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Text by Peter Gwin

Currently one rhinoceros is killed by poachers every 16 hours in South Africa. Over the last three years, more than a thousand of the animals have been slaughtered. In response, police gunned down 22 poachers and arrested more than 200 last year. At the bloody heart of this conflict is the rhino's horn, a prized ingredient in traditional Asian medicines. Though black market prices vary widely, as of last fall dealers in Vietnam quoted prices ranging from $33 to $133 a gram, which at the top end is double the price of gold and can exceed the price of cocaine.

Although the range of the two African species—the white rhino and its smaller cousin, the black rhino—has been reduced primarily to southern Africa and Kenya, their populations had shown encouraging improvement. In 2007 white rhinos numbered 17,470, while blacks had nearly doubled to 4,230 since the mid '90s. For conservationists these numbers represented a triumph. In the 1970s and '80s, poaching had devastated the two species. Conservation groups were able to convince several consuming nations to crack down on the sale of rhino horn, including China and Yemen. Now, however, much of the trade centers on Vietnam, where rhino horn has been recently rumored to be used as a traditional treatment for cancer.

Meanwhile, in South Africa, attracted by spiraling prices—and profits—crime syndicates began adding rhino poaching to their portfolios. Rhinos have been targeted on private game ranches, provincial reserves, and especially in the country’s vast Kruger National Park. South African authorities have responded by sending military units to bolster patrols and instituting a shoot-poachers-on-sight policy. Private activists have responded to the crisis, helping train and equip game rangers and boosting education campaigns in communities that live close to wildlife.

Amid all these efforts to combat poaching, some game farmers are questioning the international ban on selling rhino horn. They point out that unlike elephant ivory, rhino horn can be sustainably harvested without hurting the animals and that the horns will grow back fully in two years. Allowing the sale of responsibly harvested horn would make the animals attractive to farmers, who would be incentivized to invest in better security, and legalized trade would allow prices to stabilize and decrease speculation.

In the meantime, the killings continue, the carcasses pile up, and the world’s rhino population shrinks toward oblivion.

Brent Stirton’s photographs, published in National Geographic March 2012, won the World Press Photo first prize for Nature stories. Peter Gwin, who authored National Geographic’s story, is writing a book entitled Rhino Wars: A Journey into the Violent Underworld of Black Market Medicine, to be published in Fall 2012.