Global and regional human population carrying capacity.
Many people in the USA and UK say that they think their country is too crowded. Some of my friends put me on the spot recently and asked me to say what the carrying capacity of the UK is, without importing resources like oil and food. I guessed that it was probably close to the current population of about 60 million. Oops! It appears I was out by a ?factor of two, with a more realistic estimate about 27 million.
But Wait! As they say in the Yorkshiremen sketch by Monty Python "you're lucky!", because the global human carrying capacity is less than 1 billion with a current population of about 8 billion. The rest of the world is in a greater pickle than us in the West.
Let's go through the numbers.
Global human population carrying capacity without oil production
Estimated Range, speculative and based on current understanding. A sustainable population without fossil fuels could be:
- Around 1 billion people, according to some experts
- Possibly as low as 500 million (1/2 billion) people, considering factors like topsoil depletion, climate change, and resource scarcity
Why is it a complex calculation?
- Significantly Reduced Capacity: Without fossil fuels, especially oil, the Earth's carrying capacity would be drastically lower than the current population of about 8 billion people.
- Historical Context: Before the widespread use of fossil fuels in the 1800s, the global population was around 1 billion people.
- Agricultural Limitations: Modern agriculture is heavily dependent on fossil fuels for machinery, fertilizers, and transportation. Without these inputs, food production would decrease dramatically
- Factors Reducing Capacity: Loss of synthetic fertilizers, Reduced mechanization in agriculture, Limited long-distance food transportation, Depletion of natural resources, Climate change impacts, Loss of modern medical technologies and treatments.
- Transition Challenges: An abrupt shift away from fossil fuels could lead to significant population decline due to food shortages, lack of essential products, and breakdown of global supply chains
- Regional Variations: Carrying capacity would vary greatly by region, depending on local resources, climate, and agricultural potential.
For the UK specifically
?Agricultural Production Capacity
- The UK has approximately 6.1 million hectares of arable land.
- Cereal crops, which are a staple food source, account for about 3.1 million hectares (51% of arable land).
- The average cereal yield in the UK is around 8 metric tons per hectare.
- Assuming a simplified diet based primarily on cereals, we can estimate that a person requires about 2.5 kg of cereals per day (912.5 kg per year).
Calculation
Using these figures, we can make a rough calculation:
- Total potential cereal production: 3.1 million hectares * 8 tons/hectare = 24.8 million tons of cereals
- Number of people this could feed: 24.8 million tons / 0.9125 tons per person per year ≈ 27.2 million people
Limiting Factors
However, this simplistic calculation doesn't account for several crucial factors:
- Dietary Diversity: A balanced diet requires more than just cereals, including fruits, vegetables, and protein sources.
- Land Use Efficiency: Not all arable land is used for food production; some is used for biofuels, animal feed, or other non-food crops.
- Livestock: The UK has significant livestock populations, which require land and feed that could otherwise be used for human food production.
- Climate and Environmental Constraints: Crop yields can vary significantly due to weather conditions and climate change.
- Population Distribution: The UK's population is heavily urbanized, which affects food distribution and land availability.
- Technology and Farming Practices: Current yields rely on imported fertilizers and machinery, which might not be available in a closed system.
Realistic Estimate
Considering these factors, a more realistic carrying capacity would likely be lower than the 27.2 million calculated above. Some experts suggest that without imports and with current agricultural practices, the UK might only be able to support about 20-30 million people
Conclusion
Without oil for mechanized agriculture and fertilizer production, the global human population carrying capacity is about 1 billion and the only questions are not if but when this will occur, and how to make this transition as smoothly and equitably as possible.
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