Prince William is calling for humanity to "reset our relationship with nature and our trajectory as a species" in a bid to avoid a climate disaster.
In a special video message broadcast at the Conservation International Gala in the US, the Duke of Cambridge said the next decade would be "one of our greatest tests".
He said the most vulnerable people around the world "and those who have done the least to cause climate change" would be the worst hit.
The royal urged those present to take their lead from the millions of young people who are trying to solve the global crisis.
"All of us, across all sectors of society, and in every corner of the globe, must come together to fundamentally reset our relationship with nature and our trajectory as a species," William said.
"I truly believe that humans have an extraordinary capacity to set goals and strive to achieve them. The remarkable development of the COVID-19 vaccine in record time is a case in point."
In October last year, the duke launched the Earthshot Prize – an ambitious Nobel-style environmental award with a £50m prize fund to recognise and celebrate ideas and technologies that can target the climate crisis.
The prize, which takes its inspiration from the Apollo moon landings, nicknamed Moonshot, has five goals for the next decade: protect and restore nature, fight air pollution, revive the oceans, build a waste-free world and fix the climate.
The duke added in the video message: "We want to find the brightest minds and boldest ideas that will help us to achieve these Earthshots.
"But it will require our collective energy, determination, and optimism to get there."
He continued: "Together we must unite every business, every community, every government and every person around our common goal to repair the earth."
William said he hoped people around the world regardless of background or beliefs could "join this shared optimism for the future and conviction that change is truly possible".
"Together, I’m confident that we can begin to heal our planet, protect nature, and improve lives for billions of people, today and for generations to come," he said.
William previously said it would be "a mistake" not to use his position to help the environment, and that he’s ready to take on any criticism and have uncomfortable conversations if he can bring people together.