The blaze broke out near The Parade in Parkgate on Saturday evening.
Pictures and videos shared on social media show the fire raging on the marshland.
Eyewitness Peter Guy said the blaze “billowed into a huge wall of fire” in seconds.
He told Liverpool Echo: “We’d just been eating a fish and chips enjoying the sunset when we turned around and saw a small fire about 300 yards away.
“Within seconds it billowed into a huge wall of fire which ripped through the marshland – it was scary and spectacular all at the same time.
“I’m sure lots of wildlife will have been affected or destroyed.”
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