Today, 90% of paper pulp is made of wood. Paper production accounts for about 35% of felled trees, and represents 1.2% of the world’s total economic output.]Recycling one ton of newsprint saves about 1 ton of wood while recycling 1 ton of printing or copier paper saves slightly more than 2 tons of wood. This is because kraft pulping requires twice as much wood since it removes lignin to produce higher quality fibres than mechanical pulping processes. Relating tons of paper recycled to the number of trees not cut is meaningless, since tree size varies tremendously and is the major factor in how much paper can be made from how many trees. Trees raised specifically for pulp production account for 16% of world pulp production, old growth forests 9% and second- and third- and more generation forests account for the balance. It has been estimated that recycling half the world’s paper would avoid the harvesting of 20 million acres (81,000 km²) of forestland.