The UK's Prince William called for humanity to "reset our relationship with nature and our trajectory as a species" if the planet is to avoid a climate crisis.
He suggested activists follow the lead of inspirational young leaders such as Greta Thunberg, who have turned climate action into a cause for immediate action.
Prince William is a long-time supporter of climate action, as is his father Prince Charles, who was a voice for environmentalism in the late 20th century.
In a special video message broadcast to the Conservation International Gala in the US, the Duke of Cambridge said the next decade would be "one of our greatest tests".
"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," he 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."
Last year, the duke launched the Earthshot Prize to recognise, celebrate and fund breakthrough ideas that can help tackle climate change.
"We want to find the brightest minds and boldest ideas that will help us to achieve these Earthshots," he said of the launch.
"But it will require our collective energy, determination, and optimism to get there.
"Together we must unite every business, every community, every government and every person around our common goal to repair the earth.
"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."
Severe heatwaves and drought have tripled crop losses in Europe over the past 50 years, a study found.
In addition, flooding and cold snaps became more prevalent during this period – but it was drought that was the most "disproportionately severe".
In the US, activists hope that President Joe Biden's government will take the issue seriously after his predecessor, Donald Trump, withdrew from the Paris climate agreement.
US climate envoy John Kerry was in the UAE on Saturday for a regional climate summit.