water supply is when the National Water Commission of Jamaica hired contractors to transport water from outside of the affected area to the dry spell afflicted area until the dry spell passed. The contractors used water trucks with multi-thousand gallon tanks attached to them to fill residential and business rooftop (and elsewhere) water tanks so that people could at least wash dishes and do other basic tasks.

## Scarcity of Minerals and their Importance

Increased population growth increases the demand for basically everything, and everything has to be manufactured using materials. For example: All electronics and household appliances are constructed of a variety of metals, including steel/iron, copper, aluminium, lead, mercury, brass, silicon, yttrium, cadmium, germanium, and many more materials. Some of which are rare and expensive, and some of which are abundant and inexpensive.

Despite the fact that some materials, such as iron, are abundant and inexpensive, that is just for the moment. The cost of these materials increases as demand increases, due to two reasons:

1. Higher material demand generally entails a price increase, but supply can be increased to remedy this, in the event of a supply shortfall, and improve the demand to supply ratio.
2. Demand can be considered the rate at which iron reserves are depleted, hence: Greater demand means that the scarcity of iron worsens faster, and it’s value increases. An increase in supply cannot solve this problem.

#### Recycling is One Remedy

Iron ore (for example) and other material mines are being excavated incrementally, reducing the amount of these materials left. Iron will inevitably become expensive at some point. Waiting until iron becomes expensive to start recycling or try and find alternatives to it is not a good idea. This is because recycled iron is already affordable.

Recycling iron more extensively could enable iron to last hundreds of years longer. This also applies to aluminium and copper. Copper is no longer inexpensive, though.

## Waste Accumulation

Overpopulation can result in excessive garbage accumulation which is of course due to the simple fact that more people = more garbage. This sometimes forces waste management organizations to transport waste to a location outside of the overpopulated area.

Landfills are sites at which rubbish decomposes and one environmentally important byproduct of that is methane. Methane (CH4) is a greenhouse gas which is 20 times more effective at trapping heat in the atmosphere than CO2. which is one of the main greenhouse gases of concern to climate change.

Methane from landfills is combustible and is sometimes used to generate heat and power required for factories. BMW and S.C Johnson did this.

## Overpopulation/Excessive Population

Is the world overpopulated?: In this article, I do not focus on the big picture of overpopulation, but more on what is most important, it is not that the world is overpopulated, but that certain parts of it are overpopulated, which some are the opposite. It does not make any sense to judge the overpopulation issue globally, but where exactly it is an issue.

Overpopulation is defined as excessive population count for an area of a given size, but whether or not population count is excessive is determined not only by the ability of a given area to supply the resources necessary to sustain life, but also the ability of the population to live together in a physically and economically healthy and safe manner. Some of what I mentioned below is discussed in more detail on other parts of this page.

Overpopulation can cause the population density of an area to become so high that the local water supply is rendered insufficient, for example. Scroll up to the water shortages section It can also render the food supply of the given area inadequate because it is not enough for everyone. This means that food will have to be imported from other areas.

## Effect of Overpopulation on Food Supply

Overpopulation can result in food shortages in some cases and it can also cause existing food producers to use growth hormones and pesticide to not only produce more but pesticide also prevents pests from eating the food itself which can affect supply to some extent.

## Effect of Overpopulation on Seafood Demand

As population count increases, the demand for food increases, including seafood. Seafood is normally captured from bodies of water by fishing.

When demand exceeds fish supply, there is an enormous sustainability problem.

## Effect of Overpopulation on Energy Demand

Globally, most electricity is generated by fossil fueled power plants which produce carbon monoxide (CO), carbon dioxide (CO2), and other pollutants depending on the plant. As the population of any area grows, electricity demand increases with it and the result is that more power plants will eventually have to be constructed to meet that increased demand, and consequently, pollutant emissions per square km increases.

Transportation: More people often means (though not always, because not everyone drives) that more cars will be on the road because it is very common for people to drive to work and sometimes school. Automobiles are propelled by fossil fueled combustion engines which emit CO, CO2, and other pollutants.

#### Effect of Overpopulation on Energy Reserves

As electricity demand grows with population, the reserves of finite energy sources such as coal, petroleum, uranium, and natural gas shrink at a higher rate.

Nicholas Brown is a writer and Android developer. He writes on CleanTechnica as well as Green Building Elements every now and then.

He has a keen interest in physics-related topics such as electricity generation, refrigeration and air conditioning technology, energy storage, and geography.