The popular 13-acre woodland, Bird Wood in Tiptree was sold at auction for £168,000 in October last year.
Since 1970, the reservoir on the site was used by Kelvedon District Angling Association and some residents in Tiptree have memories of enjoying the woods beyond that.
Now the site is privately owned it has been fenced off.
The Facebook Group set up in September, Save Tiptree/Birch Woods now has more than 800 members.
Members of the group are now asking the public to fill out a public rights of way evidence form to submit to Essex County Council with the hope of regaining some access to the now private site.
Gates and fences closing off the site have been damaged by unhappy residents and the group is now warning members against doing this.
A spokesman for the group said: “The new owner has excluded local residents from the wood.
“He has fenced and gated the wood with barbed wire and anti-climb paint.
“The wood has been available for use by local residents for generations. Everyone enjoyed free access to a beautiful wooded green space.
“As the wood is an old coppiced wood, local use and enjoyment is possibly centuries old.
“Generations have taken their children to the wood. This will not happen anymore if we, you, do not do what you can to protest.
“The leaflet is to ask you to report your use of the tracks in the wood shown on Ordnance Survey maps.
“Everyone’s opinion matters – everyone in your family and friends over 18 years should complete a form if they have ever used the tracks.
“Parents, grand-parents and great grand-parents are especially asked to complete a form.”
Forms can be picked up and dropped off at Staines and Brights, at 81 Church Road, or at The Cheap Shop, at 108 Church Road.