Landscaper Kim Noble grooms the grass after it was given its annual mowing on the roof of the Vancouver Convention Centre in Vancouver, British Columbia November 15, 2012. The six acre roof is one of the 10 largest green roofs in the world with some 400,000 indigenous plants and grasses that includes four beehives. REUTERS/Andy Clark (CANADA - Tags: SOCIETY ENVIRONMENT TPX IMAGES OF THE DAY)