Another look at population and global warming

The author addresses two questions: First, how much could feasible reductions in projected rates of population growth in the developing countries help reduce greenhouse gas emissions? Second, how much would it cost to ensure such reductions in population growth, compared with other options for reducing emissions? The answer to the first question is that reductions in population growth would matter, but not much. Based on current econometric estimates linking population growth to deforestation, feasible reductions in population growth could reduce emissions from deforestation (relative to what they otherwise would be) by 8 percent over the next 35 years. Feasible reductions in population growth rates could reduce fossil fuel emissions by about 10 percent. The percentage reductions, though substantial, are small relative to projections of a tripling or more in emissions under any baseline scenario in the next 50 years. Thus there is little basis for the view that the South could contribute to major reductions in global warming by taking new and stronger steps to reduce its population. The answer to the second question is that reducing population growth is cost-effective compared with other options to reduce emissions. The author estimates the costs of reducing carbon emissions by reducing births through increased spending on family planning at between $6 and $12 per ton; and by educating girls at between $4 and $8 per ton. These compare to a marginal cost of $20 per ton to reduce current emissions by 10 percent, using a carbon tax. Discounting reduces the cost advantage of the population reduction strategies over the tax, but does not eliminate them as a critical part of an overall global strategy to reduce emissions. The implication of the cost analysis is simple: The global negative externality represented by rapid population growth in developing countries provides a strong, new rationale for developed countries, in their own interests, to finance programs that would reduce population growth in developing countries. This is true even though feasible reductions in population growth would represent only a modest contribution to reducing greehouse gas emissions. Spending to reduce rates of population growth in developing countries makes sense as part of any optimal carbon reduction strategy.