The sixth mass extinction?
The Earth's growing human population is leaving less room for other species, many of them vital to our survival, writes Alex Kirby.

Brazil's 'Noah's Ark' forest
Tim Hirsch visits a fragment of one of the world's most threatened ecosystems, as part of BBC News Online's "Planet under pressure" series.

Quiz: Species and extinction
Test your knowledge of global flora and fauna and the threats that species around the world are facing.

Viewpoints: Saving species

Map: Biodiversity hotspots
BBC News Online looks at some of the biodiversity hotspots where large numbers of the planet's species are concentrated.

Running dry?
Alex Kirby explores fears of an impending global water crisis.

Marble trade sucks villages dry
Sanjoy Majumder visits a village in India's desert state Rajasthan, where farmers face chronic water scarcity as local marble factories deplete supplies.

Quiz: World water crisis
You drink it, wash in it and flush the toilet with it every day. But how much do you appreciate the finer points of the liquid that sustains life?

Viewpoints: The water debate
Can we solve the world's water problems, and if so, how? BBC News Online gathers a range of views.

Map: The world's water hotspots
Clickable guide to key places around the world where water scarcity is causing deep concern.

Heading for a crisis?
The BBC's Alex Kirby looks at the challenge of providing the world with energy without damaging the environment.

China's dirty energy takes its toll
The human toll of booming China's thirst for energy

Quiz: Renewable energy
Test your knowledge about the clean, green energy sources of the future with the BBC News quiz.

Viewpoints: Powering the planet
Can we solve the world's energy problems, and if so, how? BBC News Online gathers a range of views.

Can the planet feed us?
Alex Kirby explores the challenge of feeding the world without destroying the planet, as part of the Planet Under Pressure series.

Polish factory farms cause a stink
BBC News visits one of the new pig factories springing up across Poland

Quiz: How green is your food?
Test your knowledge about the hidden costs of the contents of your supermarket trolley with this BBC News quiz.

Viewpoints: Food for all?
Can we solve the world's food problems, and if so, how? BBC News website gathers a range of views.

Pollution: A life and death issue
Alex Kirby explores our struggle for food and clean water on a planet which is no-longer pristine.

Durban poor's pollution battle
Grant Clark visits South Durban, where outdated pollution legislation has left local residents' fighting their own battle.

Quiz: Are you pollution-savvy?
Pollution is a growing problem in our chemically-dependent world - how much do you know about the everyday substances around you?

Map: Pollution hotspots
BBC News looks at some of the places around the world which are hardest hit by pollution.

Entering uncharted waters?
Alex Kirby explores the implications of climate change

Bangladesh faces flooded future
As part of the BBC's Planet Under Pressure series, Roland Buerk visits a family living in the Ganges River delta.

Quiz: Clued up on climate?
Do you know your acid rain from your methane and your emissions from your carbon credits? Test your knowledge on global climate change.

Viewpoints: The way forward
Is climate change really worrying and, if so, what should we do about it? BBC News website gathers a range of views.