Almost all the world’s illegal ivory comes from elephants that have been recently killed, researchers say. The new study shows that seized ivory isn’t coming from old stockpiles, but from African elephants that have been poached less than three years before the tusks were seized. That means that poaching — one of the biggest threats to elephants — is widespread and may be a bigger problem than we think.

Poachers kill elephants for their valuable tusks — a single pound of ivory can sell for $1,500, and tusks can weigh 250 pounds. For a long time, conservationists weren’t sure whether illegal ivory was actually coming from a steady supply of recent killings. But today’s study, published in the journal Proceedings of the National Academy of Sciences confirms that’s the case. “It is really shocking that it’s all come from recently killed animals,” says study author Kevin Uno, a geochemist at Columbia University. “This shows how serious the problem is, and how we need to continue to attack this problem from many different angles: enforcement, forensics, education.”

Poaching has been soaring in the past decade. A recent report said that poachers killed off nearly a third of the savannah elephants in Africa from 2007 to 2014, leaving only about 352,000 of the animals. There have been many attempts to protect elephants: one long-standing poaching ban makes it illegal to trade ivory internationally if the elephant was killed after 1989. In the United States, there is already a near-complete ban on ivory, but other countries have not enacted domestic bans yet. In China, where ivory is culturally valued and the black market is rampant, politicians have promised to crack down on illegal trade, but many are skeptical of this promise.

The elephants are really in trouble

In today’s study, Uno and his team analyzed 231 tusks seized in nine countries — from the Philippines to Thailand to Kenya — from 2002 to 2014. To figure out how old the tusks were, Uno’s team measured how much of a specific type of carbon, carbon-14 (or C-14), was in the ivory. C-14 was created in large quantities by nuclear weapons testing in the 1950s and ‘60s. Because all of this C-14 was absorbed by the land, including the plants the elephants ate, it creates a kind of “time stamp,” according to Uno.

By measuring how much C-14 is in the tusks, the researchers were able to figure out how old the elephant tusks are. (The tusks’ age was corrected for accuracy by also analyzing the C-14 in elephant hair.) The researchers found that 90 percent of the seized ivory was less than three years old. Of all those tusks, only four were from elephants that died more than five years ago, and just one from an elephant killed 19 years ago.

The study also showed that the lag time between killing and seizure has increased. Before 2011, the time between the elephant’s death and the seizure of the ivory shipment was 8 to 10 months. But after 2011, that time increased to two to three years. This suggests that the smugglers are finding it hard to get enough ivory to fill the large shipments — probably because there are fewer and fewer elephants. “The elephants are really in trouble,” says Uno.

Today’s study confirms how serious the problem of poaching is, says Elizabeth Bennett, vice president of the Wildlife Conservation Society. Knowing the origins of the elephants can tell us a lot about how the business works. In this case, the research suggests that the existing bans are not enough to curb the poaching trade. “Now we know that once an elephant is poached it’s going very rapidly into the trade, which is worrying,” says Bennett. “The core policy implication is that poaching is still really out of control and we need to be closing down all domestic ivory market because the international ivory trade ban in itself is not being enough.”