Absorbing carbon.

• Author: Ferguson, Andrew R.B.
• Position: From Readers - Brief Article - Letter to the Editor

The statement in Matters of Scale [January/February] that 761,000,000 trees contain carbon equal to the amount emitted during a year by a single power plant in Monroe, Michigan, is striking, but true only for small trees (the emissions are specified as 17.5 million tons of carbon dioxide). I calculate that the requirement would be for 761,000,000 trees without branches, 4 inches in diameter and 10 feet tall!

What perhaps better brings to light the nature of the problem is an overview of the entire project of carbon absorption by trees. For carbon absorption rate, we can choose the datum used in the Living Planet Report 2002, namely 0.95 tons of carbon per hectare per year (tC/ha/yr). With the world's present fossil fuel emissions, of 6.3 billion tC/ha/yr, approximately 3.3 billion tons are accumulating in the atmosphere each year (the rest are absorbed as part of the Earth's total carbon cycle). To mop this up, there would be a need for 3.3/0.95 = 3.5 billion ha of new forest. The present total area of forest is about 3.8 billion...