GREENPOINT — A bike that had been targeted by a group of environmental activists who had plotted to clip and take several bicycles chained to trees in the area has been stolen, cops said Wednesday night.

The group, The Treedom Project, had planned to remove chains and bike locks they claimed "choked" trees.

"Affixing your bike to a tree is illegal, and I don't think a lot of people are aware of that law," said Rob Birdsong, a Brooklyn resident and member of the group.

The New York City Parks Department confirmed that chaining your bike to a tree was against the law because it harmed the bark and inner layer of trees.

"A lot of these bikes have been there for years," Birdsong said.

He and his cohorts tagged about 15 bikes with warnings that the group would take the rides if no owner came to remove them from the trees. But the activist group backed away from their most audacious plans because of an "ethical question that arose regarding the thin line between 'organized group of citizen tree pruners' and 'bike thieves,'" according to Treedom's website.

"Ethical problems arose. We decided theft is equally not as cool [as affixing bikes to trees]," Birdsong said.

So Birdsong and his accomplices spent May 26 — "Treedom Day" — removing other items affixed to trees such as stand-alone bike locks and nylon netting, he said.

But at least one of the bikes Birdsong had planned to remove was stolen on or around May 26, cops and neighbors said.

"I saw the tag that said the bike would be taken...and then the bike disappeared. This is a problem," said resident Eileen Meriave, who saw a bike taken on Guernsey Street by Norman Avenue.

"That's illegal. It's stealing to remove a bike unless it's your own," said the 94th Precinct's Commanding Officer, Capt. James Ryan, who said he would investigate the theft.

And a spokeswoman for the Department of Sanitation said that even if the bike removed had been derelict, only the city had the right to clip the lock and take it.

"The Department of Sanitation is the only city agency that has the authority to remove and dispose of derelict bicycles that are attached to public property which includes trees and bicycle racks not installed by the Department of Transportation," said the spokeswoman, Kathy Dawkins.

Ryan said cops had yet to identify a suspect for the Guernsey Street theft.

Birdsong insisted that his group had not taken the bike.

"In most instances we went back and untagged the bikes," Birdsong said of the bikes he'd targeted throughout North Brooklyn for removal. "I was very surprised to hear that this had even come up."