The illegal wildlife trade takes the lives of 100 elephants a day, and rhino poaching increased by 5,000% between 2007 and 2012.
The six remaining subspecies of tiger are endangered, two of them critically. Three other tiger subspecies are already extinct.
Statistics like these are the reason it's time to treat the effort to stop the illegal wildlife trade "like a battle, because it is precisely that," says Britain's Prince Charles.
He and his son, Prince William, are among the high-profile global guests due to take part in the London Conference on the Illegal Wildlife Trade on Thursday, hosted by the UK government.
Prince William also will attend talks hosted by the Zoological Society of London and a reception at London's Natural History Museum on Wednesday.
Charles and William released a nine-minute video message Sunday calling for the world to act.
"We have come together, as father and son, to lend our voices to the growing global effort to combat the illegal wildlife trade -- a trade that has reached such unprecedented levels of killing and related violence that it now poses a grave threat not only to the survival of some of the world's most treasured species, but also to economic and political stability in many areas around the world," says Charles.
William says he and his father are optimistic the "tide can be reversed."
"We have to be the generation that stopped the illegal wildlife trade, and secured the future of these magnificent animals, and their habitats, for if we fail, it will be too late," the younger prince adds.
William, whose wife Catherine gave birth to their son George last summer, said that since becoming a father he has become "even more devoted to protecting the resources of the Earth for not only my own son but also the other children of his generation to enjoy."
The video, which was recorded in November, ends with the pair saying the phrase "Let's unite for wildlife!" in Arabic, Vietnamese, Swahili, Spanish and Mandarin.
The aim is to be understood by as many people as possible living in the countries most affected by the illegal wildlife trade.
China and Vietnam are key markets for illegal animal products, such as bones, skin and tusks.
William, who has been a patron since 2005 of the wildlife conservation charity Tusk Trust, faced criticism Saturday in UK newspaper The Sun for reportedly going on a boar hunting trip to Spain with his brother, Prince Harry.
"Prince William has gone shooting -- a day before launching a campaign to stop wildlife being killed," the popular tabloid said.
Horn 'worth more than gold and platinum'
Prince Charles, UK Prime Minister David Cameron and the Presidents of Botswana and Gabon are due to speak at the conference Thursday. The Presidents of Tanzania and Chad are also expected to be present.
The UK government says illegal ivory trade activity worldwide has more than doubled since 2007, with ivory selling for up to 1,200 pounds ($1,968) per kilogram.
"Rhino horn is now worth more than gold and platinum and is more valuable on the black market than diamonds or cocaine," a statement on the UK government website says.
With such lucrative profits to be made, criminals are eager to get in on the action. In 2006, only 60 African rhinos were poached, according to the International Union for the Conservation of Nature. The number has steadily increased to an estimated 1,000-plus in 2013.
One out of 13 elephants in Africa was killed illegally in 2012, according to the Zoological Society of London.
South Africa arrested more than 340 poachers last year -- but poachers sometimes fight back, making the work of park rangers dangerous.
At least 1,000 park rangers have been killed in the past decade, the UK government says.
Prince Charles said poachers make use of the kind of sophisticated weaponry used in warfare, hence his call to treat the fight against them like a battle.
The wildlife trade monitoring network Traffic argues that as long as demand for illegal wildlife products remains, criminals will seek to exploit it.