World Population Day has been observed on July 11 each year since 1990. This year, as people across the globe experience record-breaking heat, wildfires, smoke, storms, and floods, it’s an opportune time to consider the often overlooked but profound connections between population and climate change.

Exactly how population growth affects greenhouse gas emissions is a matter of debate. The relationship is complex, since the places where population is growing fastest tend to be places where per capita consumption of fossil fuel is very low. But the relationship between population growth and people’s vulnerability to the impacts of climate change is direct and intuitive once we take a moment to think about it.

A new report from the Population Institute studies this relationship in detail. Analyzing population trends and key indicators in 80 countries most vulnerable to negative impacts of climate change, it finds that on average their populations are growing at twice the global rate. Some of the most vulnerable countries (including Niger, Uganda, Tanzania, and Syria) are on pace to double in population before 2050 if growth rates don’t change.

The good news is, they can change, especially with robust investments in gender equity and reproductive health care. But as things stand, today’s stark demographic realities don’t bode well for climate adaptation or resilience. Fast population growth undermines governance, security, and well-being. Investing in gender equity and reproductive health care could boost people’s health and well-being in the short-term and slow population growth over time. But governments and donors are failing to make the necessary investments, both in the United States. and globally.

As a result, we’re missing critical opportunities to support reproductive rights, build climate resilience, and put the brakes on population growth. Half of all pregnancies (111 million a year) are unintended, while the need for modern contraceptives goes unmet for more than 200 million women who want to avoid pregnancy in low- and middle-income countries. Investing in voluntary family planning programs could change that, but the money just isn’t flowing. Funding from the U.S. government, once a global leader on this front, has stagnated over the past decade

All is not lost, however. On-ground organizations and communities in climate-vulnerable countries are modeling replicable ways of slowing growth and building climate adaptive capacity and resilience by fighting for gender equity and reproductive health and rights.

For example, in the world’s most climate-vulnerable country, Niger, the youth-led climate group Jeunes Volontaires pour l’Environnement is advocating for family planning as a climate resilience strategy. In the Philippines, where people are highly vulnerable to rising sea levels, typhoons, and degradation of fisheries from climate change, the PATH Foundation is helping deliver reproductive health services as part of a holistic approach to managing natural resources and improving food security. Regenerate Africa works with NGOs and government agencies to integrate gender equity and reproductive health into national climate policy, including Uganda’s Nationally Determined Contribution under the Paris agreement. In Guatemala, the NGO FUNDAECO’s REDD+ forestry project supports women’s reproductive health and empowerment, including a scholarship for girls.

The U.S. should learn from and support initiatives like these. While it may not be as climate vulnerable as many other countries, in the U.S., as in the rest of the world, the population is growing fastest in places hit hardest by climate change, such as Florida and Texas. And women in the U.S. feel the downstream effects of climate change, including on their health and employment, more acutely than men. At home as abroad, status of women’s health, rights, and opportunities are important factors in climate adaptation and resilience.

But climate policies in the U.S. generally don’t recognize that population, gender equality, and climate resilience are connected at all. The Center for Biological Diversity did an assessment of 21 municipal climate plans in the U.S. It found only two acknowledged that women had specific climate-related vulnerabilities, and only one proposed to do anything about it.

The U.S. government is the largest donor to global health, spending $13 billion a year on it. But even as the largest generation of young people in the history of the planet enters its childbearing years, U.S. investment in international family planning and reproductive health has stayed stuck at around $600 million for the last 10 years. That’s less than 5 percent of U.S. global health spending, and 0.035 percent of overall budget. In real terms, funding is falling as inflation erodes it.

It’s time for the U.S. to reverse the slide and double down on investing in voluntary family planning and the health and rights of women and girls. Programs that promote gender equality and reproductive health and rights as integral to fighting climate change need U.S. recognition and support so they can scale up. Funding such programs is more than just foreign aid. It’s key to bending the global population growth curve and building a more resilient and sustainable future for the whole planet.