Human Population Explosion

For most of history the human population grew slowly, held back by famine, disease and high infant mortality. It reached about 1 billion around 1800, 2.5 billion in 1950 and passed 8 billion in 2022. A graph of population against time is J-shaped, showing exponential growth.A population grows when the birth rate is greater than the death rate. Death rates fell sharply because of:
• improved agriculture (machinery, fertilisers, pesticides and high-yield crop varieties), giving more food;
• better sanitation and clean water;
• medical advances such as vaccines and antibiotics, which reduced infant mortality and raised life expectancy.In many countries birth rates later fell too, as access to contraception, education and economic development increased, so growth has slowed. The global growth rate peaked at about 2% per year in the 1960s and is now below 1%.Growth rate can be calculated as:% growth rate = (population change ÷ population at start) × 100Worked example: a country grows from 50 million to 52 million in a year, so its growth rate is (2 ÷ 50) × 100 = 4%.A rising population needs more food, water, energy, land and materials. This increases fossil fuel use, deforestation and demand for biological resources, which is why human population growth underlies most human effects on ecosystems.