The owners of a wood are appealing to the public to help stop thieves stealing fallen timber for firewood.
Bracket fungus grows on trees which are home to woodpeckers
Coed Cadw (Woodland Trust) said the eco-system is at risk because of the thefts at Coed Aber Artro at Llanbedr near Harlech, Gwynedd.
The disappearing timber is the "last straw", said the Trust, as the wood has already suffered fly tipping and the use of paths by off-road vehicles.
The site is part of an ongoing Trust project to restore ancient woodlands.
Some non-native trees on the site were felled to give the native trees like oak and ash the chance to regenerate, to benefit the sensitive ancient woodland flora and to give the wood a better, more balanced age structure, said Rhydian Roberts from Coed Cadw.
Thieves are stealing the fallen timber for fire wood
"The fallen timber has been left to provide the perfect habitat for small insects and invertebrates which play a critical role in the food chain," he added.
The Trust has been concerned about security at the site for a long time.
"Fly tipping and the use of the paths by off-road vehicles has been a problem, and the thefts of timber from the site is the last straw," Mr Roberts said.
Because of the problems plans to install vehicle barriers on the paths are to be bought forward.
"We are also calling on local people to keep a watch on the woodland and report any vehicle leaving the site loaded with timber to myself or the police," Mr Roberts added.
Rhydian Roberts can be contacted on 01745 818808.