In a related article on the BMC Website Rob commented:
"Winter routes often follow drainage lines and vegetated rock, which also provide habitat for some incredibly rare arctic alpine plant species. We are fortunate in England and Wales because our mountain crags hold some of the most southern populations of these plants.
We're only now discovering some of these precious populations. Thanks to overzealous Victorian plant collectors and upland sheep, they're very scarce. Many remaining populations are only found in inaccessible places where they have been safe from hungry sheep and greedy collectors – steep rocky crags...
The most important point to remember is that routes relying on turf or frozen vegetation should only be climbed when they're frozen hard. Providing the turf is fully frozen, environmental damage will be minimal.
Fully frozen turf has long been considered by winter climbers to be crucial for the obvious reason that unfrozen turf can be ripped off and the character of the route may change drastically. So if the turf is soft or loose, if your tools rip through it or remove chunks, or if there's dirt on your picks after removing them – don't climb."
- More info: BMC Website