A family pose for a photo in front of the sapling they planted during a tree planting activity of the Earth Day in Toronto, Canada, April 21, 2013. Some parks in Toronto invited the public for tree planting on Sunday to celebrate this year's Earth Day. (Xinhua/Zou Zheng)

A worker checks on saplings during a tree planting activity of the Earth Day at Downsview Park in Toronto, Canada, April 21, 2013. Some parks in Toronto invited the public for tree planting on Sunday to celebrate this year's Earth Day. (Xinhua/Zou Zheng)