Many species on Earth are endangered, from tigers and whales, to insects and plants that support whole ecosystems.
If we're to stop them disappearing forever, we need to act fast.
Conservation means preventing organisms and habitats from being lost.
There are a number of approaches, but all face difficult challenges.
Captive breeding is sometimes used when an animal's numbers are threateningly low.
But this isn't always practical, and animals bred in captivity often fail to survive when released into the wild.
Plant seeds and animal DNA banks are now being stored up as living libraries to protect against extinctions.
But this relies on freezing cells to produce test tube organisms. This is last-resort conservation.
The best approach is to stop the loss in the first place, by preventing overhunting and habitat destruction.
Armed enforcement to stop poaching is used in many areas, like here in the Congo basin.
And the fencing of land into protected parks has helped preserve habitats.
But when local people need resources to live, this can be fraught with problems.
Huge areas of Kenya were fenced in the 1990s and patrolled by armed rangers. It saved the elephants and rhinos, but it forced the Maasai people from their land.
Conservation efforts need to include local people if they're to work in the long-term.
Moises Leon, Tropical Science Center - "A tree standing or feed one of your children - what would you do?"
Nisar Malik, Conservationist - "We people sitting outside cannot enforce something on a local who has to live with life and death every day."
The challenges for conservation are only going to get bigger.
But if we don't act, the destruction of the world's ecosystems will affect every one of us.