Former First Lady Graca Machel and former UN Secretary General Kofi Annan are among dignitaries who’ve planted 100 trees in Johannesburg ahead of Tuesday’s Mandela Lecture by former US President Barack Obama.

Machel and Annan are among a group known as the Elders – prominent citizens involved in seeking peace and security across the continent.

They’ve been joined by scores of NGO’s in the “100 sparks of hope” tree planting.

Billionaire philanthropist Richard Branson says this is in line with former President nelson Mandela’s legacy.

He says: “The trees are really signifying organisations that are transforming people’s lives throughout the world. They are transforming people’s lives environmentally by promoting health in people’s lives.”

“So the trees are simply a symbolic way of remembering Nelson Mandela.”

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