The UB population projection of 11.2 billion for 2100 is only the middle of the medium scenario for the UN. The UN has been revising its population projections upward from 9.5 billion to 11.2 billion from projections made in 2000 to 2017. The 95% range of the medium projection is from 10 billion to 13 billion. The UN has been revising population projections upward because they have an assumption that African birthrates will trend downwards like in Asia and that has not happened. The UN high population variant has a midpoint of 16.5 billion and constant birthrate population for 2100 is 25 billion. African birthrates can impact the population in 2100 easily by 2 to 5 billion and as much as 14 billion.
If the world population had or was able to mimic the health of Asian Americans and had increased wealth and education levels to match Asian Americans in the USA (current life expectancy 87 for Asian Americans) then world life expectancy goes from 72.6 to 87. This would be a 15-year life expectancy boost for 12 billion people. 11.2 billion is the latest UN projection to 2100. I expect at least 0.1 to 0.2 upward family size adjustments from Africa. Family size shrinking will not be as fast as the UN projection.
But the assumption of UN population forecasts is world life expectancy goes from 72.6 to 81.6. If life expectancy goes from 87 and not 81.6. 12 billion divided by 70 about 170 million people at each age with roughly even distribution. This means 900 million more people. 13 billion just from getting to an achievable and proven level of lifestyle health. Add in metformin, senolytic drugs (get rid of badly functioning older cells). The distribution of people who get life extended and are alive in 2100 are those born from 2010 to 2020 (80-90 years old)
Add 10 more years to 97 life expectancy with better drugs, medicine then that is 1.7 billion more people. This would be 14.7 billion. Those people would mostly be those born from 2000 to 2010.
If there is radical life extension by 2100, where people are living to 150. This would mean many people born and still alive from 1950-2000 would still be alive. The number of people who get those treatments by 2040 would be half of those born from 1950-1960. If the radical antiaging treatments are just like frequent vaccine injections then deployment would be faster than the deployments of treatments for AIDS. This would mean distribution over twenty years instead of 40+ years. This means about 3-4 billion might still be alive who would not have been. This would mean a population of 18 billion.
There are thousands of early adopters using antiaging drugs. This could boost lifespans to 95 or more. Seventh-day Adventists just follow a healthy diet and lifestyle and are able to have 7 more years of life expectancy.
Feeding the People is Trivial
If the world follows France’s rules around dealing with food waste from supermarkets and restaurants then the world can feed 2 billion more people. Feeding 10 billion in the world by 2050 is doing what we are doing now and deeply discounting the food at supermarkets one week before it expires and reducing waste and spoilage from the farm and in the supply chain.
The fear of world starvation story resonates with deep caveman fears of starvation. Any individual person can experience hunger. This reinforces and validates the fear of potential starvation.
USDA recommends that adults eat 5-6 ounces of protein daily, avg person will eat 10 ounces of meat and poultry each day in 2018. 30-40% of food is wasted in the US. UK rationing during WW2 was 4-8 ounces of meat per week or about 1 ounce per day.
This means 20-30% underproduction would barely be noticed. Prices would go up on certain items which would shave demand. Eventually, this would trigger simple policies to reduce food waste. 10-20% gains from food waste reductions are relatively easy. This is so unimportant that most places do not bother. With a bit more time, an adaptation to 50-60% less food could be handled without people feeling like they are sacrificing. 90% reductions would be more like UK rationing.
Going to the Less People Solution is Wrong
The doomers answer to everything is get rid of the people. Having the answer of getting rid of people is stupid, sad and useless.
The other guy you try to get rid of will not say ok sure.
Mao in China caused the deaths of tens of millions. Stalin and Hitler killed tens of millions. Those things did not cause a year when the population of the world went down.
Food production is increasing by a lot. The productivity of agricultural land will triple by 2030-2040. This not magic. Dozens of hectares with higher productivity are being grown now. China and other nations will scale them up.
This is all before going to building a lot of greenhouses which can boost productivity by 10-30 times. This is before the possible success of factory grown meat. Factory grown meat is now sold in restaurants. People pay more for meat at high-end restaurants. It can be made to taste better. Is it unnatural? People did not ask those questions about chicken nuggets. People love those things and nuggets are a meat slurry mix of meat pieces and corn.
Factory grown meat can boost food productivity by 10X in terms of energy and water.
So we already have 2 to 3 times the food than we really need. The world can drop by 10 times and get by. Food production will go up 3 times within 20 years using business as usual agriculture. There is an option to use greenhouses on a larger scale for 30 times more food. Dedicated skyscrapers for greenhouses can boost food produced in a spot by 100X beyond greenhouses.
Factory produced meat can increase food production efficiency in terms of energy and water by 10X or even 100X.