At one of Hanoi's priciest restaurants, a group of Vietnamese businessmen meet their new American partners to celebrate their latest venture. "A toast!" someone exclaims. They raise their glasses, filled with the finest scotch, which has been sprinkled with a fine powder. Not gold powder, as lesser moguls might offer, nor even the purest cocaine. No, this is far rarer and costlier: it is pulverized white rhino horn.

A half-century ago, white rhinos abounded in Africa. Today, the International Union for the Conservation of Nature estimates that only 25,000 still roam the continent, mostly in South Africa, with a handful in Namibia and Kenya. The population of elephants — another of Africa's most iconic animals — is also dwindling fast, having fallen from between 10 million and 20 million a half-century ago to just 470,000 today.

The proximate cause of these precipitous declines is poaching. But the real reason is those businesspeople in Asia. Thanks to demand from people like them, the going rate for elephant tusk in Asian markets is around $1,500 per pound. Rhino horn fetches $45,000 or more. With prices like these, it is no surprise that poaching has become a $20 billion mega-business, reaching high into the political leadership of many African countries.