Flannery is a leading environmentalist and chief counsellor at the Climate Council.

Al Gore has for a long time been one of the world's leading environmentalist politicians.

But then Prof Maathia, Kenya's leading environmentalist, made her name planting millions of trees to tackle deforestation in Africa.

For the BBC's One Planet Mike Williams chairs a discussion with three leading environmentalists from the United States and Britain.

The Virgin Group chairman was joined by former US Vice President Al Gore and other leading environmentalists as he announced the challenge.

A leading environmentalist says tougher rules are needed to stop logging operations from causing the devastation seen in Tolaga Bay at the weekend.