Prince Charles has warned that climate change is the biggest challenge facing society.
Speaking to business leaders in Cardiff, the prince said he did not think there was a more urgent issue "for any of us".
He described the evidence on climate change as "frightening" and "alarming".
"Doing nothing is simply not an option - it can't be any more, because of the urgency of the situation," he said.
The prince said without urgent changes, the Earth would become uninhabitable.
He added: "I don't think there is a more urgent issue for any of us to be addressing at work, at home, and indeed in every facet of our lives, than climate change."
He told delegates at the Prince of Wales's Business Summit on Climate Change that companies played a key role in reducing the impact of climate change and reducing their carbon footprints.
"It must surely be clear by now that the longer we leave it before taking effective action, the more dire the situation will become and the more desperate the measures that will be needed."
"This really is the most important issue facing us as a society and as a species.
"Because, let's be clear, our planet will survive a high degree of climate change.
"Planets do survive. But only one planet, as far as we know, currently has the very precise conditions our species needs to survive. This is the problem.
"Make no mistake about it, we are well on the way to destroying those conditions, and making our planet uninhabitable."
The prince joked: "I know - I've been talking to the plants and trees for years now and you'd be amazed at what you can pick up."
He concluded by saying: "This is not about saving the planet. Actually, it's about saving us. That is where each and every one of us has a responsibility to do what we can."
Earlier, the prince officially opened the Royal British Legion's Field of Remembrance in Cardiff.
He was joined by First Minister Rhodri Morgan and his deputy Ieuan Wyn Jones for the ceremony in Cathays Park.
A bugler played the Last Post before a two minutes' silence was held.
After planting a cross, the prince said: "It is extremely humbling to look around this garden of remembrance and to see such an array of crosses.
"Each cross representing a life lost in the service of this country.
"It is a particularly poignant reminder that the significance of the poppy is as relevant today as it ever was."
The prince also paused at a new Falklands memorial and met representatives from Sama (South Atlantic Medal Association) and veterans of the Falklands campaign.