The storm ripped through the island on the night of Thursday 8 January and the trust is still dealing with the aftermath.
Its reserves at Le Catioroc and Pleinmont were damaged, but it was Talbot Valley, just behind Kings Mills, and the Ron Short Walk that saw the worst of the damage.
President Mike Brown said, to use the trust’s land manager’s own words: ‘The wind went through the Ron Short wood like a tornado.’
‘We haven’t had the final bill but it looks likely to be in the region of £10,000,’ he said.
‘That is just for tree surgeons and removing the damaged trees, not for replanting or any other works.’
Tree surgeons have now completed clearance of the Talbot Valley road and the trust’s small car park.
However, several paths within the Ron Short Walk are still blocked by fallen trees and branches, including one large Monterey pine and three substantial ash trees.
Due to the scale of damage across the island and the volume of tree work already scheduled, clearance of this walk may not take place until Easter.
Mr Brown added that the trust would just be removing trees that had fallen on paths or if judged to be unsafe.
‘Otherwise they will be left to rot down, as that is what is best for nature and to make habitat for wildlife even if they look a bit untidy, he said.
‘We will be liaising with the Nature Commission and Trees for Life to talk about replanting and what types of tree are best.’
After Storm Ciaran the trust had anticipated some of the damage that might be caused by future storms and had already removed a number of Monterey pines which were at risk.
‘They are not necessarily the best trees for Guernsey wildlife and deciduous trees are probably the best for the environment in the long term,’ he said.
Mr Brown said he firmly believed climate change would make storms like Ciaran and Goretti more frequent.
‘They used to be generational and now it seems they are happening every other week,’ he said.
‘Even if you think the change in climate might not be man-made it only makes sense to do something about it and for us all to lower our carbon footprint.’