Home » Population

Category Archives: Population

Technological Progress and Demographic Conversion


I have little faith in demographic conversion. Population is a problem we must find a way to manage, or it will manage us.


Figure 1. Data source: U.S. Census Bureau

The previous two posts have focused on the size of the world’s population and why it matters. This post will draw out additional implications.

In 7.4 Billion and Counting I reported that as of the date I wrote that post the world’s population was 7,409,620,694, and that it was increasing by more than 2 every second. That’s a million people every 4.8 days. I published Figure 1, which shows that for 11,000 years of human history, the population grew relatively slowly. In the last 250 years, however, it has spiked upward, and we added the last billion in only 13 years. What happened?

In Why Does World Population Matter? I reported that only two factors affect world population: births and deaths. If you want to add to world population, then you must either have more births or fewer deaths. Population spiked during the last 250 years because the death rate decreased, especially the rate of infant mortality. This change occurred because of improvements in farming, leading to an increased food supply, but especially because of improved public health and medical care: sewers, proper food handling and storage, immunizations, and advancements in childbirth – those sorts of things. With fewer people being removed from the world by death, but birth rates remaining the same, the population spiked.

Figure 2. An S-Curve Describes Population Growth Over Time. Source: Brodnick 2016.

In Why Does World Population Matter? I published Figure 2. It shows that over time population increases ever more rapidly until resource scarcity limits it. This point is called the carrying capacity. As population approaches carrying capacity, one of two things happens: individuals become too unhealthy to be able to bear children, or the death rate increases. Either represents a substantial uptick in misery and suffering.

The implication is that for any given level of resources, if left unchecked, population will expand to consume all of the available resources. If one wishes to avoid an increase in misery, suffering, and death, then only two options are available. One is to reduce the birth rate. The other is to increase the amount of resources available. Unfortunately, based on the same reasoning, once that new level is reached, then population will inevitably expand to the new carrying capacity, and misery will increase again. This tendency became known as the Malthusian Trap, named after John Malthus who originated the idea. Malthus wrote in the late 1700s, and he focused principally on the availability of food. In the 1960s, Paul Ehrlich adopted Malthus’s reasoning. Writing in the mid-20th Century, he expanded the analysis to include other environmental stresses besides food. Both Malthus and Ehrlich predicted imminent catastrophe from expanding human population.

Figure 3. Source: Our World in Data.

Aside from reducing the birth rate, the only other option is for technological progress to outrace population growth, to constantly increase resource availability faster than population increases. Both Malthus and Ehrlich believed that the race was about to be won by population growth. Both were wrong, at least in the short run. Humankind has proved remarkably adept at winning this race – so far, at least. Technological advances have increased food availability throughout the world, and also the availability of most of life’s necessities. To take only one example, despite the impression you get from the headlines, famine has not increased; if anything, it is at an all-time low (Figure 3).

.

Figure 4. Source: World Bank.

In the mean time, an interesting thing occurred: as standards of living increased, the birth rate decreased (Figure 4). In 2015, only 19.7 children per 1,000 people were born, compared to 36.1 in 1963. This trend is universal: data was available for 196 out of 217 nations, and in every one of them, the birth rate fell between 1960 and 2015. Demographers call this change demographic conversion, and attribute it to many factors. Perhaps primary among them are reduced child mortality and the availability of birth control technologies. If the chances are good that children will survive to adulthood, then you don’t have to have so many, and the ability to put that choice into action is available.

.

.

Figure 4. Data source: U.S. Census Bureau.

Some writers place great emphasis on demographic conversion, arguing that nothing needs to be done to control population; it will control itself as living standards improve. On the other hand, Figure 5 shows historical world population from 1950 to 2016, and projects it to 2050, with the historical data in blue and the projections in red. Looking carefully, a small flattening of the curve can be seen in the projected data. This is the vaunted demographic conversion. It is not evident in the actual historical data – it is only a projection. Look how small it is! Even if it occurs as projected, population will grow from 7.4 billion to 9.3 billion by 2050. If that is control, it is hard to imagine what uncontrolled means!

.

In Why Does World Population Matter? I reported on work at the Stockholm Resilience Center that suggests there are 9 ecological thresholds we cannot cross without degrading the capacity of the earth to support life. We have already crossed two of them, and are approaching others. It may be that technological progress has not actually been winning the race against population, but rather borrowing from the future to stave off disaster now.

I don’t personally find the theory of demographic conversion very comforting. I believe (and it’s a belief, not an established fact) that the environmental stresses piling up around the world indicate that we have already passed the carrying capacity of the earth. Ecological changes, such as the depletion of the oceans, destruction of coral reefs, species extinction, desertification, and climate change are signs that we actually are losing the race to outpace population growth. I believe that we not only have to reduce population growth, I believe we have to reverse it: we have too many people already.

To suggest such a thing is fraught. It offends people values, and it raises very thorny economic and social justice problems. But, I believe, we will either manage this problem or it will manage us via an increase in misery, suffering, and death.

Sources:

Hasell, Joe, and Max Roser (2017) “Famines”. OurWorldInData.org. Downloaded 8/22/17 from: https://ourworldindata.org/famines.

Lam, David. 2011. “How the World Survived the Population Bomb: Lessons ffrom 50 Years of Extraordinary Demographic History.” Demography, 48(4):1231-1262. Downloaded 8/20/2017 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3777609.

World Bank. Birth Rate, Crude (per 1,000 people). Downloaded 8/20/2017 from http://data.worldbank.org/indicator/SP.DYN.CBRT.IN?end=2015&start=1960&view=chart.

Historical World population data are from: U.S. Census Bureau. World Population: Historical Estimates of World Population. https://www.census.gov/population/international/data/worldpop/table_history.php.

Steffen, Will, Katherine Richardson, Johan Rockstrom, Sarah Cornell, Ingo Fetzer, Elena Bennett, R. Biggs, Stephen Carpenter, Wim de Vries, Cynthia de Wit, Carl Folka, Dieter Gerten, Jens Heinke, Georgina Mace, Linn Persson, Veerabhadran Ramanathan, B. Reyers, and Sverker Sorlin. 2015. “Planetary Boundaries: Guiding Human Development on a Changing Planet.” Science, 1/16/2015. Downloaded 8/13/2017 from https://stockholmuniversity.app.box.com/s/v8q2noqkkwk60o3uikyuy3txr7ifycc8.

USA population data prior to 2000 are from U.S. Census Bureau. Part II. Population of the United States and Each State: 1790-1990. http://www.census.gov/population/www/censusdata/Population_PartII.xls.

USA population data for 2000 and later are from U.S. Census Bureau, Population Division. Table 1. Intercensal Estimates of the Resident Population for the United States, Regions, States, and Puerto Rico: April 1, 2000 to July 1 2010 (ST-ESTOOINT-01). http://www.census.gov/popest/data/intercensal/national/nat2010.html.

Advertisements

Why Does World Population Matter?

 


If world population exceeds the world’s carrying capacity, it will result in misery, privation, and death. Unfortunately, the world’s carrying capacity is not well known.


In the previous post, I reviewed some data regarding world population. In this post I will discuss reasons that population is an essential concern for environmentalists, and try to draw out some consequences of the data in the previous post. In doing so, I am going to concern myself with world population size, not with how the population is distributed among countries, states, age ranges, genders. races, or ethnicities.

Only two things affect the population of the world: the number of births and the number of deaths. Births add to the population, and deaths subtract from it. As long as they match each other, the population of the world will neither rise nor fall. But if more people are born or fewer people die, then population will grow. On the other hand, if fewer people are born or more people die, then population will shrink.

The world has a carrying capacity, that is, a maximum population that it can sustain over time. This carrying capacity is limited by the availability of food, water, habitat, and other necessities. If the population exceeds the carrying capacity, then some of the people will not be able to obtain the necessities they need. The result will be misery, illness, and even death.

Figure 1. An S-Curve Describes Population Growth Over Time. Source: Brodnick 2016.

Figure 1 shows an s-curve, which is the curve demographers use to describe population growth. At the start, the population is low, so there are very few adults to reproduce. Consequently, population grows slowly. As the population grows, however, more and more adults are available to reproduce, so the population grows faster and faster. The growth rate continues to accelerate until the population becomes so large that competition for necessities increases. As it becomes harder and harder to gain life necessities, more and more individuals are unable to obtain them, and population growth slows. There is an eventual point above which the population cannot be sustained over time, and this is the carrying capacity.

This rather bland description hides a terrible fact: population growth slows because individuals have difficulty obtaining the necessities they need to survive. The result is hunger, disease, malnutrition, and squalor – in short, misery, privation, and even death. The idea here is that for any given level of resources, the population will expand to the point where one of two things will occur: either individuals will not be healthy enough to reproduce, lowering the birth rate, or the death rate will increase to match the birth rate. Either is terrible to contemplate.

The world is never without misery and privation. So long as population is below the world’s carrying capacity, however, it results from our inability (or unwillingness) to distribute life’s necessities to all people. On the other hand, if the world’s population exceeds its carrying capacity, the misery and privation will occur because there is not enough to go around. The amount of misery and privation will skyrocket. It is even possible that such a large population would cause so much environmental stress that it would cause a general environmental collapse, resulting in a world that had a much diminished capacity to support life. Such an outcome is not certain, but it is possible.

Figure 2. Data source: U.S. Census Bureau

Figure 2 is repeated from the previous post. It shows historical world population going back to 10,000 BCE. It is easy to see that the general shape of the curve matches the left hand side of Figure 1. The implication is that at some point, the increase in population could result in a scarcity of resources, resulting in an increase in misery, privation, and death on a global scale.

.

.

.

.

.

Figure 3. Snowshoe Hare and Wolf Population Dynamics. Source: Swatski 2010.

Overpopulation, leading to a population crash, is a dynamic that has been seen with many animals: in times of plenty they multiply beyond the carrying capacity of their local environment, and then there is a huge die-off. One example would be snowshoe hares, as shown in Figure 3. The blue line represents the population of hares, which repeatedly spikes and crashes. The red line shows the population of wolves, which prey on snowshoe hares. Shortly after the hare population spikes, so does the wolf population. Shortly after the hare population crashes, so does the wolf population. The hares multiply because there are so few of them that food is abundant, and they thrive. As their number spikes, however, tragedy occurs: they consume all the available food and then starve; they get crowded together and diseases break out; and there are more wolves to eat them. The wolves multiply because their food source, the hares, becomes abundant. Nothing eats the wolves, however. They die off because their food supply (the hares) has crashed, and they starve. Also, the increased crowding makes them vulnerable to diseases, as it did the hares.

Humans, of course, consume more than food. We need many different kinds of necessities to sustain our modern way of life. Thus, our population strains the environment in many, many ways. Air pollution, water pollution, climate change, water scarcity, habitat destruction, species extinction, desertification, forest fire – all are made worse by the size of our population. The concern is that, if we have exceeded the carrying capacity of the earth, humanity will suffer a die-off

People have been trying to estimate the carrying capacity of the earth for more than 200 years, and their estimates have ranged from less than 500 million to 1 sextillion. Methods of estimation have grown in sophistication over the years, and most modern estimates put it between 8 and 16 billion.

Figure 4. Planetary Boundaries. Source: Steffen et al, 2015.

On the other hand, the Stockholm Resilience Centre has identified 9 essential ecological systems that must remain within certain limits. If the planet remains inside these boundaries, humanity can continue to develop and thrive. If the planet does not, they believe, the earth’s ability to support life will be greatly degraded. Their assessment of the planet’s status is shown in Figure 4. The 9 systems are like wedges of a pie. Inside the green circle represents the safe area, and the red circle represents the maximum limit that must not be exceeded. We have already violated the boundaries in 2 of the 9 areas: biogeochemical flows, and biosphere integrity. We are approaching the boundary in 2 others: land-system change and climate change. The scientists at the Stockholm Resilience Center believe that the 9 areas interact and are mutually dependent: if one of them goes beyond its boundary, it will cause an imbalance that will draw the others out of their boundaries, too. Thus, according to their research, we have already gone too far, and need to go back.

Whether their work is precisely correct or not, it requires no genius to understand that the world is experiencing unprecedented environmental stress. It is occurring despite the fact that population has yet to reach 8 billion. Thus, I feel that estimates of the worlds carrying capacity tend to be overly optimistic. They may be something like theoretical estimates that cannot be achieved in real life.

The fact that we are so severely stressing the world suggests that there are already too many of us. What the right number would be, I think nobody knows. But the above discussion certainly illustrates why population is an important concern for environmentalists. Our well being depends on not exceeding the earth’s carrying capacity, but we may have done so already.

Sources:

Brodnick, Robert. 2016. Curves that Matter: S-Curve. Robert Brodnick. https://www.linkedin.com/pulse/curves-matter-s-curve-robert-brodnick.

Malthus, Thomas. 1798. An Essay on the Principle of Population. London, England: J.Johnson. Available online at The Electronic Scholarly Publishing Project, http://www.esp.org/books/malthus/population/malthus.pdf.

Steffen, Will, Katherine Richardson, Johan Rockstrom, Sarah Cornell, Ingo Fetzer, Elena Bennett, R. Biggs, Stephen Carpenter, Wim de Vries, Cynthia de Wit, Carl Folka, Dieter Gerten, Jens Heinke, Georgina Mace, Linn Persson, Veerabhadran Ramanathan, B. Reyers, and Sverker Sorlin. 2015. “Planetary Boundaries: Guiding Human Development on a Changing Planet.” Science, 1/16/2015. Downloaded 8/13/2017 from https://stockholmuniversity.app.box.com/s/v8q2noqkkwk60o3uikyuy3txr7ifycc8.

Swatski, Rob. “Boom-and-Bust Cycles.” BIOL 101 Chp 53: Population Ecology. Downloaded 8/14/2017 from https://www.slideshare.net/robswatski/biol-101-chp-53-population-ecology.

United Nations Environment Program, Global Environmental Alert Service. 2012. One Planet, How Many People? A Review of Earth’s Carrying Capacity. Downloaded 8/11/2017 from https://na.unep.net/geas/archive/pdfs/GEAS_Jun_12_Carrying_Capacity.pdf.

U.S. Census Bureau. World Population: Historical Estimates of World Population. https://www.census.gov/population/international/data/worldpop/table_history.php.

Wikipedia. List of Famines. Viewed online 8/14/2017 at https://en.wikipedia.org/wiki/List_of_famines.

People and More People!


The population of the world is more than 7.4 billion people.


Figure 1. Data source: U.S. Census Bureau

As I write (7/11/2017), the population of the world is 7,409,620,694. Actually, that’s a bit of a misrepresentation, for more than 2 people are added to the world every second, so even as I type the end of this sentence, the total is higher. By the time this post is published (10/5/2017), it will be 17.6 million higher.

Take a look at Figure 1 at right. It is a graph of world population over the history of civilization as estimated by the U.S. Census Bureau. It is one of those “hockey stick” graphs that scare environmentalists. For thousands of years the population of the world grew very slowly. Starting in the late 1600s or early 1700s, the rate of population growth began to quicken. The world population crossed 1 billion sometime just after 1800. It crossed 2 billion early in the 20th Century, 3 billion in 1959, 4 billion in 1974, 5 billion in 1987, 6 billion in 1999, and 7 billion in 2012.

That’s right, it took more than 11,000 years for the population to cross 1 billion, but in the following 200 years it grew by 6 billion. It took only 13 years for the last billion.

Figure 2. Data source: U.S. Census Bureau.

Figure 2 shows world population since 1950 in finer detail, and projects future population to 2050. In the chart, historical data is blue, projections are red. By mid-century, world population is projected to grow to 9.4 billion. The increase is remarkably consistent and relentless. If you look at the shape of the chart carefully, however, you can see a slight increase in the slope during the 1970s, and a slight flattening of the slope starting somewhere around 2025. The flattening is very slight, and world population is projected to increase by more than a billion in the 20 years from 2030-2050.

.

.

Figure 3. Data source: U.S. Census Bureau

Figure 3 shows the growth in world population since 1950 and projected to 2050. The blue line shows the number of people added each year, and it should be read against the left vertical axis. The red line shows the percentage growth rate each year, and should be read against the right vertical axis. Both lines peak and then decline. In terms of the number of people added each year, the peak came in 1988, when 87.3 million persons were added to the world. Since then, it has declined, though only very moderately, and 77.6 million persons were added in 2016. Percentage growth in population peaked in 1966, when world population grew by 2.2%. It has declined since then, and in 2016 the world added 1.1% to its population.

Demographers project that the decline in both trends will continue, and by 2050, world population will grow by 42.9 million persons each year, or 0.46%. While that is a 45% decline from the number added in 2016, it is still more than the population of even the most populated state in the USA (California) and more than 7 times the population of Missouri in 2010.

Figure 4. Data source: U.S. Census Bureau.

Figure 4 shows similar data for the United States. The data starts in 1790, the year the first national census was conducted. The blue line represents the population of the country, and should be read against the left vertical axis. The red line represents the growth rate, and should be read against the right vertical axis. The blue line curves upward – as the population grew, more people were available to reproduce, adding a larger number of people with each decade. In 2010 the population was estimated to be 309 million. The rate of growth has slowed however. When the country was small, even a little bit of immigration added a significant fraction to the population. After the country had grown, even though more people were being added, they represented a smaller fraction. In 2010 the population of the USA grew by 0.83%, but the number of people added was 27.2 million, the second largest for any decade (1990-2000 was the largest at 33.5 million). Think of it: though the percentage growth is small, in terms of people, we’re adding a state the size of Texas every 10 years!

.

Figure 5. Data source: U.S. Census Bureau

Figure 5 shows similar data for Missouri. Missouri first became a territory in 1810, so the chart begins with that year. Population is shown in blue, and should be read against the left vertical axis. The population growth rate is shown in red, and should be read against the right vertical axis. The population line for Missouri has a hump in it; the state grew very quickly during the mid-to-late 1800s. It has grown more slowly since then, and the population was about 6 million in 2010. For the same reasons as with the USA as a whole, the population growth rate was very fast when the state was small, but has slowed greatly, and in 2010 was 0.59%.

I will discuss some of what this data means in the next two posts.

Sources:

For current world population: U.S. Census Bureau. U.S. and World Population Clock. https://www.census.gov/popclock.

USA and Missouri data prior to 2000 are from U.S. Census Bureau. Part II. Population of the United States and Each State: 1790-1990. http://www.census.gov/population/www/censusdata/Population_PartII.xls.

USA and Missouri data for 2000 and later are from U.S. Census Bureau, Population Division. Table 1. Intercensal Estimates of the Resident Population for the United States, Regions, States, and Puerto Rico: April 1, 2000 to July 1 2010 (ST-ESTOOINT-01). http://www.census.gov/popest/data/intercensal/national/nat2010.html.

World population data are from: U.S. Census Bureau. World Population: Historical Estimates of World Population. https://www.census.gov/population/international/data/worldpop/table_history.php.

Birth Rate Declines in 2013

National Fertility Chart 2013The number of births and the fertility rate in the United States declined between 2007 and 2013, according to a report from the National Center for Health Statistics (NCHS). “Births” represents a simple count of how many people were born in a given year. The fertility rate means births for each 1,000 women between the ages of 15 and 44.

The first chart at right shows the data. In 2013, there were 3,932,181 births in the USA, down 9% from their 2007 peak. The decline occurred among whites, blacks, and hispanics.

(Click on chart for larger view.)

The fertility rate declined 1% in 2013, to a record low of 62.5 births per 1,000 women aged 15-44. Since 2007, the rate has declined 10%, with the largest decline occurring among hispanics.

Births and the fertility rate are important environmental concerns because they greatly influence future world population. The more people there are in the world, and the higher their standard of living, the more environmental stress is created. A declining fertility rate may present economic and social challenges, but from an environmental perspective, it is good news.

Missouri Births 1990-2012 ChartBirths and fertility rates are also important from several other policy perspectives, such as health and welfare. The NCHS report shows that the fertility rate is declining among all age groups under 30 years old, but is increasing for age groups over 30. Thus, more older women are giving birth. In addition, the preterm birth rate declined in 2013, and has declined 10% since its peak in 2006 – a very important change for public health!

The number of births each year in Missouri has been cyclical since 1990, as shown in the second chart at right. Whether people choose to have children is often said to be related to the health of the economy, and that would seem to fit the pattern for Missouri.

2009 State Fertility ChartI found a table at the National Center for Health Statistics that showed fertility rate by state from 1990 – 2009. In 2009 Missouri’s fertility rate was 66.2 births per 1,000, 29th highest among the states (see third chart at right). Lowest in the country was Vermont, with a fertility rate of 50.8, and highest was Utah, with a fertility rate of 88.4.

Since 1990, Missouri’s fertility rate had declined by 2.65%, the 28th largest decline among the states (see fourth chart at right). California had a decline of 19.7%, the largest in the nation. Sixteen states had increased fertility rates, led by Wyoming, with an increase of 11.3%.

State Fertility Rates Change 1990-2009 ChartTime will tell whether the decline in fertility rate proves to be a long-term trend, or a temporary blip due to the Great Recession.

Sources:

Martin, Joyce A., Brady E. Hamilton, and Michelle J.K. Osterman. 2014. Births in the United States, 2013. Atlanta, GA: National Center for Health Statistics. http://www.cdc.gov/nchs/data/databriefs/db175.htm.

For the number of births in Missouri: Missouri Information for Community Assessment Data Portal, http://health.mo.gov/data/mica//BirthMCA.

For state fertility rate trends: National Center for Health Statistics. Birth, fertility, and total fertility rates: each State, 1990-2009. http://www.cdc.gov/nchs/data_access/vitalstats/VitalStats_Births.htm.

Population Growth in Missouri’s Suburbs and Exurbs

STL Region Pop 1930-2000Historically, the population in urban areas has grown more quickly than in rural areas. (See previous post.) In the late 1800s and early 1900s, city centers grew most rapidly. Following World War II, however, the proliferation of automobiles led to the growth of suburbs, and for a while suburbs showed the most rapid growth. After 1980, however, even that began to change, as people moved ever farther from the city center, into what are now called exurbs.

Nowhere in the state do these trends align with county boundaries as well as in the St. Louis area. The graph at right shows the percentage population gain by decade for 6 counties in the St. Louis region. The dark blue line represents St. Louis City, the urban core. It grew most rapidly during the 1800s. By 1900, it’s growth rate had already slowed, and since 1950 it has lost population steadily. The green line represents St. Louis County, the suburbs; it grew strongly until about 1960, after which its rate of growth slowed. MO Pop Growth by County Map 1930-2000Jefferson County and St. Charles County, the red and purple lines, represent the transition between suburban and exurban areas; they show peaks in growth in 1960 and 1970, but the rate of growth lessens thereafter. Warren County and Lincoln County, the light blue and orange lines, represent the exurbs; they show the strongest growth in 1980 or later.

The Kansas City region has struggled with similar trends, where the rate of growth in Cass, Clay, and Platte Counties outstrips growth in Jackson County. Even in the Springfield region, the rate of growth of Green County is now outstripped by the rate of growth in Christian and Taney Counties.

At right are two maps. The first one shows Missouri population change by county from 1930 to 2000. The second one shows population change by county from 2000 to 2010. Counties with population loss have been colored lilac. Green means population gain, with light green being the least gain and dark green being the most gain. The maps show the trends discussed above. MO County Pop Growth 2010 MapIn addition, they show that population loss is not unique to urban city centers. Population loss has been persistent in the Missouri Bootheel and across large portions of Northern Missouri.

Sources:

The data for the graph of historical population change in counties in the St. Louis Region were assembled from sources available at the website of the U.S. Census Bureau. County population statistics for 1900-1990 are available at County Population Census Counts 1900-1990, http://www.census.gov/population/www/censusdata/cencounts/index.html.

For the 2000 census, population by county is available at Ranking Tables for Counties: Population in 2000 and Population Change from 1990 to 2000 (PHC-T-4), Census 2000, http://www.census.gov/population/www/cen2000/briefs/phc-t4/index.html.

For the 2010 census, population by county is available by selecting “Estimates for All Counties,” on the Missouri QuickLinks page of the American FactFinder, U.S. Census Bureau, http://quickfacts.census.gov/qfd/states/29000lk.html.

The maps came from these two sources:

Percent Change in Population Density by County: 1930-2000, Population Density, Thematic Maps, Geography, http://www.census.gov/geo/maps-data/maps/thematic.html. (While population density is not the same as population, unless the counties are changing in size, changes in density and changes in population must be equivalent.)

Percent Change in Population by County: 2000 to 2010: Missouri, Population Change, Thematic Maps, Geography, U.S. Census Bureau, http://www.census.gov/geo/maps-data/maps/thematic.html.

Missouri Population Growth Lags the Nation

Missour vs US ChartI haven’t looked at population so far in this blog, and it is time I did. Population is among the most important environmental issues because humans have needs. We consume stuff to meet our needs, and when we do, we create waste. Sometimes it is the consumption itself that creates environmental stress, as when entire mountains are destroyed to mine coal. Other times, it is the waste that creates environmental stress, as when toxic chemicals resulting from industrial processes are dumped into rivers.

This allows us to understand a very simple, but very important principle: the total amount of environmental stress depends on how much stress each person creates and on how many people there are. You can express this as an equation:

Total environmental stress = per capita environmental stress x number of people.

MO Urban-Rural ChartIf the number of people increases, total environmental stress will increase (unless the amount of stress each person creates decreases).

Throughout history, the population of the world has increased, with only a few, brief interruptions. However, world statistics are not the focus of this blog, Missouri is. The first graph at right shows the total population of Missouri and of the United States from 1900-2010. Total Missouri population has grown from about 3.1 million in 1900 to almost 6.0 million in 2010, a 93% increase. Meanwhile, the population of the United States grew from 76.2 million in 1900 to 308.7 million in 2010, an increase of 305%.

Population has not grown equally in rural and urban areas. The second graph shows population in Missouri divided into its urban and rural components. The urban population grew from 1.1 million in 1900 to 4.2 million in 2010, a 281% increase. Meanwhile, rural population actually declined from 1.9 million in 1900 to 1.4 million in 1970, then grew to 1.8 million in 2010, a 5% loss overall.

US Urban-Rural ChartThe third graph at right shows similar data for the United States as a whole. The urban population grew from 30.2 million in 1900 to 249.3 million in 2010, an astounding increase of 725%. Meanwhile, the rural population grew from 46.0 million to 59.5 million, an increase of 29%.

Unlike some of the graphs we’ve looked at, these graphs do not show lots of variability. The trend goes up, and it is remarkably consistent across a large number of years.

Thus, since 1900, population in Missouri has grown at 1/3 the rate it has grown nationally. In addition, both in Missouri and nationally, urban population has grown much more than rural population. Where in 1900, the rural population was the majority, now it only makes up 30% of the population of Missouri, and 19% nationally. When Thomas Jefferson imagined the United States as an agrarian utopia, I wonder if he imagined a country where 81% of the people lived in urban areas?

More on what this urban-rural change means for Missouri’s environment in future posts.

Sources:

The population data comes from 3 sources at the United States Census Bureau. I find their website to be the most difficult to use of all the websites I research. The problem is that the way they have measured population and published the data has changed over the years. Trying to find consistent data across all years can be maddening.

Urban and Rural Populations, United States, Regions, Divisions, and States: 1900-1990, Geography, U.S. Census Bureau, http://www.census.gov/geo/reference/urban-rural.html.

Table 29. Urban and Rural Population by State: 1990 and 2000, Statistical Abstract of the United States, U.S. Census Bureau, http://www.census.gov/compendia/statab/2011/tables/11s0029.pdf.

Percent Urban and Rural in 2010 by State, Lists of Population, Land Area, and Percent Urban and Rural in 2010, Geography, U.S. Census Bureau, http://www.census.gov/geo/reference/ua/urban-rural-2010.html.