Implementing K*: Choosing an optimum global carrying capacity for humans

Background/Question/Methods

Human population is on track to rise from 1 billion in 1800 to 10 billion by mid-21st century (U.N. Population Division). U.N. projections assume that low fertility countries will increase TFR while high fertility countries TFR will decrease until both approximate replacement fertility levels. U.N. projections that fertility rates in all countries will converge imply that countries will choose some K*, allowing for stable world population. Choosing a lower than maximum possible K* as a target towards which population adjusts by intention could allow lifestyles well above subsistence levels with low mortality rates and long life expectancy. In addition, intentionally allowing space and resources for other species in order to reduce risk of ecosystem dysfunction also argues for choosing lower than maximum possible human population levels. This paper discusses three questions: 1) How should humans go about choosing K*, an ideal level for human populations? 2) What K* choice might emerge from such a process (we present several alternative K* choices based on differing criteria for determining optimum population levels)? 3) What institutional (cultural, legal, economic) policies would be appropriate and feasible to help adjust human fertility/mortality rates in order to move towards and maintain population levels near K

Results/Conclusions

We posit considerations for determining a purposefully chosen K* for particular countries. These include cultural preferences regarding the tradeoffs between numbers of children and higher standards of living, valuation of the natural environment, tolerance for risks of overshoot and collapse, assessment of resources limits (including climate change) and other factors. Experience provides a set of strong arguments for population reduction and as set of tools that have proven effective in reducing fertility rates. Application of these tools is highly country or region specific and so the demographic transition cannot be regarded as an automatic outcome of modernization but rather requires intentional policies and programs to reduce fertility. The good news is countries with nearly 50% of world population have achieved below replacement fertility levels. The bad news is cultural obstacles to fertility reduction are difficult to overcome in the remaining high fertility countries. There is need to integrate the concerns of ecologists who most closely monitor and study effects of human populations on ecosystems with the policies and programs emerging from demographics and economic development efforts. Economists calling for growth as a solution to low incomes fail to appreciate the K* concept.