On Oct 31, the world's population was projected to reach 7 billion.

The 7 billionth person will be born into a world that is very different from when the United Nations was founded in 1945, when our numbers were only about a third of what they are today.

We are living 30 percent longer. More of our children survive. We are now more urban. We are more interconnected and interdependent than ever.

The 7 billionth person will also be born into a world of contradictions. While most people are having smaller families, our numbers grow globally. While some poor countries' populations are growing more quickly than their economies, the populations of some rich countries are shrinking, threatening to undermine economic growth. There are more young people in the world, but there are also more elderly.

The challenges ahead are formidable, with new pressures on land, energy, food and infrastructure and on the governments that must provide services, such as education and health, and with the global economic crisis shaking the foundations of individuals, families and communities.

We can - and must - confront these challenges. But we must act now. What we do today can have a profound impact on the lives of people everywhere tomorrow and for generations to come.

We have to protect our environment, provide clean water and energy and enough food, and address the threat of climate change.

We have to rectify inequalities between women and men, girls and boys. We must change attitudes so that violence or discrimination against women and girls becomes unacceptable everywhere. We must ensure girls have the same educational opportunities as boys. We must continue to work against skewed sex ratios.

We also need to make motherhood safe. That means caring for pregnant women, preventing deaths in childbirth, and providing nutrition to mothers and babies.

Millions of mothers must still give birth without help from a skilled birth attendant. And millions more have little or no say in basic decisions about how many children they have or when to have them. An estimated 215 million women in the developing world lack access to modern family planning.

About a quarter of the world's people are between the ages of 10 and 24. We used to say our youth will be the leaders of the future - but, as we have seen in many parts of the world, we now know that they are already leaders of today.

Young people have the potential to transform economies, politics, and whole societies. They have the potential to drive development through their creativity, ideas, enthusiasm and innovative spirit. However, in order for this potential to be realized, governments, the United Nations Population Fund (UNFPA) and the wider United Nations should take steps to ensure our youth populations are healthy and have access to education, including sex education, so they may understand how to protect themselves from HIV and have the knowledge to make informed decisions. Girls who stay in school are less likely to have unintended pregnancies, are healthier and more economically productive in adulthood.

We must ensure that our youth have jobs and opportunities for sustainable livelihoods. Today, only about half of the world's youth participate in the labor force, and almost everywhere, young women have fewer job opportunities than men do. Investments in young people's education, health and employment can enable countries to build a strong economic base and reduce poverty, a key aim of the Millennium Development Goals.

Lifting people out of poverty, maintaining a healthy planet, promoting economic growth and development, and tearing down barriers to equality are one and the same fight. Development can only be sustainable when it is equitable and serves all people.

By investing in people now - empowering them to make choices that are good for themselves and the global commons our world of 7 billion can have thriving sustainable cities, productive labor forces that can fuel economic growth and youth populations that can fully contribute to their communities and nations.

Our world of 7 billion people presents unprecedented challenges and opportunities. We must meet the challenges and seize the opportunities now to chart a sustainable, equitable, healthy and socially just path to the future.

The author is under-secretary-general of the United Nations and executive director of UNFPA.

(China Daily 11/01/2011 page9)