"The human race and everything in the world will be poorer for ever" if elephants, rhinos or tigers become extinct, William Hague has said.
The foreign secretary was speaking to BBC Radio 5 live ahead of a conference in London aiming to boost enforcement of the law and curb demand in the trade of endangered species products.
The summit could be a "turning point" in this "great moral cause", he said.
But ultimately an "African-led solution" was needed, Mr Hague added.
The government says the aim of the conference, which will focus on elephants, rhinos and tigers, is to secure a commitment from world leaders to take urgent action to tackle the illegal wildlife trade.
It will also seek ways to support "sustainable livelihoods" for people who stand to lose out financially if the fight against poaching is successful.
Mr Hague said: "It matters to many human beings, including me, that these endangered species are protected, are saved, for the world.
"It will matter for future generations.
"This conference is very important, and I hope it will be a turning point. But if it's a turning point, there's still going to be a lot more work needed after it.
"This has to be an African-led solution that is owned by African states, which we support.
"They do need Western countries, because Western countries are the best at raising finance and we have very active NGOs [non-governmental organisations], we have private individuals who will put money into it, and we have a lot of expertise in conservation.
"This is not the West dictating to anybody, and I think you'll find when the African heads of state and other ministers arrive here they're not seeing it in that light at all."
Asked about consumption in China of products derived from endangered species, Mr Hague said he was pleased that a "senior Chinese delegation" would attend, since there was a "mind-set that needs to change" in the country.
The UK was exploiting its "convening power" in calling the conference, he added.
"Because we are in the EU, in the Commonwealth, in the UN Security Council, have a big development budget, and are the sixth biggest economy in the world, Britain is one of those countries, and I find this on other issues as well, where - whatever else - we can bring people together," he said.
In response to a question on whether species such as elephants might one day only be safe within militarised zones, he said that "would be a sad world".
"This is something that you can't put into financial terms or anything else.
"We know that if that was the case, the human race and everything in the world would be poorer, for ever.
"But it would also be a world in which crime has succeeded, in which corruption has succeeded, so it would be a doubly sad world.
"We're not just going to stand by and let that happen."
He said the UK was "setting a good example with the money we're putting in, and all the effort we're putting in".
"Somebody has to take the lead," the foreign secretary said.
"Somebody has to get all these people together and create the turning point. And, well OK, that's us. Let's take on that responsibility; that leadership."