This article was first published in Newsweek on June 13, 2023.

U.S. Climate Envoy John Kerry raised eyebrows recently when he said continued high birth rates in some parts of the world and a global population of 10 billion would be unsustainable.

The problem with his remarks isn't their accuracy. Kerry is right that a population of 10 billion won't be sustainable. The problem is that a spokesperson for the world's richest and most powerful country is pointing this out without offering any solutions. It's not as if the Biden administration is powerless. In fact, effective solutions are well within its reach.

A projected global population of 10 billion by midcentury is far from inevitable, and current high birth rates underpinning the projections aren't immutable. Small changes in birth rates can have big effects on global population.

The United Nations population projection is expressed as a range rather than a single number. The low variant is around 7 billion, and the median variant is well above 10 billion. In terms of birth rates, the difference between the 7 billion and 10-plus billion is just .5 children per woman.

That incremental change in birth rates hinges on whether women have the means to choose the number and spacing of births, which in turn hinges on whether they can access modern contraceptive methods and whether they have the reproductive autonomy to use them.

Many women around the world do not. Pronatalist pressures compel them to have children whether or not they want them. This is a major factor in our current population having reached 8 billion.

From husbands who threaten violence if their wives use birth control, to religious leaders who exhort women to bear children, to doctors who refuse to perform sterilization procedures on women who request them, pronatalism is ubiquitous. It permeates the media and policy landscape. Alarmist headlines frame population declines in certain countries as a "demographic timebomb." Governments respond with pronatalist incentives for large families and/or laws restricting abortion and contraceptives.

Of course, some women genuinely want large families, and for them a social safety net that supports their choice is a good thing. But given a real choice, free from pronatalist pressures, more women tend to choose having fewer children or no children at all. Their latent desire to control their own fertility could lower overall birth rates and result in a smaller population.

Governments find that they are unable to compel women to go back to the high birth rates they left behind, despite spending staggering amounts of money trying. For example, birth rates are at a record low in Japan despite billions in government incentives for large families, and well below replacement in Sweden and Norway despite their robust social welfare programs.

Today population growth is already a major driver of climate change and other threats to our planet such as biodiversity loss. Continued growth will compound those impacts and disproportionately harm women, who already do most of the childrearing work without getting paid, and will have to do it under increasingly strained conditions in the future. The strain will be most acute in developing countries, which, as Kerry noted in his remarks, also have the highest birth rates.

Acknowledging the climate and sustainability impacts of population growth, and how unfairly they're distributed, is laudable and significant. Ditto for Kerry's recognition that lifestyle choices, especially food choices like how much meat we consume, have a big impact on the climate. It's farther than most political leaders are willing to go.

But leaders tasked with finding a way forward in the climate crisis must do more than just acknowledge these things. They must clearly lay out what we and they can do about it.

That far Kerry was not willing to go. Instead of putting more sustainable lifestyles and lower birth rates on the policy agenda, he averred that "those choices are up to people on their own." But food and family planning choices are affected by policy, and far-reaching policy decisions are made by the government Kerry represents.

U.S. actions and inactions have enormous power to influence behavior. The federal government spends $38 billion every year subsidizing the meat and dairy industries, impacting prices and influencing consumer choices.

Birth rates and population growth are no less powerfully influenced by policy. The issues may pose thorny political problems, but as a matter of policy, they're not hard to solve. Nearly 218 million women in the global South who wish to avoid pregnancy have an unmet need for contraception. The United States could easily close that gap by spending just $2 billion on international family planning assistance—a tiny fraction of the $38 billion we spend on federal meat and dairy subsidies.

Kerry's remarks may be an indication that global leaders are finally willing to acknowledge population growth and meat consumption as major threats to the climate and planetary systems that support our lives. That's good as far as it goes, but it's not enough. They need to put their money where their mouths are and take action.