Save our skins: The new boom in illegal trading driving the world's rarest species to extinction

The horn of a rhino can make an interesting souvenir, though at $8,000 it might seem a little pricey. It can be polished to make a novelty beaker, it can be the focus of an exciting though improbable holiday anecdote, or it can be ground into dust for a mildly effective remedy for fever.

In China it has for a long time been reputed to improve sexual performance, offer protection from evil spirits, and act as a prophylactic against hangovers. Western pharmaceutical research pooh-poohs all these claims except the one about reducing fever. But even that is not regarded as anything to write home about. Paracetamol is cheaper, and more readily available.

What nobody knew until a few years ago is that rhino horn is also a miraculous cure for cancer.

They didn't know it because it isn't true. Rhino horn has no effect on cancer. But suddenly, some time in the past 10 years, large numbers of people in Vietnam decided the claim could be true. For the rapidly dwindling world population of rhinos, this was bad news.

Rhinoceroses have been trundling around for some 50 million years. But with exploding human populations and shrinking habitats, many species are already extinct. In fact, only five species remain with us today.

Forty years ago, their peril was so stark that they became the focus of a determined international undertaking to save them – one which bore remarkable fruit.

The effort by the world's governments to control the illegal trade in wildlife is co-ordinated by a body called Cites, the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Back in 1975, seeing the way the rhino population was going, Cites mandated the first, limited restriction on the trade in rhino products. But the trade in horn remained legal in Asia until 1993, when the ban was tightened and extended. Crucially, and for the k first time, China joined in, issuing an official ban. Legal action was enforced by public awareness campaigns, not only in the People's Republic but also in Hong Kong, Taiwan and Singapore, where the appetite for horn and the belief in its efficacy were most widespread.

The effect was dramatic. Demand across Asia plummeted. Across Africa, populations recovered: the Southern white rhino subspecies, whose numbers had sunk to around 50, climbed to around 20,000. It was an exciting moment. A combination of internationally co-ordinated legal action, effective propaganda and intensified controls in wildlife parks and ports appeared to have halted the extinction of the rhino in its tracks.

Perhaps the Sixth Great Extinction, the one caused by us, was not, after all, a dire certainty. Our intelligence had provoked it, so perhaps our intelligence could also prevent it, or at least reverse it. So went the hopeful thoughts of the optimists. Perhaps the commitment of the American organisation WildAid to "ending demand for [illegal wildlife] products in our lifetime", as their mission statement has it, was not, after all, so wildly unattainable. Then, five years ago, everything started to go horribly wrong.

"For 16 years," Cites reports, "between 1990 and 2005, rhino-poaching losses in South Africa averaged 14 animals each year. In 2008, this figure rose to 83." It has risen dramatically every year since. The figure for 2012 was a shocking 668, 220 more than 2011.

This was not caused by human intelligence, but human stupidity. People in Vietnam suddenly started believing that rhino horn could cure cancer.

These are the waves in which extinction progresses. It does not happen at a steady speed, in a single direction. There are checks, reversals, sudden disastrous plunges, then phases of k striking progress when lessons appear to have been learnt and the world community acts as one. But with the human population growing so fast, and its wealth and the sophistication of its technology exploding too, the big picture, as with the rhino, is consistently bleak.

The fate of the tiger illustrates how hard it is to fight our civilisation's logic. Nobody consciously wants the wild tiger to become extinct. Yet there are only around 3,200 left, and they are holed up in ever-smaller pockets, and the buffaloes and deer and all the other beasts on which they prey have been decimated, too. At the same time, the tigers' own predators, the poachers, grow steadily more resourceful, more numerous, better equipped. Often they are in cahoots with the men whose job is to protect the animals.

In number terms, the rhino's prospects are bright compared to those of the tiger. And while the only part of the rhino of interest to trade is the horn, "every part of the tiger", as Cites puts it, "is illegally traded". Their heads hang on walls, their skins are used as luxury rugs, their penises are ground into impotence cures, their bones are steeped in Chinese wine. And as with rhino horn, it is Asia, and China in particular, where the trade is hottest.

If the latest peril to our remaining rhinos comes from the cancer hocus-pocus, the danger to the tiger comes from a different and surprising direction: the exploding population of China's captive tigers. While the number of wild tigers in China has dwindled to fewer than 50, those in zoos and so-called "tiger farms" number around 5,000. And according to a report by the Environmental Investigation Agency (EIA) earlier this year, a secret directive issued by the Chinese government in 2005 has given the green light to the legal trade in tiger products that the 1993 ban was supposed to halt.

This means that if you live in China and have enough money, you can quite legally buy a tiger-skin rug, a tiger head for your living-room wall or a health tonic in which tiger bones have been steeped. As the report puts it, "The use of big-cat skin rugs as luxury home décor has been actively promoted and is now a fashionable symbol of social status. Skins are often given as prestigious gifts or bribes and are seen as an investment."

If these skins come from captive animals, one may ask, where is the problem? To which the obvious retort is, who is to know whether the animal was captive or wild? The problem lies in the fact that the skins of captive cats cost up to three times more than wild ones. In this way the undercover legitimisation of the trade, in frank defiance of Cites' rules, has given a disastrous new spur to the poaching of the wild animals.

The struggle to prevent our most endangered creatures becoming extinct is an unequal one. While Western public opinion, the force of the media and the muscle of Cites are on the animals' side, ranged against them is a raggle-taggle army embracing both the poorest and the greediest: desperate indigenous villagers fighting to survive on the eroding margins of ancient forests, corrupt rangers, malleable politicians, a battalion of smugglers and dealers, and, at the top of the chain, those whose wealth and ostentatious greed drives the trade.

Over the past 10 years, the photographer Patrick Brown has trained his lens on every stage in this process: hapless, impoverished poachers caught in the act; hawkers of bear gall bladder and tiger penis on the streets of Burma; Vietnamese swillers of snake blood; the Guangzhou restaurant where a live crocodile is dragged across the tiles to the chopping block prior to cooking. Desperate need, perverse appetites, shrewd calculation, all yoked together, wreaking havoc on endangered wildlife which belongs to us all, to the whole world; and which, by this rapacious logic, belongs to nobody; and as such is fair game, until it's all gone.

To pre-order Patrick Brown's book, 'Trading to Extinction', visit tradingtoextinction.com