Unlike most large mammals, habitat loss has not been a significant factor in the decline of rhinos. Rather, poaching for their horn has decimated rhino populations.
As early as the 5th century B.C., rhino horn was believed capable of rendering some poisons harmless. In Borneo, people used to hang a rhino's tail in a room where a woman was giving birth, believing it would ease labor pains. Asians used rhino horn in traditional medicines for a thousand years without threatening the species' survival.
It was not until the 1970s that rhinos declined dramatically, due to a surprising cause: the soaring price of oil. Young men in the Arab country of Yemen covet rhino horn for elaborately-carved dagger handles, symbols of wealth and status in that country. Until the 1970s, few men could afford these prized dagger handles. But Yemen and other Middle Eastern countries are rich in oil, and prices for this "black gold" climbed dramatically in that decade due to a worldwide oil shortage.
The result was a seven-fold increase in the per capita income in Yemen, a rise in wealth that made rhino horn dagger handles within the reach of almost everyone. This small country, with a population of 6 million at the time, suddenly became the world's largest importer of rhino horn.
The value of rhino horn made it enormously profitable to poach rhinos and sell them on the black market. For example, in 1990, the two horns from a single black rhino brought as much as $50,000. Just like poaching for elephant ivory, poaching for rhino horn is simply too profitable for many subsistence farmers and herders to resist.
The value of Van Gogh's Vase with Fifteen Sunflowers was 23.8232 million GBP then, which is now valued at 45.9553 million GBP. The earliest sale of Vase with Fifteen Sunflowers by Vincent van Gogh is from 1987, tripled the previous record price, set only two years before, introducing a new era in top picture prices.