Acacia trees at Manoa Valley District Park are riddled with gashes. Large cuts can be seen on multiple trees. 

The Department of Parks and Recreation says it's received about a dozen complaints.

According to the City, taking bark is illegal and posted warning signs.

Residents say they've seen people scraping off bark at night and are furious. 

"It is unacceptable. We might be weak but we are many if you come to peel our trees aunty's going to take an issue with you," Ellen Watson from the Manoa Neighborhood Board said. "We'll just follow through till you're arrested."

Watson says residents don't understand why the bark is being taken in the first place. Some believe it may be to cook up psychedelic drugs.

"Are they sucking on this bark, are they making a tea, are they making lemonade are they giving it to kids, I don't know," Watson said.

According to drug intervention experts, bark from acacia formosa trees can be grounded up and used as a hallucinogen. But it can also be used medicinally, as well. 

The City says removing it from the park is against the law.

"This is vandalism. They're defacing our trees and really they're everyone's trees," Nate Serota of the Department of Parks and Recreation said. "Worst case scenario these trees might be undermined by all of this vandalism that they're doing."

Anyone caught stealing bark could face a $500 fine and jail time.