Richard Bonham remembers the first time he saw the massive elephant that came to be called Torn Ear. It was in the early ’90s, and Torn Ear was at a watering hole in the Kenyan park, Chyulu Hills. Bonham, an East African conservationist, was struck by the size of the animal’s ivory tusks.

“I watched his ivory grow, probably nearly doubling in size from when I first saw him,” he told National Geographic. Soon Torn Ear became “one of the few left on the continent whose tusks passed the 100-pound mark,” Bonham said.

But the tusks that made him so remarkable also made him vulnerable. He was killed by poachers using poison-tipped arrows in February. Months later, another famed elephant, Satao, believed to be the biggest elephant in the world, was also killed by poachers.

In all, more than 100,000 elephants have been killed since 2010, according to a new study National Geographic called the first reliable, continent-wide examination of illegal poaching.

“It’s been a real disaster,” lead author George Wittemyer, an assistant professor at Colorado State University, told The Washington Post in a phone interview. If current trends continue, poaching could drive the African elephant into extinction “in 100 years,” Wittemyer said. “If things continue as they are today, that’s what we can expect.”

The study, published Tuesday in the Proceedings of the National Academy of Sciences, used data compiled by Monitoring the Illegal Killing of Elephants. The researchers found that birth rates aren’t keeping pace with death rates, which have been wildly inflated due to poaching.

“Illegal killing levels were unsustainable for the species between 2010 and 2012,” the study said. In 2011 alone, when 40,000 elephants were poached, the species likely shrank by 3 percent, researchers said. “These results provide the most comprehensive assessment of illegal ivory harvest to date and confirm that current ivory consumption is not sustainable,” the study stated.

Some elephants are better protected than others, Wittemyer said. Among the most vulnerable: the elephants of Central Africa, which poachers have winnowed by more than 48,000 since 2010.

“While three-quarters of elephant populations are declining, 25 percent are stable or increasing,” Wittemyer said. “But when the low-hanging fruit and less protected elephants are maybe finished [off] or eradicated, it will turn the pressure [for ivory] onto the ones who are now more protected.”

How hot is that pressure for ivory? Scorching.

Wittemyer said when he first started looking into the ivory trade, one pound traded on the black market for $30. That figure has soared in the past five years. Today it’s around $100 per pound — and in 2011, when the killing reached its peak, a pound of ivory could fetch $150. And when China authorized a one-off sale of African ivory in 2008, business boomed. Today, some estimate a pound of ivory can go for $1,500 in China.

“This is a huge amount of money,” Wittemyer told The Post. “A big male elephant can have 40 kilos [about 90 pounds] per tusk. You’re talking about big time dollars. Even in the U.S., we’d have issues with [poaching], and these elephants are in poor areas. So there’s a lot of pressure.”

Chinese authorities operate 150 legal, government-licensed ivory shops, according to the BBC. But the thirst for ivory is significantly greater. Earlier this summer, Chinese authorities seized 32 suitcases stuffed with ivory — a value of $1 million. It was unclear where they came from, the South China Morning Post reported, but they were “covered with large quantities of dried blood.”

The cases would have likely disappeared into the Chinese market. “On the ground in China,” Wittemyer said, “it is difficult to distinguish between illegal and legal ivory. … Things are not going well right now.”