Sarah, Duchess of York reveals that since becoming a grandmother, she's become "acutely aware of my responsibility" as she prepares to head Down Under for a summit.
The author, 64, who has two grandsons and one granddaughter, will travel to Melbourne, Australia for Global Citizen NOW from 4 to 6 March, where she will engage with young leaders who are working to address the climate crisis, end poverty and improve girls' education.
Sarah, who will Co-Chair the event, said how her grandchildren, August, three, Sienna, two, and nine-month-old Ernest inspire her.
In an Instagram post showing the Duchess wearing a blue shirt dress, she wrote: "I look forward to listening to [young leaders], learning from them, and contributing whatever voice I have to speak up for the future of our planet.
"My parents always highlighted the need to champion the quiet voice of Mother Nature, and now even more so since becoming a grandmother I’ve become acutely aware of my responsibility, and that of my generation, to do everything we can to improve the state of the world we are leaving for our grandchildren."
Hugh Jackman and Charlie Puth will also be among the big names at the Global Citizen NOW action summit.
It comes after Sarah urged people not to skip their health check-ups, warning "days could make the difference between life and death" as she marked Cancer Prevention Action Week.
The Duchess was diagnosed with malignant melanoma, a form of skin cancer, in January less than a year after facing breast cancer.
Sarah – mother to Princesses Beatrice and Eugenie – said her diagnosis was a shock but she was "in the best hands and feeling positive".
"After undergoing a mastectomy and reconstruction, I could only hope that I was in the clear, which is why a new diagnosis of skin cancer came as a shock,” she wrote. "I'm now in the best hands and feeling positive with the support of my family."
Earlier this month, the Duchess travelled to the US to take part in a number of charity events.
In a speech at the Cancer Alliance of Help and Hope's Palm Beach luncheon, Sarah shared a touching tribute to her former brother-in-law, King Charles, who is currently undergoing his own cancer treatment.
"I want to thank you all for your kindness in supporting my family members who are going through a hard time, and we wish everyone well, every family in the world, that has been diagnosed or who is going through a difficult time we wish them well," she told the audience. "And of course, my brother-in-law, we wish you well, keep fighting on."