--- title: "Population explosion and declining population" subject: "Technology, Environment and Society" chapter: 3 key: "semester_7/technology_environment_and_society:population-explosion" source: https://www.bctengineer.com/q/semester_7/technology_environment_and_society/population-explosion site: BCT Engineering --- # Population explosion and declining population Technology, Environment and Society · Chapter 3: Brief History of Human Civilization - Asked in: 2079 Baisakh, 2+3+3 marks; 2072 Chaitra, 8 marks (asked 2 times) - Video: [Overpopulation – The Human Explosion Explained](https://www.youtube.com/watch?v=QsBT5EQt348) — Kurzgesagt – In a Nutshell - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/technology_environment_and_society/population-explosion - Whole chapter: https://www.bctengineer.com/md/semester_7/technology_environment_and_society/chapter-3 ## Question What is population explosion? What are the reasons for it? How do you view the current trend of decreasing population in the developed countries? ## Short answer Population explosion is rapid growth from high birth rates and falling death rates, as world population passed 8 billion in 2022. Reasons include better medicine, food, sanitation, high birth rate and illiteracy. Decreasing populations in developed countries reflect low fertility below replacement (2.1), causing ageing and labour shortage, but also less environmental pressure. ## Answer **Population explosion** is a very rapid and large increase of human population in a short time, when the birth rate stays high but the death rate falls sharply. World population was about 1 billion in 1800, 2.5 billion in 1950 and passed **8 billion in November 2022**; most of this growth happened after 1950, mainly in developing countries. #### Reasons for population explosion 1. **Fall in death rate** – better medicine, vaccines, antibiotics and control of epidemics (smallpox, cholera, plague). 2. **Better food supply** – Green Revolution, high-yield seeds, fertilisers and irrigation reduced famine. 3. **Improved sanitation and safe water** – lower infant and child mortality. 4. **Increased life expectancy** – more people live to old age. 5. **High birth rate** – early marriage, low use of contraception, desire for sons, children seen as labour and old-age security. 6. **Illiteracy and poverty** – especially low education of women. 7. **Religious and cultural beliefs** against family planning. This is explained by the **demographic transition** model: stage 1 high birth and death rates; stage 2 death rate falls but birth rate stays high (explosion); stage 3 birth rate falls; stage 4 both low. #### View on the current trend of decreasing population in developed countries Many developed countries such as Japan, South Korea, Italy, Germany and East European countries have a **total fertility rate below the replacement level of about 2.1**, and their populations are shrinking or ageing. My view: - **Causes:** high cost of living and child-rearing, women's education and careers, late marriage, easy contraception, urban lifestyle and individualism. - **Positive side:** less pressure on resources and environment, more investment per child, higher living standard. - **Negative side:** - **Ageing population** – fewer workers support more retired people; pension and health costs rise. - **Labour shortage** – slower economic growth and less innovation. - Empty villages and schools, smaller consumer market. - **Responses:** incentives for child birth, child care and parental leave, higher retirement age, automation and robotics, and **immigration** of workers (which also affects countries like Nepal through foreign employment). So the trend is a natural result of development (stage 4 of demographic transition). It is not harmful by itself, but it must be managed with balanced policies; meanwhile the global challenge remains high growth in poorer countries. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What condition produces a population explosion? A. Birth rate stays high while death rate falls sharply B. Both birth and death rates rise C. Birth rate falls while death rate stays high D. Both rates are low Answer: A. This is stage 2 of the demographic transition. (Key point: Population explosion) 2. Which is a reason for the fall in death rate? A. Spread of epidemics B. Better medicine, vaccines, sanitation and food supply C. Fall in life expectancy D. Reduced food production Answer: B. Medical and food advances lowered mortality and increased life expectancy. (Key point: Cause: death rate) 3. What is the replacement level fertility mentioned, below which many developed countries fall? A. About 1.0 B. About 3.5 C. About 2.1 D. About 5.0 Answer: C. Total fertility rate below about 2.1 makes populations shrink or age. (Key point: Replacement level) 4. What is a main negative effect of decreasing population in developed countries? A. Too many workers and unemployment of the old B. Excess pressure on natural resources C. Faster economic growth through labour surplus D. Ageing population with fewer workers supporting more retirees Answer: D. Fewer workers support more retired people, raising pension and health costs. 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