Image caption Most of the world's wild rhinos live in South Africa

South African officials have warned a major conservation meeting that the poaching of rhinos is likely to reach record levels this year.

Delegates at the Cites conference in Bangkok heard that to date 146 animals have been killed for their horns in 2013.

The South Africans said that a taboo on discussing the prospect of legalising the trade in the animals must be lifted.

But rhino welfare campaigners say the idea is flawed and dangerous for the species.

Rising demand, particularly from Vietnam, is said to be the main reason for the explosion in rhino killing last year that saw 668 animals slaughtered in South Africa.

Time for talks

Fundisile Mketeni from South Africa's environment ministry said that 146 had been killed so far this year, with 107 of them in Kruger National Park.

The South African delegate explained that while his country had not yet made a decision about calling for a lifting of the ban on selling rhino horns, the nation believed it was time for the dialogue to begin.

"We must talk about it, because all other things are spoken about, but this is taboo - no-one wants to touch it," he told the meeting.

"We are saying we have tried everything. Let us start talking about this one. There is no decision made, but we can't talk about awareness or research or range expansion without talking about this one."

A number of scientists recently published research indicating that the global demand for rhino horn could be met by permitting a trade in shavings, humanely harvested from the animals that can grow up to a kilogramme of horn in a year. The researchers said that this could stem the rhino trade.

According to the South African minister for water and environmental affairs, Edna Molewa, if something is not done by 2016 the number of rhinos being born will be outnumbered by those being killed.

"The indication is that if we do more of the same, the same work every day, more of the same will not help us produce a better result," she told the Bangkok gathering.

"By 2016, we will begin to run into trouble, the graph will begin to slide down - we shall be losing more on a continuous basis."

Economics of rhino

But the idea of lifting the rhino ban or even talking about it is upsetting for many campaigners at this meeting.

According to the charity Care for the Wild, South Africa's call for a debate on what they term "rhino-conomics" is preparing the ground for the legal sale of horn.

According to Philip Mansbridge, the charity's chief executive, this is bad news for rhinos.

"The danger is that legalising horn will feed the growth of the market rather than reduce the demand on poaching," he said.

"Most of the people calling for this are the highly influential private game-reserve owners. The legalisation of trade in rhino would make overnight millionaires of these key figures in South Africa."

Earlier a proposal that would have seen a restriction on the number of rhino horns that could be exported as sports trophies from South Africa and Swaziland was withdrawn in the face of opposition.

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