analysis, if you analyze human population growth, and at the same time looking at the phenomenon in a totally objective. OK, so we don't have any answers, but this is a way to think about it, and a lot of people are putting a lot of energy into modeling the systems, and try to figure out where we are the scariest trajectories. What caused the growth to begin with, and why it's leveling off? past and past participle of spell. You see. So. This number keeps changing, and luckily it's changing in the right direction. This is probably the prime reason that the vast majority of humanity has never heard of population overshoot. population density, when you have density, really the one that's the most important here is looking at this. And for a long time. And the really important feature, here is what's called a demographic transition. How Many People Can the Earth Support? And that’s with billions of people living in poverty, consuming next to nothing. Well, they missed it by a lot. population in the US, and this is one over N, dN/dt, and this is N in millions. this where you get a couple of oscillations in here. Huge research papers predict; Sustainable carrying capacity of Mother earth as on today is 3 billion people depending on replenishment of renewable resources. verb [past and past participle] mainly British And you could see that it's taking longer and longer to add a billion. And death rate has gone down, but they're not matching each other at all. The carrying capacity is the upper limit of a given population which can be sustained without damage to the environment. But one could argue that if you are managing a population that you want to harvest, that you try to keep them at the density at which the dN/dt, the production of organisms, is maximal. Then about 10,000 years ago man invented agriculture. introduction of real public health across the world. 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. And we don't know yet because these feedback mechanisms haven't come back. The carrying capacity of the earth is measured by its ecological footprint. Do I have something wrong? So, with no lag, we have our logistic equation, right? So that we have a line that we can put that on. leveling off. And this is 2000. same thing. And so, they projected down here there were 100 million people then. And you have a sense of that just. natural system so much that we can come back to a stable level. 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? So, let's look at the data, which is not surprising. them at the density at which the dN/dt, the production of organisms. Plants that make seeds, etc. Anyway, I've never been able to figure out why they call this the, logistic equation. So we know that there's a problem here. Maybe when we see the next slide we'll see. But these models are based on, something entirely much more complex now than the simple logistic, equation. Required fields are marked *. Our max, exactly. And this is called the logistic equation for reasons that are historically obscure. > In other words, the whole field is trying to understand what the mechanisms are in populations that limit their growth. So, they don't grow exponentially forever. But then, if you then reduce the birth rates through fertility, control to match the death rates, you then have low birth rates and. Those are catastrophic things. carrying capacity of the earth for humans. So, in Cohen's book, he analyzes this, sort of the history of humans, on Earth as having four major evolutionary changes where you have, the dramatic change in population growth. Flash and JavaScript are required for this feature. !2 billion is 2x the amount that we have right now. We can fix any of this with technology, and if things get really bad, we'll go to Mars; we'll terraform Mars. He's asking, what's the carrying capacity of the earth for humans? Because there is an inflection point, here, right? The doubling time is extending. And if you think drinking sea water is an option it’s not really a usable solution right now. but it's not important. N, is constant. The latter would not be pretty. This tells us how much area of biologically productive land and water an individual, population, or activity requires to produce all the resources it consumes and to absorb the waste it generates, using the prevailing technology and resource management practices. And for a long time, ecologists kept looking at, populations trying to see whether, indeed, they were growing according. So the question is: Can humans evolve to a species that accepts earths limitations and tries to live within them? And they predicted that we'd have 197 million when we reach the carrying capacity. In other words, there is a carrying capacity for human life on our planet. And indeed, technology has greatly increased the carrying capacity of the earth for humans. But if you have a short lag, what you get is an actual overshoot of the carrying capacity in the near term because the feedback hasn't kicked in. We were talking about exponential growth in populations. Depending on the metrics used, estimates of the earth’s carrying capacity can range from as small as a half a billion people to as large as 14 billion people.8,9Why the dramatic disparity? This is what we are. Anyway, I've never been able to figure out why they call this the logistic equation. So, let's start with where we were. So let's look at what that means in. The issue isn’t the number of people. And then birth rates, and if you want to you can easily describe a scenario that says that we have overshot, that this whole environmental movement, the measurement of toxins in our environment, the global change, all of that is really overshooting the carrying capacity. And, the doubling time of the population before and after those evolutions went from what he estimates to be 40, 00 to 300,000 years for a population to double down to 1000 to 3000 years for the population to double. Food . 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. something like this that we may overshoot. Granted, we're starting to level. 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. And they predicted that. And then, they looked at the data again using this graphical formulation. They might have one generation that's still at the same growth rate as it was before, before the biochemistry readjusts and says, whoa, we can't keep going at this rate. So, using the tools that we've developed to analyze populations, let's look at why this growth is leveling off. And this is called a density, OK, so if we look at this, remember from last time that r is. for higher birth rates, and so had a little blip, went up to 7 million here. of the Earth. We can handle as many humans as we want to put because we, smart people, with technology can increase the carrying capacity. We already know the answer to this question, because before 1820 humanity was living off of human, animal, and vegetable (i.e. In the first century AD, the global population was estimated to have been 300 million people, which then took 1,800 years to reach a population of 1 billion in the 19th century. So the real trick is, in terms of trying to level off at someplace, lower than 9 billion, is to get the birthrates in the. If you have a medium lag, you will often see something like this where you get a couple of oscillations in here. And then, of course, the pessimistic scenario is that, indeed, we've overshot, and we've overshot so much that we have eroded, the carrying capacity, and that we will level off at some, level that the Earth will no longer be able to support the level of. And that, many scientists believe, is the maximum carrying capacity of the earth. Here's the beginning of the Industrial Revolution and the. But then, it will come back and it will level off at the carrying, capacity. something like this. for those of you who don't know what I'm talking about, just ignore me. know yet because these feedback mechanisms haven't come back. So, using the tools that we've, developed to analyze populations, let's look at why this growth is. but that can be described mathematically. The populations leveled off whereas if you look at a country like Egypt over the same time frame, and you can get these curves off the web easily, it looks something like this. We can fix it; we can fix it, so let's just go with the flow. We can fix it; we can fix it, so let's just go with the, flow. Every year I check in and see where we are. The population just reaches, With a very short lag, and of course you have to play with, this to understand what I mean by short, long, and medium because you, have to change all the different parameters. The cc is somewhat dependent upon lifestyle, governing systems and how we apply our technologies. Now we know that it's so much more complicated than that that you can't just set the model is. come in and talk to you about, again, its population economy. Other sections are also multiplying for survival / existence. However, in the context of sustainability, communities have several different types of capital that need to … Please get in touch with me so I can learn about ways to raise awareness about the importance of population stabilization. So, is this the model that we want to go by? something to do with, anybody know, who speaks French? OK, let's analyze some more, features of this. But just because an equation has, certain properties, it doesn't mean that thing it's, trying to model has those properties. There's no doubt about it. You have a high birth rate. I've just got the last three years. But it levels off at the same carrying capacity. But one could argue that if you are, managing a population that you want to harvest, that you try to keep. scale, here's the bubonic plague, a decrease. We want one over N, dN/dt, to go to zero as N gets large. Another model is, if we're going to do this, here's what I call the, optimistic model. In other words, the actual growth rate of the population was decreasing as the number of humans increased. And this is called the logistic equation for reasons that are, historically obscure. We reached 200 million way before 2030. growth. And, there's this wonderful book for. they have different data points for different intervals, and their last point here was 1900 to 1910, an average of, the population size. It's a constant, but the actual change in numbers as. And then in the 50s with the introduction of real public health across the world, another reduction, and luckily in the 70s, with the introduction of fertility control, at least in the developed countries, is the first time you actually see a shift. as one over the dN/dt equals some growth rate, r. let me ask that is a question. You have local agriculture in 8000 B.C. Have we overshot K? So, come back. And so then, here you start to get, I'm not sure what started this up rise. Another reason nobody knows the upper limit for the human population is that it depends on what that limit protects. Yeah? 10 - 20 Billion . it, showing that the growth of the global population has peaked. And this is basically, what Joel Cohen's book is about, where he says, how many people can, the Earth support? OK, so here we have a nice density, dependent response. Well, the simplest way is to introduce time. Because there is an inflection point here, right? When I first started teaching about. If only that vision were plausible. So, the next two lectures Professor Martin Polz, who is a professor in civil and environmental engineering, and the microbiologist is going to come in and talk to you about, again, its population economy. one over N, dN/dt as a function of N, what does this look like? But then, if you then reduce the birth rates through fertility control to match the death rates, you then have low birth rates and low death rates. It's not on the web, but if you care about it, there is the website that keeps track of human population in the US. 20 when we were talking about biogeochemical cycles? countries, is the first time you actually see a shift. You're basically growing. But, it's from this book. So, that should be the carrying capacity. And for those of you who are interested in complex systems and, chaos theory, the logistic equation in its discrete form actually will. You have local agriculture, in 8000 B.C. low death rates. Sometime over the next millennium -- a relatively short time when you consider the age of the Earth -- the human population's carrying capacity will be realized. Right. This marks the lectures that I've given in this class. We’re way past the tipping point. This is 1800 to 1810. It hasn't even begun to level off. Debate about the actual human carrying capacity of Earth dates back hundreds of years. metabolism of the Earth, by this explosive growth of humans. Q. All right, so let's look at this. So, some people argue, so, the climate, we'll fix that with technology. You spelled the word “spelled” wrong. Well, I guess this is the super, optimistic model. the logistic, just to summarize, one over N, dN/dt as a function of N. and if we just look at the dN/dt as a function of N. for exponential we already said that this is a flat line, right? We just did it, so we are summarizing here. Density dependent factors regulate. A 2001 UN report said that two-thirds of the estimates fall in the range of 4 billion to 16 billion with unspecified standard errors, with a median of about 10 billion. as a globe, and we are going to level off in terms humans. But the long-term carrying capacity of the earth always remained at one hundred percent of what it was possible to carry. © Population Connection 2021. As N increases, r decreases in the population. But it doesn't matter what it's called, this is what it is. And, the reality is this doesn't fit, at all in an exponential model at all. This depends on whether we want other life on Earth to survive too. OK, so if we look at this, remember from last time that r is equal to the birth rate minus the death rate, right? OK, all right, so now are going to move on to, global population growth, humans on the earth, the whole shoot, and match. The comments on this website are submitted by readers. 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. But here's one that I want you to think about. It's the maximum number of organisms were the population levels off, OK? This is how we've changed the. something like this. OK, so let's go back to Pearl and Reed. 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) . is that the carrying capacity will grow with us, OK? Just think if you're living back here, and thousands and thousands of. capacity of the earth for humans? So, we can look at, this is just a simple cartoon, drawing of what's going on here. And, that came in advance of fertility control. And these are just some interesting statistics for the US, and I have them for the last three years: one birth every eight seconds, one death every 13 seconds, one migrant every 26 seconds, and a net gain of one person every 12 seconds. dNt/dT, is equal to r max times N at that. Maybe just the accumulation of people that you can't see on this scale, here's the bubonic plague, a decrease. showed that they had this density dependent response. But this view is deeply ahistorical, assuming carrying capacity to be static. And then I'll be back with some. Is it human life or is it the non-human animals that are dying off at such an alarming rate? What is the carrying capacity of the Earth? Population Dynamics The district of West and South Palu calculated to have the highest carrying capacity. Currently, we are on a path to extinction. So here we are at 6 billion people. These scientists used a combination of satellite derived images, and photo interpretation measurements, paired with global environmental software to add layers of soil, climate, population, and topographic variables (characteristics of terrain) to build a model to essentially estimate Earth’s present “tree carrying capacity”. SPELT is British for past and past participle of SPELL. And we wouldn't be worrying about things that we're, worrying about if we hadn't overshot it, but that if we get, our act together, we won't have eroded the Earth's. So, anyway, this is what some people. Plants that make seeds, etc. He'll talk to you about population genetics, and some really exciting, work that's going on in the field now using genomics to decipher, evolution and population biology. So, that should be the carrying capacity. All right, so let's look at this. So, they came up, so let's plot, this N. This is T, and here's our exponential growth, equation. Erase that from the tape! You're over here where the, exponential growth curve and the logistical curve are essentially the. OK? So, if you look at this curve, you think, oh my God, we're in the middle of this incredible exponential increase. Population Connection staff approve comments, assuming they aren’t spam and don’t contain abusive language. OK, let's analyze some more features of this. And, based on the models that we have today, in 2030 we should have, about 345 million. Joel Cohen . So, if we want to plot it this way, one over N, dN/dt, as a function of. humans that it can even support now, that we have lost so much topsoil. we were able to keep people alive a lot longer. So, it's very simple and intuitive when you understand what's, going on, but I don't think that most people really have come to the, And where we are on Earth today is the developed countries have gone, through their demographic transition. Birth rate continues to stay high. So the question is, how do we modify that equation, our simple exponential growth equation, so that it more realistically describes real populations that can't grow totally unconstrained? And for a long time, ecologists kept looking at populations trying to see whether, indeed, they were growing according to this chaos theory and it hasn't really developed to anything, but it was interesting. The populations leveled off whereas if you look at a country like Egypt, over the same time frame, and you can get these curves off the, web easily, it looks something like this. That's not that far-fetched, so why should we worry about all these humans on the Earth? In fact, some people describe the, entire field of population ecology as a field that tries to determine. The term “one-planet living” refers to a society that, on average, lives within Earth’s carrying capacity (www.oneplanetliving.org). And the real big question is when we level off, will we be above the, carrying capacity of the Earth? And for those who are interested ought to spend a minute on it. It doesn't change as density changes. So, this is an oversimplification. So, you can see these features over here at this plot, right? When the worker are numerous and poor, they will work for peanuts. People cannot continue reproducing at will. You can see that there is an inflection point here. fertility control, and we didn't have modern medicine. Carrying Capacity of the Earth. It has to do with something military. terms of, this brings us to another level of complexity. And, we said we could describe this. The low carrying capacity of water provision covers 689.31 ha or about 11.84% of the total agricultural land. So t or tao is the time lag between sensing environments, and change in growth rate. in the simplest organisms, even microbes in a culture. about it. Fill out your information and your Population Connection coordinator will contact you with ideas for hosting an informational table in your community! they got something that looked like this. We are going to explain what's happening here in a minute. So, here's what we want the characteristics to be of this. Maybe just do 12 billion-24 billion max. So that was a really interesting. So, as this goes to zero, or as N is very large, one over N, dN/dt goes to zero. And, when N is, very small, one over N, dN/dt is near our max. And they. So, they have different data points for different intervals, and their last point here was 1900 to 1910, an average of the population size. The range of estimates is enormous, fluctuating from 500 million people to more than one trillion. So, I'm not saying not to worry. And this was 1800. And, when birth rates and death rates are both uniformly high, which is the way it was back in the early days when we didn't have. And, this is back in the hunter gatherer era. There's no doubt about it. And these density dependent birth rates and death rates introduce a, stabilizing factor. If we stopped eating ruminants we could increase that number, or if we produced them more intensively. And now, we're looking at the human. 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. Learn more », © 2001–2016 Imagne twice the amount of people will just kill all other existing life. And you have a sense of that just from looking at family size in these countries. if we look at, this is Sweden as an example of a developed country. > But there's got to be a limit. dNt/dT, is equal to r max times N at that time t times K minus Nt minus tao. And, based on the models that we have today, in 2030 we should have about 345 million. So, people have tried to. high birth rate. Massachusetts Institute of Technology. New knowledge and technology raised it from the per 1820’s one billion, but new knowledge and technology can only raise it so much. 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? And this is called a density dependent response. When I first started teaching about human population growth, the projections were at 12 billion. 30 seconds . Let's replot this, because it's. We have been growing like this. Right. We cleared forests for grasslands and agriculture. up to here we are today, And, this is back in the hunter gatherer era. I believe based on our current path, we max out at 4 to 5 billion. This is also done by. We've already peaked out. And these density dependent birth rates and death rates introduce a stabilizing factor. > 1990, 250 million, and actually today, at 10:45 this morning, because I looked it up on my trusty population clock on the Web, we had 295,979, 38 people. We reached 200 million, and actually today, at 10:45 this morning, because I looked it up on, we had 295,979, 38 people. Patterns of population growthhave been studied and observed in ecology. If we don't have enough grain, we'll genetically engineer to make more grain. go chaotic for certain parameter values. just thought I would point that out. But it's just a wonderful account, analysis, if you analyze human population growth, and at the same time looking at the phenomenon in a totally objective way. And I'm not that old. So, let's just briefly, let me go back over here, and let's go back over this carrying capacity. So t or tao is the time lag between sensing environments, and, change in growth rate. And now, we're looking at the human population in the US, and this is one over N, dN/dt, and this is N in millions. 4 models. Human carrying capacity is therefore dynamic and uncertain. So the answer is one billion people. And they came up with a function that looks like this. Some of these issues have been studied by computer simulation models such as World3. Just looking at the exponential and. Great turn of phrase – ‘The fewer the people, the more destructive the elite of this world will get.’ Couldn’t agree more. As a model for population growth. And, the way we look at this, we are planning birth rates here, which is the pink one, and death rate here, which is the green one. But these models are based on something entirely much more complex now than the simple logistic equation. As a model for population growth, what's wrong with this? 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. So, those are bad things, not to be yada, yada, yada'd. introduce time lags into the equation, and we don't have time. This field is for validation purposes and should be left unchanged. The current population could be reduced by attrition. Oh, they're up there. Carrying capacity is the maximum number of a species an environment can support indefinitely. And death rate has gone down, but they're not matching each other at all. Maybe when we see the next slide we'll see. We're going to plot one over N. dN/dt as a function of N. If we want to rewrite the equation. And here we are with a steady, increase. Well, I guess this is the super optimistic model. just no change in human population on Earth. And we hit 6 billion in 1999. So the real trick is, in terms of trying to level off at someplace lower than 9 billion, is to get the birthrates in the developing countries to drop as fast as we can. 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. There is a limit and reproducing carelessly endangers our long-term survival and the survival of other species with whom we share the planet. from looking at family size in these countries. So, it kind of looked like exponential growth. So, they said, so they asked the, question: OK, we're modeling this population, we're saying it grows, according to the logistic equation, we can predict what the carrying, capacity in the United States for humans by simply doing a regression. And what we've been assuming, is that the carrying capacity will grow with us, OK? Like this? This one assumes that it'll do. If we don't have enough grain, we'll genetically engineer to make, more grain. It's smoothed over, and these are the greenhouse gases, concentration of greenhouse gases in the atmosphere. that they put on here. Many scientists think Earth has a maximum carrying capacity of 9 billion to 10 billion people. For most of the developed world, that would mean about one million. If we do and we want to continue our current lifestyle, I think the answer is closer to 2 billion. Marian Starkey, Senior Director of Publications. So, in this case, this is really a maximum growth rate. to double down to 1000 to 3000 years for the population to double. Did you know you could fit the entire population of humans on Earth shoulder to shoulder in Los angles. Yes, I would like to receive e-mail from Population Connection. And we don't. This is what we call carrying capacity, the amount of people that can be sustained based on the resources we have. this model is actually used in fisheries conservation for years. how about 13.8 billion , the number which the creator has given us by the age of universe? 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. They might have one generation that's still at the same growth rate, as it was before, before the biochemistry readjusts. off, but we've been growing like this. So, you don't have much population growth. Imagine what would happen if desperately poor people were fortunate enough to live a middle class lifestyle. And, we said we could describe this as one over the dN/dt equals some growth rate, r. And, in this case, we're talking about, let me ask that is a question. The doubling time is extending. that context, because this is an important thing. And the really important feature here is what's called a demographic transition. First of all, before we do that, I want to remind you that all of these lectures are tied together because remember this from lecture 20 when we were talking about biogeochemical cycles? Carrying capacity is the number of organisms that an ecosystem can sustainably support. But I wouldn’t try to hit that. Already, we’re consuming the Earth’s renewable resources at one and a half times the sustainable rate. I mean, this is just this little snippet of time in the history of. OK, so all right, forget that. 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. Even. This is just an approximation. Let me just make sure that's not, ambiguous. Absolutely right. and modern agriculture won't be able to overcome that, that our water will be polluted, that the climate will change so. tao hours or days or whatever, earlier than t, divided by K. So, what this says is that the growth rate of the population is a function, of the density up a little bit earlier, or some amount earlier than.