Population is a critically important variable in the quest for a sustainable and healthy world. Population dynamics of natural populations is relatively well-understood. Introducing an exotic species into a new habitat where it faces little competition and has rich resources results in a steeply rising curve usually with pronounced exponential rates of increase. Here is the curve for human population increase (I used world bank and UN data) which looks more-or-less identical to a normal natural population of an introduced species with little competition and rich resources.
Over time the resource level and/or competitive factors or disease from overly dense populations begin to tip the curve so that the slope of population increase is decreased. Here is a chart of the recent changes in human population growth and a projection to 2050.
There is a gentle inflection somewhere about 5 billion people. In the normal course of events in a natural population, there is an “overshoot” beyond the natural inflection point that rises to an amount that depends on a wide range of factors. The inflection point is essentially where the population just begins to react to declining resources, or increased competition, or disease. It can be a large or a small overshoot. However, the normal pre-existing carrying capacity of an area is roughly equal to where the inflection point occurs.
As the pressures on the population increase, the curve slows down completely and then begins to tip over and head into a declining population. The population decline has been caused by stress on the resources and/or increased competition, and disease. This stress normally damages the resource base which lowers the previous carrying capacity of the area.
Depending on the severity of the overshoot, the damage to the resources will be roughly proportional. In some cases the damage is so great that the population can never recover. If the damage is not too severe, the species will recover to the lower carrying capacity. Often it takes a number of such overshoots, crashes, and recoveries to reach a relatively stable equilibrium.
At least in terms of fit to the natural population curves, humans are not demonstrating anything other than being particularly adept at using up resources through consumption, waste, pollution, and failure to recycle. Global warming will of course put further stress on resource levels and existing coastal regions where population is high. On the above graph, humans (we) are just over the carrying capacity for comfortable living. The potential for severe overshoot is very real. According to the Global Footprint Network, humanity uses the equivalent of 1.5 planets to provide the resources we use and absorb our waste annually. This means it now takes the Earth one year and six months to regenerate what we use in a year. Moderate UN scenarios suggest that if current population and consumption trends continue, by the 2030s, we will need the equivalent of two Earths to support us. And of course, we only have one planet. Needless to say, if the overshoot is allowed to reach dramatic levels, the inevitable decline will be a horrible experience for billions of people. Suggested estimates of 11 to 14 billion have been made by demographers. Such levels would be very uncomfortable for most people. If this were the case and the decline were to begin, it would be devastating.
People certainly have the potential to be smart about the ecological management of the world. The science is not lacking in this field. Competent management would absolutely not call for continued increase in population levels. Population growth however, is encouraged in many countries by offering tax breaks for children, rewards for more than two children, and baby bonuses. Countries that desire increased populations tend to deny education to women and discourage family planning or birth control. Economic growth is politically and corporately seen to be necessary. One way to achieve economic growth is to increase the demand – have more babies. This is not true of all countries of course and many discourage having too many babies. The net result today is that population continues to increase, but at a slightly slower pace than previously. In a few cases the actual fertility rate is lower than the replacement rate. China has experimented with coercive population control with some success accompanied by much unhappiness and a degree of cheating the system. One disturbing trend is aborting female children in favour of male children, such that the country now has a potential problem of many young men (30 million by 2030) who will not have a potential mate. We need to find and implement a wide range of non-coercive means of introducing human population management. Stabilizing or reducing absolute population size will make solving other problems easier both because there are fewer of us and also because many of the solutions to birth control involve education which spills over into other relevant topics.
The conservative predictions for population growth by the time kids today are in their mid-40s is about 9 billion people on this planet. This will place the human global footprint at just about 2.0 – that is we will have overshot our planet’s ability to renew the resources we have used in one year by a factor of two. For developed countries this is much greater (the US today is at about a factor of 10 on a per capita basis if US lifestyle were extended to the entire world population). If the prediction of growth to 2100 is maintained, it could be 11 billion people.
If we consider the implications of a planetary carrying capacity of 5 billion people that means the population must fall at some point to 5 billion people or fewer to be sustainable – recognizing that the resource base of the planet will be considerably diminished by then and developing countries will want to experience improved lifestyles. Unless we drastically change our reproductive patterns, demographers predict that the peak will be about 11 billion people by approximately the year 2100. That will mean the time from inflection on the growth curve to peak population will be about 110 years. The declining side of the growth curve is usually pretty symmetrical to the increase implying that the rate of decline in population will be roughly equal to the negative of the rate of increase. So by 2200 the population will diminish to about 5 million people. That cannot happen without misery.
It would be far better to stabilize the population of the world well below these figures. The key is to empower women to make their own reproductive choices. The Worldwatch Institute suggests nine non-coercive strategies to stop short of 9 billion people and reverse the trend before 2050. I imagine we can add to that list. The immediate challenge, however, is to implement these strategies quickly enough to make the difference. With that goal met, the decline to 5 billion people would be much more manageable and while difficult it would not create uncontrollable human disasters. Here are the Worldwatch strategies:
- Provide universal access to safe and effective contraceptive options for both sexes. With nearly two in five pregnancies reported as mistimed or never wanted, lack of access to good family planning services is among the biggest gaps in assuring that each baby will be wanted and welcomed in advance by its parents.
- Guarantee education through secondary school for all, especially girls. In every culture surveyed to date, women who have completed at least some secondary school have fewer children on average, and have children later in life, than do women who have less education.
- Eradicate gender bias from law, economic opportunity, health, and culture. Women who can own, inherit, and manage property; divorce; obtain credit; and participate in civic and political affairs on equal terms with men are more likely to postpone childbearing and to have fewer children compared to women who are deprived of these rights.
- Offer age-appropriate sexuality education for all students. Data from the United States indicate that exposure to comprehensive programs that detail puberty, intercourse, options of abstinence and birth control, and respecting the sexual rights and decisions of individuals, can help prevent unwanted pregnancies and hence reduce birth rates.
- End all policies that reward parents financially based on the number of children they have. Governments can preserve and even increase tax and other financial benefits aimed at helping parents by linking these not to the number of children they have, but to parenthood status itself.
- Integrate lessons on population, environment, and development into school curricula at multiple levels. Refraining from advocacy or propaganda, schools should educate students to make well-informed choices about the impacts of their behavior, including childbearing, on the environment.
- Put prices on environmental costs and impacts. In quantifying the cost of an additional family member by calculating taxes and increased food costs, couples may decide that the cost of having an additional child is too high, compared to the benefits of a smaller family that might receive government rebates and have a lower cost of living. Such decisions, freely made by women and couples, can decrease birth rates without any involvement by non-parents in reproduction.
- Adjust to an aging population instead of boosting childbearing through government incentives and programs. Population aging must be met with the needed societal adjustments, such as increased labor participation, rather than by offering incentives to women to have more children.
- Convince leaders to commit to stabilizing population growth through the exercise of human rights and human development. By educating themselves on rights-based population policies, policymakers can ethically and effectively address population-related challenges by empowering women to make their reproductive choices.