I reverted the edit about Driessens membership of Sierra Club and ZPG. The original identified that he claimed he was a member of the organisations. To go the next step of stating that he was a member implies some evidence that can be independently checked when there isn't.
For example Bjorn Lomborg claimed he was a member of Greenpeace which helped sell his story line of 'I once was an environmentalists but now I have seen the light'. Greenpeace had no records of him and when challenged Lomborg conceded that he had never been a 'member' but said he had made some donations. If there is indeed some evidence that Driessen was a member, I'd be happy to change the entry. --Bob Burton 18:54, 21 Jul 2004 (EDT)