As the United Nations recognises a child born in Bosnia as the six-billionth inhabitant of the planet, BBC News Online's special coverage looks at the threats posed by a crowded world:

Why we should worry
If economic growth and associated consumption are left unchecked, catastrophe threatens: Dominic Casciani asks what we can do.

• Could world population stabilise?
  Listen to the BBC's Roger Harrabin report on the predictions.
• Population links guide
  At-a-glance survey of some key population-related websites.

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The planet feels the strain
If you think of the earth as a Noah's Ark, a life-friendly speck floating through space, you will appreciate its passenger capacity is limited, writes Environment Correspondent Alex Kirby.

• Case study: Madagascar
  Watch Roger Harrabin's report from Madagascar on the threats to the local ecosystem.
• Your views
  Are there too many people in the world? Send us your views and read what you've said.

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The sexual health minefield
An estimated 114 million acts of sexual intercourse take place in the world every day: Mandy Garner looks at the continuing battles over family planning and sex education.

• Death in the midst of life

Most of the thousands of women's deaths from problems associated with childbirth or pregnancy could be prevented.
• West criticised on family planning
  Dr Nafis Sadik, director of the UN Population Fund, talks to listeners on BBC's Talking Point.
• Viewpoints: Population control

BBC News Online invited two organisations with opposing views on the subject to put their cases.
• Case study: Nigeria

Maternal death takes a heavy toll in West Africa, reports Barnaby Phillips from Lagos.
• Case study: Bangladesh

The world's ninth most populous country is struggling to cope: David Chazan reports from Dhaka.