The world's great apes face extinction within decades, renowned chimpanzee expert Jane Goodall warned Tuesday in a call to arms to ensure man's closest relatives are not wiped out.

"If we don't take action the great apes will disappear, because of both habitat destruction as well as trafficking," Goodall told AFP in an interview in Nairobi.

In the past half century, chimpanzee numbers have slumped from some two million to just 300,000, spread over 21 countries, said Goodall, a British scientist who spent more than five decades studying chimpanzees in Tanzania's Gombe National Park.

"If we don't change something, they certainly will disappear, or be left in tiny pockets where they will struggle from inbreeding," said 80-year-old Goodall, the first scientist to observe that apes as well as humans use tools.

Experts predict that at the current rate, human development will have impacted 90 percent of the apes' habitat in Africa and 99 percent in Asia by 2030, according to a UN-backed report last month.

Infrastructure development and extraction of natural resources -- including timber, minerals, oil and gas -- have devastated the prime habitat of apes and pushed chimpanzees, gorillas, bonobos, orangutans and gibbons closer to extinction.

- 'We're schizophrenic' -

For Goodall, the destruction is part of mankind's wider attack on nature.

"If we don't do anything to protect the environment, which we've already partially destroyed, I wouldn't want to be a child being born in 50 years time," Goodall added.

"We're schizophrenic: we've got this amazing intelligence, but we seem to have lost the power of working in harmony with nature."

As well as a tragic loss, Goodall said the death of man's closet relatives would act as a stark warning sign of climate change and global warming.

"If we lose them (apes), it is probably because we have also lost the forests, and that would have a totally devastating impact on climate change," she said.

"Climate change is so evident everywhere. There are leaders who say they don't believe in climate change, but I can't believe they really believe that, maybe they are just stupid."

All species of apes are listed as endangered by the International Union for the Conservation of Nature (IUCN), some critically so.

- 'Your life makes a difference' -

"People are losing the connection to the natural world," said Goodall.

"You'd think that the most intellectual creature on the planet would know better than to destroy its only home, but we are destroying the planet very, very quickly."

But Goodall, who has set up volunteer conservation groups across the continent, urges people not to despair but rather take action.

"Climate change threatens every little part of the planet, and we can't stop that, but if we get together we can help to slow the effects," she said.

Goodall recounted how in war-ravaged eastern Democratic Republic of Congo, children inspired by her conservation group negotiated with a local militia force, persuading the intially puzzled commander to give them access to replant trees on a hillside.

"Within 30 minutes, all four soldiers with them had laid aside their guns and were helping the children to plant the trees," she said. "It is symbolic of what can happen if we can work together."

"My last message to everybody, really, is to understand that your life matters, your life makes a difference," she said.

"So many people give up and they feel hopeless.. and so do nothing. But if you take action locally, you can do something."