Smoke filled the skies after six grass fires broke out at Wigan Flashes.
The blazes started at the site, run by Lancashire Wildlife Trust, on Monday afternoon.
Firefighters were called to the area twice and spent several hours using hoses and beaters to put out the flames.
A statement from Wigan Flashes said: "Fire fighters were called to Wigan Flashes again today on two separate occasions to extinguish at least six different fires.
"There is no doubt that the majority had been caused by either deliberate or careless behaviour.
"The heathland near Moss Bridge is ruined for this year, one of the best habitats for bees and other pollinators on the site. Grasslands at the back of Pearsons have been decimated. Three toads, a hawk moth and a wood mouse were all seen escaping the flames.
"This is catastrophic for our wildlife, dangerous for people and dogs, and a waste of time for local firefighters, who quite simply have enough on their plates right now.
"Please folks, be careful! Don't drop lighted cigarette ends, leave the barbecue at home and take litter away with you, especially glass bottles. Let's have a great summer without any more fires. Please!"
It was the latest in a series of grass fires around the borough which already-stretched firefighters are being called out to tackle.