The illegal trade in wildlife is a most attractive crime. But it is highly destructive, and its scale is threatening the extinction of some of the world’s most iconic species.

It is also grotesquely cruel: poachers slice off the faces of live rhinos to steal their horns; militia groups use helicopters to shoot down elephants for their tusks; factory farmers breed captive tigers to marinate their bones for medicinal wine and fry their flesh for the dinner plate; bears are kept for a lifetime in tiny cages to have their gall bladders regularly drained for liver tonic. But for any criminal who wants maximum money for minimum risk, it is most attractive.

At every stage in the supply lines, the systems that are supposed to defend the animals against this global butchery are no match for the organised crime groups that dominate the trade.

This is a vast business, valued by the UN Environment Programme at $23bn (£18bn) a year – twice the gross domestic product of poached countries such as Tanzania or Kenya. The profit margins are enormous. The poacher in Africa sells ivory at up to $150 a kilo. At the other end of the supply line, in Beijing, it sells for well over ten times as much, with some sales reaching $2,025 a kilo, according to research by Chatham House. The markup is even bigger with rhino horn: from $1,000 for a pair of horns (average weight 6kg each) at poacher level to upwards of $66,000 a kilo in China.

Profits have increased dramatically over the past decade, driven by the wealthy new elites in Asia, accumulating ivory carvings and tiger skins as status symbols for their homes; buying ground powder of rhino horn and tiger-bone wine as traditional remedies for almost every ailment from hangovers to cancer, none of it based on any scientific evidence. This is a demand driven by two things: greed and superstition.

For a gangster, these animals are like bundles of cash lying almost unprotected in the wilderness. This is a profit-hungry global crime conducted by some of the same ruthless and violent groups that traffic drugs and guns. And up against this collection of highly organised and well-resourced criminals, we currently deploy some of the world’s weakest law enforcement.

The only global body tasked with protecting the world’s wildlife is a network of officials in each of the nations signed up to the Convention on International Trade in Endangered Species (Cites), which is co-ordinated by a small secretariat in Geneva.

Cites was written in 1973 when the main threat to wildlife was the encroachment of human settlements on vulnerable habitat. Now it finds itself confronting these criminal networks, even though it has no detectives, no police powers and no firearms. In short, Cites is not a law enforcement agency. It is there to regulate trade. It can try to punish rogue governments by asking its members to stop trading Cites species with them, but it has no tools to punish the criminals who have already decided to defy those governments.

The global agencies set up to fight organised crime have bigger priorities: terrorists, arms traffic, narcotics, counterfeit goods. Other agencies try to fill the gap. Interpol distributes intelligence on the worst wildlife offenders; the UN Office on Drugs and Crime publishes research; the World Bank advises on the tracing of laundered money. None of them goes out to catch criminals. The few specialists who try to work internationally find themselves swimming against a tide of inertia.

A senior law enforcement figure in southern Africa who specialised in wildlife crime told the Guardian that the crime groups enjoyed far better international links than he does. “I have to rely on people I meet at conferences,” said John Sellar, who spent 14 years as enforcement support officer for Cites before he took early retirement.

“A major reason for that,” he told the Guardian, “was that I was fed up with the complete hypocrisy of people coming to Cites meetings and passing resolutions and then going home and, frankly, doing bugger all about them – politicians and law enforcement people.”

The few traffickers who are caught are dealt with by prosecution systems riddled with failure. When the international law firm DLA Piper in 2014 investigated criminal justice in ten countries on the frontline of wildlife traffic, it found “a host of weaknesses” including legal loopholes, chronic shortage of funds for prosecutors and courts, low rates of conviction, inadequate penalties and corruption. “The only consistent theme,” it concluded, “is that significant work needs to be done in every country in order to effectively tackle the illegal wildlife trade.”

Currently, the void is being filled to some extent by a loose network of volunteers, journalists and NGOs running their own investigations and attempting to get local law enforcement agencies to make arrests and prosecute. This includes NGOs like Freeland in Bangkok running long-term investigations of the kind whose results we are publishing today. That investigation was paid for by a small English charity that has sent tens of thousands of pounds across the world to pay Freeland to do the policing that was otherwise absent.

The effect of this law enforcement void is traumatic. From African bush to Asian jungle to Russian steppe, the valuable parts of animals are ripped and sliced from their skeletal sockets and shovelled onto invisible conveyor belts, almost all headed for the same destinations in South East Asia and China. They leave Africa by sea, most often from Mombasa, Kenya, where the Elephant Action League last year ran a 12-month undercover investigation, which concluded that “massive amounts of ivory continue to pass unhindered”; or by air, from Johannesburg, where the Guardian found a long-term airline employee who was part of a smuggling network, or through Maputo, Mozambique, which was described to us by a South African policing source as “a major security problem”.

There are only 30,000 rhinos in the wild, just 5% of the number 40 years ago. Several sub-species are already extinct. Others are officially ‘critically endangered’. The biggest surviving population is the 21,000 southern white rhino, most of whom are in South Africa. And that is where the rhino poachers are busiest: 88% of the rhinos killed last year were in South Africa.

The attack on elephants is even more frenzied. The conveyor belt to Asia sags under the weight of the ivory from something like 90 dead African elephants every day. In 2013, a single seizure in Guangzhou uncovered 1,913 tusks, the product of nearly 1,000 dead animals. The US National Academy of Sciences in 2014 found that in the previous three years poachers had killed 100,000 elephants, reducing the species to a total of only 450,000 in all Africa. And the numbers are still falling: the kill rate has exceeded the birth rate every year since 2010. Central Africa has lost 76% of its elephants since 2002. Tanzania has lost 66% in the last six years alone. Mozambique has lost 48% in five years.

The scale of ivory poaching is so colossal that the UN Office of Drugs and Crimethis year concluded that it could not be explained simply by looking at its sales, legal or illegal. In his time at Cites, Sellar speculated that financial and/or criminal elites were hoarding ivory as a long-term investment and method of laundering cash.

On the conveyor belt alongside these iconic creatures there are the remains of hundreds of other animals: paws for ashtrays; teeth for pendants; genitals for sex drive; the skins of snakes; the scales of pangolin anteaters to be roasted and chewed for a health fad, 275 of them a day, 100,000 a year. There is a steady flow of tiger corpses, sometimes whole, sometimes only the skin and bones. A hundred years ago, there were some 100,000 wild tigers spread all across Asia and into eastern Russia: now there are an estimated 3,500, only 2,200 of whom are in populations big enough to make breeding and survival viable.

This trade has been allowed to grow not only because of the failure of law enforcement but because it is inextricably linked with power.

The wealthy elite in Asia that consumes illegal animal products overlaps with the political elite, and the commercial elite. The criminal entrepreneurs who run the supply lines are able to conceal their identity behind front companies, and hide their enormous profits by using the same secretive offshore jurisdictions exploited for tax avoidance by multinational corporations.

This week, the 182 signatories to Cites are debating the future of the animals currently being wiped out in their thousands by this criminal industry.

Cites secretary general John Scanlon knows the road ahead will be tough. “Cites sets the rules that these crime syndicates are trying to avoid. We do work with law-enforcement partners. I have told them: ‘This is crime, this is transnational, this is your core business.’

“They have now all bought into this. The good side is that we are in there with these agencies. The bad side is that they are not yet investing heavily in it.”