Today is the first “International Day of the Girl Child” – a day established last year by the United Nations to acknowledge the rights and unique challenges faced by young girls around the world.

The latest UN projections put the number of women under the age of 19 at about 1.18 billion today. Especially in developing countries (though not only) these young girls often face outsized barriers to happy, healthy, and productive lives.

According to the Half the Sky Movement, 20 percent of girls eligible for primary school worldwide aren’t going. “There are plenty of reasons for this discrepancy,” they write, “including families wanting a girl’s help in the house, the cost of tuition, and the fact that girls tend to drop out of school at higher rates. When schools are far away, parents may also hesitate to allow their daughters to walk the long distances alone.” When girls are denied an education, studies show that their chances of having a healthy family and higher wages decline.

A UN Environment Programme report last year also found that women and girls are more vulnerable to changing climate conditions than their male counterparts in developing countries. Executive Director Achim Steiner said that in general, “women often play a stronger role than men in the management of ecosystem services and food security.” As a result, as rain patterns shift and unexpected flooding becomes more common, climate change is impacting their lives disproportionately. In sub-Saharan Africa and South Asia, women and girls are also frequently responsible for water collection – both for household and agricultural use – and in conflict-affected areas, the long walk to water sources makes them highly vulnerable to assault.

In places with poor infrastructure, adolescent girls’ unique health requirements put them at a disadvantage as well. Poor sanitation can turn puberty itself into a factor that forces some girls out of school, and the World Health Organization reports that in low- and middle-income countries, complications related to pregnancy and childbirth are the leading cause of death for girls aged 15 to 19 years old.

All these challenges and more impact millions of young women around the world, but the particular theme for this year’s first International Day of the Girl Child is ending child marriage.

According to the UN, one in three women around the world between the ages of 20 and 24 years old were first married before they turned 18. In total, over 60 million girls worldwide are child brides, married before the age of 18, primarily in South Asia (31.1 million) and sub-Saharan Africa (14.1 million). Child marriage exacerbates all the challenges faced by girls, increasing the chances of domestic abuse, a poor or nonexistent education, isolation from family, and unhealthy pregnancy.

Earlier this week, Tom Hundley of the Pulitzer Center on Crisis Reporting, which has sponsored international journalism on these and other under-reported stories, spoke at the Wilson Center about the women’s rights issues at the core of population dynamics, and part of his presentation was on child marriage in particular. Too Young to Wed, a documentary he showed by filmmaker Stephanie Sinclair (above), was part of a story package the Pulitzer Center supported that was published by National Geographic and is featured today on Foreign Policy too. The video is powerful stuff, and a strong reminder of the human rights issues at the core of this day.