Global population surpassed 8 billion this week, a shocking milestone because back in the 1990s this threshold was not expected to be breached until 2050. Whether you’re a dour Malthusian or a technological optimist, one thing is undeniable: The 2.7 billion people added to global population since 1990 makes the task of averting a climate catastrophe vastly more challenging than it was when global warming first arose as a mainstream concern.
Getting to zero net emissions in 1990—when fossil fuels were putting 22.4 billion metric tons of greenhouse gas emissions (GHG) into the atmosphere—was hard enough. Now, we have to eliminate those emissions along with roughly 14 billion tons of annual GHG emissions resulting from population growth. Equally daunting, with climate changes here and intensifying, we have to start now. Nor can we count on the biosphere to continue to sequester a small portion of our emissions as the oceans are already showing stress from existing accumulations of carbon dioxide and our forests continue to be degraded in the quest to feed and house our ever-growing numbers.
In short, we have a bigger rock to push up the hill and ever less time to do it. We have to. The alternative is simply too dire to imagine.
Business as usual takes us to a 2.5 to 3 degree Celsius warming from pre-industrial levels. The last time the planet was that warm was during the Pliocene, some 2.6 million years ago. There was plenty of life back then, but no humans, and, given the way rising temperatures decrease yields and alter weather patterns, it’s very unlikely that a world that much warmer could feed the 8 billion alive today, much less the 2 billion people likely to be added in the coming decades.
So, we have to cut emissions and fast. How? There is no single magic bullet, but there are certain things that simply have to happen, and the global community can create the incentives to make them happen.
One of them is family planning, which until now has been largely absent from the conversation around global warming. Today, the global average for per capita carbon dioxide emissions (the dominant greenhouse gas) is about 4.4 metric tons, according to the International Energy Agency. (For comparison, India’s annual per capita CO2 emissions are about 1.7 metric tons, China’s 7 tons, and the U.S., 13 tons.)
Most of the expected 2 billion people will be born in the poorer nations. These nations burn fewer fossil fuels, but all aspire to raise their standard of living, which, given today’s energy mix, means more GHG emissions per capita. Even without economic growth, that population increase would mean roughly four billion additional metric tons of CO2 going into the atmosphere each year. That’s about a 10% increase, and, as of today, the world has never been able to voluntarily reduce annual emissions.
Population should be part of climate discussions, but I cannot remember a time when family planning has been featured in international efforts. Yes, it’s a hot button topic in many of the emerging nations, many of which take affront when the rich nations ask them to stabilize their numbers. But its absence from the agenda from last week’s COP27 is a tell that the Congress of Parties process is not a serious effort to really tackle the risk of climate change.
Population growth is the elephant in the room for climate change, but it is also the elephant in the room for ecological issues such as tropical deforestation, desertification, the extinction crisis, the destabilizing of earth’s life support systems on land and in the oceans; demographic issues such as involuntary migration, fresh water, and food insecurity; and political issues such as civil unrest and state failure. Slowing population growth will reduce pressures on all of these issues and threats.
Population growth is a fraught issue. In the last few decades, a major driver to limit family size has been the demographic shift towards urban areas. In cities, additional kids become a liability because of the higher costs of housing and food. This shows that people can change attitudes towards family size quite rapidly, given incentives and access to family planning. For governments, the incentive should be the prospect of a climate Hell if population continues to increase by several hundred million people every decade. Many emerging nations have made great strides in lowering infant mortality, but, all too often efforts on maternal and infant health are not coupled with access to family planning, which is one reason why human numbers surpassed 8 billion two decades ahead of schedule.
There are many reasons for not adding the next 2 billion to global population, but the absolute exigency of lowering global GHG emissions should be sufficient to return population pressures to the international agenda. More to the point, if humanity does not voluntarily control our numbers, climate change and its four horsemen of heat, floods, droughts, and storms, will do it for us.
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