Nearly half of all the natural World Heritage sites on the planet are being ravaged by poachers who are driving some endangered animals towards extinction, according to a new report.

The illegal wildlife trade was estimated to be worth some £15bn, making it the fourth largest international criminal trade after drugs, guns and human trafficking, according to the ‘Not For Sale’ report.

Illicit logging and fishing are also occurring on an epic scale.

The illegal felling of trees – a trade valued at between $30bn and $100bn (about £24bn-£80bn) a year – was estimated to account for up to 90 per cent of deforestation in major tropical countries.

Fish piracy, blamed by some in countries like Somalia for pushing people into actual piracy, was found to occur in 18 out of 39 marine heritage sites with protected species of sharks and rays among those being caught.

The report, commissioned by conservation group WWF, warned that species listed on the landmark Convention on International Trade in Endangered Species (Cites), adopted in 1975, were being killed in supposedly protected World Heritage sites.

“Between 1970 and 2012, global wildlife populations declined by almost 60 per cent on average, and illegal harvesting of species was one of the main drivers for this decline,” authors wrote.

“World Heritage sites now function as the last bastion for many critically endangered species, and unless protected within World Heritage sites, these species will go extinct.

“The current international approach to preventing illegal harvesting of Cites-listed species in World Heritage sites is not working, and stakeholders must redouble their efforts and address all parts of the wildlife trafficking value chain.”

According to a leaked copy of a speech by a senior Foreign Office official, some of the Government’s work on the illegal wildlife trade will be “scaled down” as trade and economic growth are given priority after the UK leaves the European Union.

But the WWF report said that unless governments, the United Nations and others took “additional, immediate measures” to address widespread poaching “some species might face local extinction and some World Heritage sites could lose their outstanding universal value” – the definition of why they are considered special.

It said threatened species, such as elephants, rhinos and tigers, were being “illegally harvested” in 45 per cent of World Heritage sites, “the pinnacle of the world’s protected areas”.

“Elephant poaching occurs in over 60 per cent of the World Heritage sites containing African and Asian elephants,” the report said.

“Selous Game Reserve in Tanzania has lost almost 90 per cent of its elephants since its inscription in 1982 and now has only 15,217 elephants left.”

The Okavango Delta, a World Heritage site in Botswana, where poachers have been active, was described as a “crucial habitat” for the elephants in northern Botswana, which make up nearly a third of all the remaining African elephants.

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

About a third of all the world’s remaining 3,890 wild tigers now live in World Heritage sites.

Trying to stop poachers is difficult and dangerous with many prepared to use lethal force.

“Wildlife trafficking has also often endangered people’s lives, and between 2009 and 2016 at least 595 rangers were killed in the line of duty, many of whom were protecting World Heritage sites,” the report said.

Chris Gee, the head of campaigns at WWF-UK, said poaching was “jeopardising the future heritage of these precious places and the people whose livelihoods depend on them”.

“Next year London will host the Fourth Illegal Wildlife Trade Conference, the UK Government must bolster efforts to support the end of this devastating trade,” he said.

“Now is not the time to drop the ball on this issue. These findings show that for the future of many of our most endangered species it’s a matter of life and death.”

And John Scanlon, the secretary general of Cites, said it was “essential” that the convention was “fully implemented and that these irreplaceable sites are fully protected”.

“In doing so, we will benefit our heritage and our wildlife, provide security to people and places, and support national economies and the rural communities that depend on these sites for their livelihoods,” he said.

Among some positive signs that the world is trying to deal with the problem, the report highlighted China’s decision to ban all trade in ivory by the end of this year as a “breakthrough” that could “provide forceful momentum for other countries to follow”.

But it said more funding was needed with Cites’ core budget running at about $6m a year – in stark contrast to the billions being made by the poachers.

Inger Andersen, the director general of the International Union for Conservation of Nature (IUCN), said: “This report is a sobering reminder of just how far this type of organised crime can reach, extending even into the supposed safety of World Heritage sites.