CO2 Offset - tree planting pledge

I agreed, with some reservations, to participate in Simon Holledge's pledge campaign to have a certain number of trees planted to offset the estimated carbon dioxide produced as a result of my daily existence. Although my calculations show that my 'impact' in CO2 terms is rather lower than the 10 trees estimated (it worked out at about 6.4 trees, according to the calculator at Trees for Life) I have gone ahead and made a donation of GBP50.00 (based on a figure of GBP5.00 per tree) toward the work of 'Trees for Life'.

To clarify what are my reservations about this kind of pledge, about which I have already commented directly with Simon Holledge, they are these:
- I support unreserveredly, in principle, the notion lying behind the wish to 'offset' one's estimated environmental impact in terms of CO2 productioon;
- the wording of the pledge itself "I will have 10 trees planted to offset my total carbon dioxide emissions for 2005 but only if 99 other people will too." is wrong-headed in my view; whether 99 other people choose to sign up to this pledge, or not, will have no impact whatsoever on my environmental impact in terms of CO2, so whether or not other people support this pledge should make absolutely no difference to whether I, or Simon, or anyone else who accepts (without necessariuly being able to verify the details as an 'expert', which of course I am not) the theory that planting trees is a 'good thing' to do to help protect our environment, from making a donation for this purpose;
- the wording of the pledge implies, no it states, that pledgees bind themselves only to fulfil their pledges if others sign-up (fallacious logic as discussed above), but signing-up to a pledge is very different to actually coughing-up the funds when called upon to do so. Pledges of this kind, in my opinion, seek to make people feel good about themselves by making a public statement about some subject or other thought to be 'good', but in reality impose no obligation upon pledgees to honour pledges other than their own sense of 'honour', but (cynic that I am) I suspect that a proportion of people, when signing-up to fine-sounding petitions go no further than making the public statement.

I make a certain number of donations on a regular basis to a variety of organisations whose aims I consider worthwhile. Obviously I am happy if others support some of these organisations too, because that will increase the total funds they have available to them for their work, but my continuing willingness to donate is in no way dependent on those other donations occurring. It is on this basis, and this basis alone, that I have made a donation for 10 trees to be planted in my name. If others wish to do so they can either do it through Trees for Life or one of the other organisations that Simon mentions - see links at the top of this message.
(NB/ I have twice attempted to, and apparently 'succeeded' in, sending trackbacks of this post to Simon's relevant blog post, but these do not seem to show up on his website, yet at least.)