A city surrounded by mountains and polluted by heavy car traffic, Los Angeles has been known for decades as the "Smog Capital of the United States". Back in 1970, when 15-year-old Andy Lipkis heard about the air pollution that was threatening the mountain forests near his hometown, he decided something had to be done about it. He rallied a group of like-minded supporters and set out to transform an area used as a parking lot into a green space, by planting smog-tolerant trees on it.

From these humble beginnings, Lipkis went on to found an NGO, TreePeople, and has since spearheaded numerous tree planting campaigns to help repair and restore urban environments. What began as one individual's mission to save his local forest has grown into one of North America's largest environmental organisations.

Sharita Hutton joins Andy Lipkis and his team of 'citizen foresters' in Los Angeles, as they plant trees in a school playground in one of the city's less affluent suburbs - providing shade and greenery where there was once only concrete and asphalt.

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