stumbling along the carbon footpath

I am intrigued by how the concept of "offsetting" my "carbon footprint" has infiltrated our everyday life. Some might see this as a departure from old habits - taking responsibility for our actions. To me, though, it seems entirely in keeping with present social and economic mores - the idea that you can pay someone some money to take the problem away. The language that is used is an important part of this illusion: "neutral", "off-setting" - it's as though the pollution never happened in the first place. So I visited a site that specialises in calculating carbon footprints

According to http://www.erasemyfootprint.com/ I and my household are directly responsible for the release of 7.32 tonnes of carbon a year into the atmosphere. The only way to expiate these miasmic sins is to plant 11 trees - and immediately my carbon lapses are forgiven. Even better I don't actually have to get hands dirty - I can pay £110 and trust that someone will do it for me, thus completely removing the inconvenience of penance.

To me, though, this raises more questions than it answers. For instance the 11 trees that are busily sucking my carbonaceous flatulence out of the atmosphere - this only actual works while the tree is growing. Forests capture and store carbon whilst establishing; once mature, the amount of carbon taken in and released by a tree "equalises", as the site delicately puts it (or to put it another way "stops working", at least for the purposes we are discussing).

I am guessing that there must be an "optimum window" when carbon absorption is at a peak in a growing tree? After all, I can't imagine a weedy sapling doing much offsetting of anything. So, in other words, the actual offsetting of my 2007 emissions will not actually take place for another, say, 20 years, allowing for an average growing tree (erasemyfootprint.com calculates a tree lifetime as 60 years). Assuming I remember to plant another 11 trees in 2008, and the years beyond, I will always be playing catch-up, a score of years of carbon behind my present consumption - not even allowing for an increase in the size of my "footprint".

And what happens when my trees die? Do they get replaced under the scheme? After all, a dead tree promptly releases all its stored carbon back into the atmosphere - the carbon doesn't magically disappear. The 550 or so trees needed to offset my life from now on (allowing for a reasonable old age) will need to remain on permanent vigil just to keep the planet as wheezy as it would have been if I hadn't been born. That's quite a lot of acreage, before you even get to offsetting members of my immediate family. Trees are the carbon equivalent of garden sheds, places to lock away unpleasant or unwanted things for the next generation to deal with.