What Is the Carrying Capacity of Earth?

It depends.

Joel Cohen is the professor and mathematician who most famously tried to calculate a definitive number, in his book How Many People Can the Earth Support?

His success was in admitting that he couldn’t determine a sustainable limit for human population because that limit depends on how people live their lives and what they choose to consume. Are they city-dwelling vegetarians who live in tiny apartments and take public transportation, omnivorous homesteaders who grow their own food and make their own clothes and furniture, wealthy estate owners who take private jets to play golf every weekend (ahem, Donald Trump), or somewhere in between? The carrying capacity estimates of 94 scientists range from 500 million to 1 sextillion (that’s 21 zeroes) and the factors listed above illustrate why.

Some scientists who look at population issues believe that we’re already past the “tipping point,” where natural systems are so overstressed that they cannot be recovered, thus effectively changing renewable resources into non-renewable ones. Already, we’re consuming the Earth’s renewable resources at one and a half times the sustainable rate. And that’s with billions of people living in poverty, consuming next to nothing. Imagine what would happen if desperately poor people were fortunate enough to live a middle class lifestyle. And then imagine what would happen if poor people joined the middle class, AND the human population grew from today’s 7.5 billion to 9, 10, or 11 billion.

Definitions matter

Another reason nobody knows the upper limit for the human population is that it depends on what that limit protects. Is it human life or is it the non-human animals that are dying off at such an alarming rate? Animal populations are, on average, less than half the size they were in 1970, and we’re currently witnessing the sixth mass extinction, wiping out entire species with our destructive activities. How long before human numbers and activities push so many species to extinction that it begins to negatively affect the natural ecosystems we all depend upon?

Population projections

Family planning programs and contraceptive services have had enormous success in promoting health, development, and gender equality since they were introduced in the 1960s. They’ve also had a tremendous effect on the trajectory of human population growth. The global fertility rate has declined from 4.92 children per woman in 1965-1970 to 2.47 today, and the rate of population growth has declined from its peak of 2.06% a year to 1.08%. With a dedicated investment in domestic and international family planning, we could bend that growth trajectory downward, leveling it off before it hits 9 billion and before we discover our planet’s true carrying capacity.

27 thoughts on “What Is the Carrying Capacity of Earth?

  1. I think it is around 1 billion. With that population recycling and renewables could sustain the population for quite sometime. We still will have to actively sequester carbon. It will happen by slow reduction of population or a biological crash. The latter would not be pretty.

      • There are currently more people on the planet than many scientists believe is sustainable long term, which is what carrying capacity refers to. A population of any species can live in overshoot for a while, but eventually lack of sustainability will catch up with it, causing suffering and strife.

          • That goal will most likely be hit. If each continent had 12 billion people there is no room for other species to thrive. !2 billion is 2x the amount that we have right now. Imagne twice the amount of people will just kill all other existing life.

        • 88 billion. Is our max 12 billion people per continent.

          But I wouldn’t try to hit that. Maybe just do 12 billion-24 billion max.

  2. Huge research papers predict; Sustainable carrying capacity of Mother earth as on today is 3 billion people depending on replenishment of renewable resources. Different sections of people are in rat race of survival like the tribes of ancient ages. One particular section of tribes want to multiply and capture the world to spread their tribal laws in name of religion . Other sections are also multiplying for survival / existence. There will never be any agreement on this issue and we will be extinct within next one hundred years as predicted by numerous specialists. We have already ignited the suicidal bomb for extinction of human species on earth and there is no escape from it

  3. People cannot continue reproducing at will. The cc is somewhat dependent upon lifestyle, governing systems and how we apply our technologies. Currently, as a whole, humans are not doing much to show that our cc is 10 billion or more. I believe based on our current path, we max out at 4 to 5 billion. Currently, we are on a path to extinction.

  4. We already know the answer to this question, because before 1820 humanity was living off of human, animal, and vegetable (i.e. wood) power only. So the answer is one billion people. Anything else is above the carrying capacity for our species.

  5. How about limiting it to 2 billion people? The current population could be reduced by attrition. That’s enough and that many people would not strain the environment. There is a limit and reproducing carelessly endangers our long-term survival and the survival of other species with whom we share the planet.

  6. This depends on whether we want other life on Earth to survive too. If we do and we want to continue our current lifestyle, I think the answer is closer to 2 billion. Part of the reason that it is lower than the current population is because we use fossil fuel based fertiliser, which is a finite resource. If we stopped eating ruminants we could increase that number, or if we produced them more intensively.

  7. I deal with nutrition, i wrote a book “in good health without diet” and I tell you this: if we want to live really healthy as our distant ancestors (30.000 years ago) were but at the same time much longer not having to endure hypothermia or infections and having unlimited natural resources available, allowing them to be recycled one hundred million would be the maximum figure

  8. Thinking we can survive without the other life on earth is irrational. Considering we need a heathy biosphere to survive, I say carrying capacity is 2 billion. New knowledge and technology raised it from the per 1820’s one billion, but new knowledge and technology can only raise it so much.
    Of course, carrying capacity depends on population X per capita consumption. For most of the developed world, that would mean about one million. because they enjoy running through nature like a mad bull in a china shop. The fewer the people, the more destructive the elite of this world will get.
    So the question is: Can humans evolve to a species that accepts earths limitations and tries to live within them?

    • Great turn of phrase – ‘The fewer the people, the more destructive the elite of this world will get.’ Couldn’t agree more. I fear for our youngest inhabitants, and theirs. We’re way past the tipping point. Climate(see food supply) and microbiological organisms will be the great winnowers. One can only hope this happens sooner rather than later – before all of the rest of the plant and animal life on the planet is destroyed

  9. I think that regardless of actual carrying capacity it’s important to note something; if we exceed this capacity, some event will occur to balance it, but EXTINCTION and ANNIHILATION (words present in more than a few comments) are extremely unlikely. A mass die-off would obviously be likely, but with the exception of nuclear war (and maybe even then) almost any event that kills of billions will still see significant amounts of survivors (even something like 3000 survivors would be biological capable of repopulation) . We’re not facing extinction of species, we’re facing the extinction of our existing civilization without change. Simply, the dilemma is we reduce/sustain population at a feasible level, or biology and chemistry will reduce it for us in a less pleasant way.

  10. I am just checking if the 19 thoughts are provided by readers or if they had been hand selected by the author for a school report.

    • The comments on this website are submitted by readers. Population Connection staff approve comments, assuming they aren’t spam and don’t contain abusive language.

  11. So far I’ve not heard it pointed out that: The rich have always known that the real value of their fortune is “how much labor will it buy?” This because almost all things humans value are merely frozen labor. When the worker are numerous and poor, they will work for peanuts. During a depression the purchasing power of the rich leaps upward as wages drop. This is probably the prime reason that the vast majority of humanity has never heard of population overshoot. Population overshoot makes the rich giddy.

  12. It’s not about space it’s about resources. It’s about access to food and water to sustain a large population. We are projected to hit somewhere between 9 and 11 billion. Whether or not we will be able to sustain this number depends on whether or not agricultural technology keeps advancing. And if you think drinking sea water is an option it’s not really a usable solution right now. Did you know you could fit the entire population of humans on Earth shoulder to shoulder in Los angles. It’s not space it’s food and resources. This is what we call carrying capacity, the amount of people that can be sustained based on the resources we have. If population continues to grow as projected our population should hit 11 billion by 2100. You can trust me I’m in AP human geography.

  13. Many people discuss availability of resources when discussing the carrying capacity of our planet. I like to include a second discussion with my students. I include the discussion of how we buffer the human impact. Pollution of our air and waterways; degradation and depletion of our soil are just a few of the impacts that reduce the viability of fundamental resources such as water. Water is life’s essence!
    I think the actual population of people that can be sustained is based upon how much science and technology can ‘step in’ to solve some problems. For example, modified crops such as corn have been with us for years in attempt to increase available food. However, the nutrient level of our processed food is anything to be desired. Science has yet to cause major change in the buffering of our existence. This is mainly due to political will and apathy of the population.
    Just wanted to share my thoughts since I came across this site. Peace out dudes & dudettes

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