JOHANNESBURG: Poaching syndicates were able to move large shipments of African elephant ivory last year despite global calls to dismantle trafficking networks that often collude with corrupt government officials, conservationists said Saturday at an international wildlife meeting.

The illegal ivory trade "has remained fairly constant at unacceptably high levels" since 2010, and a "continuing upward trend" in the seizure of shipments of more than 100 kilograms (220 pounds) in 2015 indicates the key role of organized crime in poaching, according to a document released by conference organizers.

The plight of elephants dominated discussion on the first day of the meeting of member nations of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES. Many delegates are likely to push for the tightening of an international ban on the ivory trade, as well as the closure of domestic ivory markets.

Namibia, Zimbabwe and South Africa, however, favor the sale of their ivory stockpiles, saying the money can be funneled back into conservation.

The world's main ivory consumer, China, has said it plans to close its domestic market. The United States has announced a near-total ban on the domestic sale of African elephant ivory.

Ivory has been used for centuries to make carvings, jewelry, furniture, piano keys, and other items. Many conservationists say criminal syndicates launder illegal supplies through legal markets that permit the sale of antique ivory pieces or ivory exempted from a 1989 international trade ban.

The number of Africa's savannah elephants dropped by about 30 percent from 2007 to 2014, to 352,000, because of poaching, according to a recent study. Elephant populations in Tanzania and Mozambique were among the hardest hit.

Tom Milliken, a co-author of the document released at the CITES meeting, said there are about 50 ivory seizures of more than half a ton, and sometimes as many as four tons, every year. Such big shipments indicate the involvement of organized criminal groups, Milliken, an expert with the TRAFFIC conservation organization, said.

"Nobody is really uncovering their identities and making arrests and prosecuting the people who are really behind this," he said. Poaching syndicates view occasional ivory seizures as a form of "taxation" on their lucrative activity, Milliken said.

Some governments have the capacity to target ivory syndicates in the same way they prosecute drug kingpins, but are sometimes "more comfortable" going after low-level operatives rather than their well-connected ringleaders, said Susan Lieberman of the Wildlife Conservation Society, a New York-based group.

"There's a lot of corruption," Lieberman said.