It was a young orangutan named Jenny who first convinced Charles Darwin of the link between primates and humans. The great red apes can use tools, express emotions, and learn sign language. Darwin once described their home island, Borneo, as "one great wild untidy luxuriant hothouse made by nature for herself."

But orangutans are in danger. Last week a study found that hunting and habitat loss have caused the Bornean population to drop by over half in just 16 years.

And that is just one species; according to the WWF, the planet's total wildlife numbers have more thann halved in 40 years. Many scientists now talk of a "sixth mass extinctionThe fossil record shows there have been five mass extinctions, including the asteroid strike that wiped out the dinosaurs. This time, human are responsible for the dramatic drop in biodiversity.".

But all is not lost yet - conservation projects can be successful. Giant pandas are no longer endangered in China, and neither are black bears in the USA. Wolves have returned to Belgium for the first time in a century.

Meanwhile, scientists at a conferenceA formal meeting, often over several days, for people who are interested in a particular topic. in London are considering a radical proposal to protect wildlife by turning half of the Earth into an nature reserve.

This idea was discussed by the Pulitzer Prize-winning biologist E. O. WilsonHarvard biologist and author of several books, two-time winner of the Pulitzer Prize, and the world's leading authority on ants. in his 2016 book 'Half earth.'

"We [humans] thrash about, appallingly led, with no particular goal other than economic growth and unfettered consumption," he wrote. "As a result, we're extinguishing Earth's biodiversity."

His "Half Earth" idea does not mean choosing between north or south, east or west, or even turning vast land masses into giant nature reserves. As Wilson points out, protecting Antarctica would "be an excellent idea", but it would not help lions in Africa.

Instead, Wilson suggests creating interlocking "corridors" across the planet, linking up existing nature reserves so that animals can move freely between them. "You'll almost never not be in a national park," he explained to Smithsonian Magazine.

He predicts that this would save up to 90% of Earth's species.

Yes, say some, and the sooner the better. Humans must realise that we are not the most important species on Earth. We are one among millions, and we depend on other plants and animals to survive. If you think about it that way, half the planet does not seem like a lot. We would not even have to move; part of the plan involves making cities greener, and learning to live alongside wildlife. What's not to love?

It would never work, argue others. For one thing, animals have no respect for human boundaries; there would be no way of guaranteeing that dangerous creatures stuck to their "corridors". What's more, humans should be allowed to exploit Earth's resources if it helps economies to grow. That is how people are lifted out of poverty. Giving up half the Earth is too much.