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This is a joint post with Kate McQueston.

Despite major fertility declines that have taken place in recent decades almost all over the world, population growth is far from over.  As Ken Weiss points out in a recent five-part series in the Los Angeles Times, the adverse effects of population growth are well documented and wide ranging.  But population reduction through fertility declines may also have unintended consequences if proper policies aren’t in place early on.

The world today must accommodate the largest cohort ever in human history of young people within reproductive age. According to UN data, the percentage of population under 25 years of age in less developed countries represent over 60 percent of their total population. The phenomena has been termed the “youth bulge”, and the trend has been correlated with factors such as unemployment, social unrest, and civil conflict—particularly in countries with weak governance structures.  Approximately 80% of the world’s conflicts, since 1970, have occurred in nations with high fertility rates.  In these cases, economic growth is absolutely necessary to create employment for youth under the auspices of national security.  Youth will also need marketable skills, hence the huge efforts that will be required to build human capital.

Population growth may also imply tremendous tensions on food prices and could increase the global burden of hunger. One doesn’t have to look far for such an example.  The United States is currently suffering from one of the most severe droughts in nearly  50 yearsover half the country is stricken by moderate drought or worse.  Last week, the UN food agency released findings that the overall food price index increased by 6% in July, directly correlating the prices of food commodities with drought conditions.  In populations living in extreme poverty, such as the 400 million people living in Africa on less than $1.25 a day, even small increases of food prices can have devastating effects.

Reducing population growth through fertility reduction, although beneficial in many respects, might also have unintended consequences.  As many countries reach lower fertility rates, investments in material capital and economic production also increase. For instance, China’s rapid industrialization still relies heavily on coal to supply its growing energy needs and has caused significant environmental degradation.  CGD fellow David Wheeler’s research shows that population interventions, including family planning and female education, can be more cost-effective than many environmental interventions, including solar, wind, and nuclear power, second-generation biofuels, and carbon capture and storage—and on par with forest conservation.  Kate McQueston reviews the two sides to sustainable development as it relates to fertility here.  One way to avoid the debate is to understand that fertility reduction isn’t the only answer to environmental conservation.  Economic development should also coincide with changes in traditional consumption patterns.  I argued previously that policy changes to reduce material consumption, improve education, and the implementation of natural assets accounting would develop new systems that are not necessarily dependent on material consumption.

The interconnectedness of population with a variety of issues, from environmental conservation to national security, means improving population policies would create positive externalities for a wide range of other sectors. But improving population outcomes means overcoming barriers—including funding and access to contraception, improved education and employment, environmentally friendly consumption patterns and effective national policies. Finally, let us face it: some religious and political attitudes remain a hindrance to fertility reduction efforts.  In the case of the Philippines, the Catholic Church still opposes open access to family planning, which has fostered high levels of induced abortions (almost half a million per year).  Individuals need to be able to decide for themselves on matters of reproduction, through systems free of heavy influence from social conservatives and religious institutions.

The bottom line: population growth will continue in the next decades, with major consequences for employment and food security.  And even when fertility comes down rapidly, as in China, the environmental footprint might be huge if environmentally-friendly consumption patterns are not put in place as well.