In the last edition of Tree Matters, the NZ Arbor Quarterly Journal, president Rick Mexted wrote about the rapid evolution of tree climbing equipment and techniques - good-to-go one day and abolished the next.
Rick was referring specifically to SRT (relative to the Best Practice Guidelines) but his comments are valid right across the board.
For example, up until recently the Petzl Grigri was routinely used as a lowering device configured in a 'rescue' ground anchor set-up for SRT (Treetools first blogged about the concept back in 2009 and you'll find the Petzl Grigri referenced in the authoritative VTIO SRT paper - page 18).
The Petzl Grigri was also the standard belay/lowering device, anchored to the base of the tree, for the Speed Climb and Footlock events at New Zealand Regional and National Tree Climbing Competitions.
Now Petzl are STRONGLY DISCOURAGING the use of the Grigri as a belay device when anchored to the ground (or the base of a tree.)
There is an added caution for tree climbers: the Petzl Grigri is not ideally suited to tree climbing lines rated to EN 1891A. The Petzl Grigri is designed for use with EN 892 dynamic ropes, as stated in the Instructions for Use. See previous EN 892/1891A blog. However, the same document also shows Shock Loads and Slippage for both EN 1891A and EN 892 ropes?
The new Petzl Rig or the I'D Small devices are better suited to the above applications for multiple reasons, a major one being the type of rope they are compatible with - that is, tree climbing lines rated to EN 1891A (albeit in a relatively narrow rope diameter operating window 10.5 mm - 11.5 mm).