Some misguided people, today, who may call themselves "pronatalist", and who look at future predictions of negative population growth (meaning that population will decrease in the future, instead of continuing to increase), and see this as a problem, are wrong or are not thinking clearly. Some of them may believe that African and Arab and Asian populations are in the process of "replacing" or at least are overtaking the Caucasian, European-based ethnicities that have traditionally been the majority of the population in countries like the US, the UK, Europe, Canada, Australia and New Zealand; and they are right - this is indeed happening, as is the Hispanicization of the US population because of such massive immigration. And they are right to be concerned about this. In a century there may be no nations left on Earth where Caucasians of European ancestry are the majority of the population if immigration is not stopped. And this is a problem. There will be African majority countries, Asian majority countries, Arab majority countries, Hispanic majority countries, but there will not be any Caucasian of European ancestry majority countries left if we do not take action now.

'The sixth great extinction is happening', conservation expert warns

With her signature shawl draped over her shoulders and silver hair pulled back from her face, Jane Goodall exudes serenity - even over our slightly blurry video call.

In a Vienna hotel room, a press team and a small group of filmmakers, who are documenting her latest speaking tour, fuss around her.

A tenth of the world's wilderness has vanished in the past two decades, research shows. New maps show "alarming losses" of pristine landscapes, particularly in South America and Africa, according to World Conservation Society scientists. They argue in Current Biology that wild areas are ignored in international conservation agreements, despite their ecological and cultural value.

About 20% of the world's land area is classed as wilderness. By this, scientists mean landscapes free of large-scale human disturbances such as housing, development and industry. The majority of these untouched spaces are found in North America, north Asia, north Africa and Australia. They are often home to indigenous peoples as well as endangered plants and animals.

James Watson of the University of Queensland, Australia, and the US Wildlife Conservation Society in New York said wilderness areas "are completely ignored in environmental policy". "International policy mechanisms must recognise the actions needed to maintain wilderness areas before it is too late," said Prof Watson. "We probably have one to two decades to turn this around."