Population growth is a critical driver of global planetary change. It is impossible to ignore the explosive growth of human population over the last two hundred and twenty years. Global population is estimated to have reached 1 billion around 1800. It is now 7.7 billion and despite a marked deceleration in growth from 2.1%/year between 1965-1970 to 1.1%/year, global population is still increasing by around 80 million every year. Ever growing populations coupled with extraordinary acceleration in economic and technological growth have placed equally extraordinary and growing demands on global environmental resources.

When the American Great Plains, one of the world’s largest grassland ecosystems, was ploughed up in little more than a century, converted from a vast and diverse grassland supporting millions of buffalo to a near monoculture grassland of corn and wheat, the global ramifications of this vast change in land use were viewed through the lens of economic progress and the growth of the American nation. In 1800, when the settlement of the Great Plains was beginning, there were about 1 billion people on our planet. In a world of 7.7 billion, the conversion of remaining forests and grasslands in the developing nations of the tropics is now viewed with alarm and consternation. At the same time, the demands of the billions of people living in the developing world for the same goods and services enjoyed by those of us living in more fortunate circumstances are creating unprecedented challenges.

Population growth: present and future trends

2019 Global (mid-2019):  7.7 billion

Growth Rate:  2015-2020:   1.1%/year

(Peak Global Growth Rate (1965-1970): 2.1%/year)

Population growth continues at the global level, but the rate of increase is slowing, and the world’s population could cease to grow around the end of the century.  Green shaded area denotes 95% confidence interval; medium-variant projected growth.  Population projections to 2030 and 2050 are much less uncertain than projections to 2100; global population could stabilize by 2100 (27% probability)

Projected Population

• 2030:  8.5 billion
• 2050:  9.7 billion
• 2100:  10.9 billion

Where will growth occur?

Population of the world, Sustainable Development Goals (SDG) regions and selected groups of countries, 2019, 2030, 2050 and 2100, according to the medium-variant projection

Global population trends are driven largely by trends in fertility – especially in the average number of live births per woman over a lifetime – which has fallen markedly over recent decades in many countries.

The average number of children born to women over a lifetime has fallen markedly in many regions over the past several decades

Estimated and projected total fertility by SDG region, 1950-2100, according to the medium-variant projection

With a projected addition of 1.1 billion people, countries of sub-Saharan Africa could account for more than half of the growth in the world’s population between 2019 and 2050, and the population of that region is projected to continue growing through the end of the century.wo-thirds of the projected growth of the global population through 2050 will be driven by current age structures. It would occur even if childbearing in high-fertility countries today were to fall immediately to around two births per woman over a lifetime.  Growth in sub-Saharan Africa exemplifies this trend. Source: United Nations, Department of Economic and Social Affairs, Population Division (2019). World Population Prospects 2019: Highlights (ST/ESA/SER.A/423).

Two-thirds of the projected growth of the global population through 2050 will be driven by current age structures. It would occur even if childbearing in high-fertility countries today were to fall immediately to around two births per woman over a lifetime.  Growth in sub-Saharan Africa exemplifies this trend. Source: United Nations, Department of Economic and Social Affairs, Population Division (2019). World Population Prospects 2019: Highlights (ST/ESA/SER.A/423).

In 2019, Africa’s population reached 1.32 billion, representing 17.1% of the world population.¹ The UN’s medium estimates suggest that population growth will remain strong in the coming decades so that by 2050, one in four people in the world will be African (26.2% of the world population). The accuracy and availability of population census data vary but the data that do exist suggest highly varied trends and prospects across the region. Nevertheless, by 2100, 19 African nations are expected to reach populations of >75 million people with the total population of the four most populous African countries anticipated to be approaching 1.7 billion, considerably more than the entire population of Africa in 2015 (UN, 2015a)².

These estimates are highly dependent on fertility rates, but recognise that 19 of the world’s 22 ‘high fertility’ countries (where women have 5 or more children on average) are located in Africa.  As of 2019, the median age is 19.4, and the fertility rate is 4.66³—setting the stage for dramatic population growth over the coming decades.  Africa also shows the world’s greatest increases in life expectancy and reductions in child mortality, though again there are distinct regional variations (UN, 2015a)⁴.  Source: (2018): The IPBES regional assessment report on biodiversity and ecosystem services for Africa. Archer, E. Dziba, L., Mulongoy, K. J., Maoela, M. A., and Walters, M. (eds.). Secretariat of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, Bonn, Germany, pp. 1–76.

Africa is also one of the most rapidly urbanizing continents. As of 2019, 41% of the population is urban (541,000,000) and this percentage is expected to increase to 53.0% by 2050 (1.339 billion).⁵ Rapid and unplanned urbanization puts immense pressure on urban infrastructure and demand for services, including water supply, food supply, pollution control and waste management, as well as energy supply for households and industrial development. Urban communities produce large quantities of solid and other wastes that lead to environmental pollution. There is a need for policies that encourage sustainable and equitable development by, for example, directing development opportunities to rural areas and redirecting planned urban expansion to economic development zones in rural settings, in particular those that have adequate water and renewable energy supply. Source:  IPBES (2018): The IPBES regional assessment report on biodiversity and ecosystem services for Africa. Archer, E. Dziba, L., Mulongoy, K. J., Maoela, M. A., and Walters, M. (eds.). Secretariat of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, Bonn, Germany. 492 pages. _____________________________

^1,3,5 Based on UN estimates from https://www.worldometers.info/world- population/africa-population/ as at 16 July 2019. (Revised data to 2019 as compared to IPBES)

^2,4UN. (United Nations). (2015a). Transforming our World: The 2030 agenda for sustainable development. New York, NY, USA: United Nations. Retrieved from https://sustainabledevelopment. un.org/post2015/transformingourworld

Majority of growth will occur in a handful of countries

By 2100, 6 of the 10 most populous countries will be in Africa

Percentage change in selected countries 2019-2050; dramatic increases in African nations

Midyear Population and Density – UN – Africa 

Year                      Population            Area (Sq. Km.)       Density(Persons per sq. km)

       2019              1,294,619,812       29,771,416                       43.5

       2050              2,412,737,225        29,771,416                         81.0

86% increase in population between 2019 and 2050

India is expected to add nearly 273 million people between 2019 and 2050, while the population of Nigeria is projected to grow by 200 million. Together, these two countries could account for 23 per cent of the global population increase to 2050. Source:  United Nations, Department of Economic and Social Affairs, Population Division (2019). World Population Prospects 2019: Highlights (ST/ESA/SER.A/423)

Population Density And Environmental Degradation

A new paper (Socio-economic predictors of environmental performance among African nations) concludes that “ the strongest predictor of environmental performance among nations in Africa is population density means that countries with the most people per unit area suffered relatively more environmental degradation on average.”

2018–An Urbanized World

• 55% of the world’s population lived in urban settlements
• 23% of the world’s population lived in a city with at least 1 million inhabitants
  • 48 cities had populations between 5 and 10 million
  • 467 cities had between 1 and 5 million
  • 598 cities had between 500,000 and 1 million
• Rural areas were home to 45% of the world’s population
• 529 million people (6.9%) of the world’s population lived in cities of 10 million or more (megacities)
• Urbanization will continue in all size classes
• Most of the world’s fastest growing cities are in Asia and Africa

Increasing urbanization…

World’s ten largest cities

• Of the world’s 33 megacities—that is, cities with 10 million inhabitants or more—in 2018, 27 are located in the less developed regions or the “global South”.
• China alone was home to 6 megacities in 2018, while India had 5.
• Nine of the 10 cities projected to become megacities between 2018 and 2030 are located in developing countries.

Growing percentages of slum dwellers with urbanization

Global levels of extreme poverty are falling, but rural areas are being left behind…

• As of 2013, 767 million people (>10% of global population) were living in extreme poverty
• And 2.1 billion people (~30% of global population) were living on less than US$3.10/day
• In 2013, nearly 80% of the extreme poor lived in rural areas (Eight out of ten children living in extreme poverty live in rural areas

Vulnerability Of Urban Areas To Natural Disasters

(Source:  Risks of Exposure and Vulnerability to Natural Disasters at the City Level:  A Global Overview; https://population.un.org/wup/Publications/Files/WUP2014-TechnicalPaper-NaturalDisaster.pdf;

 United Nations, Department of Economic and Social Affairs, Population Division (2018). The World’s Cities in 2018—Data Booklet (ST/ESA/ SER.A/417).

Megacities are more likely to be highly exposed to disasters and are more vulnerable than cities of other sizes.

• Cities in the less developed regions, which, on average, were experiencing faster growth than cities elsewhere, were more likely to be exposed to both the risk of natural disasters and the potentially adverse consequences of such natural disasters. (see next table)

The Asia-Pacific is historically the most vulnerable region on Earth to natural hazards and extreme events such as tropical cyclones, flash/seasonal floods, prolonged droughts, king tides, earthquakes, tsunamis and volcanic eruptions.

The American Coastline

2017:  About 29% of the total U.S. population of 325.7 million people lived in coastline counties

Coastal population has grown fastest in the Gulf of Mexico, adding 3 million people between 2000 and 2017, an increase of 26.1%, nearly 10% faster than the U.S. as a whole