For info:
Estimated CO2 emissions from the aviation industry per annum = c.700 million tonnes
Amount of carbon dioxide that a typical new growth tree in Toronto absorbs per year = 341 kg year.
Number of trees needed to absorb CO2 from aircraft: 2 billion.
Average density of trees in Toronto forests: 247 / hectare
Number of hectares of new growth Toronto forest needed: 8.3 million = 32,000 square miles (or an area of 400 miles by 80 miles of forest. Land area of England = 50,000 sq miles)
Forest planting isn't really the answer (but is a good thing). Trouble is, we are losing forest, and most of the carbon is being released into the atmosphere, so adding to the problem.
D.