Volunteer reserve manager of Eskrigg Jim Rae discovered the remnants of the blaze last week close to the wooden centre building, along with beer bottles and litter.
A mature birch tree was severely damaged in the fire, and Mr Rae said it is likely the tree will die as a result.
Explaining how close the fire was to the areas used regularly by visitors, he said: “It was just about ten feet from the centre, and when I went down there were photographers just a couple of feet from it trying to get pictures of squirrels.
“There were some people down here earlier in the month and I found a few beer bottles in the pond.
“They left a bit of a mess inside the hide and there was still smoke inside when I arrived down — I had to open all the windows to be able to see the extent of it.”
Slamming the behaviour, Constable Lisa Duff at Lockerbie said: “This reckless act of starting a fire in the reserve actually defies belief.
“As a result a mature tree has been damaged and may not recover.
“The consequences could have been much worse had the fire spread through the reserve.”
Mr Rae explained it is not the fire time he has discovered signs of fire at the reserve and commented: “Some young people don’t seem to appreciate that it’s a nature reserve, not a playground.”
Anyone with any information about the fire and those responsible is encouraged to contact Police Scotland by calling 101.
