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.

12 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.

  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

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