By Alex Kirby
BBC News Online environment correspondent
The eminent wildlife expert Dr Richard Leakey says fencing in protected areas in Africa and Asia could help to arrest the decline of endangered great apes.
Rwanda's mountain gorillas are increasing
Dr Leakey, former director of Kenya's wildlife service (KWS), says many great ape species are in a critical state.
He says their problems may be much worse than those confronting species such as giant pandas and elephants.
Dr Leakey says there need not be any conflict between saving wildlife and alleviating the poverty of the people.
He is patron of the United Nations Environment Programme's Great Apes Survival Project (Grasp), and will be the guest speaker at a fund-raising dinner in London on 24 May. The project is appealing for $25m over three years.
Last November, Grasp said all the great apes - gorillas, chimpanzees, bonobos (small chimps), and orang-utans - faced a very high risk of extinction within 50 years at most.
Dr Leakey said: "There is some good news. One of the most exciting things is that the mountain gorillas of Rwanda were left alone during the war there, and the population has increased by about 4% over the last five years.
"Both rebels and government recognised them as hugely important to a future Rwanda and went out of their way to leave them alone.
"There are some very interesting negotiations going on in western Africa, involving Congo-Brazzaville, the Democratic Republic of Congo and I think Cameroon.
In safe hands: But wild bonobos are precarious
"In fact, five African presidents have talked about creating a mega-park in the region.
"But the great apes are in crisis, partly because their habitat is under pressure from human population growth, and partly from commercial development.
"That's opening up vast swathes of the forests for logging. They used to be impenetrable, and apes have survived there for several million years, but now they're open to anyone."
Dr Leakey told BBC News Online: "We need to talk about success, and Rwanda's experience could be important for other countries.
"The doom and gloom and mayhem post-colonial Africa has seen these last 40 years can't be a permanent condition.
"And fences can work. Private property remains private because it's fenced, and people don't cross the line. We've tried this in Kenya, and it's been successful.
"I think you could create a transnational park in the Virunga mountains straddling the borders of Uganda, Rwanda and the DRC, and if it were fenced it would greatly ease the pressure on that ecosystem.
"I'm not saying there are no problems for the pandas and the elephants. I just think the great apes' problems may be far greater. Something has to be done very fast.
Paying their way
"There's a lot of waffle about how the apes are our closest relatives, and so on, but while we talk, they go."
Dr Leakey said he recognised the problems facing millions of people in Africa, and also in south-east Asia, where the orang-utans were probably as threatened as the bonobo.
He said: "The plight of Africa's people bears comparison to no-one else for poverty, disease and repression. But allowing gorillas and chimpanzees to die, or killing them off, won't improve people's lives: it will impoverish them.
Orang-utans are in extreme peril
"In places like western Uganda the apes are a hugely important revenue stream for the government, because of tourism.
"They're sentient beings, and saving them would cost peanuts compared with rescuing destitute people. But poor countries can't carry the financial burden of saving their wildlife simply because wealthy countries feel sentimental."
Dr Leakey said saving the apes was not about money alone. He said: "It costs a European government nothing to bring up the apes' icon status constantly, and that's what I'll be saying to the UK environment minister, Elliot Morley, at the Grasp dinner.
"If he raised their plight with everyone he met for the next three years, that would be enormously effective."
He said the bonobos were probably more vulnerable than common chimps and lowland gorillas.