A tenth of the world’s wild land – an area equivalent to half the vast Amazon basin – has been lost in just two decades in an “alarming” trend that requires urgent action on an international scale, experts have warned.

At the current rate of decline there will be no significant areas of wilderness – defined as an area “mostly free of human disturbance” – left on the planet in less than 100 years, the researchers said.

Mining, illegal logging, deliberately set fires to clear forest for agriculture, and oil and gas exploration were all contributing to the devastation of essentially natural environments, which are home to many of the world’s endangered species.

10 per cent of the world's wildernesses disappearing in 20 years

Writing in the journal Current Biology, the researchers said: “All wilderness areas, regardless of their size threshold, warrant immediate scrutiny for conservation action, especially in regions with low levels of remaining wilderness areas.

“The continued loss of wilderness areas is a globally significant problem with largely irreversible outcomes for both humans and nature: if these trends continue, there could be no globally significant wilderness areas left in less than a century.”

A map of the wildernesses still left shows the main remaining areas are in the Sahara, the northern tundras of Russia and Canada, the Amazon basin and central Australia.

The researchers concluded there was a total of 30.1 million square kilometres of wilderness left, amounting to just 23 per cent of Earth’s land mass.

An estimated 3.3 million square kilometres has been lost since the early 1990s, equating to a 9.6 per cent decline over that period.

The one glimmer of hope was that most wilderness areas were large – with 82 per cent extending for more than 10,000 square kilometres.

The international team of researchers, led by Professor James Watson of the Wildlife Conservation Society, found vast areas of the Amazon had been lost since the 1990s with other major declines in west Africa, Russia and Indonesia.

Some scientists believe the Earth has entered the sixth mass extinction of life in its history – comparable to the meteor that wiped out the dinosaurs 66 million years ago.

This is one of the reasons why geologists are considering declaring a new epoch, called the Anthropocene, because of humans’ widespread effects on the planet.

The paper said the loss of wilderness could tip already endangered species over the edge.

“Earth’s remaining wilderness areas sustain the last strongholds of many imperilled species,” it said.

“The geographic ranges of one-third of all terrestrial mammal species overlap with globally significant wilderness areas, including extensive parts of the distribution of 12 per cent of all threatened mammal species.

“Thus, ongoing and rapid loss of wilderness increases the risk of extinction for species that are already highly threatened.”

It noted the ‘rewilding’ movement in Europe and North America and some conservation efforts by individual countries, but added such “positive examples” were too few to make a significant difference.

Animals in decline Show all 8 1 /8 Animals in decline Animals in decline Harbour seal (Phoca vitulina) Where: Orkney Islands. What: Between 2001-2006, numbers in Orkney declined by 40 per cent. Why: epidemics of the phocine distemper virus are thought to have caused major declines, but the killing of seals in the Moray Firth to protect salmon farms may have an impact. Alamy Animals in decline African lion (Panthera leo) Where: Ghana. What: In Ghana’s Mole National Park, lion numbers have declined by more than 90 per cent in 40 years. Why: local conflicts are thought to have contributed to the slaughter of lions and are a worrying example of the status of the animal in Western and Central Africa. Animals in decline Leatherback turtle (Dermochelys coriacea) Where: Indonesia, Malaysia, Mexico, Costa Rica. What: Numbers are down in both the Atlantic and Pacific. It declined by 95 per cent between 1989-2002 in Costa Rica. Why: mainly due to them being caught as bycatch, but they’ve also been affected by local developments. Alamy Animals in decline Wandering albatross (Diomedea exulans) Where: South Atlantic. What: A rapid decline. One population, from Bird Island, South Georgia, declined by 50 per cent between 1972-2010, according to the British Antarctic Survey. Why: being caught in various commercial longline fisheries. Alamy Animals in decline Saiga Antelope (Saiga tatarica) Where: Kazakhstan, Mongolia, Russia, Turkmenistan, Uzbekistan. What: fall in populations has been dramatic. In the early 1990s numbers were over a million, but are now estimated to be around 50,000. Why: the break up of the former USSR led to uncontrolled hunting. Increased rural poverty means the species is hunted for its meat Animals in decline Swordfish (Xiphias gladius) Where: found worldwide in tropical, subtropical and temperate seas. Why: at risk from overfishing and as a target in recreational fishing. A significant number of swordfish are also caught by illegal driftnet fisheries in the Mediterranean Animals in decline Argali Sheep (Ovis mammon) Where: Central and Southern Asian mountains,usually at 3,000-5,000 metres altitude. Why: domesticated herds of sheep competing for grazing grounds. Over-hunting and poaching. Animals in decline Humphead Wrasse (Cheilinus undulatus) Where: the Indo-Pacific, from the Red Sea to South Africa and to the Tuamoto Islands (Polynesia), north to the Ryukyu Islands (south-west Japan), and south to New Caledonia. Why: Illegal, Unregulated and Unreported (IUU) fishing and trading of the species

Professor Watson, of Queensland University, urged world leaders to take action before it was too late.

“The amount of wilderness loss in just two decades is staggering and very saddening,” he said.

“We need to recognise that wilderness is being dramatically lost and that without proactive global interventions we could lose the last jewels in nature’s crown.

“You cannot restore wilderness. Once it is gone, the ecological process that underpin these ecosystems are gone, and it never comes back to the state it was. The only option is to proactively protect what is left.”

Paul de Zylva, a nature campaigner with Friends of the Earth, said a healthy natural environment “underpins everything else – our economy, health and well-being”.

“World governments must take drastic action now to meet their pledges to reverse nature’s decline by 2020,” he said.