Behind the green

Landscaping a city takes more than just putting trees into holes. These are living creatures that constantly demand attention. Erik Nilsson and Wu Wencong talk to the tree doctors who keep Beijing green and lush.

Zhang Yinshan never killed anyone when he was a military fighter pilot, but now he exterminates pests with the greatest determination.

The 50-year-old has regularly flown air strikes to poison and starve invaders en masse since he became a helicopter operator for the Beijing municipal bureau of landscape and forestry's air protection section.