The Human Population - Online Tutor, Practice Problems & Exam Prep

Human population growth has accelerated over the last four centuries due to advancements in agriculture, medicine, and technology. While the total population is projected to rise to 9.7 billion by 2050, the growth rate has been declining since the 1960s, influenced by factors like disease and voluntary population control methods such as contraception. Age structure plays a crucial role in understanding population dynamics, with developing nations exhibiting high birth and death rates, while developed nations show lower rates. Estimating Earth's carrying capacity is complex, with current ecological footprints exceeding sustainable limits, highlighting the need for responsible resource management.

The Human Population

This video, we're going to shift our focus over to the human population. Human population growth has actually been increasing faster than even exponential population growth models predict over the last four centuries. This is due to advances in agriculture, medicine and health care, living conditions, and technology. However, despite the fact that the human population size has been increasing and is projected to continue to increase through the year 2050, it's very important to be aware that the rate of human population growth has actually been decreasing since about the 1960s, and it's projected to continue to decrease through the year 2050. This is believed to be due to density-dependent factors, such as disease, which spreads more easily and faster to individuals in larger populations, and it's also believed to be due to voluntary population control, like contraception and policies that encourage smaller family sizes.

And so we can actually see this down below in this graph, which has the year on the x-axis from 1600 all the way up through projecting through the year 2050, and we've got these two y-axes. We've got this right y-axis, which has the world human population size in billions, which corresponds with this blue curve you can see in the graph, and then we've got this left y-axis over here, which is the population growth rate in annual percent change, which corresponds with this purplish-pinkish curve you can see in the graph. A few things to point out here is that way back in the 1600s the human population size was estimated to be just below one billion, but right around today's date the human population size is estimated to be just above eight billion. And so this is a drastic increase in population size and it's faster than even exponential models predict because the exponential models might predict somewhat of a gradual increase like that, but what we see here is this drastic increase. Now, another thing to point out is that, again, the human population growth rate has also been steadily increasing, but right around the 1960s or so, you'll notice that there has been this decrease in the human population growth rate.

And notice that it's projected to continue to decrease through the year 2050. Now, there is this weird little peak here, and this is likely due to the world wars in the 1900s, but, you can pretty much just disregard that and just focus on this decrease here. And so this here concludes our brief introduction to the human population, and we'll be able to continue to learn more as we move forward. So I'll see you in our next video.

Age-Structure Affects a Country's Human Population Growth

This video, we're going to briefly discuss age structure and how it can affect the country's human population growth. Age structure is really just the number of living individuals in a population at each age group, and it is often displayed as an age structure pyramid like the ones you can see down below, where each level of the age structure pyramid corresponds with a very specific age group. These age structure pyramids are color coded so that males appear in a blue color and females appear in a pink color. The size of each of these blue and pink bars tells us the percentage of the population that each of these groups makes up of the whole. It turns out that the age structure alone can actually reveal a pretty decent amount of information about the development and the industrialization of a country.

Developing non-industrialized nations, such as Zambia, for example, a country in Africa, tend to have these really bottom-heavy age structure pyramids where they have quite a lot of really young individuals and relatively few older and middle-aged individuals. These developing non-industrialized nations tend to have really high birth rates and high death rates as well, which creates high mortality rates and low survivorship from age group to age group in the age structure pyramid, and this leads to relatively low life expectancy. On the other hand, already developed and industrialized nations, such as the USA, tend to have more balanced age structure pyramids, and they tend to have relatively low birth rates and low death rates, which creates relatively low mortality and high survivorship from age group to age group, and this leads to relatively high life expectancy. The transition from a developing non-industrialized nation to a developed industrialized nation is referred to as demographic transition. Demographic transition is really just this shift from having really high birth rates and death rates to having really low birth rates and death rates as the country industrializes.

Notice that this purple arrow down below is representing demographic transition. Again, this shift from developing and industrialized nations to a developed industrialized nation. This here concludes our brief lesson, and we'll be able to apply these concepts and problems moving forward, so I'll see you in our next video.

The Human Population Example 1

So here we have an example problem that asks, in the stages of industrialization graph down below, the mortality rate drops rapidly in stage 2. What is the primary reason for this? And we've got these 4 potential answer options down below. And so notice that this graph here is actually showing you a different perspective of demographic transition, which recall from our last lesson video is when a country develops and industrializes, and goes from having really high birth rates and mortality or death rates, indicated by these really high green and red lines, to having really low birth rates and mortality rates. And so, again, this problem wants us to determine what is the primary reason for the mortality rate dropping rapidly in stage 2.

So notice here is stage 2 and the red line dropping rapidly that decreased. They want to know what's the primary reason for that. Now notice that answer option a says birth rates have increased so that more people are alive at any given time. But notice that in this graph, the birth rates indicated by these green lines, aren't really going up at any point. It's really just going down. And so, the birth rates have not increased and that's not going to be the main reason.

So, we can eliminate answer option a. And notice that answer option d says birth rates decrease so fewer people are alive at any given time. Now it is true the birth rates here, this green line, it does decrease, but it decreases after the mortality rates decrease. So the decrease in birth rates is not going to be the main reason for the decrease in mortality rates. So for that reason, we can eliminate answer option d.

So now we're between either option b or option c, and notice option c says farming technology improves, so fewer people are required to work on farms. Now although this may be true that the farming technology improves and there are fewer people working on farms, that's not going to be the primary and most direct reason for the drop in mortality rate in stage 2. And so for that reason, we can cross that off, and this leaves answer option b, which is the correct answer. And it says healthcare improves, allowing people to live longer. And so as people are able to live longer, that's going to reduce the amount of deaths that are occurring, and that is really the main reason for the mortality rate drop in stage 2.

And so b here is the correct answer to this example problem, and that concludes this problem. So I'll see you all in our next video.

Which of the following occurs in a country that is going through demographic transition?

• A. Birth rate drops rapidly while death rates remain constant.
• B. Death rate drops rapidly while birth rate remains constant.
• C. Life expectancy increases, death rates drop, & birth rates remain high at first but then gradually decrease.
• D. Life expectancy increases & birth rates gradually increase.

Estimating Earth’s Human Carrying Capacity

In this video, we're going to talk about estimating Earth's human carrying capacity, which turns out to be extremely difficult as estimates have varied widely from about 13,000,000,000 humans up to over 1 trillion humans in some cases. There are many different methods that can be used to help us estimate Earth's carrying capacity for humans, including this concept of ecological footprint. What's important for you to realize is that all of our human activities consume resources and produce wastes, and nature needs to have the capacity to handle these demands. The ecological footprint is really just a way for us to measure if nature is capable of meeting the demands of our human activities or not.

Another important thing for you to realize is that every single individual has an ecological footprint, including me and you. This ecological footprint can be scaled up from individuals to a household, to a city, to a country, and ultimately to a global human ecological footprint. Ecological footprint can be defined as the amount of land and water that's needed to support current human activities, and it's often measured in GHAs or global hectares. To understand a global hectare, we first need to define a hectare, which is simply a unit of area that's equivalent to 10,000 meters squared and is approximately equal to 2.47 acres.

For you football fans out there, this is an area that's just a little bit less than 2 American football fields, including the end zones. A global hectare, abbreviated as GHA, is a hypothetical hectare of land or water with world average biological activity. GHAs only include hectares that are capable of supporting human activities, and those not capable are disregarded from the calculation of global hectares. As an average, global hectares are a standardized measurement, allowing us to compare ecological footprints of individuals and countries in completely different parts of the world. Let's take a look at the image down below where on the left-hand side, we're showing you the entire earth.

It's estimated that the Earth's entire surface has about 51,000,000,000 total hectares. However, not all of those hectares are capable of supporting human activities, and not all hectares are equivalent in terms of their biological activity or productivity. It's estimated that there are only about 12,000,000,000 globally productive hectares. With a human population size today of about 8,100,000,000 humans, if we were to evenly distribute these 12,000,000,000 global hectares to each of these 8,100,000,000 humans, we get the maximum sustainable ecological footprint. This is a kind of carrying capacity. By dividing 1 2 , 000 , 000 , 000 by 8 , 100 , 000 , 000 , we get an answer of about 1.5 global hectares per person.

Unfortunately, it's believed that humans currently have an unsustainably large ecological footprint greater than the maximum sustainable one, estimated at 2.7 global hectares per person. This is larger than 1.5 and signifies that, if maximum sustainable ecological footprint represents the carrying capacity, we are somewhat already beyond the carrying capacity in some ecologists' eyes. Notice the image on the right-hand side where we've got some interesting features on the shoes, showing different human activities. In the shoe with the actual ecological footprint, we're depicting human activities that are more environmentally demanding, such as using individual cars for transportation, coal-burning factories for energy, deforesting areas, using animals as a primary food source, and cargo ships with oil spills which can be devastating to aquatic biomes.

Ultimately, it's important for us to be aware that the actual ecological footprint on average per person is estimated to be greater than the maximum sustainable ecological footprint. By being aware, we can each do our part to reduce our ecological footprints and help others around us reduce theirs so that we are less demanding on nature and can ensure a sustainable and happy human population over time. This concludes our lesson, and we'll be able to apply these concepts moving forward. See you all in our next video.

The Human Population Example 2

Here we have an example problem that says, France has a population of 68,000,000 and a total ecological footprint of 312,800,000 global hectares. Qatar has a population of 2,670,000 and a total ecological footprint of 39,700,000 global hectares. Which of these nations has the higher per capita ecological footprint? Below are four potential answer options. Notice that this image of the world map is color-coded to the per capita ecological footprint in global hectares. That's what these values represent.

To calculate the per capita ecological footprint, which, recall, means per individual, all we need to do is take the total ecological footprint for each of these countries and divide it by their total population size. When we do that for France, the calculation will come out as:

312,800,000 global hectares 68,000,000 people

When you type this in your calculator, you get an answer of 4.6, with the units being global hectares per person. Now when you do this for Qatar, the calculation will be:

39,700,000 global hectares 2,670,000 people

And when you type this in your calculator, you get an answer of about 14.9, with the units being global hectares per person.

Clearly, Qatar has the larger per capita ecological footprint. Thus, answer option b, which says Qatar, is the correct answer to this problem. That concludes this example problem, and I'll see you all in our next video.

The USA currently has one of the highest per capita ecological footprints of any country in the world. Which of the following steps can be taken to reduce the USA’s ecological footprint?

• A. Transition to more renewable energy sources such as solar & wind power.
• B. Introduce more public transport to areas with large amounts of traffic & pollution.
• C. Eating more locally sourced food.
• D. All of the above

Suppose it’s now the year 2100, the human population size has soared to 10.7 billion, and technology advancements allowed us to increase the biologically productive global hectares to 35 billion gha. Considering this, what would be the maximum sustainable per capita ecological footprint? If the actual per capita ecological footprint is estimated to be 3.00 gha per person, what could all of this imply about the Earth’s carrying capacity for humans?

• A. 1.43 gha per person.
• B. 2.34 gha per person.
• C. 3.27 gha per person.
• D. 3.70 gha per person.