11/07/2016 08:04 BST | Updated 08/07/2017 06:12 BST

World Population Day: Building a Sustainable Future

In 2015, more than 60 million people were forced to flee their homes - a record high. This means that one in 122 humans are displaced. Refugee numbers fleeing their country of origin are soaring, but the number of internally displaced people is even higher. As United Nations Secretary-General Ban Ki-moon stated in 2015:

"With nearly 60 million individuals having fled conflict or disaster, women and adolescent girls are particularly vulnerable. Violent extremists and armed groups are committing terrible abuses that result in trauma, unintended pregnancy and infection with HIV and other diseases."

It is no coincidence that, at the same time, human numbers have now grown beyond seven billion. This pressure contributes to conflict, poverty, climate change and the impact of natural disasters, all factors underlying large scale migration.

World Population Day, celebrated each year on July 11th, was established in 1989 to create a greater awareness of the impact of population growth on sustainable development. It arose from an appreciation that the world's ever growing population poses serious threats to mankind and the environment alike. Natural resources become depleted, natural amenities are polluted and the wellbeing of ever more people is threatened.

This year's theme for the day is 'Investing in teenage girls'. Women are disproportionally affected by conflict and disaster. Their generally disadvantaged position makes them more likely to suffer from poverty, lack of access to education and employment. They are, moreover, often reduced to a purely childrearing role. Poor access to reproductive services places their health at risk. Moreover, many couples want to avoid pregnancy in times of crisis, but lack the means to do so. It is estimated that one in five women of childbearing age in crisis situations is pregnant.

There is hope for a better future. Globally, the number of schools in which equal numbers of boys and girls attend has increased by three quarters since 2000, Nepal has reduced its maternal mortality sharply since the early 1990s, and the position of women in Tunisia has improved greatly since the Arab Spring. Such gains should be seen as a sign that greater empowerment of women, improved family planning facilities and better sex and reproductive health education in school really makes a difference.

It is not simply a human right to have access to these services: they are also the key towards smaller populations. Smaller families are a necessary condition for long-term poverty alleviation, reduced conflict and sustainable development, all part of the 17 sustainable development goals adopted by the UN which came into force on 1 January 2016. In the context of sustainability and environmental conservation, each additional human consumes and pollutes. While we have the ability to develop technologies and strategies to reduce our ecological footprint, our existence will always leave marks on the environment. As we grow more numerous, we must harvest more crops. Not only does that cause a dilemma of space - there is only so much land available - but it also creates competing demands where other scarce resources are concerned. Fresh water shortages in particular will affect more than half of humanity by 2050 if we do not actively protect and conserve life's most vital ingredient. Thirst and hunger would cause serious political tensions and likely force the movement of ever greater numbers of environmental refugees.

We know that population growth exacerbates every challenge we face. To address that, population growth, which is continuing at 80 million a year, should no longer be accepted as inevitable. Instead, we should mark World Population Day by calling on people to have smaller families and advocating for policies that support them, both in the UK and abroad, so that we can build a sustainable future with a healthy environment and decent living standards for all.

Simon Ross is Chief Executive of Population Matters, a UK membership based charity that address population size and environmental sustainability.