On Fri, 18 Sep 2009 14:18:38 +0100, Steve Thackery wrote:

They have no nett CO2 reduction effect when considered over their
whole life.

Unless the practice of the ancients is followed and the wood converted
to charcoal and then added to the soil, which of course, enriches it
for growing more plants.

http://www.ecogeek.ORG/agriculture/2173

This practice was extensively employed in the Amazon region to turn
the very poor soil into sustainable crop producing land to feed millions
of people.

http://news.mongabay.COM/2005/1017-amazon.html