France, April 13 -- Private jets, superyachts and red carpet speeches... when celebrities champion climate action, do they help the cause or expose their own hypocrisy? It's a question worth asking again, as Prince William announces that the 2025 Earthshot Prize ceremony will be held in Brazil - a star-studded prelude to the UN climate summit set to take place there months later.

In a promotional videothis month, David Beckham, Cate Blanchett and Heidi Klum lent their celebrity clout to the cause, calling for urgent action to protect the planet's ecosystems.

Initiatives such as Earthshot aim to link visibility with concrete action - but critics say star-led campaigns can just as easily blur the lines between advocacy and image managemen...