Historical Patterns and Future Projections
Human population growth has changed dramatically over time. For most of history, populations grew slowly due to high death rates from disease, famine, and limited medical knowledge. The Agricultural Revolution (~10,000 years ago) allowed for more stable food supplies, leading to gradual growth. The Industrial Revolution in the 18th and 19th centuries brought advances in medicine, sanitation, and food production, causing death rates to fall and triggering exponential growth. The global population now exceeds 8 billion.
Can we use this or find a graph that shows this info? Human population growth from 1 CE to 2050, and the years noted that we reached each billion.
https://worldpopulationhistory.org/carrying-capacity/
However, growth is slowing. The global population growth rate peaked in 1963 at about 2.3% per year. Since then, it has steadily declined due to falling fertility rates worldwide. The annual growth rate is now below 1%, the slowest rate since 1950 (United Nations 2024). This decline is largely driven by women having fewer children and by increasing access to education, healthcare, and family planning. UN projections estimate that the global population will peak at around 10.3 billion in the mid-2080s. This peak is 700 million lower than projections made a decade ago, largely due to declining fertility rates. Over half of all countries now have fertility rates below the replacement level of 2.1 children per woman.
Add figure – https://en.wikipedia.org/wiki/Population_growth#/media/File:Population-growth-rate-2023-OWID.png
Age Structure and Economic Development
Age structure is the distribution of individuals across age groups. Age structure diagrams visually represent the number of individuals in different age groups, typically separated by sex. These diagrams help illustrate whether a population is growing, stable, or declining. A wide base indicates a high proportion of young people and potential for rapid growth, while a narrow base and wider top suggest an aging population and potential population decline.
Copy Fig 16.11 from https://uen.pressbooks.pub/biology1010revision/chapter/the-human-population/
*Can we edit to Stage 4: Declining
Age structure has major implications for economic development and social planning. Countries with a young population face challenges in providing education, jobs, and healthcare for a growing youth population. In contrast, countries with an aging population must support a shrinking workforce and increasing healthcare needs for the elderly.
Carrying Capacity of Humans
Calculating the carrying capacity for humans is particularly complex because it depends not only on population size, but also on consumption patterns, technology, and lifestyle choices.
One way to measure our impact is through the ecological footprint, which calculates how much biologically productive land and water area a population requires to produce the resources it consumes and absorb its waste. This is compared to biocapacity, the Earth’s ability to regenerate those resources and absorb waste, especially carbon emissions.
According to the Global Footprint Network, the global ecological footprint is about 2.5 global hectares (gha) per person. The Earth’s biocapacity is only about 1.6 gha per person. This means that humanity is using resources at a rate that would require 1.7 Earths to sustain long-term. This condition is known as ecological overshoot – when demand exceeds nature’s ability to regenerate. Overshoot leads to deforestation, soil erosion, biodiversity loss, and climate change.
The gap between ecological footprint and biocapacity is not evenly distributed. High-income countries tend to have much larger footprints per person, while low-income countries often live within or below their biocapacity. For Canada, the average ecological footprint per person is 8.7 gha. If everybody on Earth lived like Canadians, we would need over 5 Earths to stay within biocapacity.
Figure (or link, if necessary) of the map of Ecological Footprints per Person.
https://data.footprintnetwork.org/#/
This highlights the importance of addressing not just population size, but also inequities in consumption and resource use. To live within Earth’s carrying capacity, we must:
- Reduce overconsumption and waste
- Transition to renewable energy
- Protect and restore ecosystems
- Shift toward sustainable food systems and urban planning
Ultimately, the planet’s ability to support human life depends not just on how many people there are, but on how sustainably we live.
