Prince Charles and Prince William have said urgent action must be taken to curb the illegal trade of wildlife.
At a conference at St James's Palace, the Duke of Cambridge said there are only two possible ways the trade will end - either world leaders take action, or "we will run out of the animals".
"There is no other outcome possible," he added.
Charles, a long-term advocate of wildlife, said it was "unthinkable" that animals that have roamed the planet for so long could become extinct.
He said the "destruction of animal species will diminish us all" and that we must "act swiftly, as we are in a terrible race against time".
The event was attended by high-profile guests including environment secretary Owen Paterson and Grant Miller, senior officer at Convention on International Trade in Endangered Species of Wild Fauna and Flora (Cites).
It focused on three endangered species - the elephant, tiger and rhino. Demand for rhino horn has increased significantly in recent years, largely because it is used in traditional Chinese medicine despite having no medicinal value.
As part of the conference, the UK Border Force exhibited illegal products it had seized.
William said: "I sincerely hope that my generation is not the first on this planet to consider elephants, rhinos or tigers as historical creatures - in the same category as the Dodo. These creatures are still with us, their magnificence more wonderful than anything we could ever create in our imaginations, and they enrich our world immeasurably.
"Their majesty contrasts to the ugliness of the illegal trade that destroys them through greed or ignorance.
"The poaching crisis and illegal trade is, I believe, a form of 'economic sabotage' of diverse communities in the range states. Tackling illegal wildlife trade would bring about numerous benefits ... in poverty alleviation, the reduction of organised crime and better security.
"So, I ask myself - what can be done about it? The problem is enormous. The destruction of whole species in order to flaunt their parts as ornaments is not a thing of the past anywhere in the world."
According to ITV, Prince Charles added: "As a father and soon-to-be grandfather I find it inconceivable that our children should live in a world bereft of these animals."